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Antice
2009-Mar-05, 09:34 PM
Looks like the skylon project is going forward and might have a working spaceplane flying around 2020
BBC news article (http://news.bbc.co.uk/2/hi/science/nature/7898434.stm)
Skylon concept page (http://www.reactionengines.co.uk/skylon_overview.html)

highlights from the info i have found so far:
the craft will be a ssto vehicle
it will use the air breathing sabre engine for it's ascent to orbit.
projected cargo capacity is about 12 tons to LEO
it is designed to be fully reusable up to 200 flights between refurb and rebuild.
also. it will use active cooling during reentry.

somehow i get the feeling that 200 flights between engine refurb might be a tad optimistic. but i could be wrong.
what i do wonder the most about tho is the use of active cooling during reentry. has that ever been done before?
what do you guys think of the progress of these kinds of vehicles so far?

oh yeah. i didnt want to open up the old dead thread about air breathing rocket engines. Esp. since it's in the wrong place imho. So
linky (http://www.bautforum.com/astronomy/16489-hybrid-engines-cheaper-space-access.html#post359434) instead :)

Larry Jacks
2009-Mar-05, 10:02 PM
While I wish them well, this article (http://www.newscientist.com/blogs/shortsharpscience/2009/03/rockets-not-air-breathing-plan.html) points out why airbreathing space vehicles are difficult to achieve.

For the engines, we can compare rockets to jets, and the rockets come out ahead. Rocket engines generally are simpler than jet engines, not more complicated. And although they have to lift more weight, they can do that: the best modern jet engines produce thrust equal to about 10 times their weight. But 40-year-old rocket engines can lift 100 times their own weight. For a given thrust, a rocket engine is much smaller and lighter than the corresponding jet engine.

Why the difference? It's all about density. A litre of LOX contains as much oxygen as about 4500 litres of sea-level air. At high altitudes, the air is much thinner yet, and the LOX is unchanged. Jet engines are huge and heavy because they must handle such enormous volumes of air to gather each kilogram of oxygen. As the old sailor's adage goes: "the wind may be free, but the sails bloody well aren't".

Yes, LOX weighs a lot, but the tanks to put it in, and the engines to carry it, are light - and it's the tanks and engines that you have to build and maintain. Moreover, in a single-stage spaceship, the liquids in the tanks burn off on the way to orbit, but the engines have to be carried all the way... so how much they weigh is actually rather important.

Argos
2009-Mar-05, 10:09 PM
That´s an old idea. All you get on their website is the description of the concept. I´d like to see an actual explanation of how they´re going to make it work.

Larry Jacks
2009-Mar-05, 10:20 PM
I´d like to see an actual explanation of how they´re going to make it work.

More to the point, I'd like to see how they're going to pay for the R&D. It'll cost quite a bit more than the million pounds mentioned in the article.

Antice
2009-Mar-06, 12:17 AM
some of the enabling technologies appear top have other commercial uses outside of rocketry. like the highly advanced heat exchanger they are developing for cooling down the air input, Before compressing it for use in the rocket stage of the engine.
Also. going by the business model they portray. the company uses the developement of these technologies as a way to keep ahead and as a selling point for their real business: consultant services for technological development.
call it "know how" farming if you like.

back to rocket planes in general:
One of the advantages of a rocket plane that is not readily aparent is that it needs not accelerate to high speed until it is pretty high up.
you don't just use air to reduce on board oxidiser weight. you also use it to help you lift your ship up to altitude before starting the real burn to orbit.
it would be interesting to see a comparison between this concept and the 2 stage spaceship one concept on mass savings on the ground. most of the fuel in a rocket is spent just getting the first couple of km off the ground after all. the third dataset in that comparison should be a normal rocket.
i have assembled arguments both for and against the use of rocketplanes:

points in favor of rocketplanes:
1. reduced need for initial thrust due to aerodynamic lifting help from the wings. can be further enhanced by using a steam catapult to help the craft gain speed on the runway
2. reduced need for oxidiser in the initial part of the ascent profile.
3. using a runway for both lifting off and landing means reduced need for specialized launch pads with a slow turnaround. one runway multiple preparations bay's can enhance the turnaround rate by a magnitude or more.
4. reusability puts hardware investement per kg cargo put in orbit lower. resulting in cheaper access to space

points against rocketplanes:
1. increased complexity due to complicated dual mode engines.
2. wings makes re-entry harder on the craft. might demand new and experimental tech to accomplish safe return at all.
3. can only lift small payloads in the 10 to 12t range. also severe volume restrictions apply. (this might change over time as the concept matures with use)
4. initial capital investement is very high compared to normal launchers, and is dependant on having enough customers for all the launches the vehicle can do within a reasonable time frame.

To me it seems that the biggest issue is to actually have enough cargo to carry to orbit so that you utilize your shiny launcher in a profitable way. a hangar queen ain't making money, and unless you have cargo to carry you aren't getting off the ground no matter what kind of launch system you employ.


imho. there will always be a market for big boosters. large oversized cargoes like big station modules etc needs be launched only now and then during construction phases, and would be outside the normal market for fast turnaround rlv's.

Van Rijn
2009-Mar-06, 06:35 AM
I had some comments on air breathing hybrids back here in 2005:

http://www.bautforum.com/astronomy/16489-hybrid-engines-cheaper-space-access.html#post359434

I see them as missing the point. The idea is to get the cost of operations down, and the air breathing schemes will add great complexity and mass. Anyway, in that post, I linked here, which had mentioned Skylon:

http://www.aerospaceweb.org/question/spacecraft/q0202.shtml

From that page:


Although Reaction Engines has been pursuing this concept [Skylon] for over 15 years, it does not appear to have attracted much interest. In 1992, the company estimated that it would take 10 years and $10 billion to develop the Skylon. To date, the group has only been able to raise a small fraction of that total, most of which has been invested into basic research on the Sabre engine. Given the number of unproven technologies incorporated into its design and the lack of capital to develop them, it seems unlikely that Skylon will be completed anytime soon. Additional information is available at Reaction Engines.
- answer by Jeff Scott, 14 November 2004

So, they've been pushing this idea for a long time, and a million euros isn't going to cut it.

Damburger
2009-Mar-06, 08:55 AM
Not a chance. Our government will toss money at failing banks, and when that fails they even start printing more money - but they won't invest in R&D.

Skylon is a good project. It isn't just a bunch of random nutters, the men behind if have serious aerospace pedigree, and they deserve a shot at trying to make this work. They just simply won't get it.

(I should also point out that the company has plans to use a variant of the same air-breathing rocket engine for a hypersonic antipodial passenger jet that can go from Europe to Australia in 4 hours or something daft. Having common parts with a commercial airliner helps the economy of a space plane a lot)

Antice
2009-Mar-06, 11:22 AM
i can see several non space launch uses for a hybrid engine like the one they are developing.
passenger suborbital flights being just one of them.
The engines could easily be used to make a mach 5+ long range strike aircraft. i am certain there would be some military uses for that.
secondly. the engine runs on hydrogen. altho hydrogen is very bulky to move it's as clean a fuel you can get.
so even kept in just air breathing mode as a engine for supersonic passenger craft it would have some nifty benefits. however that means solving some of the issues that kept Concorde ticket prices so high in the first place.

as long as they develop the engine, witch btw is what they are doing. then there is potentially a pretty decent market for it.
If the engine sells then cash for making skylon is liable to be available at some future date.
btw. how much of that 10 bill figure is needed for the engines is hard to say. since it seems like a lot of the enabling technologies are already nearing the maturity levels to start half scale prototype building.
however in my experience it's the last 5% of the development that really cost the big $$ as it is at that point you have to build working prototypes of the entire system and actually fly them. so let's hope they get it funded properly.

samkent
2009-Mar-06, 12:39 PM
What is the cost of hydrogen compared to kerosene? I don't even know how they produce it. If they use an electrolysis then it has to be very expensive.
The whole thing sounds like the areocar concept.

NEOWatcher
2009-Mar-06, 01:41 PM
What is the cost of hydrogen compared to kerosene?
I don't know, but for its use in an expensive application is probably negligable in the entire picture.

I don't even know how they produce it. If they use an electrolysis then it has to be very expensive.
That's one way. It's also produced by chemical reactions and extracted from hydrocarbon sources like natural gas.

Electrolysis is expensive now, but if we can bring the cost of renewable electric sources low enough, it might not matter.
I think I recall some country (Iceland?) uses geothermal to produce it for a comperable price to petroleum products.

Antice
2009-Mar-06, 02:23 PM
hydrogen can be produced from natural gas with the help of steam reforming (http://en.wikipedia.org/wiki/Steam_reforming) of natural gas. this method invalidates the no co2 release of the hydrogen cycle tho. it just moves the co2 release to the hydrogen manufacturing plant. where it potentially could be sequestered.
alternate methods involve high temp electrolysis in steam cycle nuclear reactors. but none of those reactors are built yet. and might never get built unless we have a big political shift about nuclear power in general.
generally hydrogen is a more expensive fuel than kerosene, since the cheapest manufacturing methods rely on natural gas to make hydrogen.
Ironically. in some places. like my own country hydrogen is cheaper than kerosene due to high amounts of taxes on kerosene/diesel used in vehicles.

how viable it is to convert the rocket part of the sabre engine in order to use the cheaper fuels is unknown. it could be a fairly easy thing to do since as far as i can see from the design specs on the sabre engines the rocket part is distinct from the air breather/pre-cooler part. with helium used as coolant in the pre-cooler.
I guess that sort of development would be market driven, as a means to lower cost per flight. it depends on hydrogen costs at the time the engine nears completion of development.

even as a layman with only hobbyist interest in these matters i am aware of some of the fallacies regarding the production and use of hydrogen as a fuel.
methane/ethanol and other waste to energy cycling technologies might very well provide far cheaper and more sustainable fuels than hydrogen.

One Skunk Todd
2009-Mar-06, 02:27 PM
I look at the concept and I can't help but think: "Thunderbirds are GO!" :)

Larry Jacks
2009-Mar-06, 02:27 PM
One of the biggest drawbacks of an airbreathing booster is that it must spend a lot of time flying at high speed within the atmosphere where the heating loads are extreme. This drives up the weight of the thermal protection system and structure. A rocket can climb vertically until it is above most of the atmosphere before beginning its horizontal acceleration to orbital velocity. This greatly reduces the thermal and aerodynamic loads on the rocket leading to lower weight. The article I linked to above claims that a Goddard Space Flight Center study showed a pure rocket powered spaceplane (if that's the approach you'd want to take) outperforms an air-breathing spaceplane by a significant margin. Also, you'd save the R&D costs of developing the air-breathing engine and required thermal protection system.

NEOWatcher
2009-Mar-06, 02:37 PM
One of the biggest drawbacks of an airbreathing booster is that it must spend a lot of time flying at high speed within the atmosphere where the heating loads are extreme.
Does that matter with an SSTO? It needs the protection for re-entry anyway.

Antice
2009-Mar-06, 03:10 PM
is it not so that the greatest thermal and aerodynamic loads are encountered upon re-entry?
any rocket plane that is fully reusable would need some form of active cooling instead of a tile based shuttle derived or expendable Apollo derived system.
I can imagine quite a lot of development being required to pull that off. afaik that is as of today a rather immature concept that might not be doable currently.

pure rocket propulsion might very well outperform the air breathing tech altogether. time will be the judge of that. i think it depends on wither extra engine weight is higher or lower than the oxidiser saved by using them. again we can only wait and see how the end performance of this concept will end up. at least we know that there is a lot of margin for improvement from the lace experimental engines from earlier times, and what will come out of the engineering labs in 10 years or so.
However a lifting body do save on fuel for lifting the launcher up to altitude. a 2 stage system might be more sensible for this tho. again. time will tell.

One thing i have noticed, is that most manned launch architectures needs a depressed trajectory for reducing g loads on abort. this means that a lot of the savings for going straight up first are not really there any more. effectively negating one of the key advantages to using a rocket in the first place.

IMHO rocket planes dont really make sense for bulk cargo. they make more sense for flying people, and experiments to a station and back down to earth.
however i do see the need for verifying such radically different designs in a long series of unmanned flights first.

one thing that a lot of ppl seem to overlook tho. it's not always about efficiency of fuel and lift that makes sense. but also how many launches you can get done on the same amount of capital investment, and amounts of recurring costs associated with one launch. ground crew and infrastructure maintenance is the biggest factor here. a craft that uses a runway can share crew with other non space based craft thereby utilizing the infrastructure and ground crew's capacity more fully.
If done right, rocket planes can have a lot lower cost per launch than rockets by simply being able to do a lot of runs in a fairly short time frame. however this demands that the craft is 100% reusable, and can perform multiple launches between servicing rounds.
I don't think that we are at that stage in development for quite a while yet. i might get to see it happen in my lifetime tho.

Van Rijn
2009-Mar-12, 10:10 PM
Does that matter with an SSTO? It needs the protection for re-entry anyway.

Yes, in this case there would be a long sustained thermal load, not a relatively short period for just reentry.

Van Rijn
2009-Mar-12, 10:16 PM
one thing that a lot of ppl seem to overlook tho. it's not always about efficiency of fuel and lift that makes sense. but also how many launches you can get done on the same amount of capital investment, and amounts of recurring costs associated with one launch. ground crew and infrastructure maintenance is the biggest factor here. a craft that uses a runway can share crew with other non space based craft thereby utilizing the infrastructure and ground crew's capacity more fully.


Yes, that was a point I made earlier in thread, and in more detail in my earlier post (http://www.bautforum.com/359434-post6.html) that I previously linked to. That's one of the arguments against hybrid designs, as they add a great deal of complexity and are likely to inhenerently require more maintenance than a much simpler pure rocket design.

Van Rijn
2009-Mar-12, 10:24 PM
The engines could easily be used to make a mach 5+ long range strike aircraft. i am certain there would be some military uses for that.


I think a military application for a long range aircraft is about the only likely one, assuming they weren't worried about complexity, maintenance, or cost, but were concerned about range and speed in atmosphere.

SpaceCowboy
2009-Mar-15, 01:28 AM
I don't see much point if it's unpiloted. LOL

Antice
2009-Mar-15, 09:57 AM
military aircraft makes more sense unpiloted than piloted imo.
unpiloted crafts can endure higher G-loads and tighter manoeuvres than a piloted one.
all the space and weight and complexity inherent in keeping the pilot functioning can also be dropped in favour of a bigger payload or more range.

I have to admit tho that it's the engines that have my main interest. they are a novel approach to the air breathing theme. and are very different than scramjets.

publiusr
2009-Mar-16, 06:55 PM
They just need to talk to the right sheiks over a Dubai and convince them---aww, to heck with it.

Burj Dubai's follow ons will wind up being space elevator tall :)

dgavin
2009-Mar-18, 01:38 PM
Yes, that was a point I made earlier in thread, and in more detail in my earlier post (http://www.bautforum.com/359434-post6.html) that I previously linked to. That's one of the arguments against hybrid designs, as they add a great deal of complexity and are likely to inhenerently require more maintenance than a much simpler pure rocket design.

While I think they will likely get it working, you have a good point.

Thats why I like Spaceship One's approach. Use a huge carrier wing craft to get the bulk of the ship as high and fast as possible with minimal fuel. Then use a small rocket to get it into orbit.

Technically, you could opperate a heavy lift opperation with Spaceship One's approach (as long as you were not bringing the weight back in reentry) on about 1/10th of the fuel of conventional heavy lifters.

cjameshuff
2009-Mar-18, 08:53 PM
Thats why I like Spaceship One's approach. Use a huge carrier wing craft to get the bulk of the ship as high and fast as possible with minimal fuel. Then use a small rocket to get it into orbit.

Technically, you could opperate a heavy lift opperation with Spaceship One's approach (as long as you were not bringing the weight back in reentry) on about 1/10th of the fuel of conventional heavy lifters.

First, fuel's cheap. It's the vehicles that are expensive, and the launch operations and infrastructure.

Second...no, you can't. You need a rocket nearly as big as you do for a launch from the ground, and an enormous carrier aircraft:

A launch from 15.2 km altitude at 4200 km/h (what WhiteKnight2 is expected to do with a much smaller suborbital payload) only gets you about 2% of the way to a circular 350 km altitude orbit, in terms of energy. You've gained almost nothing with the altitude, and only dropped required delta-v from about 8.1 km/s to about 7 km/s, and the rocket still needs 70-78% of the fuel it needs for a ground launch using plain old LOX/RP-1.

Proportion of energy saved =
(15 km*9.8 m/s^2 + 0.5*(4200 km/h)^2)/(350 km*9.8 m/s^2 + 0.5*(7.69 km/s)^2) = 0.025

Delta-v required for ground start (rough approximation):
sqrt(2*(350 km*9.8 m/s^2 + 0.5*(7.69 km/s)^2)) = 8.12 km/s

Delta-v required for 15.2 km altitude, 4200 km/h start (again, a rough approximation):
sqrt(2*((350-15.2) km*9.8 m/s^2 + 0.5*(7.69 km/s - 4200 km/h)^2)) = 7.01 km/s

Tsiolkovsky's rocket equation: Ve*ln(m0/m1) = deltaV
deltaV/Ve = ln(m0) - ln(m1)
e^(deltaV/Ve + ln(m1)) = m0
Setting m1 to 1 so the result is total vehicle mass in units of dry mass, ln(1) = 0, so:
e^(deltaV/Ve) = m0

For LOX/RP-1 engines, Ve is around 3240 m/s.
e^((7.01 km/s)/(3240 m/s))/e^((8.12 km/s)/(3240 m/s)) = 0.7

For LOX/LH2 engines (lighter, but bulkier, meaning more aerodynamic drag on the resulting vehicle), Ve is around 4420 m/s.
e^((7.01 km/s)/(4420 m/s))/e^((8.12 km/s)/(4420 m/s)) = 0.78

These are very approximate calculations, but they get the point across. There's tank mass for the ~25% larger fuel tanks for the ground launch version, but that only makes for slightly heavier tanks. There's also further subtleties with staging on both alternatives, structure to allow the air-launched vehicle to survive being carried and dropped by an aircraft after prolonged supersonic flight, the difference in aerodynamic losses, etc.

Notice that air launch is very complicated. Wings aren't magic, it takes the same amount of energy to lift a payload to a certain altitude whether you do it vertically or up an inclined plane...though the inclined path will often require more energy overall due to friction and gravity losses, even if it can be done with less power over a longer interval of time. On top of this, just altitude gets you very little. Reaching orbit requires about an order of magnitude more energy to accelerate the payload up to orbital velocity than it does to lift the payload up to orbital altitude. And as airspeed goes up, aircraft become less and less efficient and more complicated. You need a complex and enormous supersonic carrier craft, and a booster that can handle stresses and heating conditions that are actually worse than reentry. All this for saving a bit of fuel that's practically free?

TrAI
2009-Mar-21, 08:39 PM
I see there is a Wikipedia Article on the sabre engine (http://en.wikipedia.org/wiki/Reaction_Engines_SABRE).

I am not so sure either of how feasible the concept is, it looks interesting. It doesnt' seem as complex as a traditional jet engine. At first I wondered if it was some sort of pulsejet, but I see that it actually do have a fan based compressor...

Hmmm... Ah well, if nobody invests in projects based on risky technologies, no new approaches will ever get proven, we will be stuck with the current approaches forever. We are bound to learn something, if they get it of the computer and into actual testing, at least.

The space craft has a pretty nice design, kind of a classic sci-fi feel.

RGClark
2009-Mar-22, 03:06 PM
I had some comments on air breathing hybrids back here in 2005:

http://www.bautforum.com/astronomy/16489-hybrid-engines-cheaper-space-access.html#post359434

I see them as missing the point. The idea is to get the cost of operations down, and the air breathing schemes will add great complexity and mass. Anyway, in that post, I linked here, which had mentioned Skylon:

http://www.aerospaceweb.org/question/spacecraft/q0202.shtml

From that page:

So, they've been pushing this idea for a long time, and a million euros isn't going to cut it.

The Skylon proposal for using hybrid engines may work but they still need to use rocket propulsion to make the final push to orbital velocity. Note also the jets they use lower in the atmosphere are heavy which will cut down on performance.
This is because of the characteristic known as thrust-weight ratio, which has always been quite poor for jets compared to rockets. See here:

Thrust-to-weight ratio.
http://en.wikipedia.org/wiki/Thrust-to-weight_ratio#Engines

Henry Spencer also discusses the poor performance of jets compared to rockets on this one measure in this article:

Rockets, not air-breathing planes, will be tomorrow's spaceships.
March 4, 2009 5:33 PM
"For the engines, we can compare rockets to jets, and the rockets come out ahead. Rocket engines generally are simpler than jet engines, not more complicated. And although they have to lift more weight, they can do that: the best modern jet engines produce thrust equal to about 10 times their weight. But 40-year-old rocket engines can lift 100 times their own weight. For a given thrust, a rocket engine is much smaller and lighter than the corresponding jet engine.
"Why the difference? It's all about density. A litre of LOX contains as much oxygen as about 4500 litres of sea-level air. At high altitudes, the air is much thinner yet, and the LOX is unchanged. Jet engines are huge and heavy because they must handle such enormous volumes of air to gather each kilogram of oxygen."
http://www.newscientist.com/blogs/shortsharpscience/2009/03/rockets-not-air-breathing-plan.html

I have an alternative method for producing a hybrid engine: circulate the incoming air around and around to allow sufficient time for combustion to occur even at the high hypersonic speeds required to reach orbit:

From: Robert Clark <rgregorycl...@yahoo.com>
Date: Sat, 8 Mar 2008 06:26:00 -0800 (PST)
Newsgroups: sci.astro, sci.physics, sci.space.policy, sci.engr.mech
Subject: Could we just circulate the air in scramjet propulsion?
http://groups.google.com/group/sci.astro/browse_frm/thread/8f8d9a4b4f0a9be9

In that post I suggested using regular jets or ramjets in the lower atmosphere but it occurs to me a key advantage here would actually be to use the same engine all the way from launch to orbital velocity, thus saving on the weight of traditional jet engines.
Note that a key component for propulsive efficiency specifically for jets is the compression they generate of the air before they direct it into the combustion chamber: the more compression they can generate the more efficient the jet engine.
This is why they use the huge turbine compressors in front of the engines. This contributes most to their heavy weight. Then the method of having the air just circulate around and around would dispense with this heavy weight. Note also that according the the formula for acceleration around a circle a = v^2/r, the pressure, and therefore the compression, would be greater for the higher velocities. Henry Spencer mentions in his article the problem of the huge amount of air that has to be gathered to get sufficient oxygen for combustion with jet engines, but note that at the high supersonic and hypersonic velocities, where the efficiency would be greatest, the high incoming velocity of the air automatically makes it so that you can acquire that large amount of air, and oxygen.


Bob Clark

Damburger
2009-Mar-22, 09:51 PM
The Skylon proposal for using hybrid engines may work but they still need to use rocket propulsion to make the final push to orbital velocity. Note also the jets they use lower in the atmosphere are heavy which will cut down on performance.

You seem to misunderstand what they are doing; they are attempting SSTO using just one kind of engine - that can either draw oxygen from the air at low altitudes or draw from an on board supply and function as a rocket engine at higher altitudes.

Antice
2009-Mar-22, 11:03 PM
it seems to me that there is a lot of confusion to what the sabre engine is supposed to do and how it does it.
i do recommend taking the time to read about them before calling them jet engines. because even from layman's perspective they clearly are not jet engines. neither are they scram jet engines.
they are in effect a rocket engine that has 2 possible sources for oxidiser. one is a lox tank, the other is a very nifty very innovative supersonic air compression system. the point of using air as oxidiser for a craft like this is that it do not fly the most efficient trajectory like a rocket can do. it flies a much more gentle slope and spends time in the air. at high speeds. this costs extra fuel. so much so that saving on the oxidiser for this leg of the trip actually saves on launch mass. if they cant swing that then dropping the air breathing and go pure rocket engine is liable to happen.
the entire craft takes off goes to space and returns to the airport that it started from.
and before you ask why one would want that. ask yourself. what is the biggest expense on a rocket. it is not fuel as has been pointed out. it's in the people costs that comes with building them and integrating the payload. getting them to the pad and off the ground. and rockets need specialized pad's to be launched. specialized buildings to stack them. and a whole lot more that i probably have no idea about.
a fully reusable ssto space plane wont need those things. all it needs is a runway able to handle the weight. it can get cargo loaded pretty much with the same methods we use for cargo aircraft today. load er up. and send her off. just like an aircraft.
the peeps behind skylon are designing it to be fully reusable for 200 trips before refurb.
that is where your savings are going to come. not fuel. not building costs. but form the simple fact the same craft can do so many trips before it needs to be rebuilt.
however. if you want to build something big. 12 tonne cargoes wont cut it. would need some real large volume modules up there in the beginning.

As with any ambitious design project. if you don't try you wont succeed ever. imho. even if it never get off the ground. there is still a net gain in knowledge as a result from trying it.

TrAI
2009-Mar-22, 11:36 PM
Hmmm...It seems to me, from the images and the descriptions, that the engine have one ramjet part, the area between the outer walls of the engine and the turbojet/rocket motor assembly(this is mounted in the center of the whole engine assembly).

The precooler apperantly uses more hydrogen for cooling than the turbojet can burn, so the surplus is used to feed the ramjet part of the engine. Precooling allow the use of lighter parts than in a traditional supersonic jet engine, and you supposedly do not need to ramp back the power on this engine like the traditional supersonic jets. The numbers given estimates the thrust to weight to be about 14 in atmosphere, that isn't that bad for a jet engine, supersonic jet engines are rarely much above 5 or so.

A point of the Skylon design I found interesting is that it doesn't need to use as heavy heat shielding as the shuttle, the maximum reentry temperature being estimated to less than 850 celcius, so no tiles to fall of or break.

Though I am not really that enthusiastic to the probability of this project succeding, getting enough money to make the thing is probably a bigger challenge than the engineering itself... Still, It will be interesting to see if they get an engine up and running.

I expect even if the Skylon fails, the data collected would be a help in the design of the other project, the A2 hypersonic liner, and its Scimitar engines, though if anyone wants such a thing is another issue...

Noclevername
2009-Mar-25, 03:43 AM
SSTOs have been "just a few more years now" away since before I was born. Pardon me for being skeptical, but I'm skeptical. A two-stage approach seems like the closest we'll come in the forseeable future.

publiusr
2009-Mar-30, 09:53 PM
Technically, you could opperate a heavy lift opperation with Spaceship One's approach .

And technically, you could replace one supertanker or container ship with a million john boats too.

Antice
2009-Dec-02, 11:07 AM
this thread has been asleep for a long time. Now I'ma brush it off again since it seems like skylon is about to get a jump up in it's technology readiness level.
Linky (http://www.reactionengines.co.uk/news_nov09.html) to Ractionengines ltd,s news page.

And also. a direct link (http://www.reactionengines.co.uk/downloads/spaceflight_article-nov_2009.pdf) to a news article where Alan bond is making a statement about the readiness level of skylon. (oopsie. 3,5Mb PDF behind that link)

Here is the relevant statement for the connectively impaired.


The technology Demonstration Programme will last around 2.5 years and will benefit from another €1 million from ESA at the halfway point of the programme. It will take Reaction Engines from a Technology readiness Level (TRL) of 2/3 up to 4/5.
Managing director Alan Bond said: "It is a very exciting time for the company and our innovative spaceplane. We are relishing the opportunity to demonstrate its concepts and findings. Skylon's first flight is planned for 2018 with its entry into service expected to take place in 2020."
credit: Spaceflight (http://www.bis-spaceflight.com/spaceflight.htm)

Garrison
2009-Dec-02, 09:29 PM
this thread has been asleep for a long time. Now I'ma brush it off again since it seems like skylon is about to get a jump up in it's technology readiness level.
Linky (http://www.reactionengines.co.uk/news_nov09.html) to Ractionengines ltd,s news page.

And also. a direct link (http://www.reactionengines.co.uk/downloads/spaceflight_article-nov_2009.pdf) to a news article where Alan bond is making a statement about the readiness level of skylon. (oopsie. 3,5Mb PDF behind that link)

Here is the relevant statement for the connectively impaired.


credit: Spaceflight (http://www.bis-spaceflight.com/spaceflight.htm)

I really hope this is going to work, they could make back the costs just charging people to watch it take off. :)

Antice
2009-Dec-02, 09:44 PM
I really hope this is going to work, they could make back the costs just charging people to watch it take off. :)

Yeah. they could set up a stand along the runway at a safeish distance. not too safe. we wanna feel the ground rumble as it accelerates down the runway right?
The income on the beer sales alone would finance a launch or 2 :lol:

Antice
2010-Mar-03, 10:05 PM
Another month and some news (http://http://reactionengines.co.uk/news_feb10.html) from the makers of the skylon.

Looks like they are working hard on refining the design and finalizing the D1 revision. no timeframe for when we can look at it tho. so for now we have to live with the C1 specs from the first revision of the users manual.
all docks can be found at their website.

Have to admit i am eagerly waiting for the specs on the D1 configuration. skylon is slowly crawling towards becoming reality.

Antice
2010-Jul-05, 08:15 AM
June update (http://www.reactionengines.co.uk/news_june10.html) is finally here. I skipped the last two months since so many where discussing it on other threads. besides there weren't all that many interesting details to report.



a) a larger wing as D1 is heavier, and
b) the rear fuselage is not a circular cross section but is flattened, a little like the Space Shuttle, to give more rearward lift at high speeds.

These are the major changes so far.
Apparently they are awaiting the SABRE 4 engine model before refining the design further.
In other areas: The reports from DLR are in, They are currently working on recommendations for improving the D1 configuration in light of these results.

All in all i think they are making fine progress towards realizing the skylon concept into a working space plane. I'm really looking forward towards seeing the D1 design unveiled.
Watching a project grow like this is very fascinating indeed.

Garrison
2010-Jul-05, 08:06 PM
June update (http://www.reactionengines.co.uk/news_june10.html) is finally here. I skipped the last two months since so many where discussing it on other threads. besides there weren't all that many interesting details to report.


These are the major changes so far.
Apparently they are awaiting the SABRE 4 engine model before refining the design further.
In other areas: The reports from DLR are in, They are currently working on recommendations for improving the D1 configuration in light of these results.

All in all i think they are making fine progress towards realizing the skylon concept into a working space plane. I'm really looking forward towards seeing the D1 design unveiled.
Watching a project grow like this is very fascinating indeed.

It is, and they are just quietly working their way through the practicalities, now if they could just quietly acquire £10 billion they would be all set. :)

KB73RR
2010-Jul-07, 04:41 PM
The whole thing sounds like the areocar concept.

There is an areocar available in the US beginning in 2011.

http://www.flightglobal.com/blogs/flight-international/2010/06/flying-car-a-reality.html

However, I agree with the spirit of your comment. In my opinion, SSTO might be technically possible at some point in the distant future. At best it will always be a compromise just like the aerocar, which is really neither a very good car nor a very good aircraft.

Thus far even partially re-usable launchers have failed to live up to cost expectations. STS is a prime example. The Orbital Sciences Pegasus XL system is better, but that's only because of the L-1011 part of the system. The Pegasus itself is more or less a conventional rocket - three stages at that. SpaceShipOne and SpaceShipTwo are not capable of orbit so in my opinion they don't really qualify as launchers. The fastest airbreather so far is the X-51A Waverider and it has only managed about Mach 6 for 200 seconds. That demonstrates the extreme difficulty of achieving sustained hypersonic velocities.

The Wiki article (http://en.wikipedia.org/wiki/Reaction_Engines_SABRE) about the SABRE engine makes some amazing claims. To quote, "The engine gives good fuel efficiency peaking at about 2800 seconds within the atmosphere. Typical all-rocket systems are around 450 at best, and even "typical" nuclear thermal rockets only about 900 seconds." Are they talking about specific impulse or specific thrust or what? Are they claiming efficiencies in the range of ion engines? Then there is the matter of the helium powered turbopumps re-cycling waste heat. Why not do the same using the hydrogen fuel? The helium system just seems like extra mass.

My gut feeling is that this whole concept is fundamentally flawed. I find it hard to believe that they can achieve the engine performance claimed. I don't believe it is possible to design an airframe that can be sufficiently aerodynamically efficient across such a wide range of airspeeds. I don't believe they can build it light enough to carry sufficient fuel for SSTO and still handle the dynamic stresses and thermal issues of SSTO. And even IF they could do all that, I seriously doubt that the life cycle cost could be competitive with more conventional commercial launchers such as those being demostrated already by SpaceX.

whoops - I forgot the X-43A 2nd and 3rd flights. The 2nd flight reached Mach 7 and the 3rd almost Mach 10. Both included very brief periods of scramjet (airbreathing) operation and there was I believe some acceleration during the 2nd flight.

Garrison
2010-Jul-07, 05:01 PM
There is an areocar available in the US beginning in 2011.

http://www.flightglobal.com/blogs/flight-international/2010/06/flying-car-a-reality.html

However, I agree with the spirit of your comment. In my opinion, SSTO might be technically possible at some point in the distant future. At best it will always be a compromise just like the aerocar, which is really neither a very good car nor a very good aircraft.

Thus far even partially re-usable launchers have failed to live up to cost expectations. STS is a prime example. The Orbital Sciences Pegasus XL system is better, but that's only because of the L-1011 part of the system. The Pegasus itself is more or less a conventional rocket - three stages at that. SpaceShipOne and SpaceShipTwo are not capable of orbit so in my opinion they don't really qualify as launchers. The fastest airbreather so far is the X-51A Waverider and it has only managed about Mach 6 for 200 seconds. That demonstrates the extreme difficulty of achieving sustained hypersonic velocities.

The Wiki article (http://en.wikipedia.org/wiki/Reaction_Engines_SABRE) about the SABRE engine makes some amazing claims. To quote, "The engine gives good fuel efficiency peaking at about 2800 seconds within the atmosphere. Typical all-rocket systems are around 450 at best, and even "typical" nuclear thermal rockets only about 900 seconds." Are they talking about specific impulse or specific thrust or what? Are they claiming efficiencies in the range of ion engines? Then there is the matter of the helium powered turbopumps re-cycling waste heat. Why not do the same using the hydrogen fuel? The helium system just seems like extra mass.

My gut feeling is that this whole concept is fundamentally flawed. I find it hard to believe that they can achieve the engine performance claimed. I don't believe it is possible to design an airframe that can be sufficiently aerodynamically efficient across such a wide range of airspeeds. I don't believe they can build it light enough to carry sufficient fuel for SSTO and still handle the dynamic stresses and thermal issues of SSTO. And even IF they could do all that, I seriously doubt that the life cycle cost could be competitive with more conventional commercial launchers such as those being demostrated already by SpaceX.

Well luckily your 'belief' isn't relevant. Try expanding your research beyond Wiki, perhaps even to, for example the company actually building the SABRE and Skylon:

Reaction Engines (http://www.reactionengines.co.uk/)

Seriously if you think this bears any relation to the aerocar you really have no clue about the Skylon project.

KB73RR
2010-Jul-07, 07:24 PM
Well luckily your 'belief' isn't relevant. Try expanding your research beyond Wiki, perhaps even to, for example the company actually building the SABRE and Skylon:

Reaction Engines (http://www.reactionengines.co.uk/)

Seriously if you think this bears any relation to the aerocar you really have no clue about the Skylon project.

Thanks for the suggestion. I was intrigued by the OP and progress reports in the previous posts so I actually did look at their site, the previously cited wiki article, all readily available info about the principals, and I ran a D&B on the company too. The bottom line is they are just a handful of smart guys with a grand vision, an apparently politically-related ESA contract, and a slick web site. I wish they would succeed with their grand vision, but it's just a CGI spaceplane - and that's probably all it will ever be. "No Clue"? Perhaps, but for now my venture capital is going elsewhere.

Garrison
2010-Jul-07, 07:31 PM
Thanks for the suggestion. I was intrigued by the OP and progress reports in the previous posts so I actually did look at their site, the previously cited wiki article, all readily available info about the principals, and I ran a D&B on the company too. The bottom line is they are just a handful of smart guys with a grand vision, an apparently politically-related ESA contract, and a slick web site. I wish they would succeed with their grand vision, but it's just a CGI spaceplane - and that's probably all it will ever be. "No Clue"? Perhaps, but for now my venture capital is going elsewhere.

Errant nonsense, and no doubt your money will going on a bridge to lurk under...

KB73RR
2010-Jul-07, 07:52 PM
Errant nonsense, and no doubt your money will going on a bridge to lurk under...

Ha ha ha - no, bridges are so passe. Carbon nanotube space elevators are the way of the future and much better for lurking under!

Antice
2010-Jul-08, 06:27 AM
Ha ha ha - no, bridges are so passe. Carbon nanotube space elevators are the way of the future and much better for lurking under!

well.. you better be much more patient than Skylon supporters if you are investing in space elevators. Skylon may not be quite ready for the main dev cycle yet. there are still some technology readiness issues, but at least all the puzzle pieces for the skylon is being worked on. no item on the list of need to have for skylon is missing. It's all a matter of incremental development if each component system.

I do not see any benefit in arguing trough the entire list of components needed for skylon however. so if anyone disagrees with the above statement then by all means include what component you are objecting to, and why.

Antice
2010-Jul-25, 04:39 PM
Skylon is featuring on The Register (http://www.theregister.co.uk/2010/07/22/skylon_engine_tests_farnborough/).

They are talking about engine tests in 3 or 4 years if enough funding is appropriated.
Fingers crossed and all that for a successful final push towards a working SABRE engine.

TrAI
2010-Aug-01, 06:16 PM
...

The Wiki article (http://en.wikipedia.org/wiki/Reaction_Engines_SABRE) about the SABRE engine makes some amazing claims. To quote, "The engine gives good fuel efficiency peaking at about 2800 seconds within the atmosphere. Typical all-rocket systems are around 450 at best, and even "typical" nuclear thermal rockets only about 900 seconds." Are they talking about specific impulse or specific thrust or what? Are they claiming efficiencies in the range of ion engines? Then there is the matter of the helium powered turbopumps re-cycling waste heat. Why not do the same using the hydrogen fuel? The helium system just seems like extra mass.

The Skylon user's manual gives the following projected data for the engines on the Skylon C2:
Maximum air-breathing thrust 2 x 1350 kN
Isp in air-breathing mode 35000 N s / kg
Maximum thrust in rocket mode 2 x 1800 kN
Isp in rocket mode 4500 N s / kg

The helium system is in fact one of the improvements in this engine design over earlier precooled designs. These earlier precooler systems using hydrogen tended to become brittle and break as the hydrogen diffused into the metal(a process called hydrogen embrittlement). This would pose a problem to the reliability and rapid re-usability of a craft using SABRE engines.

Antice
2010-Aug-01, 10:43 PM
I've been looking around at other air turborocket (http://en.wikipedia.org/wiki/Air_turborocket) concepts lately.
SABRE is a derivative form of air turborocket after all.
SABRE is the only one that uses a closed Helium loop brayton cycle to drive the turbocompressor tho. but there are some fairly distinct advantages to it.
for one they can exploit the hot incoming air to help drive the cycle. this saves on fuel/oxidizer in the preburner that it has in common with Air turborockets. A secondary benefit is that they can get precooling without having to dump coolant into the incoming air-stream like some of the concepts out there plan to do.
The drawback is the extra fuel consumption caused by using the LH2 as a heatsink. RE solved that pretty elegantly by adding ramjet bypass burners to the mix. The engine is actually more efficient the faster it goes. until it reaches mach 5 and max air breathing altitude. there is no good reason for why the engine could not handle even higher speeds. but for an SSTO mach 5 at 26km altitude is about optimal in terms of oxidizer mass saved. any faster and drag losses starts to eat into your propellant budget again. at that point it is more mass economical to nose up and blast direct for orbit in rocket mode.

This is why i think scramjets are useless for orbital launch. scramjet's do force one to stay deeper into the atmosphere for longer than what is sensible. the faster you go the bigger the drag loss one has to overcome.

RGClark
2010-Aug-03, 04:09 PM
...The engine is actually more efficient the faster it goes. until it reaches mach 5 and max air breathing altitude. there is no good reason for why the engine could not handle even higher speeds. but for an SSTO mach 5 at 26km altitude is about optimal in terms of oxidizer mass saved. any faster and drag losses starts to eat into your propellant budget again. at that point it is more mass economical to nose up and blast direct for orbit in rocket mode.
This is why i think scramjets are useless for orbital launch. scramjet's do force one to stay deeper into the atmosphere for longer than what is sensible. the faster you go the bigger the drag loss one has to overcome.

No, if Mach 5 turns out to be the most economical max speed for airbreathing mode, you just do that with a scramjet.

Bob Clark

NEOWatcher
2010-Aug-03, 04:52 PM
No, if Mach 5 turns out to be the most economical max speed for airbreathing mode, you just do that with a scramjet.
And a whole lot more equipment to get the craft up to the speed that a scramjet needs.

Garrison
2010-Aug-03, 05:51 PM
And a whole lot more equipment to get the craft up to the speed that a scramjet needs.

Exactly. Here's a quote from the Wikipedia page on scramjets (http://en.wikipedia.org/wiki/Scramjet):


Due to the nature of their design, scramjet operation is limited to near-hypersonic velocities. As they lack mechanical compressors, scramjets require the high kinetic energy of a hypersonic flow to compress the incoming air to operational conditions. Thus, a scramjet-powered vehicle must be accelerated to the required velocity by some other means of propulsion, such as turbojet or rocket engines. In the flight of the experimental scramjet-powered Boeing X-51A, the test craft was lifted to flight altitude by a turbofan powered B-52 before being released and accelerated by a detachable rocket to near Mach 4.5.

And once it get up where the air is too thin it's going to need secondary propulsion, or a separate vehicle, to make orbit. That's one of the pluses of SABRE; one engine from concrete to orbit.

Antice
2010-Aug-03, 05:59 PM
Scramjet's have severe heating issues as well. going faster than mach 6 starts to levy TPS requirements that will compete with that of re-entry. the thermal load is different, in that it is sustained heating instead of short term heating. it's not enough that the aeroshell can stand the temp. the internals will be affected too unless active cooling is used. this is why a hypersonic passenger craft like the LAPCAT has a higher dev risk than skylon. The extra requirements on the aeroshell is going to add dry mass. this mass is directly going to lower payload capability.

The dev risk with SABRE is about to be retired as well. Their future programs director has talked in public about a full up engine demonstration in the 2012 - 2013 time-frame. With all the standard disclaimers about possible delays ofc.

Garrison
2010-Aug-03, 08:04 PM
Scramjet's have severe heating issues as well. going faster than mach 6 starts to levy TPS requirements that will compete with that of re-entry. the thermal load is different, in that it is sustained heating instead of short term heating. it's not enough that the aeroshell can stand the temp. the internals will be affected too unless active cooling is used. this is why a hypersonic passenger craft like the LAPCAT has a higher dev risk than skylon. The extra requirements on the aeroshell is going to add dry mass. this mass is directly going to lower payload capability.

The dev risk with SABRE is about to be retired as well. Their future programs director has talked in public about a full up engine demonstration in the 2012 - 2013 time-frame. With all the standard disclaimers about possible delays ofc.

It can't come soon enough for me! :)

Antice
2010-Aug-03, 08:43 PM
It can't come soon enough for me! :)

Yeah. i wanted this like... yesterday.

Something funny tho... when using some back of the envelope estimate for a SSTO based on turborockets i find that even with an ISP of around 2000 sec and air breathing to only mach 3.5 then an isp at the shuttle level for the rest of the trip to orbit gives a marginal positive payload for a vehicle the size of skylon. I'm not going to publish the math i used here, because i am certain I have messed it up somehow. I am not even certain that one can just convert air breathing into ISP in sec just like that.
but if someone with a better grasp on the rocket equation wants a go i would be interested in looking at the methods used.

Another reason I am sceptical of my own result is that turborocket ISP numbers were just something i found on a blog. I havent found any credible sources giving any kind of efficiency numbers on pure turborocket engines. besides. my payload came out higher than what is advertised for skylon when i tried it with the numbers published. I do not know how much of a performance margin they are planning on keeping in reserve to handle weight growth in their plans.

Garrison
2010-Aug-03, 09:05 PM
Yeah. i wanted this like... yesterday.

Something funny tho... when using some back of the envelope estimate for a SSTO based on turborockets i find that even with an ISP of around 2000 sec and air breathing to only mach 3.5 then an isp at the shuttle level for the rest of the trip to orbit gives a marginal positive payload for a vehicle the size of skylon. I'm not going to publish the math i used here, because i am certain I have messed it up somehow. I am not even certain that one can just convert air breathing into ISP in sec just like that.
but if someone with a better grasp on the rocket equation wants a go i would be interested in looking at the methods used.

Another reason I am sceptical of my own result is that turborocket ISP numbers were just something i found on a blog. I havent found any credible sources giving any kind of efficiency numbers on pure turborocket engines. besides. my payload came out higher than what is advertised for skylon when i tried it with the numbers published. I do not know how much of a performance margin they are planning on keeping in reserve to handle weight growth in their plans.

It's possible some of the accurate info just isn't available because it's commercially sensitive, and I suspect some of the older assumptions about turborockets are a little off. :)

Antice
2010-Aug-04, 07:47 AM
It's possible some of the accurate info just isn't available because it's commercially sensitive, and I suspect some of the older assumptions about turborockets are a little off. :)

Probably. But turborockets do save tonnes of lox compared to traditional rockets. the penalty is the much lower T/W ratio of these engines compared to rockets. SABRE has a much improved average T/W ratio compared to traditional turborockets tho. It's up by almost 50% compared to older concepts. I suspect the added ramjet has something to do with this. SABRE also has close to 50% better airbreathing ISP than traditional turborocket numbers i could find. but this could be attributed to the precooling technology. it does allow the turborocket part of the engine to use the air much more effectively.
But as you said. turborocket performance numbers are somewhat suspect since nobody has actually flown one and measured the performance in flight. :think:
All the concepts i have seen so far never got past ground testing, and in those cases they were cobbled together from spare parts more or less. :wall:
I'm going to try to look a bit more closely at the numbers for several more concepts. but it's kinda hard to get anything really useful from it since the SABRE is so markedly more complex than any other turborocket concept out there. I can just about visualize everything going on in that engine inside my mind if i concentrate really hard. :doh:

VASIMR was never this hard to visualize the workings of.

Antice
2010-Aug-04, 07:16 PM
Well. it's that time of the month again. The latest news update from REL is here. (http://www.reactionengines.co.uk/news_july10.html)

Some highlights: Rel has been in the news as mentioned earlier in this thread. both in the independent and the register. They also had a stand at the farnborough Inernational airshow. Wish i could have been there and pickled some brains, but C'es el a Vie.
Alan Bond has been awarded the degree doctor of engineering as well. I've not heard of many that has gotten such a distinguished title in engineering. I wonder if it will make investors sit up and listen closely when he talks now. :razz:

All in all i had hoped to see more news about progress on the Skylon and SABRE. but i guess there cant be much to report every month at this stage in the process.

RGClark
2010-Aug-04, 08:23 PM
Probably. But turborockets do save tonnes of lox compared to traditional rockets. the penalty is the much lower T/W ratio of these engines compared to rockets. SABRE has a much improved average T/W ratio compared to traditional turborockets tho. It's up by almost 50% compared to older concepts. I suspect the added ramjet has something to do with this. SABRE also has close to 50% better airbreathing ISP than traditional turborocket numbers i could find. but this could be attributed to the precooling technology. it does allow the turborocket part of the engine to use the air much more effectively.
But as you said. turborocket performance numbers are somewhat suspect since nobody has actually flown one and measured the performance in flight.
All the concepts i have seen so far never got past ground testing, and in those cases they were cobbled together from spare parts more or less.
I'm going to try to look a bit more closely at the numbers for several more concepts. but it's kinda hard to get anything really useful from it since the SABRE is so markedly more complex than any other turborocket concept out there. I can just about visualize everything going on in that engine inside my mind if i concentrate really hard.

In other words you are estimating the performance of a launch vehicle by switching out the engine for a different engine.

Bob Clark

Garrison
2010-Aug-04, 08:45 PM
In other words you are estimating the performance of a launch vehicle by switching out the engine for a different engine.

Bob Clark

No Bob, Antice's saying that it's hard to estimate the performance of one system based on the performance of another, a fact you seem sadly unable to grasp. Oh and do you get now why your last post:


No, if Mach 5 turns out to be the most economical max speed for airbreathing mode, you just do that with a scramjet.

was just plain wrong?

RGClark
2010-Aug-04, 09:24 PM
Oh and do you get now why your last post:
was just plain wrong?

Actually Antice and I are doing the same thing; we are making an estimate. You won't know what the actual numbers are until you do a full vehicle analysis.
About the scramjet, remember the Skylon also uses turbojet propulsion until the hypersonic airbreathing mode takes over, except that the design of the Skylon is to combine them into a single engine.
But keep in mind that is the intent for scramjet engines as well to combine them into a single engine:

X-43 Hyper-X Program.
"The X-43 program was originally intended to feature two additional vehicles. As envisioned, the X-43B would demonstrate an engine capable of operating in several modes. The X-43B’s combined cycle engine would function as a normal turbojet at low altitudes and switch to scramjet mode at high altitudes and speeds. Planned X-43B flights were to occur sometime in 2009 after the completion of another Hyper-X test vehicle, the X-43C. The X-43C was intended to demonstrate the operation of a solid hydrocarbon-burning scramjet engine at speeds between Mach 5 and 7 sometime in 2008.
"Both vehicles were cancelled in March 2004 because of a shift in NASA’s strategic goals following the announcement of the President’s Vision for Space Exploration in January of that year. However, because of the success of the X-43A , the U.S. Congress added $25 million to the NASA 2005 budget to continue development of the X-43C research vehicle."
http://www.globalsecurity.org/space/systems/x-43.htm

The successful flight test of the long-burning X-51 scramjet would give impetus for this one as well to be transitioned to use combined-cycle propulsion.
Supporters of the Skylon on this forum seem to be taking the view that anyone who supports some other method of low cost space access must be opposed to the Skylon. No, I fully expect and want the Skylon to succeed within 10 years when it is deployed. I also expect scramjet propulsion to succeed in lowering the cost of space access. And I also expect pure rocket, fully reusable vehicles to succeed in cutting the cost of space access.
Having all three of these different vehicle types operating at the same time would serve to increase the competition to further reduce the costs of space access.


Bob Clark

Antice
2010-Aug-04, 09:56 PM
In other words you are estimating the performance of a launch vehicle by switching out the engine for a different engine.

Bob Clark

Yes. with a poorer performing engine. I'm trying to figure out how much of a performance gain they are counting on trough the extra complexity. I'm not trying to make a workable vehicle concept. it's more a matter of getting a feel for the expected benefits gained with the SABRE concepts.
Also it's interesting to see if the HOTOL SSTO case could have been closed earlier with older tech within the same mass limit as the skylon.
I'm not ready to make a judgement on wither it could, The performance numbers for turborockets seem to be as reliable as if i was pulling them out of thin air. Unless more reliable data is obtained I will abandon the attempt as an exercise in futility.

About those under carriages. since mass is at such a premium it makes sense to go to a higher ground pressure, but there is a pretty nasty economic penalty for doing so. needing all that reinforcement in the runway and attending tarmac areas around the support is going to add to the overall costs a bit. On the bright side, if all the airports upgrade we could get to see larger airliners come into use as well. It's kinda like the panamax size limit on container ships.

Garrison
2010-Aug-04, 10:08 PM
The successful flight test of the long-burning X-51 scramjet would give impetus for this one as well to be transitioned to use combined-cycle propulsion.
Supporters of the Skylon on this forum seem to be taking the view that anyone who supports some other method of low cost space access must be opposed to the Skylon. No, I fully expect and want the Skylon to succeed within 10 years when it is deployed. I also expect scramjet propulsion to succeed in lowering the cost of space access. And I also expect pure rocket, fully reusable vehicles to succeed in cutting the cost of space access.
Having all three of these different vehicle types operating at the same time would serve to increase the competition to further reduce the costs of space access.
Bob Clark

No Bob, I simply think you have no clue what you are talking about. The X-43 program was looking to develop an engine that could operate from subsonic to hypersonic velocities and save weight by drawing Oxygen from the atmosphere. Great idea and exactly what the SABRE is designed to do. If you actually read and understood the material you would have realized that the SABRE is the engine NASA wanted to develop, only Reaction Engines are 10-20 years ahead of them.
As for rocket powered SSTO's well that's been argued to death in other threads and if you want to take it up yet again why don't you revive your X-33 thread.

Garrison
2010-Aug-04, 10:19 PM
Yes. with a poorer performing engine. I'm trying to figure out how much of a performance gain they are counting on trough the extra complexity. I'm not trying to make a workable vehicle concept. it's more a matter of getting a feel for the expected benefits gained with the SABRE concepts.
Also it's interesting to see if the HOTOL SSTO case could have been closed earlier with older tech within the same mass limit as the skylon.
I'm not ready to make a judgement on wither it could, The performance numbers for turborockets seem to be as reliable as if i was pulling them out of thin air. Unless more reliable data is obtained I will abandon the attempt as an exercise in futility.

About those under carriages. since mass is at such a premium it makes sense to go to a higher ground pressure, but there is a pretty nasty economic penalty for doing so. needing all that reinforcement in the runway and attending tarmac areas around the support is going to add to the overall costs a bit. On the bright side, if all the airports upgrade we could get to see larger airliners come into use as well. It's kinda like the panamax size limit on container ships.

I suspect there might be one or two places that might gamble on the investment to turn themselves into a major space hub, in the way New Mexico (http://www.spaceportamerica.com/) is hoping to with suborbital tourism. I could certainly see somewhere like the UAE making the investment, look at the money Dubai has spent essentially creating a tourist industry from scratch, and a spaceport would be child's play compared to some of the projects in Dubai (http://en.wikipedia.org/wiki/Palm_Islands). It would obviously be a risk but if the Skylon works as advertised the rewards could be huge.

Antice
2010-Aug-04, 10:39 PM
Scramjet's may be useful one day. but nobody has actually combined one with another engine in the way that has been done with ramjets. ramjet turbojet combined cycle was done with the SR71 among others. Scramjet may be a possible future upgrade path, but it may also turn out to be no benefit from using it. mach 5 to 6 has been identified as in the ballpark area for optimal speed prior to changing into rocket mode. If you could make a scramjet upgrade that could bring the vehicle from 26km mach 5 to say 50 km and mach 10 you may have something worthwhile. but as it is it is altitude and not speed alone that dictates the swap to internal LOX for the rest of the climb. it just does not pay to go any faster that low in the atmosphere.

The SABRE engine does not operate as a turbojet under any part of the flight. it is a turborocket. the main combustion chamber is a rocket chamber in design. It's even part of the name. Synergistic Air Breathing Rocket Engine. A turbojet uses the combustor exhaust to drive a single shaft turbine. SABRE does not. The SABRE engine uses a closed helium loop to drive the turbo compressors. A case could be made that it is not truly a turborocket either. but it does share quite a lot in common with them. the use of rocket chambers for the main thrust as well as a pre burner to drive the turbo-compressors. but the pre burner is not used in the same manner. it is rather used as a heating source for the helium loop to get enough power out of the system at low speeds. the pre burner is throttled back as the speed increases to accommodate the higher heat flux from the pre cooler.

I generally do not ignore other concepts. but i do take exception to betting the farm on scramjets. they will be too late to the party to make a difference in the race to achieve a viable RLV. 2STO RLV's are the closest competitors, and they have their own issues to contend with. It all depends on their methodology. There is as many flavours as there are space advocates it seems. So until the 2STO advocates get their stuff together and start getting more serious i will be cheering the guys at REL on. They are at this time the most likely bet to get there first.

Antice
2010-Aug-05, 07:45 PM
I found this a couple of hours ago. A very interesting lecture about Skylon and the SABRE engine in particular.
Linky (http://ewds.strath.ac.uk/space/OnDemandSeminar/tabid/4560/articleType/ArticleView/articleId/288/Travelling-at-the-edge-of-space--10-March-2010.aspx)
I recomend either owning a very speedy line or chosing the download option on the page i linked to. it's a pretty large movie.
Of particular interest in light of the recent scramjet discusions re airbreathing. look at about 18 to 22 minutes into the lecture movie (the full version not the youtube one)
Alan bond demonstrates pretty clearly why airbreathing beyond mach 6 - 7 is going to turn the vehicle into a Single Stage TPS system to orbit.

RGClark
2010-Aug-06, 02:57 AM
I found this a couple of hours ago. A very interesting lecture about Skylon and the SABRE engine in particular.
Linky (http://ewds.strath.ac.uk/space/OnDemandSeminar/tabid/4560/articleType/ArticleView/articleId/288/Travelling-at-the-edge-of-space--10-March-2010.aspx)
I recomend either owning a very speedy line or chosing the download option on the page i linked to. it's a pretty large movie.
Of particular interest in light of the recent scramjet discusions re airbreathing. look at about 18 to 22 minutes into the lecture movie (the full version not the youtube one)
Alan bond demonstrates pretty clearly why airbreathing beyond mach 6 - 7 is going to turn the vehicle into a Single Stage TPS system to orbit.

Thanks for that. Very informative on the Skylon.


Bob Clark

RGClark
2010-Aug-06, 07:39 PM
No Bob, I simply think you have no clue what you are talking about. The X-43 program was looking to develop an engine that could operate from subsonic to hypersonic velocities and save weight by drawing Oxygen from the atmosphere. Great idea and exactly what the SABRE is designed to do. If you actually read and understood the material you would have realized that the SABRE is the engine NASA wanted to develop, only Reaction Engines are 10-20 years ahead of them.

This member of the X-51A team estimates optimistically the time frame to when scramjets can be used as part of the propulsion system to reach space as 15 to 20 years:

Air Force Sees Hypersonic Weapons and Spaceships in Future.
By Jeremy Hsu
SPACE.com Staff Writer
posted: 17 June 2010
05:30 am ET
"Rise of the space planes.
"If scramjet technology advances far enough, it could become part of a system that helps propel unmanned or manned vehicles into space. Space planes might even emerge that can fly into space at just about any time, without launch window constraints.
"A scramjet-powered vehicle would need to rely upon a regular rocket or jet engine to reach Mach 4, so that the scramjet could take over for hypersonic speeds during the first stage to Earth orbit.
"The X-51A scramjet engine would not be enough by itself to allow a vehicle to reach orbit, said Joseph Vogel, hypersonics director and X-51 program manager at Boeing Phantom Works/Defense, during the teleconference. Both Boeing and Pratt & Whitney Rocketdyne formed part of the private consortium that helped design and build the X-51A.
"Any future space-lift system would also need a more energetic hydrogen-based fuel, rather than the JP-7 jet fuel used in supersonic aircraft, Vogel explained.
"I would say that within the next 15 to 30 years — I'll give you the broad side — but probably 15 to 20 years, you could start to see this technology being expanded to the point where you could get aircraft into outer space," Vogel said."
http://www.space.com/businesstechnology/hypersonic-weapons-spaceships-future-100617.html

So you may be right that the Skylon would reach operation before scramjets for space access purposes. Still optimistically you could have two types of hypersonic airbreathing propulsion in operation in short order after the Skylon enters service which would serve to produce competition to drive down the costs of space access.


Bob Clark

Antice
2010-Aug-06, 08:40 PM
True. having competing technologies is good. but we also have to take into account other aspects of space launch. Scramjet's by themselves do not address the heating issues that once mach 6 is passed surpasses that of re-entry.

Alan bond stated pretty clearly that as far as physical materials limits is concerned that any vehicle going that fast in the denser parts of the atmosphere is going to end up as a TPS to orbit launch system. He also admitted that some of the choices in HOTOL was a big mistake. the HOTOL project would at best have delivered a hydraulics system to LEO vehicle. the compensation requirements against the bending moments on the vehicle would have eaten up all the possible payload mass. Moving the engines to the wings solved this tho. a neat solution that required almost no mass increase at all.
Got to love a guy that is willing to stand up in public and admit that they goofed it the first time, then explain what went wrong and how to bypass the problem entirely.

Something else from that lecture: Alan Bond claimed that they were nowhere near the physical limitations for heat exchanger technology. I read that as meaning that they indeed have ideas of how to make even more efficient heat exchangers that could push the speed limit for the engines even further up the temp scale. but unless aeroshell materials that can withstand even higher temps is invented the issue is moot. you can have the best engines in history and not get anywhere if your vehicle melts before you are halfway there. Adding active cooling turns what was a SSTO into a TPS to orbit vehicle instead. This kind of real world physics limitation is hard to beat. not impossible, but don't hold your breath kinda hard.

The problems with SSTO's has always been that the earth is 10% too big for it to work well. Skylon is pushing the envelope so that it becomes possible to get off this ball of dirt. Hopefully they will get all the funds they need once the engines have been demonstrated.

Garrison
2010-Aug-06, 09:43 PM
True. having competing technologies is good. but we also have to take into account other aspects of space launch. Scramjet's by themselves do not address the heating issues that once mach 6 is passed surpasses that of re-entry.

Alan bond stated pretty clearly that as far as physical materials limits is concerned that any vehicle going that fast in the denser parts of the atmosphere is going to end up as a TPS to orbit launch system. He also admitted that some of the choices in HOTOL was a big mistake. the HOTOL project would at best have delivered a hydraulics system to LEO vehicle. the compensation requirements against the bending moments on the vehicle would have eaten up all the possible payload mass. Moving the engines to the wings solved this tho. a neat solution that required almost no mass increase at all.
Got to love a guy that is willing to stand up in public and admit that they goofed it the first time, then explain what went wrong and how to bypass the problem entirely.

Something else from that lecture: Alan Bond claimed that they were nowhere near the physical limitations for heat exchanger technology. I read that as meaning that they indeed have ideas of how to make even more efficient heat exchangers that could push the speed limit for the engines even further up the temp scale. but unless aeroshell materials that can withstand even higher temps is invented the issue is moot. you can have the best engines in history and not get anywhere if your vehicle melts before you are halfway there. Adding active cooling turns what was a SSTO into a TPS to orbit vehicle instead. This kind of real world physics limitation is hard to beat. not impossible, but don't hold your breath kinda hard.

The problems with SSTO's has always been that the earth is 10% too big for it to work well. Skylon is pushing the envelope so that it becomes possible to get off this ball of dirt. Hopefully they will get all the funds they need once the engines have been demonstrated.

I'm wondering, would that greater efficiency allow for lighter engines/ Or more power from the same size engine? Would it in short allow for a higher payload with essentially the same airframe?

Antice
2010-Aug-07, 03:44 AM
I'm wondering, would that greater efficiency allow for lighter engines/ Or more power from the same size engine? Would it in short allow for a higher payload with essentially the same airframe?

I would think so, but the growth in that direction would not be very drastic I'd guess. but every kg counts. I suspect he is hinting more towards the capability to use these precoolers as parts of other engine configurations to improve efficiency and overall power on those. LAPCAT is one such post skylon type of capability growth project at least. It's a much bigger and more challenging project goal than skylon technology wise.

Frodz
2010-Aug-07, 05:18 PM
Something else from that lecture: Alan Bond claimed that they were nowhere near the physical limitations for heat exchanger technology. I read that as meaning that they indeed have ideas of how to make even more efficient heat exchangers that could push the speed limit for the engines even further up the temp scale. but unless aeroshell materials that can withstand even higher temps is invented the issue is moot. you can have the best engines in history and not get anywhere if your vehicle melts before you are halfway there. Adding active cooling turns what was a SSTO into a TPS to orbit vehicle instead. This kind of real world physics limitation is hard to beat. not impossible, but don't hold your breath kinda hard.

That’s one interpretation but then thinking about it, doesn’t the helium loop ultimately require stored hydrogen to function? I’m sure I heard him say that the pre-cooler system draws more hydrogen than is needed for combustion and the overspill gets fed into the bypass ramjets. If the pre-cooler had greater efficiency could you reduce the systems hunger for hydrogen, thereby saving propellant and ultimately hauling more payload? Or am I missing something?

Also did I hear it right when he said the new Sabre 4 design is intended to increase theoretical Veff from 16k/s to nearer 46 km/s implying that it could reach much higher Isp’s?

So I think what is being implied is it’s possible to greatly reduce hydrogen propellant required during the air breathing mode as a way to increase payload.



And to answer some points from earlier,


The Wiki article (http://en.wikipedia.org/wiki/Reaction_Engines_SABRE) about the SABRE engine makes some amazing claims. To quote, "The engine gives good fuel efficiency peaking at about 2800 seconds within the atmosphere. Typical all-rocket systems are around 450 at best, and even "typical" nuclear thermal rockets only about 900 seconds." Are they talking about specific impulse or specific thrust or what? Are they claiming efficiencies in the range of ion engines?

Yes they are talking about specific impulse, but you should take it with a pinch of salt as specific impulses for rockets and air-breathers are not directly compatible. Air breathers like commercial jet engines do tend to have relatively high Isp’s like ion engines (though of course radically different thrust!), it is an artefact of the air being the propellant mass.

That’s kind of the point this rocket has the best of both worlds as it’s air breathing mode can have the performance of a supercharged commercial jet engine, albeit one that can fly much faster, and then switch to a high performance closed cycle once air breathing is no longer more efficient.

2800 seconds Isp for a turbojet, while relatively high, is certainly not beyond the realms of possibility. It’s a lower Isp than for a turbofan but then a turbofan cannot work at higher speeds.



Then there is the matter of the helium powered turbopumps re-cycling waste heat. Why not do the same using the hydrogen fuel? The helium system just seems like extra mass.

Because the material they want to use for the pre-cooler would be damaged by the hydrogen stream, without the helium loop the pre-cooler (a significant part of the engine) would be less efficient and heavier. So the helium loop is required, turbopump or not, so getting as much efficiency out of it is the best idea.

TrAI
2010-Aug-08, 12:39 AM
That’s one interpretation but then thinking about it, doesn’t the helium loop ultimately require stored hydrogen to function? I’m sure I heard him say that the pre-cooler system draws more hydrogen than is needed for combustion and the overspill gets fed into the bypass ramjets. If the pre-cooler had greater efficiency could you reduce the systems hunger for hydrogen, thereby saving propellant and ultimately hauling more payload? Or am I missing something?

Also did I hear it right when he said the new Sabre 4 design is intended to increase theoretical Veff from 16k/s to nearer 46 km/s implying that it could reach much higher Isp’s?

So I think what is being implied is it’s possible to greatly reduce hydrogen propellant required during the air breathing mode as a way to increase payload.

Yes, the cooling loop uses the hydrogen for cooling. As I understood it it was an inescapable problem with precooled engines that they use more hydrogen for sinking the heat then for powering the engine, and that they actually had improved the efficiency over the earlier hydrogen cooling loop used in the HOTOL study. I should think that an increase in efficiency would mean less hydrogen is used, but how much that affects the total fuel use, I am not sure, but I should think some increase is likely.

Also, it seems to me that the amount of excess hydrogen draw depends largely on the speed of the craft, as the higher speeds would mean more heat. so I would think that if they could make the ram-burners more efficient at a wider speed range, some gain could be got there too, I believe the predicted max eff of the SABRE ram-burners being somewhere between Mach 3 and 4.

But it seems to me that the priority should be on getting the system to work, further improvements can be done when the concept is realized. Firstly to reduce development time, secondly to reduce cost, and thirdly I should think that experience with the actual engine in use will help in testing such improvements.


As a more general observation, it is interesting to look at the work they have done on how the Skylon might actually be used, the Fluyt and the Troy look nice and practical, not like some of the streamlined sci-fi stuff, but like something that actually could get the job done, and may be adapted to other mission profiles relatively easily due to modularity. Of course, the Skylon itself looks rather like something from some sci-fi story, but in that case the shape have a practical purpose, it being designed for atmospheric flight.

And there are those mysterious engine system studies the project name document(27kiB PDF) (http://www.reactionengines.co.uk/downloads/REL_Engine_Names.pdf) mentions but that doesn't seem to be mentioned anywhere else...

Frodz
2010-Aug-08, 05:15 PM
Just had a look over at Reaction Engines and found this pdf from 2007, turns out what I thought about the hydrogen consumption is exactly what Bond was on about.

http://www.reactionengines.co.uk/downloads/JBIS_v60_188-196.pdf



Further, it is demonstrated that the precooler is a major source of thermodynamic irreversibility within the engine cycle and that further reduction in entropy can be realised by increasing the heat transfer coefficient on the air side of the precooler. If this were to be achieved, it would improve the payload mass delivered to orbit by the Skylon launch vehicle by between 5 and 10%.

Very interesting pdf that, worth a read.



But it seems to me that the priority should be on getting the system to work, further improvements can be done when the concept is realized.

Undoubtedly true, but it is interesting to see how far (theoretically) the technology can go. :)



And there are those mysterious engine system studies the project name document(27kiB PDF) (http://www.reactionengines.co.uk/downloads/REL_Engine_Names.pdf) mentions but that doesn't seem to be mentioned anywhere else...

After some digging I think I found the answer, many of them were related to the above studies you mention.

For example on this site, http://www.ukrocketman.com/space/index.shtml - (interesting insiders view on the STERN project) it mentions,


Reaction Engines is developing 2 classes of rocket engines; the air breathing rocket engines (Sabre, SCIMITAR and STERN), and the bi-prop rocket engines (SERAPH and SANGRAIL).

After some more digging SANGRAIL appears to be an engine studied for use on a type of Earth return capsule for mars missions.

This pdf discusses some aspects and briefly touches on Excalibur,

http://www.astronist.demon.co.uk/space-age/essays/Three_ways_to_Mars.pdf


We need a reusable launcher (Skylon), an in-space boost stage, and a
capsule for return from interplanetary space. Hempsell has designed an Earth
return capsule called Excalibur; superficially it resembles an Apollo/Orion
capsule, but is in fact very different from them, as the JBIS papers describing it illustrate.

I had the paper references but now I can’t find where I bookmarked the page! :wall:

SERAPH mentioned above is the proposed Mars Ascent Vehicle's LOx/CO engine found near the end of the Troy pdf.

SERPENT could be the nuclear mars engine referred to in the Three ways to Mars pdf above.


As for the rest on that list;
SOMA is pretty straight-forward from the description, and STRICT I believe is the other engine referred to on the ukrocketman site as part of the STERN tests.

SAPPHIRE though I have no clue!

Antice
2010-Aug-10, 09:27 PM
I've been trying to find some info about the SAPPHIRE project on the net, but google is no help there.
STRICT and STERN is basically about the same technology. The plug nozzle upgrade that they want for the SABRE engine.

I've been thinking about those numbers given in the 2007 PDF about how improved heat exchangers could in theory give a 10% increase in payload... that would entail a 20% or more reduction in Hydrogen use during air breathing mode since it is not a 1 for 1 when it comes to mass savings. it's more like 2 for 1 or even 3 for 1 since we are talking about very early in the flight savings. That is no small fuel efficiency increase indeed.

I'm looking into and trying to convert some Isp numbers so that they match up. And i have noticed my flaw in reasoning when i tried to do calculate the airbreathing mode with the rocket equation. The problem is that when air breathing Isp is not a static value, but a dynamic one that changes along with the speed and altitude of the vehicle. and it changes a LOT.
According to wikipedia the N s/kg measure is specific impulse from mass, and is equal to effective exhaust velocity (Veff). we can therefore divide it by g to derive Isp in sec.
The Data given for ISP in the skylon manual is as follows.
Air breathing: 35000 N s/kg = 3569sec (this is probably a rounded average value)
Rocket mode: 4500 N s/kg = 458sec (vacuum level)
SSME (Shuttle) 452.5 sec 4423m/s (vacuum level)
turbofan jet engine: 3000sec or 29000m/s

This is were we stand today at least. and this is with SABRE 3 since SABRE 4 is not ready yet. they are still waiting for it in order to finish the D1 version. I wonder where you got the 16000m/s Veff from. boosting the Veff to 46000m/s that I've not seen any source for would in practice mean an comparative ISP of almost 4700sec. now that is high. Ofc. some of this enhanced fuel mass efficiency increase compared to jet engines is actually due to the higher specific energy of hydrogen. it's energy density however, is lower than for hydrocarbons, so in effect one has traded tank volume for mass efficiency. witch is fine for a SSTO since the greater tank volume helps lessen the heat of reentering.

Garrison
2010-Aug-10, 09:42 PM
I've been trying to find some info about the SAPPHIRE project on the net, but google is no help there.
STRICT and STERN is basically about the same technology. The plug nozzle upgrade that they want for the SABRE engine.

I've been thinking about those numbers given in the 2007 PDF about how improved heat exchangers could in theory give a 10% increase in payload... that would entail a 20% or more reduction in Hydrogen use during air breathing mode since it is not a 1 for 1 when it comes to mass savings. it's more like 2 for 1 or even 3 for 1 since we are talking about very early in the flight savings. That is no small fuel efficiency increase indeed.

I'm looking into and trying to convert some Isp numbers so that they match up. And i have noticed my flaw in reasoning when i tried to do calculate the airbreathing mode with the rocket equation. The problem is that when air breathing Isp is not a static value, but a dynamic one that changes along with the speed and altitude of the vehicle. and it changes a LOT.
According to wikipedia the N s/kg measure is specific impulse from mass, and is equal to effective exhaust velocity (Veff). we can therefore divide it by g to derive Isp in sec.
The Data given for ISP in the skylon manual is as follows.
Air breathing: 35000 N s/kg = 3569sec (this is probably a rounded average value)
Rocket mode: 4500 N s/kg = 458sec (vacuum level)
SSME (Shuttle) 452.5 sec 4423m/s (vacuum level)
turbofan jet engine: 3000sec or 29000m/s


Those numbers seem like magic when you compare them to pure rockets, heck even the NERVA2(Nuclear Engine for Rocket Vehicle Application) was only projected to be have these ISP values:

825 s (vacuum)
380 s (sea level)

And the NERVA numbers are far superior to any chemical rocket ever built.

Antice
2010-Aug-10, 10:27 PM
Yeah. The numbers do look like magic compared to rockets. and I suspect that is why some people remain sceptical of the SABRE concept. Careful reading of the
A Comparison of Propulsion Concepts for SSTO Reuseable Launchers document available on the REL website is a must before one can even start to understand how they are going to accomplish this. It's not just the precooler that makes it possible. it's also the highly efficient brayton cycle with an extreme temperature gradient between the hot and cold side of the cycle. A lot of original thought has gone into SABRE. I'm really looking forward to seing this baby move the last steps into a practical functional engine.

Garrison
2010-Aug-10, 10:52 PM
Yeah. The numbers do look like magic compared to rockets. and I suspect that is why some people remain sceptical of the SABRE concept. Careful reading of the
A Comparison of Propulsion Concepts for SSTO Reuseable Launchers document available on the REL website is a must before one can even start to understand how they are going to accomplish this. It's not just the precooler that makes it possible. it's also the highly efficient brayton cycle with an extreme temperature gradient between the hot and cold side of the cycle. A lot of original thought has gone into SABRE. I'm really looking forward to seing this baby move the last steps into a practical functional engine.

And there is an element that people have gotten their hopes up for plans like Venturestar, the X-30, heck even the STS and been disappointed. They just can't bring themselves to believe that something truly revolutionary could really be about to come to fruition.

Frodz
2010-Aug-10, 11:54 PM
The problem is that when air breathing Isp is not a static value, but a dynamic one that changes along with the speed and altitude of the vehicle. and it changes a LOT.

http://www.reactionengines.co.uk/downloads/JBIS_v56_108-117.pdf

At the end, by the looks of it it matches Skylon's air breathing flight-profile.



This is were we stand today at least. and this is with SABRE 3 since SABRE 4 is not ready yet. they are still waiting for it in order to finish the D1 version.

If you notice the updated User Manual on the Reaction Engines website is the C2 specification, not the old C1 version. For example the quoted mass to LEO for C2 is 15,000 kg, larger than C1’s 12,000 kg and the same as the D1. I think the C2 is an interim D1 specification and its performance based on “known” SABRE 4 capabilities.

Hence I think some information out there on the SABRE/Skylon specs is in fact a synthesis of different specifications.



I wonder where you got the 16000m/s Veff from. boosting the Veff to 46000m/s that I've not seen any source for would in practice mean an comparative ISP of almost 4700sec. now that is high.

Starts around 40:50 on the video you posted. Note, this is the Isp at mach 5 and if you look on the Isp profile I posted above at mach 5 the engine would be well below it’s peak of 3600 s and at around ~1600 s Isp, the 16000m/s Veff on the video appears consistent with that (16,000/9.8). So basically what he is saying is that they want with SABRE 4 to at least maintain the peak Isp over the higher mach numbers.



Ofc. some of this enhanced fuel mass efficiency increase compared to jet engines is actually due to the higher specific energy of hydrogen.

Hmm, good point, isn’t the exhaust relatively faster though which would help to balance that out?



Those numbers seem like magic when you compare them to pure rockets, heck even the NERVA2(Nuclear Engine for Rocket Vehicle Application) was only projected to be have these ISP values:

825 s (vacuum)
380 s (sea level)

And the NERVA numbers are far superior to any chemical rocket ever built.

As I said above, you cannot directly compare air breathing engines to closed cycle ones based on Isp, look at the wiki page,

http://en.wikipedia.org/wiki/Specific_impulse

It’s not magic, it’s just how the property is calculated.

In fact SABRE’s values are quite standard for Turbofans, there are some which have much higher Isp’s, and even then it’s only a peak value which it will sustain for something like a minute at most. After all, although many of it’s components are different, it is effectively doing much the same thing as a (very high speed) Turbofan. Indeed come to think of it SABRE is actually conceptually very simple, it’s a conventional rocket with the business end of a high-performance turbofan strapped on the front! :D

It is essentially this “high-performance” bit (the precooler/helium cycle etc) that makes this engine viable for SSTO’s. I think it is far less mystical than a lot of people believe, the “tricks” the RE lot have used to make the engine work seem to have a lot of people confused.

Antice
2010-Aug-11, 06:06 AM
There is plenty confusion about what SABRE is. far to many confuse it with other concepts that they have heard about. I've seen it confounded with ram/scramjet's, LACE and even in some cases ACE. When people confuse it thus i tend to chalk it up to people not bothering to read the materiel presented propperly... Something that I have noticed is a pretty endemic tendency among Internet airmchair "engineers" in general.

Garrison
2010-Aug-11, 07:53 PM
http://www.reactionengines.co.uk/downloads/JBIS_v56_108-117.pdf

It’s not magic, it’s just how the property is calculated.


In fact SABRE’s values are quite standard for Turbofans, there are some which have much higher Isp’s, and even then it’s only a peak value which it will sustain for something like a minute at most. After all, although many of it’s components are different, it is effectively doing much the same thing as a (very high speed) Turbofan. Indeed come to think of it SABRE is actually conceptually very simple, it’s a conventional rocket with the business end of a high-performance turbofan strapped on the front! :D

It is essentially this “high-performance” bit (the precooler/helium cycle etc) that makes this engine viable for SSTO’s. I think it is far less mystical than a lot of people believe, the “tricks” the RE lot have used to make the engine work seem to have a lot of people confused.

Yes I know that, I was simply pointing out that anyone familiar with the ISP figures for ordinary rocket engines might be taken aback by the raw numbers for the SABRE, it wasn't meant to be taken seriously, or to imply that i don't believe them. I thought that was pretty clear but apparently not.

Frodz
2010-Aug-12, 10:35 AM
Yes I know that, I was simply pointing out that anyone familiar with the ISP figures for ordinary rocket engines might be taken aback by the raw numbers for the SABRE, it wasn't meant to be taken seriously, or to imply that i don't believe them. I thought that was pretty clear but apparently not.

Ah sorry, no it didn't seem clear to me, as I'm sure you're aware many people do make similar comparisons genuinely complaining that SABRE sounds unrealistic!

It's a useful general comment anyway for someone who does actually think the stats for SABRE seem incredulous for a rocket engine.



There is plenty confusion about what SABRE is. far to many confuse it with other concepts that they have heard about. I've seen it confounded with ram/scramjet's, LACE and even in some cases ACE.

Yeah I know, LACE/ACE is understandable given that is is effectively an evolution of that design but the ramjet confusion shows that they haven't actually read anything about what SABRE does. "oh look, it has ramjets, it must be some sort of ramjet/turboramjet engine!" :rolleyes:



When people confuse it thus i tend to chalk it up to people not bothering to read the materiel presented propperly... Something that I have noticed is a pretty endemic tendency among Internet airmchair "engineers" in general.

Yeah, reading all those pdf's on the website is essential. A lot of the Reaction Engines public relations bumf stresses their innovations, which is understandable, but there's far less talk of how the overall engine design conforms to already well-established principles and hence is easily one of the most feasible SSTO concepts around. IMO they would do better in the PR stakes stressing many of the similarities with existing engine concepts like the Turbofan and showing why their design is a natural evolution of that that can be used in rockets.

Oh well, that's the opinion of an internet armchair PR agent........:razz:

Antice
2010-Aug-21, 05:48 AM
found this yesterday (http://www.flight.moroccohotel.info/flight-international/skylon-spaceplane-ssto-designer-alan-bond-talks-to-flight-international). i tried to trace back to the original news article refered to but was unable to find the correct one.
In any case. it's interesting to note the level of confidence mr Bond displays in regard to skylon happening once the engines have been proven. It may not be the skylon REL has proposed that happens, but he fully expect some sort of vehicle to result from this within 10 years after engine completion.

Garrison
2010-Aug-21, 12:29 PM
found this yesterday (http://www.flight.moroccohotel.info/flight-international/skylon-spaceplane-ssto-designer-alan-bond-talks-to-flight-international). i tried to trace back to the original news article refered to but was unable to find the correct one.
In any case. it's interesting to note the level of confidence mr Bond displays in regard to skylon happening once the engines have been proven. It may not be the skylon REL has proposed that happens, but he fully expect some sort of vehicle to result from this within 10 years after engine completion.

That's interesting because I came across something that took me by surprise(apologies if everyone else already knows about it); Lockheed Martin didn't give up on RLV's after the X-33 debacle:

Reusable Rocket Test (http://www.msnbc.msn.com/id/33329828/ns/technology_and_science-space/)

With a working SABRE would REL be looking for a partner in the aerospace industry to build a vehicle around it, be it the Skylon or something else?

RGClark
2010-Aug-21, 04:49 PM
That's interesting because I came across something that took me by surprise(apologies if everyone else already knows about it); Lockheed Martin didn't give up on RLV's after the X-33 debacle:
Reusable Rocket Test (http://www.msnbc.msn.com/id/33329828/ns/technology_and_science-space/)


I'm fairly sure this is for a reusable first stage booster for an expendable upper stage:

Plans for future re--usable space launch X-plane hatched.
Posted by Guy Norris at 3/31/2009 3:41 PM CDT
"Concept models of the fly-back winged booster and a similar winged booster with a rocket-powered payload module carried piggy-back, were revealed at the National Space Symposium. The models bore a strong resemblance to the scaled model booster flight tested by Lockheed Martin early in 2008. These tests, conducted in New Mexico, were primarily to investigate guidance and control concepts for the two-stage to orbit vehicle which will be autonomously controlled at speeds for up to Mach 6 for the first-stage and up to Mach 9 and beyond for the second-stage."
http://sitelife.aviationweek.com/ver1.0/Content/images/store/9/3/690498aa-3212-4ec9-83a3-ced03dd74ae2.Large.jpg
http://www.aviationweek.com/aw/blogs/space/index.jsp?plckController=Blog&plckBlogPage=BlogViewPost&newspaperUserId=04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog%3a04ce340e-4b63-4d23-9695-d49ab661f385Post%3a515cca66-2055-4902-bce3-400832bdc2a4&plckScript=blogScript&plckElementId=blogDest

Bob Clark

Antice
2010-Aug-21, 08:30 PM
That's interesting because I came across something that took me by surprise(apologies if everyone else already knows about it); Lockheed Martin didn't give up on RLV's after the X-33 debacle:

Reusable Rocket Test (http://www.msnbc.msn.com/id/33329828/ns/technology_and_science-space/)

With a working SABRE would REL be looking for a partner in the aerospace industry to build a vehicle around it, be it the Skylon or something else?

REL will only accept a partner that is free of ITAR issues according to most of the interviews I've seen where such questions were asked. But selling SABRE engines to a company that wants them for making a 2STO. yeah i expect that they will be willing to do that. it would be a pop up/fly forward type 2STO then. those avoid a lot of the staging issues by doing it on a suborbital jump out of the atmosphere. SABRE is just about the only engine that could enable those as well as SSTO. that is the big issue with pop up flyback boosters. you really are a good portion of the way to orbit when you finally stage..
But i think skylon makes more sense than a 2STO. staging adds so much extra groundwork that the extra payload may not be worth it. the SUS REL has proposed would be sufficient to allow exploiting any extra potential gained with staging. The SUS can be mated to the payload at the customers facilities (the customer uses a clean-room for building their payload in the first place) then shipped in a sealed container to the launch facility.
Getting rid of the expensive launch prep facility at the launch site is a pretty important economic issue you know. not all payloads need a clean-room facility.

It is a given however that REL are going to need multiple partners in order to realize skylon. they are not planning on building it on their own AFAIK.
But they may actually end up doing just that. Big industry players are being somewhat reticent towards buying into skylon for some reason.

Garrison
2010-Aug-21, 08:40 PM
REL will only accept a partner that is free of ITAR issues according to most of the interviews I've seen where such questions were asked. But selling SABRE engines to a company that wants them for making a 2STO. yeah i expect that they will be willing to do that. it would be a pop up/fly forward type 2STO then. those avoid a lot of the staging issues by doing it on a suborbital jump out of the atmosphere. SABRE is just about the only engine that could enable those as well as SSTO. that is the big issue with pop up flyback boosters. you really are a good portion of the way to orbit when you finally stage..
But i think skylon makes more sense than a 2STO. staging adds so much extra groundwork that the extra payload may not be worth it. the SUS REL has proposed would be sufficient to allow exploiting any extra potential gained with staging. The SUS can be mated to the payload at the customers facilities (the customer uses a clean-room for building their payload in the first place) then shipped in a sealed container to the launch facility.
Getting rid of the expensive launch prep facility at the launch site is a pretty important economic issue you know. not all payloads need a clean-room facility.

It is a given however that REL are going to need multiple partners in order to realize skylon. they are not planning on building it on their own AFAIK.
But they may actually end up doing just that. Big industry players are being somewhat reticent towards buying into skylon for some reason.

May be the old problem of 'not made here', or just concerns about what Skylon would do to to their existing infrastructure and product range. To find a partner or partners they may have to look to some of the newer players in the industry with less baggage. Though REL have said they do have some private investment that their keeping close to their chest so who knows? From a bigger picture perspective it's good to see that Lockheed are least looking to new technology and new approaches, especially after getting burned so badly with the X-33.

Antice
2010-Aug-22, 04:05 AM
May be the old problem of 'not made here', or just concerns about what Skylon would do to to their existing infrastructure and product range. To find a partner or partners they may have to look to some of the newer players in the industry with less baggage. Though REL have said they do have some private investment that their keeping close to their chest so who knows? From a bigger picture perspective it's good to see that Lockheed are least looking to new technology and new approaches, especially after getting burned so badly with the X-33.

It's definately good to see that there are more than newspace/alt.space companies looking into reusability. It's about time that we started to see more serious attempts at breaking this very tough nut. All the lethargy have given REL a real whooper of a leg up on the competition tho. Unless there are some very black projects out there we don't even know about at all.

Garrison
2010-Aug-22, 12:33 PM
It's definately good to see that there are more than newspace/alt.space companies looking into reusability. It's about time that we started to see more serious attempts at breaking this very tough nut. All the lethargy have given REL a real whooper of a leg up on the competition tho. Unless there are some very black projects out there we don't even know about at all.

The USAF might have something lurking in the shadows behind the X-37B but I do agree that barring that REL are out in the lead here. It's all about getting the cost per kilo down for launching, without that all the lofty deep space goals will either be abandoned or wind up as nothing more than PR stunts for whichever country carries them out.

RGClark
2010-Aug-24, 08:07 PM
The import of the Dr. John C. Whitehead article Single Stage To Orbit Mass Budgets Derived From Propellant Density and Specific Impulse is that it shows that for a rocket SSTO even though hydrogen has a higher Isp than kerosene its low density means that it's actually easier to make a rocket SSTO using dense fuels such as kerosene:

Single Stage To Orbit Mass Budgets Derived From Propellant Density and Specific Impulse.
John C. Whitehead
32nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference
Lake Buena Vista, FL July 1-3, 1996
http://www.osti.gov/bridge/servlets/purl/379977-2LwFyZ/webviewable/379977.pdf

This result very well may also apply to a partial airbreathing system such as Skylon that uses airbreathing propulsion in the first part of the trip, switching to rockets in the later part. The key reasons why dense hydrocarbon-fueled rockets can supply multiple times greater payload in the same size vehicle than a hydrogen-fueled one is that their engine T/W ratio is twice as good and their propellant weight to tank weight ratios are 3 times as good as hydrogen, resulting in major reductions in vehicle dry mass.
These factors should also apply to a partially airbreathing system, and an example from the past strongly implies this is the case. Back in the fifties the Air Force wanted a long range reconnaissance craft. Based on the fact that hydrogen has a higher Isp the belief was the vehicle should be hydrogen fueled. The vehicle proposed by Lockheed under this top secret "Suntan" program was the CL-400:

LIQUID HYDROGEN AS A PROPULSION FUEL,1945-1959.
Part II : 1950-1957
8. Suntan
Lockheed CL-400.
http://history.nasa.gov/SP-4404/p145a.jpg
http://history.nasa.gov/SP-4404/ch8-3.htm

Notice the similarity to the Skylon with the long thin fuselage and the engines on the ends of the wings. The main difference would be the lack of a tail section on the Skylon, probably because the engines need to gimbal for the flight to space which can also be used for vehicle control in the air.
However, note that the range given on this page is only 4,000 km, for a mission radius of 2,000 km for missions returning to the starting point. This is for a vehicle 160 feet long. But the smaller kerosene-fueled SR-71 at only 100 feet long has a range of 4,800 km:

Lockheed
SR-71 Blackbird
Strategic Reconnaissance.
http://www.aerospaceweb.org/aircraft/recon/sr71/

Indeed the legendary Kelly Johnson soured on the Suntan program when he found despite hydrogen's higher energy content that its use would result in such short range:

LIQUID HYDROGEN AS A PROPULSION FUEL,1945-1959
Part II : 1950-1957
8. Suntan
Suntan Fades.
http://history.nasa.gov/SP-4404/ch8-12.htm

Another key advantage of a kerosene-fueled version is that fuel can be carried in the wings, as with the SR-71, but not in a hydrogen-fueled version:

Suntan fades.
"Ordinarily, range can be extended by adding more fuel or improving the fuel consumption of the propulsion system for a given thrust. Johnson could see a range growth of only a paltry 3 percent or so from adding more fuel. ". . . we have crammed the maximum amount of hydrogen in the fuselage that it can hold. You do not carry hydrogen in the flat surfaces of the wing," he explained.42 Johnson turned to Perry Pratt for estimated improvements in the 304 engine and his answer was equally pessimistic: no more than 5 or 6 percent improvement in specific fuel consumption could be expected over a five-year period. The very low growth estimates were compounded by operational logistics problems of liquid hydrogen. As Ben Rich asked: 'How do you justify hauling enough LH2 around the world to exploit a shortrange airplane?'"
http://history.nasa.gov/SP-4404/ch8-12.htm

So both for the rocket propulsion and the airbreathing propulsion components dense propellants provide better performance despite hydrogen's greater Isp. For this reason I suggest Reaction Engines do a trade study on replacing the hydrogen with kerosene or other hydrocarbon.
Hydrogen does have advantages for the Skylon system in that it has greater cooling capacity for the heat exchangers and it is lighter so requires lower wing weight. Still, careful trades would be required to see if these advantages are enough to counteract the advantages of dense propellants for a SSTO.


Bob Clark

djellison
2010-Aug-24, 08:28 PM
So both for the rocket propulsion and the airbreathing propulsion components dense propellants provide better performance despite hydrogen's greater Isp.

Care to make your brush a little broader? If what you say is true - where are there ANY LOX/LH2 LV's at all.

Garrison
2010-Aug-24, 09:00 PM
The import of the Dr. John C. Whitehead article Single Stage To Orbit Mass Budgets Derived From Propellant Density and Specific Impulse is that it shows that for a rocket SSTO even though hydrogen has a higher Isp than kerosene its low density means that it's actually easier to make a rocket SSTO using dense fuels such as kerosene:

Single Stage To Orbit Mass Budgets Derived From Propellant Density and Specific Impulse.
John C. Whitehead
32nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference
Lake Buena Vista, FL July 1-3, 1996
http://www.osti.gov/bridge/servlets/purl/379977-2LwFyZ/webviewable/379977.pdf

This result very well may also apply to a partial airbreathing system such as Skylon that uses airbreathing propulsion in the first part of the trip, switching to rockets in the later part. The key reasons why dense hydrocarbon-fueled rockets can supply multiple times greater payload in the same size vehicle than a hydrogen-fueled one is that their engine T/W ratio is twice as good and their propellant weight to tank weight ratios are 3 times as good as hydrogen, resulting in major reductions in vehicle dry mass.
These factors should also apply to a partially airbreathing system, and an example from the past strongly implies this is the case. Back in the fifties the Air Force wanted a long range reconnaissance craft. Based on the fact that hydrogen has a higher Isp the belief was the vehicle should be hydrogen fueled. The vehicle proposed by Lockheed under this top secret "Suntan" program was the CL-400:

LIQUID HYDROGEN AS A PROPULSION FUEL,1945-1959.
Part II : 1950-1957
8. Suntan
Lockheed CL-400.

Notice the similarity to the Skylon with the long thin fuselage and the engines on the ends of the wings. The main difference would be the lack of a tail section on the Skylon, probably because the engines need to gimbal for the flight to space which can also be used for vehicle control in the air.
However, note that the range given on this page is only 4,000 km, for a mission radius of 2,000 km for missions returning to the starting point. This is for a vehicle 160 feet long. But the smaller kerosene-fueled SR-71 at only 100 feet long has a range of 4,800 km:

Lockheed
SR-71 Blackbird
Strategic Reconnaissance.
http://www.aerospaceweb.org/aircraft/recon/sr71/

Indeed the legendary Kelly Johnson soured on the Suntan program when he found despite hydrogen's higher energy content that its use would result in such short range:

LIQUID HYDROGEN AS A PROPULSION FUEL,1945-1959
Part II : 1950-1957
8. Suntan
Suntan Fades.
http://history.nasa.gov/SP-4404/ch8-12.htm

Another key advantage of a kerosene-fueled version is that fuel can be carried in the wings, as with the SR-71, but not in a hydrogen-fueled version:

Suntan fades.
"Ordinarily, range can be extended by adding more fuel or improving the fuel consumption of the propulsion system for a given thrust. Johnson could see a range growth of only a paltry 3 percent or so from adding more fuel. ". . . we have crammed the maximum amount of hydrogen in the fuselage that it can hold. You do not carry hydrogen in the flat surfaces of the wing," he explained.42 Johnson turned to Perry Pratt for estimated improvements in the 304 engine and his answer was equally pessimistic: no more than 5 or 6 percent improvement in specific fuel consumption could be expected over a five-year period. The very low growth estimates were compounded by operational logistics problems of liquid hydrogen. As Ben Rich asked: 'How do you justify hauling enough LH2 around the world to exploit a shortrange airplane?'"
http://history.nasa.gov/SP-4404/ch8-12.htm

So both for the rocket propulsion and the airbreathing propulsion components dense propellants provide better performance despite hydrogen's greater Isp. For this reason I suggest Reaction Engines do a trade study on replacing the hydrogen with kerosene or other hydrocarbon.
Hydrogen does have advantages for the Skylon system in that it has greater cooling capacity for the heat exchangers and it is lighter so requires lower wing weight. Still, careful trades would be required to see if these advantages are enough to counteract the advantages of dense propellants for a SSTO.


Bob Clark

These vehicles were/are all designed to operate at high Mach numbers, not surprising that they share some similarities in the aerodynamics. Look at the SST's designed in the 60's and 70's, they all have a similar layout. As for the rest, once again you know better than Alan Bond et al, they are clearly just idiots who have missed your brilliant insight, what's their decades of experience versus your Googling skills...:wall: How about you keep your crackpot nonsense in your own threads and keep it out of those dedicated to real projects with real engineering?

RGClark
2010-Aug-25, 03:13 AM
These vehicles were/are all designed to operate at high Mach numbers, not surprising that they share some similarities in the aerodynamics. Look at the SST's designed in the 60's and 70's, they all have a similar layout. As for the rest, once again you know better than Alan Bond et al, they are clearly just idiots who have missed your brilliant insight, what's their decades of experience versus your Googling skills...:wall: How about you keep your crackpot nonsense in your own threads and keep it out of those dedicated to real projects with real engineering?

In no way am I suggesting Bond et.al. don't know what they are doing. When in the 50's a long range reconnaissance aircraft was being considered the obvious assumption to make then was that it should be hydrogen fueled since hydrogen has the highest energy per mass of any fuel. Most of the smartest guys in aircraft design then made that assumption. It was only after a careful study of all the physical characteristics of a hydrogen fueled vehicle was done, was it realized you could get better performance just by using kerosene. This is primarily just because of hydrogens very low density (you can fit 10 times as much kerosene as hydrogen in the same size tanks.) This is not my conclusion. It's the conclusion of Kelly Johnson, widely regarded as the greatest aircraft designer who ever lived.
In regards to the design of the Skylon, if you look at REL's article A Comparison of Propulsion Concepts for
SSTO Reusable Launchers you'll note they assume these SSTO's have to be hydrogen-fueled since that was what was proposed for most other earlier SSTO designs. This suggests they never did the trade studies to compare a kerosene-fueled version of the Skylon to the hydrogen-fueled version. Keep in mind then the conclusion that for a pure rocket a kerosene-fueled SSTO would provide better performance than a hydrogen-fueled one came from experts in the industry who actually did make those trade comparisons. Since this is also true for an airbreathing aircraft, it is likely to be true for a SSTO that uses both airbreathing and rocket propulsion, such as the Skylon. However, this can't be known for sure until those careful trade comparisons are made.


Bob Clark

danscope
2010-Aug-25, 04:49 AM
This won't be known " Untill one flies" . Have any of these "skylon" things Ever flown? No? Point taken.

Antice
2010-Aug-25, 06:30 AM
Bob clark. can you please stop using guesswork about the skylon design? It would please me greatly if you actually checked the facts before making claims about how something is suposed to work.
The skylon engine does not gimbal. pitch and roll is done with flight controll surfaces. pitch is controlled by forward canards. (those little wing like thingies on the nose of the vehicle you know) and roll is controlled with an all moving tailfin. once out of the atmosphere controll is maintained with the use of fixed forward and aft RCS thrusters.
The main reason for using hydrogen as fuel in skylon is not ISP. it's the fact that a vehicle of this kind needs an enourmous amount of very cold coolant. Luck has it that hydrogen is excelent as both. Denser fuels cannot act as a coolant in this manner, and is hence limited to an air breathing speed below mach 3,5 barring any revolutions in high temperature alloys.

The second advantage to using hydrogen is that it fits with a large volume low density vehicle of the kind that get's to have a fairly benign re-entry. This allows the use of much more dammage resistant materials than what the shuttle is allowed to use. This is of critical importanse to the safety and practicality of skylon as a launch vehicle.

If you actually read the 2004 documents on REL's website you will find the exact trades done when selecting fuel type. ISP was a minor factor. so minor it's hardly even mentioned.
You are the one doing the asuming here. not REL. You are asuming that RP1 is a superior fuel because it's denser. but that is just one factor in the kind of trades you need to do when selecting fuel types.

@Danscope. If everyone was thinking like you we would still be living in caves and eating our food raw. I'f you havent actually noticed yet the skylon vehicle is dependant on a critical item of brand new technology. without whitch a vehicle like skylon would not be capable of working at all. Namely preecooled air breathing rocketry. nobody has made that work all that well before. REL is changing that trend as we speak. so how about waiting with the doom and gloom til they have concluded their technology demonstration programme hey? We will know for sure in 2012 or thereabouts.

RGClark
2010-Aug-25, 12:07 PM
Bob clark. can you please stop using guesswork about the skylon design? It would please me greatly if you actually checked the facts before making claims about how something is supposed to work.
The skylon engine does not gimbal. pitch and roll is done with flight controll surfaces. pitch is controlled by forward canards. (those little wing like thingies on the nose of the vehicle you know) and roll is controlled with an all moving tailfin. once out of the atmosphere controll is maintained with the use of fixed forward and aft RCS thrusters.
The main reason for using hydrogen as fuel in skylon is not ISP. it's the fact that a vehicle of this kind needs an enourmous amount of very cold coolant. Luck has it that hydrogen is excelent as both. Denser fuels cannot act as a coolant in this manner, and is hence limited to an air breathing speed below mach 3,5 barring any revolutions in high temperature alloys.
The second advantage to using hydrogen is that it fits with a large volume low density vehicle of the kind that get's to have a fairly benign re-entry. This allows the use of much more dammage resistant materials than what the shuttle is allowed to use. This is of critical importanse to the safety and practicality of skylon as a launch vehicle.
If you actually read the 2004 documents on REL's website you will find the exact trades done when selecting fuel type. ISP was a minor factor. so minor it's hardly even mentioned.
You are the one doing the asuming here. not REL. You are asuming that RP1 is a superior fuel because it's denser. but that is just one factor in the kind of trades you need to do when selecting fuel types.

By 'gimbal', I did not mean rotating on pylons as I referred to on another thread, I meant the type of gimbaling usually done in rockets where the nozzles on the engines can be angled:

The SKYLON Spaceplane.
RICHARD VARVILL AND ALAN BOND
Reaction Engines Ltd, D5 Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB, UK.
JBIS, vol. 57, pp. 22-32, 2004
"Control authority
whilst in the atmosphere is exerted by
foreplanes in pitch, ailerons in roll and an aft mounted
fin in yaw. During the ascent main engine gimballing
takes over progressively as the dynamic pressure
reduces until finally handing over to reaction control
thrusters at main engine cutoff."
http://www.reactionengines.co.uk/downloads/JBIS_v57_22-32.pdf

Kerosene can be used for cooling; its just that hydrogen has a better capacity for it. For instance the kerosene itself is used for the cooling for kerosene-fueled, regeneratively-cooled engines, where the temperatures are even higher than in the Skylon application. For this heat exchanger use though there is a large mass of air that needs to be cooled and hydrogen can do it more effectively. However, there are other hydrocarbon fuels such as methane and propane that have higher energy density than kerosene and better cooling capacity. A trade study would need to be done to see if the lower cooling capacity of using a hydrocarbon fuel would be made up by the greater density of the fuel.
I read the "Comparison of Propulsion Concepts" article and some of the heat exchanger articles, and I did not see any that made a comparison of using hydrocarbon as the coolant or as the engine propellant in the ones I read. If you've read some that made this comparison, point me to them and I will read them.


Bob Clark

djellison
2010-Aug-25, 01:14 PM
People have pointed you towards facts, data, evidence and proffesio al opinion in many other threads many other times, and it has achieved nothing. Not a damn thing. PLEASE take your pseudo-engineering elsewhere.

TrAI
2010-Aug-25, 05:39 PM
By 'gimbal', I did not mean rotating on pylons as I referred to on another thread, I meant the type of gimbaling usually done in rockets where the nozzles on the engines can be angled:

The SKYLON Spaceplane.
RICHARD VARVILL AND ALAN BOND
Reaction Engines Ltd, D5 Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB, UK.
JBIS, vol. 57, pp. 22-32, 2004
"Control authority
whilst in the atmosphere is exerted by
foreplanes in pitch, ailerons in roll and an aft mounted
fin in yaw. During the ascent main engine gimballing
takes over progressively as the dynamic pressure
reduces until finally handing over to reaction control
thrusters at main engine cutoff."
http://www.reactionengines.co.uk/downloads/JBIS_v57_22-32.pdf

Kerosene can be used for cooling; its just that hydrogen has a better capacity for it. For instance the kerosene itself is used for the cooling for kerosene-fueled, regeneratively-cooled engines, where the temperatures are even higher than in the Skylon application. For this heat exchanger use though there is a large mass of air that needs to be cooled and hydrogen can do it more effectively. However, there are other hydrocarbon fuels such as methane and propane that have higher energy density than kerosene and better cooling capacity. A trade study would need to be done to see if the lower cooling capacity of using a hydrocarbon fuel would be made up by the greater density of the fuel.
I read the "Comparison of Propulsion Concepts" article and some of the heat exchanger articles, and I did not see any that made a comparison of using hydrocarbon as the coolant or as the engine propellant in the ones I read. If you've read some that made this comparison, point me to them and I will read them.


Bob Clark

Hmmm... I have this feeling something doesn't work out, but I am not sure exactly what...

This will probably be a rather rambling series of thoughts, but perhaps something will be understandable and somewhat correct...


Lets see, Our hydrocarbon fueled craft can carry 10 times the reaction mass in the same volume, however, this fuel has less heat capacity, was that the idea? Hmmm. So you have to use what... 7 times?(I seem to remember HC fuels being around 2 and hydrogen around 14 on some list or other for heat capacity) the fuel mass to cool the same amount of air(is it even practical to use HC as a sink for cooling air from around 1000C to cryogenic temperatures?). Then, as you carry 10 times the fuel, the engines will have to larger, so you need even larger precoolers. and the structure of the craft is would have to be reinforced to carry the extra load, I should think. Still, wouldn't you have a lot more HC fuel in mass relative to a LH system that can not be used for the rockets, what would we do with this? more ram burners? or just dump it? That last does not seem practical, as there is no point in carrying the weight just to dump it... and I would think there was a limit to how practical the rams would be in larger numbers or sizes... Are you sure we get any significant improvement from using HC?

Hmmm.. Wait a minute... Doesn't the Skylon design use the remaining liquid hydrogen for the reentry thermal rejection screens, and basically keeping its insides cool by allowing the fuel to evaporate? I have a feeling that the LH would have a lot more capacity than HC for evaporative cooling... Is it feasible, or are we going to loose the ship on reentry(if we do get it into space) as everything inside gets cooked? Do we need to carry some additional coolant for this use?

Hmmm... seems to me that one of the integral parts of the skylon design is the relatively low mass it has in relation to the size, I can't really see how it would be practical to add all the reenforcement stuff needed for carrying 10 times the fuel mass...

I expect that if the Skylon or some derivative gets of the ground, we will see some research into improvements, but for now getting there is the important thing, not trying to improve the wheel before it has been created, that sort of thing can kill a project. It may forever be just trying to keep up with the changing requirements, especially for projects where a lot of new technologies are involved, you may find that just to facilitate the new requirements you actually end up with an abomination worse than the original design or any derivative it might have had once the technologies and real world challenges was better known.

Garrison
2010-Aug-25, 05:46 PM
Kerosene can be used for cooling; its just that hydrogen has a better capacity for it. For instance the kerosene itself is used for the cooling for kerosene-fueled, regeneratively-cooled engines, where the temperatures are even higher than in the Skylon application. For this heat exchanger use though there is a large mass of air that needs to be cooled and hydrogen can do it more effectively. However, there are other hydrocarbon fuels such as methane and propane that have higher energy density than kerosene and better cooling capacity. A trade study would need to be done to see if the lower cooling capacity of using a hydrocarbon fuel would be made up by the greater density of the fuel.

Bob Clark

And you have an example of your 'for instance' that's actually under development? You know something with actual engineering rather than a Kerosene fetish? Not to mention you seem to have ignored Antice's point about the alloy's necessary for higher temperature operation. You simply cannot accept that there are applications where LOX/LH2 is the better choice. Kerosene has it's applications as rocket fuel, air breathing SSTO's do not appear to be one of them.

Garrison
2010-Aug-25, 05:49 PM
I expect that if the Skylon or some derivative gets of the ground, we will see some research into improvements, but for now getting there is the important thing, not trying to improve the wheel before it has been created, that sort of thing can kill a project. It may forever be just trying to keep up with the changing requirements, especially for projects where a lot of new technologies are involved, you may find that just to facilitate the new requirements you actually end up with an abomination worse than the original design or any derivative it might have had once the technologies and real world challenges was better known.

TrAI I think you just summed up what happened to the X-33...

Antice
2010-Aug-25, 07:54 PM
About the gimbaling on the engines. my bad.
I forgot about the intermediate step between the area of the flight were air control surfaces are effective and the short period until RCS becomes truly effective. Gimbaling can not be used early in the flight because a fair amount of the thrust coming from the engine is trough the bypass system and not trough the gimbaled nozzles. A pretty unique issue for turbo-rockets. Thrust vectoring would require a separate system mounted outside the nozzles of the rocket part. this is a mass trade-off where it might be lower mass to use thrust vectoring instead of canards. but thrust vectoring is a higher risk technology than canards so going with canards for a first gen vehicle makes a lot of sense.

Kerosene is useless as a heat sink for the helium loop because at the temperatures that is required in that regard is below the freezing point of not only kerosene, but more or less all reasonable fuels we know of, except hydrogen. The hydrogen is sub cooled even. to increase it's heat capacity.
Thrust has been traded away on skylon. so much so that the vehicle has a TW at takeoff of only around 0.5

LH2 is giving us these benefits:
Fluffy vehicle with a low mass to volume ratio allowing a benign re-entry profile.
High heat capacity as well as deep cryogenic temp cold side for the heat engine cycle.
High caloric energy content per unit mass, translates into a high ISP upper stage burn mode for the final ascent to orbit.
That last point translates into a benign ascent environment with low G loading on the cargo. especially important if the cargo is going to be passengers, but also for some science experiments and satellites.

LH2 usually have some drawbacks, but they do not apply for skylon because skylon is designed so that it turns them into strengths instead. Which I think is a very nifty way of doing things. Trying to change the fuel type to anything but hydrogen simply breaks the design entirely. it no longer works at all.

RGClark
2010-Aug-25, 11:09 PM
Hmmm... I have this feeling something doesn't work out, but I am not sure exactly what...
This will probably be a rather rambling series of thoughts, but perhaps something will be understandable and somewhat correct...
Lets see, Our hydrocarbon fueled craft can carry 10 times the reaction mass in the same volume, however, this fuel has less heat capacity, was that the idea? Hmmm. So you have to use what... 7 times?(I seem to remember HC fuels being around 2 and hydrogen around 14 on some list or other for heat capacity) the fuel mass to cool the same amount of air(is it even practical to use HC as a sink for cooling air from around 1000C to cryogenic temperatures?). Then, as you carry 10 times the fuel, the engines will have to larger, so you need even larger precoolers. and the structure of the craft is would have to be reinforced to carry the extra load, I should think. Still, wouldn't you have a lot more HC fuel in mass relative to a LH system that can not be used for the rockets, what would we do with this? more ram burners? or just dump it? That last does not seem practical, as there is no point in carrying the weight just to dump it... and I would think there was a limit to how practical the rams would be in larger numbers or sizes... Are you sure we get any significant improvement from using HC?
Hmmm.. Wait a minute... Doesn't the Skylon design use the remaining liquid hydrogen for the reentry thermal rejection screens, and basically keeping its insides cool by allowing the fuel to evaporate? I have a feeling that the LH would have a lot more capacity than HC for evaporative cooling... Is it feasible, or are we going to loose the ship on reentry(if we do get it into space) as everything inside gets cooked? Do we need to carry some additional coolant for this use?
Hmmm... seems to me that one of the integral parts of the skylon design is the relatively low mass it has in relation to the size, I can't really see how it would be practical to add all the reenforcement stuff needed for carrying 10 times the fuel mass...
I expect that if the Skylon or some derivative gets of the ground, we will see some research into improvements, but for now getting there is the important thing, not trying to improve the wheel before it has been created, that sort of thing can kill a project. It may forever be just trying to keep up with the changing requirements, especially for projects where a lot of new technologies are involved, you may find that just to facilitate the new requirements you actually end up with an abomination worse than the original design or any derivative it might have had once the technologies and real world challenges was better known.

Thanks for that insightful analysis. I think the Skylon is a great design, and I definitely think it will work. Because these speculations of mine might be interpreted as criticisms of its feasibility I'll just leave it at that.

Bob Clark

Antice
2010-Sep-03, 07:30 AM
Newsflash. August news report just in (http://www.reactionengines.co.uk/news_aug10.html). No news to report except that they claim to have a treat for us in store for the next update, and that the first tube manufacturing unit is online at the heat exchanger factory. (now that was a bit of a downplay for what i would consider worthy of a better write up. but that's just me I guess)

/wild speculation

I am hoping that next month will feature the much anticipated D1 revision of the skylon. If it does it will definitely tickle my cerebral pleasure centers greatly. But It may not, so don't get our collective hopes up to much now ya hear :whistle:

/end speculation

Antice
2010-Sep-06, 07:13 PM
Skylon is getting some more press (http://www.theengineer.co.uk/in-depth/analysis/out-of-this-world/1004713.article). A pretty nice article overall.
Nothing we havent heard before, but it is worth repeating imho.

Garrison
2010-Sep-06, 07:37 PM
Skylon is getting some more press (http://www.theengineer.co.uk/in-depth/analysis/out-of-this-world/1004713.article). A pretty nice article overall.
Nothing we havent heard before, but it is worth repeating imho.

Point in the article that's worth picking out is that the science minister in the new Westminister government has said he isn't going to abandon good policies just because they were put in place by the previous administration. That's almost more radical than the Skylon. :)

Antice
2010-Sep-22, 07:44 AM
Even more skylon in the news. (http://www.bbc.co.uk/blogs/thereporters/jonathanamos/2010/09/it-is-one-of-those.shtml) The project is really gaining momentum now.
Cant wait to see the results from the skylon systems requirements review (http://www.ukspaceagency.bis.gov.uk/19661.aspx) hosted by UKSA.

I'd say this rates a :dance: and a :clap:

Antice
2010-Oct-05, 10:09 AM
The latest news update is in (http://www.reactionengines.co.uk/news_sept10.html).
there isn't much controversy in it. It's mostly about the skylon systems requirements review. The results of which we may get to see in the next update in a month or so. They are also starting the first financing round for obtaining the funds to push forward and start bending metal for the rest of skylon. :cool:

All in all it's good news I'd say. but not exactly what I was wishing for. (I really wanted to see the D1 updated configuration) :cry:

Garrison
2010-Oct-05, 10:26 AM
The latest news update is in (http://www.reactionengines.co.uk/news_sept10.html).
there isn't much controversy in it. It's mostly about the skylon systems requirements review. The results of which we may get to see in the next update in a month or so. They are also starting the first financing round for obtaining the funds to push forward and start bending metal for the rest of skylon. :cool:

All in all it's good news I'd say. but not exactly what I was wishing for. (I really wanted to see the D1 updated configuration) :cry:

I think they are saving that up for your Xmas present...:)

Damburger
2010-Oct-08, 02:36 PM
I do like Skylon, enough in fact to be quite wary that it seems too good to be true. Always bear in mind that when Reaction Engines talk about 2 week turn arounds, that is precisely what they were saying about the Space Shuttle in the 1970s. Many launcher projects have promised to give us airline-like access to space, and they've all running into crippling technical difficulties.

Also, unless it delivers prices that completely decimate the rest of the launch market and everyone and their dog puts their satellite in a Skylon, it runs the risk of being a remarkable piece of engineering with nothing to do. A recent video they did showed Skylon visiting the ISS - is it worth going to this much trouble to develop something that would only be used as a Soyuz replacement?

Garrison
2010-Oct-08, 05:05 PM
I do like Skylon, enough in fact to be quite wary that it seems too good to be true. Always bear in mind that when Reaction Engines talk about 2 week turn arounds, that is precisely what they were saying about the Space Shuttle in the 1970s. Many launcher projects have promised to give us airline-like access to space, and they've all running into crippling technical difficulties.

Well actually I would say that in many, if not most, cases the porblems were political not technical. The shuttle is a good example of this. It's worth looking up the original design ideas for the shuttle and comparing them to what was actually built; the differences are startling and mostly the product of budget cuts and politicians adding ever more requirements onto the STS. Skylon has avoided the grasp of the politicians to date, which is a big plus.


Also, unless it delivers prices that completely decimate the rest of the launch market and everyone and their dog puts their satellite in a Skylon, it runs the risk of being a remarkable piece of engineering with nothing to do. A recent video they did showed Skylon visiting the ISS - is it worth going to this much trouble to develop something that would only be used as a Soyuz replacement?

Well that's pretty much the point of the project, to drastically reduce the costs of space access. The video just shows one role that is envisioned for the Skylon, it's primary objective is the satellite launching market. Of course if it can open the way for people like Bigelow to get their plans off the ground then people moving could be big business. REL also has plans for an orbital tug that would transfer Satellites to higher orbits than the Skylon can reach directly.

NEOWatcher
2010-Oct-08, 05:37 PM
... in many, if not most...
While agreeing with that statement...
I think another issue was they never decided to use the shuttle to it's full capacity either.


A recent video they did showed Skylon visiting the ISS - is it worth going to this much trouble to develop something that would only be used as a Soyuz replacement?
Why would you think a video like that would indicate that kind of restriction? I'm not familiar with the video, but my suspicion is that it is meant for PR purposes. What better PR than to show something people can be impressed with? Satellites are boring, and other potential applications are out of their control.

Daggerstab
2010-Oct-08, 05:52 PM
Why would you think a video like that would indicate that kind of restriction? I'm not familiar with the video, but my suspicion is that it is meant for PR purposes. What better PR than to show something people can be impressed with? Satellites are boring, and other potential applications are out of their control.

It's the video for the Passenger & Logistics Module (http://www.reactionengines.co.uk/skylon_pax.html) (video at YouTube (http://www.youtube.com/watch?v=7BEdOM2W180)). They got BRIAN BLESSED! to narrate it. :)

I thinks it's more of an example destination. It may be also subtle advertising: "We can build the Skylon before they de-orbit the Station." Or, "It can do the same stuff the Shuttle did, only safer/cheaper, so please fund the development of the module."

Garrison
2010-Oct-08, 09:10 PM
While agreeing with that statement...
I think another issue was they never decided to use the shuttle to it's full capacity either.


True, the irony of insisting on building a vehicle designed to do everything, and then deciding they didn't want it to do those things after all. Fortunately the bulk of REL's funding still comes from the private sector, with a little help from governmental agencies like the ESA, so fingers crossed.

Damburger
2010-Oct-09, 10:09 AM
Why would you think a video like that would indicate that kind of restriction? I'm not familiar with the video, but my suspicion is that it is meant for PR purposes. What better PR than to show something people can be impressed with? Satellites are boring, and other potential applications are out of their control.

Because I assume they wish to promote their spacecraft, and if that is the best mission they envision for it then it indicates a worrying lack of purpose. Personally, I wouldn't build a Skylon to visit the ISS, I would build a Skylon to visit Space Station V.

Antice
2010-Oct-09, 12:07 PM
Because I assume they wish to promote their spacecraft, and if that is the best mission they envision for it then it indicates a worrying lack of purpose. Personally, I wouldn't build a Skylon to visit the ISS, I would build a Skylon to visit Space Station V.

This is just one of several promotional videos of skylon. why get so hung up on the ISS being used in this one? The other vids don't even use it. the skylon mission animation show a satelite deployment and a trip to the envisioned Orbital Base Station used in the Troy mission study.

TrAI
2010-Oct-11, 12:42 AM
Because I assume they wish to promote their spacecraft, and if that is the best mission they envision for it then it indicates a worrying lack of purpose. Personally, I wouldn't build a Skylon to visit the ISS, I would build a Skylon to visit Space Station V.

Hmmm... On what basis do you conclude this video shows the definitive best mission? The Skylon mission animation (http://www.youtube.com/watch?v=3bkjiGGy0gc) shows the Skylon placing a satelite into orbit, and delivering a passenger module to the Orbital Base Station, in the Troy Mars Mission video (http://www.youtube.com/watch?v=Uj45Au3KCRg) it is described how the Skylon would transport the Troy modules to the Orbital Base Station for assembly, and how the PLM would be used for ferrying crew to the Troy space craft. Why are these, to your mind, not showing any alternative purpose for the Skylon than to visit the ISS?

Actually, it is probably a good idea to show that you can use the Skylon to support existing infrastructure. The ISS may be considered something of a money sink without a future by many people that are interested in space topics, but in most people's minds I suspect it is The Space Station, the only real destination for people in space that isn't some science fiction thing, it may be easy to dismiss this as just another of a long line of fictional space ships with even more fictional destinations, showing some uses that is a bit more tangible, like launching satellites or going to the ISS may help get a bit more support. After all REL is not like a space agency, they will have to convince a wider segment of the population to get support.

danscope
2010-Oct-11, 01:34 AM
Your link to " The Space Station " does not function. Hmmm......

ravens_cry
2010-Oct-11, 04:37 AM
Well, I must say this is a very ambitious undertaking and I wish it all the best.

TrAI
2010-Oct-11, 08:53 AM
Your link to " The Space Station " does not function. Hmmm......

Probably because it isn't a link at all, it is underlined text :)

Damburger
2010-Oct-11, 12:13 PM
I picked the ISS mission because, unlike the Troy Mars Mission (which seems a bit BSG to me, but thats another story) its a real mission that Skylon would have right from the start. As for satellite launch - the low price they promise looks to be based on a fast turnaround which itself is only useful if you've got a substantial increase in the demand for satellites - so again, the need is for a mission worthy of the design.

As I said above, I am excited by the Skylon idea, but I also have in my possession a book written in the late 1970s promising basically the same stuff from the Space Shuttle. I'm just trying to moderate excitement with a little realism (pessimism?)

danscope
2010-Oct-11, 04:57 PM
Did you have a particular concept in mind for "The Space Station " ?

Antice
2010-Oct-11, 05:01 PM
I picked the ISS mission because, unlike the Troy Mars Mission (which seems a bit BSG to me, but thats another story) its a real mission that Skylon would have right from the start. As for satellite launch - the low price they promise looks to be based on a fast turnaround which itself is only useful if you've got a substantial increase in the demand for satellites - so again, the need is for a mission worthy of the design.

As I said above, I am excited by the Skylon idea, but I also have in my possession a book written in the late 1970s promising basically the same stuff from the Space Shuttle. I'm just trying to moderate excitement with a little realism (pessimism?)

Your idea that skylon needs a higher launch rate to make launches cheaper is false.
The worst case estimate presented for launch prising by REL is based on the assumption that the market is totally unchanged.
The price per launch in this scenario is 40 mill. so still cheaper than anything else out there on a per kg cost basis.

Then there is the added value of having on orbit checkout capability as well as earth return capability in case the satelite does not pass all it's comissioning tests on orbit. In fact 40 mill is almost cheap enough to make it viable to go fetch a satelite that has failed on orbit and return it home for repairs and relaunch. a big telecom sat can easily cost a bill$ or more depending on the capabilities of the satelite in question. No other vehicle sans the shuttle has ever been able to offer such a service. and the shuttle no longer offers it due to safety issues unique to the shuttle.
The skylon vehicle has a market able to sustain it. the biggest unknowns at this time is if it can be delivered on schedule and on target cost wise.

danscope
2010-Oct-11, 05:11 PM
We know little about the skylon motors peformance and especially durability and in particular it's material condition after re-entry . And when you talk about a mars mission(?) what about the motor's ability to re-start for Earth return? None of these questions have solid answers.
Good wishes, yes.

Garrison
2010-Oct-11, 05:32 PM
We know little about the skylon motors peformance and especially durability and in particular it's material condition after re-entry . And when you talk about a mars mission(?) what about the motor's ability to re-start for Earth return? None of these questions have solid answers.
Good wishes, yes.

The Skylon wouldn't actually be part of the Mars mission per se, it would simply launch the components of the mission vehicles. More details here:

Troy (http://www.reactionengines.co.uk/troy.html)

And again it's more of an illustration of what the Skylon might make possible at this point, which is important for generating interest and funding.

Antice
2010-Oct-11, 09:37 PM
While i like the skylon concept a lot. I'm not overly fond of the Troy concept.
First of all it's using chemical propulsion. with the timeframes involved we can easily manage to get a SEP or NEP vehicle developed in time for a post 2030 launch window for mars.

I suspect they used Troy more as a sanity check for weither Skylon could be useful for more than satelite launches than a serious mars mission architectural proposal. This makes it somewhat of a cludge that is more designed to showcase what skylon can do rather than trying for a truly workable mars mission scenario. Troy sort of tosses in a lot of stuff that is probably not really needed, but are what one would call nice to haves. like having a full enclosure on the orbital assembly facility. Not to mention sending a grand total of 3 missions to mars in the same launch window. I'd say that Troy is a tad excessive in that regard. :whistle:

TrAI
2010-Oct-25, 02:28 AM
While i like the skylon concept a lot. I'm not overly fond of the Troy concept.
First of all it's using chemical propulsion. with the timeframes involved we can easily manage to get a SEP or NEP vehicle developed in time for a post 2030 launch window for mars.

I suspect they used Troy more as a sanity check for weither Skylon could be useful for more than satelite launches than a serious mars mission architectural proposal. This makes it somewhat of a cludge that is more designed to showcase what skylon can do rather than trying for a truly workable mars mission scenario. Troy sort of tosses in a lot of stuff that is probably not really needed, but are what one would call nice to haves. like having a full enclosure on the orbital assembly facility. Not to mention sending a grand total of 3 missions to mars in the same launch window. I'd say that Troy is a tad excessive in that regard. :whistle:

Hmmm... Actually, it seems more like REL have tried to make a modular system, the Orbital Base Stations, for instance, would not be made for the Troy mission, and then abandoned, they would already be in place by the time a Mars mission was started, as when the Skylons are operational multi-module launches would be much more feasible than at present, and so orbital assembly would be much more common. It is hard to predict how the market would work, probably either you would buy launch and assembly separately, or as a package deal, the latter would probably be the most common, as I suspect that large operators that have their own OBS would not want to carry your stuff to a competing OBS(The things are quite an investment, after all, so they would want to have business), at least not unless you payed extra, and it may be that an OBS would not accept your modules unless they come in a Skylon. The enclosed design seems to be chosen because it affords protection for whatever is inside from micrometeorites and debris, and it prevents lost objects from floating of, something that may very well become an issue with orbital assembly where you may have to handle things like pins, bolts, nuts, small tools and what not, it may become rather common to loose stuff, so a way to contain it is very desirable. Of course, for a single mission you wouldn't need to worry much about these things, but as the Skylon is designed to make it easier and cheaper to get to space, it may become a much larger issue, it may even become required by law for such structures to be enclosed.

The choice of a chemical propulsion is probably because the mission is designed to use as little unavailable technology as possible, but as the setup is modular, there is no reason why the engine modules may not be exchanged with some other technology if it is available.

As for the three missions, I think that they did the study with this because it provides redundancy and a good coverage of Mars, with 3 bases placed at 1/3 circumference distance from each other, they estimate that you could travel to over 90% of the surface of the planet using the surface vehicles. The bases wold be relatively isolated from each other, though the ferry craft can do an suborbital hop to carry people between the bases if needed. This would be useful in an emergency, of course, but I also would think that this allows you to move personel with special qualifications if some situation arises where you would have use for them at some other base, like if some discovery of a significant scientific value was made, you may want to concentrate scientists with the expertise in that field at one base. Of course, I expect that you would want to do this only in special situations, as even though the fuel generators would extract fuel for your ferry craft, I would think there is a limit on how much fuel could be extracted within a specific time

CJSF
2011-Apr-18, 08:35 PM
This was on Space.com this morning. Hope things stay on track. I hadn't realized how HUGE Skylon is proposed to be.

http://www.space.com/11414-skylon-space-plane-british-engine-test.html

CJSF

Garrison
2011-Apr-18, 09:06 PM
This was on Space.com this morning. Hope things stay on track. I hadn't realized how HUGE Skylon is proposed to be.

http://www.space.com/11414-skylon-space-plane-british-engine-test.html

CJSF

Interesting article, I have my fingers crossed for June. My attention was really caught by this:


Private funding is lined up to see it through all stages of development, culminating with the start of commercial operations in 2020. That funding, however, is contingent on Skylon hitting some key milestones along the way, and a big one looms just a few months off.

If accurate it suggests backers with very deep pockets.

publiusr
2011-Apr-18, 11:12 PM
I just hope all this sub-orbital nonsense doesn't drain Branson. Did he and Bond ever have a falling out? I would have thought that Sir Richard would want to help his mates...

Antice
2011-Apr-19, 01:00 AM
skylons financial backers are all being very quiet about their involvement and who they are. they have been there for a long time now. supplying a good 80% of REL's cashflow for developing the preecooler system.
Somebody paid for the preecooler factory they built. and somebody paid for all those long years of preecooler development. and it wasn't any government organization that did it. the money from ESA was only 20% of what REL claims it cost to develop this technology. I do suspect that some very bright people have been working a lot of unpaid overtime to achieve what they got so far.

I'm very much looking forward to seeing the public preecooler/viper engine test. and the release of the design requirements review documents. they should become available for download at around the end of this month.

Frodz
2011-Apr-19, 02:17 AM
Interesting article, I have my fingers crossed for June. My attention was really caught by this:


Private funding is lined up to see it through all stages of development, culminating with the start of commercial operations in 2020. That funding, however, is contingent on Skylon hitting some key milestones along the way, and a big one looms just a few months off.

If accurate it suggests backers with very deep pockets.

Not only that, it goes on to say;


If the precooler works, investors will chip in another $350 million, helping take the Skylon project to another level of development. That next phase would likely see vehicle design completion and a full engine demonstration by 2014, Longstaff said.

That's a pretty serious amount of commited investment for just full scale tech demonstrators, which is still just an early stage in the development of the commercial vehicle, they've obviously managed to convince the right people. Now they'd better get this test right!

Exciting times.

Craigboy
2011-Apr-19, 03:27 AM
This was on Space.com this morning. Hope things stay on track. I hadn't realized how HUGE Skylon is proposed to be.

http://www.space.com/11414-skylon-space-plane-british-engine-test.html

CJSF
And how small its payload is.

Noclevername
2011-Apr-19, 03:42 AM
And how small its payload is.

If it's truly reuseable with anything like the proposed two-day turnaround, or even two weeks, it'll still come off better than the Shuttle in terms of both overall load per year, and cost.

Not that I think it'll work anything like advertised. I've heard all this before, and I will hear all this again.

Antice
2011-Apr-19, 04:01 PM
And how small its payload is.

humm... for a SSTO skylons payload to takeoff mass ratio is actually huge.

let's compare it to spacex F9. since the masses of this one is so readily available.

F9 mass at launch = 333 400kg (it's got a fairly small volume tho. but that is due to greater propellant density and matters little, mass is what matters in the launch business)
F9 payload to LEO. (unspecified altitude) = 10 450kg
10 450 / 333 400 = 0,031, or about 3% of the initial mass on the pad.

skylon mass (C1 config) = 345 000kg
skylon payload (C1 config) = 13 000 @ 400km 0deg inclination.
13 000 / 345 000 = 0,0376 or about 3,5% of the mass at the start of the runway.

That is a payload ratio that is better than F9. so say again. do you still think that the payload is too little/the vehicle too large? BTW. all LH2 based rockets tend to be on the voluminous side as well. it's all because LH2 has such low density.

Antice
2011-Apr-19, 04:25 PM
If it's truly reuseable with anything like the proposed two-day turnaround, or even two weeks, it'll still come off better than the Shuttle in terms of both overall load per year, and cost.

Not that I think it'll work anything like advertised. I've heard all this before, and I will hear all this again.

There wont be enough payloads to utilize that kind of turnaround times for many years after skylon enters service. these birds will be on the ground waiting for customers most of the time at first. turnaround times are going to be strongly affected by the ground crew experience as it is with most flying vehicles of any kind. however. having an all reusable TPS of the kind skylon is going to get does eliminate a lot of the headache that came with the shuttle. I'm not all that well versed in shuttle history but weren't all metallic TPS one of the things they originally wanted before all the horse trading and feature creep set in and ruined the original design?

What i do know for certain is that overall vehicle density does have a strong effect on how much abuse the TPS has to endure, and therefore it also has as strong effect on TPS re-usability. if it needs repairs between every flight then it fails the re-usability criterion. this is one of the flaws that got traded into the shuttle. as features and requirements went up vehicle density also went up and a truly reusable TPS became impossible to employ. the shuttle TPS is refurbish-able, and not truly re-usable. (each tile may be reused several times. but the TPS system as a whole needs repairs between each flight due to the amount of damage it sustains during both launch and re-entry)
The same is unfortunately true for the SME's. in order to gain enough performance to reach orbit they had to design the engines to work on the fine edge of the possible. that makes them hangar queens on maintenance. not a deal killer by itself tho since engines swaps can be done in less than a week if needed.
making rocket engines capable of hundreds of hours of operation is not hard. but the engines then tend to be much heavier compared to their performance then. reliability is bought with bigger margins. bigger margins = more mass. it's all a tradeoff. getting rid of vertical launch eliminates a lot of the performance requirements on the engines. T/W ratio becomes less of an issue and engine mass may grow to allow better reliability and a longer work-life between service stops.

I think skylon can pull it off. as long as they do not allow any feature creep but keep ruthlessly to making everything as reliable as possible without trying for max payload capability per kg on the ground.
Full re-usability is worth a ton more than a few extra kg of payload.

Damburger
2011-Apr-19, 04:41 PM
And how small its payload is.

Skylon's payload bay is pretty large. Its payload mass limit isn't as high as some operating vehicles, but the payload bay is a decent size. Its 13m long, compared to 11.4m for Falcon 9, is 10cm wider, and critically isn't forced to taper due to aerodynamics - so you can use the full width all the way along the length.

Mass isn't everything. Sometimes you need volume, and in almost all cases you can use additional volume because it means you don't have to fold up stuff like solar panels and booms as tightly, reducing mechanical complexity.

Craigboy
2011-Apr-19, 04:43 PM
If it's truly reuseable with anything like the proposed two-day turnaround, or even two weeks, it'll still come off better than the Shuttle in terms of both overall load per year, and cost.

The Shuttle isn't hard to beat when it comes to cost, what its really going to be going agianst is Soyuz, Delta IV, Falcon 9, and the Atlas V.


humm... for a SSTO skylons payload to takeoff mass ratio is actually huge.

I don't care about the ratio. Its a $15 billion dollar launch system that can only carry 10 kg into LEO. And last time I checked the 130,000 kg Space Launch System (NASA's HLV) is only funded at $11.5 billion.

Source: http://ww.space.com/11414-skylon-space-plane-british-engine-test.html


Skylon's payload bay is pretty large. Its payload mass limit isn't as high as some operating vehicles, but the payload bay is a decent size. Its 13m long, compared to 11.4m for Falcon 9, is 10cm wider, and critically isn't forced to taper due to aerodynamics - so you can use the full width all the way along the length.

Mass isn't everything. Sometimes you need volume, and in almost all cases you can use additional volume because it means you don't have to fold up stuff like solar panels and booms as tightly, reducing mechanical complexity.
SpaceX and Lockheed both offer custom payload fairings. From the Atlas V Launch Services User's Guide they have written "Should a customer have a unique requirement to accommodate a larger payload, longer and wider payload fairings can be developed. Payload fairings as large as 7.2m (283 in.) in diameter and up to 32.3m (106 ft) in length have been considered."

Source1:http://www.spacex.com/falcon9.php
Source2:http://www.lockheedmartin.com/data/assets/ssc/cls/AVUG_Rev11_March2010.pdf

Damburger
2011-Apr-19, 05:38 PM
If it's truly reuseable with anything like the proposed two-day turnaround, or even two weeks, it'll still come off better than the Shuttle in terms of both overall load per year, and cost.

The Shuttle isn't hard to beat when it comes to cost, what its really going to be going agianst is Soyuz, Delta IV, Falcon 9, and the Atlas V.

Competition with Soyuz - really? 3 highly trained cosmonauts in a very confined space, versus *30* relatively untrained passengers with as much space as they would have in a commercial airliner? http://www.reactionengines.co.uk/skylon_pax.html

Don't get me wrong - Soyuz is a reliable and economical way of transporting cosmonauts. However, it is not and never will be a true commercial vehicle due to the stringent requirements on travelers. A system that has been known to throw up 8g eyeballs-out reentries can't be offered to the general public. Even if Soyuz remains cheaper per person, its a cosmonaut transportation system, not a people transportation system, so its not in competition with any eventual manned Skylon flights.

I really can't see it being difficult for it to undercut Falcon 9, Atlas V, and Delta IV. These are all fairly conventional launch systems with the inherent high costs.

Damburger
2011-Apr-19, 05:41 PM
I don't care about the ratio. Its a $15 billion dollar launch system that can only carry 10 kg into LEO. And last time I checked the 130,000 kg Space Launch System (NASA's HLV) is only funded at $11.5 billion.

Source: http://ww.space.com/11414-skylon-space-plane-british-engine-test.html

10kg? It can lift a little more than that...



SpaceX and Lockheed both offer custom payload fairings. From the Atlas V Launch Services User's Guide they have written "Should a customer have a unique requirement to accommodate a larger payload, longer and wider payload fairings can be developed. Payload fairings as large as 7.2m (283 in.) in diameter and up to 32.3m (106 ft) in length have been considered."

Source1:http://www.spacex.com/falcon9.php
Source2:http://www.lockheedmartin.com/data/assets/ssc/cls/AVUG_Rev11_March2010.pdf

Saying they can develop a custom payload for your needs is not offering one.

Garrison
2011-Apr-19, 06:11 PM
I don't care about the ratio. Its a $15 billion dollar launch system that can only carry 10 kg into LEO. And last time I checked the 130,000 kg Space Launch System (NASA's HLV) is only funded at $11.5 billion.

Source: http://ww.space.com/11414-skylon-space-plane-british-engine-test.html



The Skylon is projected to lift 12,000kg, so where you got 10kg from I don't know. That's in the same range as the EELVs. Also you comparison is not really like with like. Skyon is new technology pushing the boundaries, the SLS is a bunch of rearranged shuttle parts, it really should be a lot cheaper to develop. Also you've missed out cost per launch and number of launches per annum from your consideration, oh and of course your figure for the SLS is for the initial 70 tonne version, they haven't costed the upgrade to 130 tonnes yet.

Craigboy
2011-Apr-19, 08:22 PM
Competition with Soyuz - really? 3 highly trained cosmonauts in a very confined space, versus *30* relatively untrained passengers with as much space as they would have in a commercial airliner? http://www.reactionengines.co.uk/skylon_pax.html

Don't get me wrong - Soyuz is a reliable and economical way of transporting cosmonauts. However, it is not and never will be a true commercial vehicle due to the stringent requirements on travelers. A system that has been known to throw up 8g eyeballs-out reentries can't be offered to the general public. Even if Soyuz remains cheaper per person, its a cosmonaut transportation system, not a people transportation system, so its not in competition with any eventual manned Skylon flights.

I was referring to the Soyuz rocket and I wasn't referring to crew transportation which if Skylon is developed will most likely never incorporate.

http://en.wikipedia.org/wiki/Soyuz-FG


Saying they can develop a custom payload for your needs is not offering one.
Yes it is.


The Skylon is projected to lift 12,000kg, so where you got 10kg from I don't know.
I got it from the link listed as "source".

Garrison
2011-Apr-19, 08:47 PM
I got it from the link listed as "source".

You only provided one link on Skylon, the one about the engine test and this is a quote from that:



The space plane is expected to have a payload capacity of about 11.3 tons (10,275 kg), though Longstaff said future designs aim to boost that to 16.5 tons (15,000 kg).

So still not sure where you got 10kg from but do you accept that figure was just plain wrong?

Damburger
2011-Apr-19, 08:51 PM
I was referring to the Soyuz rocket and I wasn't referring to crew transportation which if Skylon is developed will most likely never incorporate.

http://en.wikipedia.org/wiki/Soyuz-FG


If it achieves even 10% of the economy that REL promise, it will be competitive with Soyuz-FG. Also, what basis do you have for suggesting the passenger carrying version will never happen?



Yes it is.

Except for the miniscule detail of having to pay money to develop a new payload fairing?



I got it from the link listed as "source".

The source says 11.3 tons (10,275kg) - even if you read the comma as a decimal point the fact that its also given in (imperial) tons should trigger some alarm bells surely? You thought a group of experienced engineers, taken seriously enough to be funded by ESA, were building an 84m long, 270 tonne nanosatellite launcher?

Craigboy
2011-Apr-19, 08:52 PM
You only provided one link on Skylon, the one about the engine test and this is a quote from that:



So still not sure where you got 10kg from but do you accept that figure was just plain wrong?
I think about now its pretty obvious I meant 10,000 kg.

Garrison
2011-Apr-19, 08:59 PM
I think about now its pretty obvious I meant 10,000 kg.

But that contradicts with you last post where you said you got 10kg from a link, so what you really mean is you misread the figure and made a misguided comment based on it?

Craigboy
2011-Apr-19, 09:06 PM
But that contradicts with you last post where you said you got 10kg from a link, so what you really mean is you misread the figure and made a misguided comment based on it?
No it means I thought 10,000 kg but wrote 10 kg.

Craigboy
2011-Apr-19, 09:16 PM
If it achieves even 10% of the economy that REL promise, it will be competitive with Soyuz-FG. Also, what basis do you have for suggesting the passenger carrying version will never happen?

With the Space Shuttle it was proposed to add a crew pod in the Shuttle bay (I'm still trying to find the link) but that didn't go anywhere in part because they didn't need 30 or so people in orbit.

Even if they achieve the 40 million per launch number (which may be a few years old) its just not very good in comparison with SpaceX. Who developed a system for under 1 billion and has a 60 million per flight cost and that's without the re-usability of the first stage. With that kind of competition its going to be very hard for Reaction Engines to earn back that 15 billion investment.


Except for the miniscule detail of having to pay money to develop a new payload fairing?

My point is if somehow payload volume is Skylon's greatest advantage it would be easier, cheaper and more cost effective to order a custom payload instead of investing $15 Billion on a new transportation system.



The source says 11.3 tons (10,275kg) - even if you read the comma as a decimal point the fact that its also given in (imperial) tons should trigger some alarm bells surely? You thought a group of experienced engineers, taken seriously enough to be funded by ESA, were building an 84m long, 270 tonne nanosatellite launcher?
I meant 10,000 kg, that's why I compared it to the Soyuz (7,800 kg), Delta IV (8,600-22,560 kg), Falcon 9 (10,450 kg) and Atlas V (9,797 kg-29,420 kg).

Garrison
2011-Apr-19, 09:31 PM
With the Space Shuttle it was proposed to add a crew pod in the Shuttle bay (I'm still trying to find the link) but that didn't go anywhere in part because they didn't need 30 or so people in orbit.

So there wasn't a need in the past so there won't be one in the future? Bigelow will be disappointed to hear they are wasting their time.



My point is if somehow payload volume is Skylon's greatest advantage it would be easier, cheaper and more cost effective to order a custom payload instead of investing $15 Billion on a new transportation system.

Who claimed that it's volume was its 'greatest advantage'? It is an advantage that's not the sole reason for creating the Skylon, and you have offered up no figures that would back up the assertion that custom payload would be more cost effective.



I meant 10,000 kg, that's why I compared it to the Soyuz (7,800 kg), Delta IV (8,600-22,560 kg), Falcon 9 (10,450 kg) and Atlas V (9,797 kg-29,420 kg).

Then your 'so little' comment earlier makes no sense since Skylon's lifting capacity is in the same range as it's competitors.

Craigboy
2011-Apr-19, 09:45 PM
So there wasn't a need in the past so there won't be one in the future? Bigelow will be disappointed to hear they are wasting their time.

Neither Alpha nor Beta can hold that many people.


Who claimed that it's volume was its 'greatest advantage'? It is an advantage that's not the sole reason for creating the Skylon, and you have offered up no figures that would back up the assertion that custom payload would be more cost effective.
That was Damburger's entire post. I guarantee you a custom fairing doesn't cost more than $5 billion.


Then your 'so little' comment earlier makes no sense since Skylon's lifting capacity is in the same range as it's competitors.
My point was that for the amount of money you're investing you're not getting that large of a payload.

Damburger
2011-Apr-19, 09:46 PM
With the Space Shuttle it was proposed to add a crew pod in the Shuttle bay (I'm still trying to find the link) but that didn't go anywhere in part because they didn't need 30 or so people in orbit.

Even if they achieve the 40 million per launch number (which may be a few years old) its just not very good in comparison with SpaceX. Who developed a system for under 1 billion and has a 60 million per flight cost and that's without the re-usability of the first stage. With that kind of competition its going to be very hard for Reaction Engines to earn back that 15 billion investment.

So.... $60 million for 10 tonnes for Falcon 9 versus $40 million for 12 tonnes for Skylon, and you don't know how it will compete? Where did you learn economics?

Also... $60 million per flight for 7 crew (with stringent medical requirements) against $40 million for 30 people whose experience will not go outside the G-forces permitted for the more hardcore end of fairground rides (albeit for longer periods).



My point is if somehow payload volume is Skylon's greatest advantage it would be easier, cheaper and more cost effective to order a custom payload instead of investing $15 Billion on a new transportation system.

It isn't the only advantage...



I meant 10,000 kg, that's why I compared it to the Soyuz (7,800 kg), Delta IV (8,600-22,560 kg), Falcon 9 (10,450 kg) and Atlas V (9,797 kg-29,420 kg).

...nor is the payload mass.

Garrison
2011-Apr-19, 09:56 PM
Neither Alpha nor Beta can hold that many people.

And you think that's the limits of Bigelow's ambitions?



That was Damburger's entire post. I guarantee you a custom fairing doesn't cost more than $5 billion.

But neither he nor anyone else used the phrase 'greatest advantage' did they? So you were essentially setting up a strawman argument.



My point was that for the amount of money you're investing you're not getting that large of a payload.

Which apart from a specious comparison to the SLS you have provided no evidence for. It's cost per kilo that defines whether its worth operating or not.

Craigboy
2011-Apr-19, 09:58 PM
So.... $60 million for 10 tonnes for Falcon 9 versus $40 million for 12 tonnes for Skylon, and you don't know how it will compete? Where did you learn economics?

Also... $60 million per flight for 7 crew (with stringent medical requirements) against $40 million for 30 people whose experience will not go outside the G-forces permitted for the more hardcore end of fairground rides (albeit for longer periods).
$40 million is an estimated cost, SpaceX's estimated cost for the Falcon 9 was $27 million per flight, Skylon will not fly for $40 million. But what's really frustrating me is that you people seem to think $15 billion is a small number. Even if there were no costs associated with each flight and 40 million was pure profit to Reaction Engines it would take 375 flights just to break even.



...nor is the payload mass.
It was the mass listed in the article.

Garrison
2011-Apr-19, 10:06 PM
$40 million is an estimated cost, SpaceX's estimated cost for the Falcon 9 was $27 million per flight, Skylon will not fly for $40 million. But what's really frustrating me is that you people seem to think $15 billion is a small number. Even if there were no costs associated with each flight and 40 million was pure profit to Reaction Engines it would take 375 flights just to break even.

Again you seem to be missing some important points about Skylon. REL and its backers would be looking to make their money back selling vehicles, not running flights themselves. Spread the costs across a number of vehicles capable of around 200 flights each over a number of years and the numbers add up. Sure it might fall short but no one will know unless they try.

Craigboy
2011-Apr-19, 10:14 PM
And you think that's the limits of Bigelow's ambitions?
Its starting to sound like Skylon will be flying to Space Station Fairy Land no matter what any detractors say.


But neither he nor anyone else used the phrase 'greatest advantage' did they? So you were essentially setting up a strawman argument.
When I said the payload was small, he said but its voluminous. I responded that EELVs can carry even larger volumes. Don't turn it into something malicious.



Which apart from a specious comparison to the SLS you have provided no evidence for. It's cost per kilo that defines whether its worth operating or not.
I'm really getting tired of this. Do you honestly believe that the EELVs development costs was about the same as Skylon's? It can't achieve a 40 million per launch and turn a profit.

Craigboy
2011-Apr-19, 10:15 PM
Sure it might fall short but no one will know unless they try.
We already have.

Garrison
2011-Apr-19, 10:21 PM
We already have.

Really? When? And please don't mention the shuttle, we are discussing a HOTOL SSTO here, not a partially reusable 1.5 stage vertical launcher.

kamaz
2011-Apr-19, 11:11 PM
Again you seem to be missing some important points about Skylon. REL and its backers would be looking to make their money back selling vehicles, not running flights themselves. Spread the costs across a number of vehicles capable of around 200 flights each over a number of years and the numbers add up. Sure it might fall short but no one will know unless they try.

It all depends how much it costs to make one. I'm going to guess $1B. So if REL sells them at $5B each, they need to sell 4 of them to recoup costs and produce profit. (Actually more income would be needed because of the capital cost, but I am too lazy to account for that).

The operator pays $5B for a vehicle, it will want to recoup that within no more than 3 years (I guess vehicle lifetime to be 5 years). If the craft can do 100 flights per year, that means 300 flights. So the vehicle amortization cost is $16.6M per flight. On the other hand, if the craft can do 10 flights per year then the vehicle amortization cost is $166M per flight.

If the payload is 10 tons and flight cost is $40M, then operator has to charge $56.6M per flight ($5'660/kg) at 100 flights per year. At 10 flights per year, it has to charge $206M per flight ($20'600/kg). The latter is more expensive than an ELV ($10'000/kg). In order to be cheaper than that, the each vehicle must do at least 28 flights per year.

However. 4 vehicles each doing 100 flights per year means 400 flight per year, each with 10 t payload, or 4'000 tons of stuff delivered to LEO per year (at $5.6K/kg). Here's the problem: to be cheap, Skylon must have a high flight rate. But even if it manages to do so technically, there is not enough demand for cargo to LEO.

If you want to ferry people, then you have $56.6M per 30 seats or $1.8M per seat. That means 3'000 passengers per year per vehicle or 12'000 passengers per year in total. Can you find 12'000 people willing to pay $1.8M for a 0g vacation each year?

Antice
2011-Apr-20, 04:11 AM
It all depends how much it costs to make one. I'm going to guess $1B. So if REL sells them at $5B each, they need to sell 4 of them to recoup costs and produce profit. (Actually more income would be needed because of the capital cost, but I am too lazy to account for that).

The operator pays $5B for a vehicle, it will want to recoup that within no more than 3 years (I guess vehicle lifetime to be 5 years). If the craft can do 100 flights per year, that means 300 flights. So the vehicle amortization cost is $16.6M per flight. On the other hand, if the craft can do 10 flights per year then the vehicle amortization cost is $166M per flight.

If the payload is 10 tons and flight cost is $40M, then operator has to charge $56.6M per flight ($5'660/kg) at 100 flights per year. At 10 flights per year, it has to charge $206M per flight ($20'600/kg). The latter is more expensive than an ELV ($10'000/kg). In order to be cheaper than that, the each vehicle must do at least 28 flights per year.

However. 4 vehicles each doing 100 flights per year means 400 flight per year, each with 10 t payload, or 4'000 tons of stuff delivered to LEO per year (at $5.6K/kg). Here's the problem: to be cheap, Skylon must have a high flight rate. But even if it manages to do so technically, there is not enough demand for cargo to LEO.

If you want to ferry people, then you have $56.6M per 30 seats or $1.8M per seat. That means 3'000 passengers per year per vehicle or 12'000 passengers per year in total. Can you find 12'000 people willing to pay $1.8M for a 0g vacation each year?

this is another of your strawmen.
vehicles don't have a use by date. Rel's figure of 40 mill was based on a 0 growth scenario where there were no passenger capability added to the mix.
also. if you had actually read the paper on the SPLM on Rel's site you would have known that 30 passengers was a long range goal. the initial SPLM would have ejector seats and only 5 people. it would also carry 3 000kg of supplies. it's baseline design is for supporting the ISS or a biggelow or even a chinese station.

skylon offers not a single killer advantage, but rather a long list of minor ones and a couple of major ones that generally counts towards some of the more special scenarios.
turnaround times are only truly relevant if something like project troy or solar power satelites are going to be built. in this scenario each flight cost drops to around 2 mill. that is far lower than eelv's can ever theoretically achieve.
skylon may offer transport of up to 30 passengers. only truly relevant under a space travel becomes routine scenario. (orbital tourism and large space stations.)
Skylon is the only vehicle that offers on orbit deployment checkout and return on fault capability. Very valuable in the current satellite market. and is going to be an early deal closer for buying skylon flights rather than eelv's.
Skylon offers shuttle like on orbit operations. like space station assembly support. it can do this by having one skylon meet another skylon on orbit to assemble the first 2 components between them then have a third flight deliver a robotic crane that will then continue to assemble the station as well as unloading the remainder of the needed skylon flights during the assembly process. (assumed ISS like assembly sequence with a human presence since the fourth flight and onwards)

Craigboy
2011-Apr-20, 05:14 AM
this is another of your strawmen.
vehicles don't have a use by date. Rel's figure of 40 mill was based on a 0 growth scenario where there were no passenger capability added to the mix.
also. if you had actually read the paper on the SPLM on Rel's site you would have known that 30 passengers was a long range goal. the initial SPLM would have ejector seats and only 5 people. it would also carry 3 000kg of supplies. it's baseline design is for supporting the ISS or a biggelow or even a chinese station.

skylon offers not a single killer advantage, but rather a long list of minor ones and a couple of major ones that generally counts towards some of the more special scenarios.
turnaround times are only truly relevant if something like project troy or solar power satelites are going to be built. in this scenario each flight cost drops to around 2 mill. that is far lower than eelv's can ever theoretically achieve.
skylon may offer transport of up to 30 passengers. only truly relevant under a space travel becomes routine scenario. (orbital tourism and large space stations.)
Skylon is the only vehicle that offers on orbit deployment checkout and return on fault capability. Very valuable in the current satellite market. and is going to be an early deal closer for buying skylon flights rather than eelv's.
Skylon offers shuttle like on orbit operations. like space station assembly support. it can do this by having one skylon meet another skylon on orbit to assemble the first 2 components between them then have a third flight deliver a robotic crane that will then continue to assemble the station as well as unloading the remainder of the needed skylon flights during the assembly process. (assumed ISS like assembly sequence with a human presence since the fourth flight and onwards)
The term strawman is being used incorrectly. Skylon is unmanned (at least without a crew pod in the bay). The reason why he was talking about crew transportation was because Damburger and Garrison were going on about it.

The ISS has Progress, ATV, HTV and will soon have Cygnus and Dragon. China has the ingeniously developed Shenzhou for the Mir-class three man spacestation. Bigelow plans to launch in 2015 (or at least that's the current plan) but before he does he's going to make sure he has two providers. On the spacestation side of things there's no need that Skylon would fill.

Skylon will never fly for 2 million. As far as I know returning a satelite from orbit isn't really being demanded, in fact I believe the only Space Shuttle mission they ever did it was STS-51-A. The payload is kind of small for space station assembly.

Antice
2011-Apr-20, 06:43 AM
taking arguments out of context IS the definition of a strawman. using the 40 mill per flight figure from a 0 growth no passenger flights scenario and using it to show that skylon is too expensive as a crew ferry is on par with saying that carrying passengers is the only use for skylon. it is not. it's a possible mission rate growth item. if there ever is a need for 30 passengers at a time then the flight rate would necessarily have risen to the point where the price has dropped to at least 10 mill per launch or lower. just building a destination for 30 people at a time will have such an effect. As for station building capability. do not conflate current domestic capability with future desired capability. It would cost the chinese on par with the development costs of the entire skylon programme to match it's capabilities. the chinese are smart enough to realize that just buying a vehicle and operating that one is cheaper and faster than designing their own. the Chinese are just one such potential buyer. there are others who also wants their own space programs on the cheap.
The market for skylon is there. once the shuttle dies then skylon is the only thing matching it's capabilities. except it's going to be much cheaper/safer to run thanks to being uncrewed unless crew is part of the cargo. there is according to satellite owners a desire for a having return to earth capability on launchers. primary reason is to return to earth any satellite that does not check out on deployment. this is a capability that they are not allowed to buy from the shuttle due to safety related decisions. Risking the lives of crew for launching satellites was a bad idea. altho i wont fault the shuttle designers on that one. they didn't have the computer technology we have now and could hardly avoid needing a crew from something as complex as the STS.

Return to earth capability is valuable. the extra launch cost is more than offset by the reduced risk of loosing a multi billion dollar investment like a major telecom satellite.


as a finishing paragrap i am going to compare SpaceX official launch cost figures with those claimed by REL

Falcon 9. single cargo cost fetched from their website is 54 to 59 mill per flight for launches in the 2010 to 2013 timeframe. I assume estimated inflation is used in the high number and current price in the low number. (makes me wonder where people get those lower launch cost numbers often thrown around when SpaceX is used in comparisons??)
REL's 40 mill is a bit old. inflation adjusted that amounts to 44 mill or so today. (numbers on their site are from 2005)

Skylon is projected to put more cargo for less cost into space than SpaceX is currently doing. Skylon is most definitely competitive with current best case prising on launches. even when assuming 0 growth in the launch market. assuming a modest growth causes the picture to just go more and more in favour of skylon compared to the alternatives. economy of scale benefits RLV's more than it benefits ELV's

mike alexander
2011-Apr-20, 09:30 AM
Interesting discussion, but this Skylon is still a bunch of pretty ones and zeroes in a computer. Arguing relative costs for a device that does not exist is like two fishermen arguing who will catch the biggest fish, when only one is holding a fishing rod.

Damburger
2011-Apr-20, 10:35 AM
Interesting discussion, but this Skylon is still a bunch of pretty ones and zeroes in a computer. Arguing relative costs for a device that does not exist is like two fishermen arguing who will catch the biggest fish, when only one is holding a fishing rod.

Skylon does not yet exist, but the nice thing about engineering is that you can predict the performance of something before you build it, and thus determine if its worth building. People in the UK government and ESA who've been shown the evidence so far have come to the conclusion the answer is 'yes' provided the one piece of unproven technology - the precooler - is viable. Everything else is just a LOX/LH2 rocket, a very well understood technology.

I do accept that, to be really game changing, it would have to launch at a significantly higher rate that current demand for payloads supports. I'm skeptical that commercial space ventures will do this - but hopefully there will be political will for a Mars mission or something on similar scale by 2020.

Antice
2011-Apr-20, 03:10 PM
Skylon does not yet exist, but the nice thing about engineering is that you can predict the performance of something before you build it, and thus determine if its worth building. People in the UK government and ESA who've been shown the evidence so far have come to the conclusion the answer is 'yes' provided the one piece of unproven technology - the precooler - is viable. Everything else is just a LOX/LH2 rocket, a very well understood technology.

I do accept that, to be really game changing, it would have to launch at a significantly higher rate that current demand for payloads supports. I'm skeptical that commercial space ventures will do this - but hopefully there will be political will for a Mars mission or something on similar scale by 2020.

yes. no matter what launch system you prefer it would take a radical increase in launch rates to bring costs down significantly. The good thing about the skylon concept is that it can indeed bring costs down quite a lot at current launch rates instead of relying on launch rates to go up first.

One of the main reasons is that REL's business model deviates from the norm in the launch industry and is more like an aircraft manufacturers. Skylon's will be sold to any and all interested parties that has the money to pay for it. this is the business model of both Airbus and Boeing. if you have the money you can buy a 747 or an A380. they don't come cheap and unless you know what the heck you are doing you are probably going to go broke, but that does not affect either aircraft provider. they made their money the moment you paid for the vehicle. the same economic risk reduction can be done on the launch facilities. by not having the launch vehicle owner build and run these facilities, but instead have a separate economic entity running the spaceport.
rent levels and usage fees will have to be set based on expected usage levels and is therefore shared among multiple providers and indeed, to a certain degree by those delivering other services to the vehicle owners, but also in a secondary manner by potential passengers, spectators and whomever else would want proximity to the launch business. it's not hard to imagine a combined airport/spaceport run more or less like any other modern day commercial airport.
the Airliners don't pay for the entire airport. a lot of the income the airport relies on is rent from the various providers of food/beverages. tax free shops and assorted companies providing the myriad of services a full blown airline needs in order to function. like catering, security, workshops, fuel, etc. It's a bit mind blowing actually to be faced with just how many businesses that are either directly or indirectly living off of revenue streams that originate from a single transport industry like airline companies. and they are all paying rent to the airport.

Standard launch operators don't operate like this. They have just as complex a supply chain as airliners, even more so I suspect, but none of the money that goes into third party pockets helps pay for any of the facilities used. this is because ONLY the launch provider uses the launch facilities. neither are there much if any secondary businesses gathering extra revenue from spectators and travellers alike contributing anything to the bottom line for the launch provider. This means that 100% of the facility cost is internalized. and it has to be internalized regardless of wither you launch 1 rocket a year or 100 rockets a year.

kamaz
2011-Apr-20, 03:19 PM
this is another of your strawmen.
vehicles don't have a use by date.


But business plans do.

The point is not if the flight costs $40M or $2M. The point is that REL will have a sunk R&D cost of $15B which it will have to recoup. It doesn't also matter if REL will fly it themselves, or the operator will. Either way, the initial R&D spending appears in the operations budget as vehicle amortization. And this is not real estate investment which can be amortized over 50 years. The amortization period will likely be about 5 years, maybe 10 if they can find a gratuitous creditor.

So you have to amortize $15B over 5 years, which is $3B per year. At n flights per year (all vehicles combined), the amortization cost per flight is $3B/n. The amortization cost is pased on the customer atop of actual operation costs. So:

- at 1 flight per year, the amortization cost is $3B per flight or $300K/kg of payload;
- at 10 flights per year, the amortization cost is $300M per flight or $30K/kg of payload;
- at 100 flights per year, the amortization cost is $30M per flight or $3K/kg of payload;
- at 1000 flights per year, the amortization cost is $3M per flight or $0.3K/kg of payload;

This is on top of actual flight costs (fuel, maintenance, etc.). That means, that even if vehicle was free to operate, it would have to perform at least 30 flights per year to be competitive with EELV, as the amortization cost in this case is $10K/kg of payload. Getting down to $5K/kg of payload requires 60 flights per year.

And here is the problem. 60 flights per year, with 10'000kg each means 600'000kg of delivery to LEO per year. This is equivalent to 30 EELV launches per year. And there is currently no customer in the world which uses, or envisions, 30 EELV launches per year.

In other words, there is not enough demand for LEO transport which would require Skylon flight rate at which the operation could reach a financial breakeven.

Since in reality the vehicle is NOT free to operate, minimum flight rate will likely have to be at least twice that, over 100 flights per year.

TrAI
2011-Apr-20, 05:36 PM
But business plans do.

The point is not if the flight costs $40M or $2M. The point is that REL will have a sunk R&D cost of $15B which it will have to recoup. It doesn't also matter if REL will fly it themselves, or the operator will. Either way, the initial R&D spending appears in the operations budget as vehicle amortization. And this is not real estate investment which can be amortized over 50 years. The amortization period will likely be about 5 years, maybe 10 if they can find a gratuitous creditor.

So you have to amortize $15B over 5 years, which is $3B per year. At n flights per year (all vehicles combined), the amortization cost per flight is $3B/n. The amortization cost is pased on the customer atop of actual operation costs. So:

- at 1 flight per year, the amortization cost is $3B per flight or $300K/kg of payload;
- at 10 flights per year, the amortization cost is $300M per flight or $30K/kg of payload;
- at 100 flights per year, the amortization cost is $30M per flight or $3K/kg of payload;
- at 1000 flights per year, the amortization cost is $3M per flight or $0.3K/kg of payload;

This is on top of actual flight costs (fuel, maintenance, etc.). That means, that even if vehicle was free to operate, it would have to perform at least 30 flights per year to be competitive with EELV, as the amortization cost in this case is $10K/kg of payload. Getting down to $5K/kg of payload requires 60 flights per year.

And here is the problem. 60 flights per year, with 10'000kg each means 600'000kg of delivery to LEO per year. This is equivalent to 30 EELV launches per year. And there is currently no customer in the world which uses, or envisions, 30 EELV launches per year.

In other words, there is not enough demand for LEO transport which would require Skylon flight rate at which the operation could reach a financial breakeven.

Since in reality the vehicle is NOT free to operate, minimum flight rate will likely have to be at least twice that, over 100 flights per year.


Hmmm... It is hard to say what the depreciation period for such a craft would be, as there is no real comparison with current ventures. But I would think the maximum safe and useful time would have to be calculated based on the expected turnaround, but it may be possible that investors will compare these space planes to aircraft and so chose a depreciation time similar to these, something like 10 to 15 years perhaps. That does not mean that the space frame is scrapped after this, though, a company would probably calculate with getting some years operation after this time.

It may be possible that some risk schedule could be used, so that the newer craft is used for the more valuable things, the older for less valuable cargo, this would minimize the loss should the craft break up, but also let you get the the full life out of the craft. Of course, the personnel module is designed for safety, and is supposed to be able to survive even the disintegration of the frame during flight, but it is probably best not to fly people on the oldest craft as it would probably tend to make the public skeptical of the safety of your service should something happen.

The transport of the less valuable cargo would probably be offered at a lower rate, too, as it seems unlikely that someone would ship 10 tonnes of structural components for space construction at the same price as, for instance, the latest state of the art space telescope that has taken years and huge amounts of money to develop, but they may accept a small increase in risk.

kamaz
2011-Apr-20, 07:05 PM
Hmmm... It is hard to say what the depreciation period for such a craft would be, as there is no real comparison with current ventures.

If REL wants to sell craft(s) to the operator, it must price it in a way which includes previous R&D costs. However, since such craft has not flown before, the operator may have a problem finding a lender willing to finance craft lease over, say, 20 years. In my opinion, it is unlikely that the lender would risk more than 3-5 years lease. In such case, the craft must be aggressively amortized over the lease period, which requires large income, which in turn requires a high flight rate. And high flight rate is questionable, because demand for such services is still limited.

So the economics here is actually driven by the problem of getting capital, not the durability and operating costs of the spacecraft. Even if the spacecraft could work 20 years without problems, it would still have to be fully amortized over the first 5 years.

I don't want to get into politics, but this is one of these situations, when you really want the government to step in and help start the venture by guaranteeing loans or something like that.

Craigboy
2011-Apr-20, 08:18 PM
using the 40 mill per flight figure from a 0 growth no passenger flights scenario and using it to show that skylon is too expensive as a crew ferry is on par with saying that carrying passengers is the only use for skylon.
You are really misreading my posts.


As for station building capability. do not conflate current domestic capability with future desired capability.
But in the near future no destination exists.


It would cost the chinese on par with the development costs of the entire skylon programme to match it's capabilities. the chinese are smart enough to realize that just buying a vehicle and operating that one is cheaper and faster than designing their own. the Chinese are just one such potential buyer. there are others who also wants their own space programs on the cheap.
From a capability standpoint the only thing that makes it different is return from orbit. The Chinese already have a cargo vehicle. How much would a "Sklyon" cost and who are these alleged customers?


once the shuttle dies then skylon is the only thing matching it's capabilities.
Skylon can carry 12,000 kg less than the Shuttle, so it cannot match its "capabilities".


there is according to satellite owners a desire for a having return to earth capability on launchers.
You really need to cite this.


this is a capability that they are not allowed to buy from the shuttle due to safety related decisions.
But they did do it (on STS-51-A). Maybe you mean after the Challenger incident?


Risking the lives of crew for launching satellites was a bad idea. altho i wont fault the shuttle designers on that one. they didn't have the computer technology we have now and could hardly avoid needing a crew from something as complex as the STS.
I don't know to respond to this.


Skylon is projected to put more cargo for less cost into space than SpaceX is currently doing. Skylon is most definitely competitive with current best case prising on launches. even when assuming 0 growth in the launch market. assuming a modest growth causes the picture to just go more and more in favour of skylon compared to the alternatives. economy of scale benefits RLV's more than it benefits ELV's
And the Falcon 9 was projected to put it into orbit for even less.

Antice
2011-Apr-20, 10:09 PM
@ craigboy. the nested quotes don't work so quoting dont work all that well for responding. :(
The shuttle got effectively banned from being used as a satellite launcher post challenger.
It was one of those things that is pretty obvious in retrospect. but may not really have been so at the time.

as for matching capabilities. those are more than just the up-mass. the shuttle is pretty much overpowered in that regard. the capabilities i am talking about is among others the ability for supporting the construction of space stations and return to earth on deployment failure of satellites. shuttle is the only vehicle in terran history that has had this capability. it was only used once, but that was not from lack of a market. but a choice made with safety considerations in mind.

How much would a skylon cost? I have no idea. what i do know is what you find on REL's website and a few tidbits they have said in public here and there. We can only know what they claim. altho i do assume that their investors are better informed than we are. it was the same with spaceX before they proved themselves. the viper test this summer is a similar delivery of proof. just like SpaceX did when they publicized engine test etc.

then onto this: misreading your post. did or did you not use the most pessimistic no growth assumption number for your passenger costs? if you did then no. i did not misread you. those numbers are based on current launch market rates. there are no destinations for 30 passengers. the only possible use would be ISS or ISS replacement resupply for the SPLM.only when space tourism and alternate destinations is taken into account does the SPLM come into being as a potentially profit earning capability. there wont be enough flights to ISS alone to really justify the SPLM. government money would have to close the gap. In fact i do not think we have enough data to even guess at per seat costs yet.

Before the chinese can realize their goals of going anywhere except LEO they have to either replicate former US HLV capability. OR learn to assemble big stuff in space. both options are costly and the US ain't selling last i heard. buying off the shelf capability like the skylon can easily shave a lot of cost even for them. it's up to those in charge of the chinese space program to decide. China is not the only nation with a space program however. others are following suit. The later into the game they join into the race the more benefit they gain from buying a vehicle rather than developing their own.

@Kamaz:
you are using amortization wrong in this case. R&D is an intangible resource and is amortized differently than tangible assets. that is it is divided between all the vehicles that they expect to build. and is time independent. this is one of those things that wikipedia actually got right (http://en.wikipedia.org/wiki/Amortization_(business)#Amortization_of_intangible _assets). in practice this means that operators are freed from any cost risks related to lack of sales on REL's part.
I think your launch market analysis is suspect. 2010 saw 74 launches. granted quite a few of them were pretty small payloads. but even if all of them could double up in the payload bay you get more than 30 ELV's worth. I think it is a safe bet to expect at least a modest growth into the future even without a serious drop in launch costs. we are getting more and more dependent on our birds in the sky. it's impossible to predict exactly how future markets will look. it all boils down to speculation at that point. and that is what investing in skylon boils down to right now. speculation on guesses about the future.

Craigboy
2011-Apr-21, 12:05 AM
those are more than just the up-mass. the shuttle is pretty much overpowered in that regard.
It depends on what it needs to carry, for station assembly flights I believe it used all of it.


the capabilities i am talking about is among others the ability for supporting the construction of space stations.
You don't need a RLV for that, look at how Russia assembles stations. And if you really want an arm than you can just attached to the space station. Skylon can't lift any large seized ISS modules or Bigelow's BA-330.

http://en.wikipedia.org/wiki/Assembly_of_the_International_Space_Station#Assemb ly_sequence
http://www.space.com/855-progress-inflatable-private-space-module.html


How much would a skylon cost? I have no idea.
That's the golden ticket.


then onto this: misreading your post. did or did you not use the most pessimistic no growth assumption number for your passenger costs?
I never mentioned passenger costs.


Before the chinese can realize their goals of going anywhere except LEO they have to either replicate former US HLV capability.
China is considering a HLV.

http://www.bbc.co.uk/news/science-environment-10762634


China is not the only nation with a space program however. others are following suit. The later into the game they join into the race the more benefit they gain from buying a vehicle rather than developing their own.
Specifically list who.


there is according to satellite owners a desire for a having return to earth capability on launchers.
You really need to cite this.

NEOWatcher
2011-Apr-25, 11:19 PM
China is considering a HLV.

http://www.bbc.co.uk/news/science-environment-10762634
.

...and up to 14 tonnes to the so-called geostationary transfer orbit, where
most communications satellites are released after launch.

So-called? :confused:

Craigboy
2011-Apr-26, 03:32 AM
So-called? :confused:
Seems like you skimmed and mistook the Long March-5 for the heavy lift vehicle that the article talks about.

NEOWatcher
2011-Apr-26, 12:07 PM
Seems like you skimmed and mistook the Long March-5 for the heavy lift vehicle that the article talks about.
No, did you skim the part I quoted? The adjective "so-called" is about the orbit.
Besides, even if I did mistake one for the other. Where does the "so-called" come into play?

Craigboy
2011-Apr-26, 09:25 PM
The adjective "so-called" is about the orbit.

In that case I have no clue what you're talking about.

CJSF
2011-Apr-26, 10:05 PM
I think in this case, "so-called" was meant to be synonymous with "known as"; however, in my experience "so-called" has an almost pretentious connotation to it. Usually when I say (or hear) something like "so-called," it means that it isn't REALLY what it says it is, or that the person(s) involved don't REALLY know what they are talking about.

CJSF

cjameshuff
2011-Apr-26, 10:13 PM
In that case I have no clue what you're talking about.

It's right there in his quote. A more complete quote:

When operational, Long March-5 is expected to deliver up to 25 tonnes of payload, including space station modules to the low Earth orbit, and up to 14 tonnes to the so-called geostationary transfer orbit, where most communications satellites are released after launch.

Craigboy
2011-Apr-26, 11:36 PM
Ha, okay it looks like I was the one who was wrong.

Garrison
2011-May-24, 07:06 PM
A couple pieces on The BBC website about Skylon passing an important ESA review:

Main Article (http://www.bbc.co.uk/news/science-environment-13506289)

Spaceman blog (http://www.bbc.co.uk/news/science-environment-13520948)

Key points are that the ESA review sees no 'showstoppers' and assuming the intercooler passes the tests due next month REL would unlock £200-300 million in private funding.

kzb
2011-May-26, 05:56 PM
The wikipedia entry for Skylon is very interesting. I can't see why so many on here are so negative about it.

The payload bay is 4.6x12.3 metres, compared to the space shuttle's 4.6x18 metres.

Payload to LEO is 12 tonne, compared to space shuttle 24.4 tonne. (Skylon payload to ISS is 9.5T).

According to Wiki, the thrust of each engine is 3,600kN "with afterburner", considerably MORE than the SS main engine (1800kN each), although not anywhere near the solid fuel boosters of course.

Still should be quite spectacular. You'd think one of the worlds mega-rich ie Bill Gates et al would want to bank roll something like this even if they did lose a bit of money.

http://en.wikipedia.org/wiki/Skylon

Noclevername
2011-May-26, 07:17 PM
The wikipedia entry for Skylon is very interesting. I can't see why so many on here are so negative about it.

Not negative, just a bit cynical and tired from having heard the same promises and seen similar pretty concept art dozens of times in our lifetimes-- and some from before that.



You'd think one of the worlds mega-rich ie Bill Gates et al would want to bank roll something like this even if they did lose a bit of money.

They're cynical for the same reason plus more, they have people asking them to give money to this, that, and the other thing that will "revolutionize the world, man, I promise!" all the time.


Don't get me wrong, I do hope this one works, just like I've hoped the others would.

kzb
2011-May-28, 03:57 PM
Noclevername wrote: Not negative, just a bit cynical

I know what you mean. This Skylon though does seem a cut above the usual.

I must admit you'd never get me up in it. The passenger module would go in between two huge liquid hydrogen tanks for and aft and the two engines to either side.

Noclevername
2011-May-28, 04:04 PM
I must admit you'd never get me up in it. The passenger module would go in between two huge liquid hydrogen tanks for and aft and the two engines to either side.

Riding any rocket into orbit means riding a potential deathtrap. But since you're surrounded by the most vital components of the ship, that's the area that they're likely to have most protected and carefully inspected. I'd go, and I'm a scaredy-cat.

Cruithne3753
2011-May-29, 05:36 PM
Love the retro 1950s look of the thing. Like something out of a Chesley Bonestell illustration.

TrAI
2011-May-29, 11:06 PM
Noclevername wrote: Not negative, just a bit cynical

I know what you mean. This Skylon though does seem a cut above the usual.

I must admit you'd never get me up in it. The passenger module would go in between two huge liquid hydrogen tanks for and aft and the two engines to either side.

The SPLM is apparently designed to be relatively safe for the passengers, according to the manual it is designed to survive the Skylon crashing by the rest of the craft absorbing most of the impact, it's life support is independent from the rest of the vehicle, so the module can keep the occupants alive for several days in space. If the vehicle for some reason breaks up inside the atmosphere or the module for some other reason finds itself separated from the vehicle, the SPLM has a parachute system. The module also has heat shielding to protect the occupants from things like propellant fires.

The internal life support is rated for a 2 day mission length plus 2 days of reserve for a full passenger complement, if I read the manual correctly, though, of course, it can be used for longer missions if external support is available, for example if it was connected to a space station. The idea is that if the module is stranded in space, for instance if the vehicle is damaged so that it is deemed unable to survive reentry, a second Skylon can be sent up to recover the passengers in that time. The storage space of the passenger seat is equipped with a light pressure suit in case the module should be breached, but I am not sure how long these suits can support life. The manual mentions a 4 day supply of oxygen and lithium hydroxide in the seat storage space, but this may be part of the general life support supplies.

kzb
2011-May-31, 05:36 PM
The SPLM is apparently designed to be relatively safe for the passengers, according to the manual it is designed to survive the Skylon crashing by the rest of the craft absorbing most of the impact, it's life support is independent from the rest of the vehicle, so the module can keep the occupants alive for several days in space. If the vehicle for some reason breaks up inside the atmosphere or the module for some other reason finds itself separated from the vehicle, the SPLM has a parachute system. The module also has heat shielding to protect the occupants from things like propellant fires.

The internal life support is rated for a 2 day mission length plus 2 days of reserve for a full passenger complement, if I read the manual correctly, though, of course, it can be used for longer missions if external support is available, for example if it was connected to a space station. The idea is that if the module is stranded in space, for instance if the vehicle is damaged so that it is deemed unable to survive reentry, a second Skylon can be sent up to recover the passengers in that time. The storage space of the passenger seat is equipped with a light pressure suit in case the module should be breached, but I am not sure how long these suits can support life. The manual mentions a 4 day supply of oxygen and lithium hydroxide in the seat storage space, but this may be part of the general life support supplies.

I've not read up too far on the passenger module to be honest. Anyway, I believe is much further down the line; in other words, we test the thing perhaps for several years with unmanned missions before we trust it with human cargo. That's a sensible approach to my mind at least.

The engine thrust works out to over ten times that of a 747, and that is apparently in jet, not rocket, mode. That is if the wiki article is accurate. You would think there'd be immense military interest in something like this.

TrAI
2011-Jun-02, 02:56 AM
I've not read up too far on the passenger module to be honest. Anyway, I believe is much further down the line; in other words, we test the thing perhaps for several years with unmanned missions before we trust it with human cargo. That's a sensible approach to my mind at least.

It is probable that Skylon would be used for unmanned missions at first, since that is what it is designed to do, the SPLM is part of REL's Advanced Studies research.


The engine thrust works out to over ten times that of a 747, and that is apparently in jet, not rocket, mode. That is if the wiki article is accurate. You would think there'd be immense military interest in something like this.

I suppose military organizations would be interested in such engines, but i am not clear on what it is you are aiming at here.

kzb
2011-Jun-02, 05:27 PM
It is probable that Skylon would be used for unmanned missions at first, since that is what it is designed to do, the SPLM is part of REL's Advanced Studies research.



I suppose military organizations would be interested in such engines, but i am not clear on what it is you are aiming at here.


I've read a bit more about the SPLM. No windows, unless they are in the roof, and even then the cargo bay doors have to be open for you to see out. No windows in takeoff and landing, I think I would find that disconcerting !

The military reference was about funding the development of the engines and other technology. The ability to fly at mach 5+ is surely of interest.

TrAI
2011-Jun-02, 07:08 PM
I've read a bit more about the SPLM. No windows, unless they are in the roof, and even then the cargo bay doors have to be open for you to see out. No windows in takeoff and landing, I think I would find that disconcerting !

True, there is no windows in the craft itself, the reason is that the heat caused during the hypersonic flight in the atmosphere would make the windows prohibitively massive, complex and serve little purpose in most missions. So if you want to look outside, you'll have to install cameras and displays instead.


The military reference was about funding the development of the engines and other technology. The ability to fly at mach 5+ is surely of interest.

I suspect that REL have reasons for their choice in who they solicit funding from and how they do it, perhaps getting military funding carries some undesirable limitations?

I seem to recall that the HOTOL had some such encumberments under the UK Official Secrets Act, its RB545 engine seems to be classified under this... perhaps their experiences from this project may have influenced them.

kzb
2011-Jun-03, 12:13 PM
TrAI wrote: I suspect that REL have reasons for their choice in who they solicit funding from and how they do it, perhaps getting military funding carries some undesirable limitations?

I seem to recall that the HOTOL had some such encumberments under the UK Official Secrets Act, its RB545 engine seems to be classified under this... perhaps their experiences from this project may have influenced them.

I remember that about the HOTOL engine being classified also. In fact I believe it is why it got cancelled. However, the source of the funding surely has no bearing on whether a technology becomes Classified or not?

Noclevername
2011-Jun-03, 04:39 PM
I remember that about the HOTOL engine being classified also. In fact I believe it is why it got cancelled. However, the source of the funding surely has no bearing on whether a technology becomes Classified or not?

Governments tend to have a certain proprietary attitude towards potential military technology, and purse strings can also act as a leash. They particularly don't want potential missile tech to go public.

Garrison
2012-Apr-27, 01:25 PM
Well perhaps unsurprisingly it took longer than anticipated but the intercooler testing is underway:

Key tests for Skylon spaceplane project (http://www.bbc.co.uk/news/science-environment-17864782)

Cross your fingers and think good thoughts (Disclaimer: crossing fingers and thinking good thoughts are not proven to produce desired results. :))

MAddis
2012-Apr-27, 02:56 PM
It seems that work has continued on this project - as it has for years now - but that Reaction Engines Limited are still making progress. They still don't have a full working model of the Sabre engine, but they have a working version of one of it's enabling technologies: a special type of pre-cooler heat exchanger.
"Reaction Engines' breakthrough is a module containing arrays of extremely fine piping that can extract the heat and plunge the intake gases to minus 140C in just 1/100th of a second. Ordinarily, the moisture in the air would be expected to freeze out rapidly, covering the pre-cooler's pipes in a blanket of frost and compromising their operation. But the REL team has also devised a means to stop this happening, permitting Sabre to run in jet mode for as long as is needed before making the transition to a booster rocket."
http://www.bbc.co.uk/news/science-environment-17864782

The company is understandably talking things up in a big way, as they are still desperate for further investment. Does this development deal with any of the concerns people had about the viability of this idea in the previous posts?

Antice
2012-Apr-28, 12:46 AM
It seems that work has continued on this project - as it has for years now - but that Reaction Engines Limited are still making progress. They still don't have a full working model of the Sabre engine, but they have a working version of one of it's enabling technologies: a special type of pre-cooler heat exchanger.
"Reaction Engines' breakthrough is a module containing arrays of extremely fine piping that can extract the heat and plunge the intake gases to minus 140C in just 1/100th of a second. Ordinarily, the moisture in the air would be expected to freeze out rapidly, covering the pre-cooler's pipes in a blanket of frost and compromising their operation. But the REL team has also devised a means to stop this happening, permitting Sabre to run in jet mode for as long as is needed before making the transition to a booster rocket."
http://www.bbc.co.uk/news/science-environment-17864782

The company is understandably talking things up in a big way, as they are still desperate for further investment. Does this development deal with any of the concerns people had about the viability of this idea in the previous posts?

They are talking things up in a big way because they are on the verge of having absolute proof that they got something that is potentially game changing for not just one, but 2 whole industries. both the launch, and the airliner industries can potentially see some pretty revolutionary changes enabled by this technology.

I'd say that REL has been decidedly low key about their stuff compared to other companies that have far less to brag about than they do.
These precoolers do not actually need a high speed test tho. the most difficult part of the technology is to make them work at low altitude and high mass throughput close to the ground where the air moisture is high. That is what the viper test stand was built to prove.

danscope
2012-Apr-28, 03:50 AM
Got any anticipated numbers on operating speeds per altitude?

Antice
2012-Apr-28, 04:21 AM
Got any anticipated numbers on operating speeds per altitude?

Why don't you just browse trough their ascent simulation results? available here (http://www.reactionengines.co.uk/downloads/C1_trajectory_output.xls)

The short answer is that air breathing ascent is going to be from 0 to mach 5+ @ 28 km then the switchover from air to internal lox occurs and it's pure rocket mode the rest of the way to orbit.

danscope
2012-Apr-28, 05:15 PM
"Skylon configuration C1 typical Reentry data - from ... " Read " Re-entry " as in return from orbit. Not take off.
Just curious.

Garrison
2012-Apr-28, 07:10 PM
"Skylon configuration C1 typical Reentry data - from ... " Read " Re-entry " as in return from orbit. Not take off.
Just curious.

There is a lot of data available at the REL site, any which isn't is probably commercially sensitive so no one will have it.

Antice
2012-Apr-28, 07:42 PM
"Skylon configuration C1 typical Reentry data - from ... " Read " Re-entry " as in return from orbit. Not take off.
Just curious.

Dude... try a bit harder will ya? there are several pages to that spreadsheet. it's unfortunately imposible to directly link to a specific page inside a dokument. otherwise i would have done so.
for those not familiar with excel type spreadsheets. there are 3 tabs on the lower part of the screen. one of them is titled air breathing ascent. that is the one that has the data on max velocity durign the airbreathing part of the launch. the second one is rocket ascent, with self explanatory content, and the last one is for descent.
This is sim data from the C1 configuration, and not the still under review D1 config. so these numbers are not final and should only be used as an aproximation.

danscope
2012-Apr-28, 08:06 PM
Fair enough. I'll dig some. It would seem though, that there might be some wishfull extrapolation . We will just have to wait untill they actually build a test engine for real.

lok32
2012-May-01, 03:10 PM
What does the Sabre air-breathing rocket engine breath when it gets to space :)
Just joking, this looks like a very cool project, I wouldn't be surprised though if an independent company creates something like this before 2020, possibly virgin.

Antice
2012-May-02, 05:03 AM
What does the Sabre air-breathing rocket engine breath when it gets to space :)
Just joking, this looks like a very cool project, I wouldn't be surprised though if an independent company creates something like this before 2020, possibly virgin.

I find that highly unlikely. Virgin is already invested in the White knight/Spaceship 2 thing.
One of the EADS subsidiaries are much more likely. like Airbus or Astrium, Or even possibly a new EADS subsidiary. Going by their naming style i guess they would call it Spacebus :p

Nicolas
2012-May-02, 09:52 AM
Or maybe this time around Concord, sans e.

Garrison
2012-May-02, 01:06 PM
I find that highly unlikely. Virgin is already invested in the White knight/Spaceship 2 thing.
One of the EADS subsidiaries are much more likely. like Airbus or Astrium, Or even possibly a new EADS subsidiary. Going by their naming style i guess they would call it Spacebus :p

I suspect REL would go the ARM route, licensing the SABRE technology to say Rolls-Royce to do the actual manufacturing and as you say someone like EADS builds the airframe(spaceframe?).

Antice
2012-May-02, 04:17 PM
I suspect REL would go the ARM route, licensing the SABRE technology to say Rolls-Royce to do the actual manufacturing and as you say someone like EADS builds the airframe(spaceframe?).

Yeah. I think we are pretty much on the same page here. It's overly likely that the full system is going to be built by a consortium of various EADS subsidiaries and even some parts from independent companies.
And yes. Skylon uses a spaceframe structure, so that name suits it altho spaceframe refers to the truss structure beneat the aeroshell rather than the outer skin itself. An airframe, mostly refers to monocoque designs. (moostly that is. historically there has been some spaceframe type structures used in the early days of aviation).

but really. I'm just splitting semantic hairs here because I'm bored :p

lok32
2012-May-04, 10:36 AM
"I find that highly unlikely. Virgin is already invested in the White knight/Spaceship 2 thing."

I never knew about the White Knight/Spaceship 2 thing (Is that its technical name :)) going to have a read about it though, thanks.

Antice
2012-May-04, 05:59 PM
"I find that highly unlikely. Virgin is already invested in the White knight/Spaceship 2 thing."

I never knew about the White Knight/Spaceship 2 thing (Is that its technical name :)) going to have a read about it though, thanks.

There is a thread about Spaceship 2 around on this forum somewhere. but basically it's based on the Ansari X prize winner scaled composites SS1.
Unfortunately tho. it's suborbital only.

NEOWatcher
2012-May-04, 06:11 PM
There is a thread about Spaceship 2 around on this forum somewhere. but basically it's based on the Ansari X prize winner scaled composites SS1.
Actually; there's lots of threads.

Unfortunately tho. it's suborbital only.
It is, but they already started the next step and we have a thread on that.
Stratolaunch (http://www.bautforum.com/showthread.php/125530-Stratolaunch-Allen-Rutan-and-SpaceX?)
Basically; it's a very heavy version of White Knight 2 for launching an orbital rocket.

Garrison
2012-May-04, 09:46 PM
Actually; there's lots of threads.

It is, but they already started the next step and we have a thread on that.
Stratolaunch (http://www.bautforum.com/showthread.php/125530-Stratolaunch-Allen-Rutan-and-SpaceX?)
Basically; it's a very heavy version of White Knight 2 for launching an orbital rocket.

Strap a Dreamchaser (http://en.wikipedia.org/wiki/Dream_Chaser)on that booster and there's SpaceShipThree.:)

publiusr
2012-May-05, 06:15 PM
On Falcon 9 heavy yes. The capsule is probably lighter than Dreamchaser, so is better for the smaller air drop Falcon rocket.

Antice
2012-Jul-11, 02:49 PM
Time to revive this necrotic thread to a semblance of life again. under a new forum name to boot.
Latest news:
REL has gotten a new look on their website, also. there is some news of the precooler testing on there.
Get it here: Linky (http://www.reactionengines.co.uk/press_release.html)

The next stage after this is a full scale engine demonstrator. Woot. Looking very very forward to that.

Antice
2012-Jul-11, 04:20 PM
sorry for posting 2 in a row, but this bears being mentioned:
bbc article (http://www.bbc.co.uk/news/science-environment-18784866)

Regulations are already being looked at in order to make them able to allow the certification of skylon for commercial services... Good to see that the bureaucrat's are trying to plan ahead for a change.

Garrison
2012-Jul-11, 10:58 PM
Very good news about the intercooler. I understand the people calling for government funding have their hearts in the right place but given the track record I would say REL should stay with private funding as long as possible.

Antice
2012-Jul-12, 01:23 AM
Very good news about the intercooler. I understand the people calling for government funding have their hearts in the right place but given the track record I would say REL should stay with private funding as long as possible.

I Completely agree. I think that for a concept like this that maybe government money got too many strings attached.

danscope
2012-Jul-12, 04:38 AM
Well, the govmint might want to see it work before they pay. :)

Antice
2012-Jul-12, 05:36 AM
Well, the govmint might want to see it work before they pay. :)

The "govmint" isn't involved in financing skylon, so regardless of wither skylon works or not they ain't paying out.

kzb
2012-Jul-12, 11:50 AM
The senior government minister has given them a supportive statement for their press release (see link on website in Post #205). We are told separately there is £110bn (US$170bn) available to lend to "business", just there for the asking.

Garrison
2012-Jul-12, 06:49 PM
The senior government minister has given them a supportive statement for their press release (see link on website in Post #205). We are told separately there is £110bn (US$170bn) available to lend to "business", just there for the asking.

Don't hold your breath. Courtesy of all that public money the banks liquid assets have gone by 50% while lending has increased by 0.2% Frankly choosing between funding from the UK government and UK banks is like being asked if you want to be shot or hung...
Fortunately REL has stated in the past they have several hundred million in private funding lined up to carry on to the next phase.

publiusr
2012-Jul-14, 05:25 PM
Maybe space advocates across the pond should suggest funding Skylon by raiding the Carrier budget:
http://www.bbc.co.uk/news/magazine-18237029

Antice
2012-Jul-14, 06:03 PM
Carriers shmarriers. They are needed you know. the rest of the world does not like to be dominated by the US as much as it is when it comes to military might. Sooo.. if the US will scrap theirs then the rest of us may scap ours.

on a more serious note. carriers are extremely useful for more than just force projection. they are capable of policing an immense amount of ocean all by it's lonesome. someone got to keep an eye out for those pesky pirates you know.
The oceans have never been safer to traverse at any time during history than they are right now. this is partly so thanks to carriers and their huge area of influence.
I could not in good conscience demand that any nation shirk their responsibility to partake in the continuing work that is required to safeguard the international merchant fleets we are all critically dependent on to transport goods and fuel across the globe.

I would love to see space opened up as a proper frontier for expansion asap. but not at any cost like that.

Swift
2012-Jul-14, 07:04 PM
Maybe space advocates across the pond should suggest funding Skylon by raiding the Carrier budget:
http://www.bbc.co.uk/news/magazine-18237029

Carriers shmarriers. They are needed you know. the rest of the world does not like to be dominated by the US as much as it is when it comes to military might. Sooo.. if the US will scrap theirs then the rest of us may scap ours.
Unless someone is going to launch a rocketplane off of a carrier, please do not discuss military budgets, force projection, or similar issues on BAUT.

aquitaine
2012-Jul-15, 09:28 PM
Unless someone is going to launch a rocketplane off of a carrier, please do not discuss military budgets, force projection, or similar issues on BAUT.


I have to admit it would be really awesome if someone managed to pull that off.


Fortunately REL has stated in the past they have several hundred million in private funding lined up to carry on to the next phase.

Good. Do they have enough to make it through the whole thing, or just enough to develop the engines?

Garrison
2012-Jul-16, 08:55 PM
Good. Do they have enough to make it through the whole thing, or just enough to develop the engines?

I think that's to take them through a prototype engine; going further will take a lot more money but it's what they need for now.

Antice
2012-Jul-17, 06:21 AM
I think that's to take them through a prototype engine; going further will take a lot more money but it's what they need for now.

I think i saw mr Hempshell say something along these lines in an interview somewhere. been a while since i saw it, so i cannot remember where atm. At any rate. without an engine there is no vehicle. So it makes sense to complete the engine prototype phase before going much further with the rest of the vehicle.

Nicolas
2012-Jul-18, 07:53 AM
That was also the approach we used: rough design of the whole craft so you know what your engines need to be capable of (and to verify that the craft as a whole is more or less achievable), and then focus on detail design of the engine first as that's the major bottleneck (unless the rough design of the whole craft points out differently).

Antice
2012-Oct-08, 01:56 PM
Been quiet in this thread for a while. No big news to report really, but i stumbled across this Q/A session (http://www.theengineer.co.uk/sectors/aerospace/in-depth/skylon-and-sabre-your-questions-answered/1014164.article) where REL answers questions from the readers of the Engineer.

Garrison
2012-Nov-28, 11:06 PM
Well it appears the major test of the intercooler has been passed!:

Skylon spaceplane engine concept achieves key milestone (http://www.bbc.co.uk/news/science-environment-20510112)

Next step a scale SABRE prototype, and history in the making!

Antice
2012-Nov-29, 02:08 AM
Well it appears the major test of the intercooler has been passed!:

Skylon spaceplane engine concept achieves key milestone (http://www.bbc.co.uk/news/science-environment-20510112)

Next step a scale SABRE prototype, and history in the making!

Indeed. I'm really stoked about this. I think this is the best shot we got for making space access cheap enough to make us a truly space faring civilization.

Garrison
2012-Nov-29, 09:06 PM
Indeed. I'm really stoked about this. I think this is the best shot we got for making space access cheap enough to make us a truly space faring civilization.

I know, I was slightly depressed to see the proposed design for Ariane 6 (another lets shuffle the engines around a bit rocket), so the new from REL was excellent; hopefully the fund-raising goes well.

MaDeR
2012-Nov-30, 07:38 PM
I seen a lot of people from MY side of pond hunging up on Skylon like Second Coming or something like that. It is even funny.

I see Skylon as something that will need a lot of luck. It will be in 30s (generous, as I assume it will actually exist at all!). Real Skylon will have worse parameters than paper Skylon. And it will have to compete with reusable rockets of future fielded by SpaceX, LockMart, Boeing and whatever will survive until then.

Garrison
2012-Nov-30, 09:39 PM
I seen a lot of people from MY side of pond hunging up on Skylon like Second Coming or something like that. It is even funny.

I see Skylon as something that will need a lot of luck. It will be in 30s (generous, as I assume it will actually exist at all!). Real Skylon will have worse parameters than paper Skylon. And it will have to compete with reusable rockets of future fielded by SpaceX, LockMart, Boeing and whatever will survive until then.

Same old. same old. Every time they cross one of the major hurdles someone comes up with a post like this. Frankly I'll take the wild optimists over sour pessimists any day of the week.

swampyankee
2012-Dec-01, 02:53 PM
Same old. same old. Every time they cross one of the major hurdles someone comes up with a post like this. Frankly I'll take the wild optimists over sour pessimists any day of the week.

I saw an aphorism: Optimists invented the airplane; pessimists invented the parachute.

I've worked in aerospace; even projects that are not as leading-edge as Skylon routinely run over budget and late. It's also routine for performance goals to be unmet.

Skylon is, regardless of anything else, most definitely a high-risk project, in that it requires several major technical innovations, not least the engines, to work to expectations to succeed. Good luck to them, but they're not guaranteed success.

Garrison
2012-Dec-01, 06:26 PM
I saw an aphorism: Optimists invented the airplane; pessimists invented the parachute.

I've worked in aerospace; even projects that are not as leading-edge as Skylon routinely run over budget and late. It's also routine for performance goals to be unmet.

Skylon is, regardless of anything else, most definitely a high-risk project, in that it requires several major technical innovations, not least the engines, to work to expectations to succeed. Good luck to them, but they're not guaranteed success.

Oh I don't think it's guaranteed but its the people who seem to almost be willing the likes of REL and SpaceX to fail I don't have time for.

publiusr
2012-Dec-01, 07:53 PM
I want as many in the game as possible. The intercooler is what had me worried. I'm hoping the worst part is over. The European LEA/hexafly programs might pick up interest over this. If one country tries its hand in a certain type of space acess, it causes others to look in the same direction.

The recent AV Week showed a lot of recent hypersonic advances, with Scramspace on the cover. The H-Magjet concept is interesting (hypermach.com_. I wonder what Musk's hyperloop is supposed to be.

Antice
2012-Dec-01, 09:09 PM
I want as many in the game as possible. The intercooler is what had me worried. I'm hoping the worst part is over. The European LEA/hexafly programs might pick up interest over this. If one country tries its hand in a certain type of space acess, it causes others to look in the same direction.

The recent AV Week showed a lot of recent hypersonic advances, with Scramspace on the cover. The H-Magjet concept is interesting (hypermach.com_. I wonder what Musk's hyperloop is supposed to be.

The more teams working on achieving a goal the bigger the chance of overall sucess is. most of these attempts are going to fail. there is no doubt about that, but REL is definately one of the favorites in this race.

Garrison
2013-Aug-06, 09:41 PM
Can not find the other thread on Skylon so apologies for starting a new one. ESA has commissioned a study of the business case for Skylon. BBC article on it:

Esa study examines Skylon space plane (http://www.bbc.co.uk/news/science-environment-23590080)

Swift
2013-Aug-06, 10:53 PM
Can not find the other thread on Skylon so apologies for starting a new one.
No appology necessary, but I merged the two threads. The new Google search box actually works pretty well.

Garrison
2013-Aug-07, 08:17 AM
No appology necessary, but I merged the two threads. The new Google search box actually works pretty well.

I think it was because I put in 'spaceplane' instead of 'rocketplane'. :)

Antice
2013-Aug-07, 08:44 AM
I think it was because I put in 'spaceplane' instead of 'rocketplane'. :)

OT: I used to have it linked in my signature, but signatures seems to have disapeared during the changeover to cosmoquest :confused: /OT

Seeing that ESA is finally doing some independent research on the economics of skylon is great. So far we gave only had the business reviewed case made by REL itself.
I haven't been maintaining the thread tho, not because there haven't been any news, but because the debate has mostly been going on elsewhere.

In other news: Skylon has gotten 60 mill in funding from the UK government (http://www.independent.co.uk/news/science/government-to-spend-60m-on-revolutionary-sabre-rocket-engine-that-will-be-used-on-spaceplane-skylon-8710542.html).
Granted, this is not all the funds needed at this step in the dev program, but government money tend to make private money flow a little bit easier. must be that guberminty taste ya know :D

publiusr
2013-Aug-10, 07:19 PM
It's going to take more than that 60 mil.

In the past, people tried to use the venture capitalist model. But we saw the disaster that came with that what with the Very Light Jet/air taxi debacle. Now money may be made with VLJs now that a lot of debt has been discharged and the work already done. Someone picks up the pieces and just makes a profit selling smaller bizjets to folks who cannot afford a Gulfstream. If someone tries that with Skylon the results will be the same.

We saw that with something as simple as the Felix Baumgatner jump. Red Bull thought jumping out of a balloon would be cheap. It wasn't. Then they sent a kid from the home office to try to tell older engineers their job. Lutz talked about this in his book on bean counters vs Car Guys.

Some thought they could bootstrap their way up. Send out pamphlets. Find somebody to fund a few thousand--then send out some nice glossy hand outs, get some more money, make a video. That doesn't last either.

The DOT.COM billionaire here already have their projects.

Here is what I might suggest. Now a lot of folks regard Donald Trump as a fool...and maybe he is. But he has a presence. Now if someone could convince him to fly some engineers to Russian Billionaires, or to the Saudi's, that will give the engineers the look that they have already made it. Trump acts like he really doesn't want to be bought out, and you try to play things that way. If nothing else, Trump could lend them a plane ride, not even be there, offer use of a building, etc.

You have to have a nice shiny dais for your product. Offering nice Skylon models in the BIS journals read by the same 300 broke space advocates worldwide will not cut it.

Antice
2013-Aug-11, 09:46 AM
It's going to take more than that 60 mil.

In the past, people tried to use the venture capitalist model. But we saw the disaster that came with that what with the Very Light Jet/air taxi debacle. Now money may be made with VLJs now that a lot of debt has been discharged and the work already done. Someone picks up the pieces and just makes a profit selling smaller bizjets to folks who cannot afford a Gulfstream. If someone tries that with Skylon the results will be the same.

We saw that with something as simple as the Felix Baumgatner jump. Red Bull thought jumping out of a balloon would be cheap. It wasn't. Then they sent a kid from the home office to try to tell older engineers their job. Lutz talked about this in his book on bean counters vs Car Guys.

Some thought they could bootstrap their way up. Send out pamphlets. Find somebody to fund a few thousand--then send out some nice glossy hand outs, get some more money, make a video. That doesn't last either.

The DOT.COM billionaire here already have their projects.

Here is what I might suggest. Now a lot of folks regard Donald Trump as a fool...and maybe he is. But he has a presence. Now if someone could convince him to fly some engineers to Russian Billionaires, or to the Saudi's, that will give the engineers the look that they have already made it. Trump acts like he really doesn't want to be bought out, and you try to play things that way. If nothing else, Trump could lend them a plane ride, not even be there, offer use of a building, etc.

You have to have a nice shiny dais for your product. Offering nice Skylon models in the BIS journals read by the same 300 broke space advocates worldwide will not cut it.

60 mill is just part funding for the next step in the engine dev program. actually making skylons would require a consortium of aerospace firms to work together. each firm would presumably have some serious skin in the game themselves. the program risks will then be mostly spread around those companies who would wish to be part of the skylon consortium.
Governments would have to get involved as well. both for legislative reasons and for at least some of the funding, maybe even some loan guarantees. we'l see how it all plays out in the long run.

Garrison
2013-Aug-11, 11:52 PM
It's going to take more than that 60 mil.

And if you had read the article you would know that this was a contribution towards the costs; so if you couldn't be bothered to find out that little detail one cannot hold out much hope for the rest of your comments.


In the past, people tried to use the venture capitalist model. But we saw the disaster that came with that what with the Very Light Jet/air taxi debacle. Now money may be made with VLJs now that a lot of debt has been discharged and the work already done. Someone picks up the pieces and just makes a profit selling smaller bizjets to folks who cannot afford a Gulfstream. If someone tries that with Skylon the results will be the same.

So one failure extrapolates to REL can't successfully raise money to fund development from venture capitalists? Do you actually know what they are?


We saw that with something as simple as the Felix Baumgatner jump. Red Bull thought jumping out of a balloon would be cheap. It wasn't. Then they sent a kid from the home office to try to tell older engineers their job. Lutz talked about this in his book on bean counters vs Car Guys.

Another not remotely relevant anecdote.


Some thought they could bootstrap their way up. Send out pamphlets. Find somebody to fund a few thousand--then send out some nice glossy hand outs, get some more money, make a video. That doesn't last either.

The DOT.COM billionaire here already have their projects.


And what does the above have to do with REL who have raised funds from private investors, ESA and now the UK government?



Here is what I might suggest. Now a lot of folks regard Donald Trump as a fool...and maybe he is. But he has a presence. Now if someone could convince him to fly some engineers to Russian Billionaires, or to the Saudi's, that will give the engineers the look that they have already made it. Trump acts like he really doesn't want to be bought out, and you try to play things that way. If nothing else, Trump could lend them a plane ride, not even be there, offer use of a building, etc.

You have to have a nice shiny dais for your product. Offering nice Skylon models in the BIS journals read by the same 300 broke space advocates worldwide will not cut it.

And this is just plain ridiculous; Trump is a man with a dubious track record who knows nothing about aerospace. Could you please try and learn something, anything, about REL and Skylon before you comment again?

profloater
2014-Jan-13, 05:05 PM
from the reaction engines website:

London, Monday 13th January 2014

Reaction Engines Ltd is pleased to announce that it has entered into a Cooperative Research and Development Agreement ('CRADA') with the Air Force Research Laboratory's Aerospace Systems Directorate (AFRL/RQ).

selvaarchi
2014-Jul-06, 12:08 PM
I could not find any reference this British development in the forum. It must have advanced in its technology as the article talks about filing for some patents soon.

http://timesofindia.indiatimes.com/home/science/British-engineer-building-rocket-to-revolutionize-space-travel/articleshow/37893396.cms

joema
2014-Jul-06, 01:33 PM
I could not find any reference this British development in the forum. It must have advanced in its technology as the article talks about filing for some patents soon.

http://timesofindia.indiatimes.com/home/science/British-engineer-building-rocket-to-revolutionize-space-travel/articleshow/37893396.cms

It has been discussed at great length, although it can be difficult to find as it is often intertwined in other related topics. Here are a few examples:

http://cosmoquest.org/forum/showthread.php?118445-Roscosmos-The-age-of-Soyuz-has-started

http://cosmoquest.org/forum/showthread.php?86728-Passenger-market-for-suborbital-hypersonic-transports

http://cosmoquest.org/forum/showthread.php?118956-How-far-into-the-future-An-aircraft-that-launches-from-a-runway-and-enters-low

Noclevername
2014-Jul-06, 02:01 PM
Let's not forget the thread that's directly about Skylon:

http://cosmoquest.org/forum/showthread.php?85589-british-rocketplane-by-2020

selvaarchi
2014-Jul-06, 02:14 PM
Thanks, they are all at least two years ago, so there must be some new development to hit the news now.

Noclevername
2014-Jul-06, 02:37 PM
Thanks, they are all at least two years ago, so there must be some new development to hit the news now.

The last post in the Rocketplane thread is dated January of this year.

Swift
2014-Jul-06, 03:34 PM
The last post in the Rocketplane thread is dated January of this year.
I've merged the new thread with the big Skylon thread

Garrison
2014-Jul-06, 06:18 PM
I could not find any reference this British development in the forum. It must have advanced in its technology as the article talks about filing for some patents soon.

http://timesofindia.indiatimes.com/home/science/British-engineer-building-rocket-to-revolutionize-space-travel/articleshow/37893396.cms


Which simply speaks volumes about the poor quality of you research. That link of yours has to be one of the worst I've seen about Skylon since they couldn't even come up with one of the many PR shots for the Skylon that Reaction Engines have created.

Swift
2014-Jul-06, 06:45 PM
Which simply speaks volumes about the poor quality of you research.
The criticism of the reference is fine, but let's not make this personal.

selvaarchi
2014-Jul-06, 09:56 PM
Which simply speaks volumes about the poor quality of you research. That link of yours has to be one of the worst I've seen about Skylon since they couldn't even come up with one of the many PR shots for the Skylon that Reaction Engines have created.
I must be doing something wrong with my search using "Tapatalk" as it did not find any reference to the search on "Skylon". The same thing happened when I did a search for "New Horizons" but in this case I knew it existed and found it manually.
It is most likely my fault as I have only been using a smart phone for 3 months and am doing something wrong with the way I do the search.

selvaarchi
2015-Apr-20, 02:46 PM
Some positive news for Reaction Engines Ltd.’s Synergetic Air-Breathing Rocket Engine, SABRE.

"The U.S. Air Force Research Laboratory (AFRL) has answered with a qualified “yes” the question of whether a British company’s revolutionary air-breathing rocket engine, designed for a horizontal-takeoff vehicle climbing to orbit with a single stage, holds promise."

http://spacenews.com/afrl-gives-seal-of-approval-to-british-air-breathing-engine-design/


AFRL’s Aerospace Systems Directorate looked at Reaction Engines Ltd.’s Synergetic Air-Breathing Rocket Engine, SABRE, as part of a Cooperative Research and Development Agreement.

The key component of the engine is its heat exchanger, designed to convert incoming air from 1,000 degrees Celsius to minus 150 degrees Celsius in one-hundredth of a second.
SABRE Reaction Engines

As announced by Reaction Engines March 15, AFRL’s assessment is generally good news for a company that has been trying to win support for its technology for well over a decade.

publiusr
2015-Apr-25, 07:22 PM
An old but useful page http://www.astronautix.com/lvs/skylon.htm

Garrison
2016-Jul-12, 08:56 PM
I was going to post the most recent news on the Skylon/SABRE project only to discover some important developments from the end of last year hadn't been added:

BBC article from November 2015:

BAE invests in space engine firm Reaction Engines (http://www.bbc.co.uk/news/business-34694935)


BAE Systems has bought a 20% stake in a company developing a radical engine that could propel aircraft into space.

BAE is paying £20.6m for the stake in Reaction Engines, which is developing a hybrid rocket/jet engine called Sabre.

And the new news is:

Funding flows for UK’s ‘revolutionary’ Sabre rocket engine (http://www.bbc.co.uk/news/science-environment-36773074)


The £60m UK government investment in the "revolutionary" Sabre rocket engine concept has finally started to flow.

Why you may ask has it taken so long for this promised funding to be released?


Part of the reason for the delay was the need to win a state aid, fair competition ruling from the European Commission. Another reason lay in agreeing the complex terms of what will be a "grant", not a "loan".

Yes, wouldn't want to be unfair to all those competing European SSTO projects...:doh:

danscope
2016-Jul-13, 05:02 AM
How will that square with the Brexit ?