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Rocket Man
2007-Feb-09, 05:25 PM
I wanted to get people view of the Crew Exploration Vehicle. Do you thing it's a good idea, a step backwards, a waste of money, etc?

Rocket Man
2007-Feb-09, 05:30 PM
Rats! Can a mod fix my typo in the thread title? I tried to edit the title but it didn't work for some reason.

gaetanomarano
2007-Feb-09, 05:30 PM
just better than nothing

NEOWatcher
2007-Feb-09, 05:46 PM
I wanted to get people view of the Crew Exploration Vehicle. Do you thing it's a good idea, a step backwards, a waste of money, etc?
Can I pick 2 of the choices?
It's a good idea to take a step backwards to keep the momentum going while trying to determine the best step forward.

Doodler
2007-Feb-09, 06:21 PM
I wanted to get people view of the Crew Exploration Vehicle. Do you thing it's a good idea, a step backwards, a waste of money, etc?

Its a sidestep. To call the Orion a backstep because the shuttle was ultimately a failure is akin to saying the Airbus A380 is a backstep because the Concorde was a failure.

Somewhat apples to oranges, maybe more akin to green apples and red apples. The Orion picks up where the Apollo program was regrettably left off. I would not consider the Shuttle to be a linear descendant of the Apollo program at all, just a Concorde we got a little too overreliant on.

Rocket Man
2007-Feb-09, 09:05 PM
I see the CEV from a few perspectives. In a way it's a return to a simplier and successful design. It has a specific purpose and that is to get us back to the moon and eventually perhaps Mars. NASA probably still has a bitter taste in their mouth over the failed X-33 project. But I think their mistake with the X-33 was they tried to do too much with the SSTO design. Instead of trying to build a simplier one man or two man SSTO vehicle they went for broke trying to design a SSTO vehicle that would do everything. That I feel was a mistake. It's like as if NASA, instead of first building the Mercury spacecraft, intsead tried to design and build the Apollo spacecraft. However, with NASA going with the CEV there will be no push to develop a true SSTO vehicle with has far more future potential for deep space exploration (by this I mean exploration of our own solar system). In a way, CEV is like a evolutionary dead-end where the capacity to adapt it to other types of missions is limited.

But there is good news in that there are various small companies trying to develop SSTO or similar suborbital vehicles (Masten Space Systems, Blue Origin Benson Space, Sclaed Composites, etc). I believe that the private sector will be at the forefront in developing revolutionary new spacecraft in the next 5-10 years.

JonClarke
2007-Feb-09, 11:37 PM
In a way, CEV is like a evolutionary dead-end where the capacity to adapt it to other types of missions is limited.

I would see it as the complete opposite. It is a very flexible spacecraft with considerable potential that can not only serve LEO and lunar missions but provide crew return from flights to Mars, NEOs, and Venus.

Jon

cjl
2007-Feb-09, 11:47 PM
Why do you assume that SSTO is the best way for deep space exploration? Expendable staged vehicles can carry FAR more payload for their size, allowing for larger and more capable spacecraft.

Rocket Man
2007-Feb-10, 01:02 AM
Why do you assume that SSTO is the best way for deep space exploration? Expendable staged vehicles can carry FAR more payload for their size, allowing for larger and more capable spacecraft.

The problem with expendable rockets is that they are expendable. That will always make them very expense. Can you imagine if airlines had to use expendable aircraft to fly passengers or freight? What financial sense does that make? Actually, I can see in the not-to-distant future a series of orbiting space stations and large spacecraft for deep space missions that are stationed at these space stations. These large spacecraft would never land on earth. You would also have smaller spacecraft to ferry people and supplies up to the space stations. Or perhaps even use reusable staged rockets like the the Kistler Aerospace is developing to travel up and down from the space stations.

JonClarke
2007-Feb-10, 01:24 AM
The problem with expendable rockets is that they are expendable. That will always make them very expense. Can you imagine if airlines had to use expendable aircraft to fly passengers or freight? What financial sense does that make? Actually, I can see in the not-to-distant future a series of orbiting space stations and large spacecraft for deep space missions that are stationed at these space stations. These large spacecraft would never land on earth. You would also have smaller spacecraft to ferry people and supplies up to the space stations. Or perhaps even use reusable staged rockets like the the Kistler Aerospace is developing to travel up and down from the space stations.

Given the present realities of spaceflight expendable is generally cheaper because of the enormous refurbishment costs associated with resuable systems. Shuttle experience has shown that. The Ares 1 may turn that about, but it remains to be seen.

SSTO is theoretically very attractive, but requires mass ratios that appear impossible to achieve using current technology except (perhaps) for very large boosters. The ROMBUS rocket is a prime example.

Jon

cjl
2007-Feb-10, 01:46 AM
The problem with SSTO however is much larger, and what JonClarke said: Mass ratios. Staged are quite simply FAR more efficient than a SSTO, and therefore are actually significantly cheaper right now. That won't change without a significant propulsion technology change.

Rocket Man
2007-Feb-10, 01:46 AM
Given the present realities of spaceflight expendable is generally cheaper because of the enormous refurbishment costs associated with resuable systems. Shuttle experience has shown that. The Ares 1 may turn that about, but it remains to be seen.

SSTO is theoretically very attractive, but requires mass ratios that appear impossible to achieve using current technology except (perhaps) for very large boosters. The ROMBUS rocket is a prime example.

Jon
Based on my reading of various SSTOs systems, SSTO vehicles may be incapatible with chemical rocket engines.

What's your take on reusable staged rocket designs like the Kistler K-1 (if they ever actaully launch it)?

cjl
2007-Feb-10, 03:49 AM
I haven't seen it, but it would seem to be inordinately difficult to reuse the second to last stage, as it would be jettisoned at almost full orbital velocity. That could require significant heat shielding...

First stage reusability may be possible though without too much of a weight penalty, depending on the exact details of the vehicle used.

Rocket Man
2007-Feb-10, 05:40 AM
I haven't seen it, but it would seem to be inordinately difficult to reuse the second to last stage, as it would be jettisoned at almost full orbital velocity. That could require significant heat shielding...

First stage reusability may be possible though without too much of a weight penalty, depending on the exact details of the vehicle used.

Here's a detailed description of the Kistler K-1 launch vehicle. (http://www.kistleraerospace.com/k1vehicle/k1vehicle.html)

Rocket Man
2007-Feb-10, 05:47 AM
I haven't seen it, but it would seem to be inordinately difficult to reuse the second to last stage, as it would be jettisoned at almost full orbital velocity. That could require significant heat shielding...

First stage reusability may be possible though without too much of a weight penalty, depending on the exact details of the vehicle used.

Here's a detailed description of the Kistler K-1 launch vehicle (http://www.kistleraerospace.com/k1vehicle/k1vehicle.html) and a nice exploded assembly (http://www.kistleraerospace.com/newsinfo/publications/vehiclestatus083104.pdf).

Maksutov
2007-Feb-10, 05:57 AM
Rats! Can a mod fix my typo in the thread title? I tried to edit the title but it didn't work for some reason.Once you've committed to a title that's it, until a mod mods it.

But I find the slip appropriate. Crew Exploration VW-hicle. A Volkswagen-type approach to manned spaceflight: cheap, simple, and dependable.

Drbuzz0
2007-Feb-11, 05:43 PM
I wanted to get people view of the Crew Exploration Vehicle. Do you thing it's a good idea, a step backwards, a waste of money, etc?

I do not like it. Nobody ever claimed that a space capsul and disposable rocket was an economical way of getting routine robust and simple access to orbit. It was used in the apollo program and before because there was a need to get into space with avaliable technology for political and other reasons.

The idea for the shuttle was to have a reusable space craft which could provide access to space which would not require the crazy infrastructure, costs, logistics and such. The shuttle was supposed to be a sort of spaceplane, a two stage fully reusable system which would be designed primary for human flight and space station service. Though not as cheap or simple as a standard aircraft, it was hoped that it could eventually be on par with the costs of flying an sr-71 or xb-70 or something similar.

Then came budget cuts, unrealistic military demands, time constraints, compromises and numerous other problems with resulted in the current shuttle, which is more expensive to launch than previous systems and has a dismal safety record. It has some decent capabilities, but as far as re usability? Well, technically it is, but it has to be completely refurbed and overhauled each time.

I would favor a space plane concept, using ram/scramjets for the first phase of liftoff or a SSTO approach (single stage to orbit) or something similar. It may cost more in the short run, but it will ultimately be the future, as opposed to trying to milk a very imperfect technology for you can get from it.

Right now, the Space Station cannot be easily supplied or accessed on relatively short notice. The US has lost most of the satellite launch maret to cheaper alternatives, the current human space exploration system is unreliable and unsustainable. A space plane would only be useful for LEO missions, not moon exploration, but it's an issue of priorities. There's no reason in stretching to go to the moon, if you can't have a sustainable and managable program.


The argument against this is that this technology would be new, unproven, exotic and has not been tested in a full vehicle. Such a vehicle would require inventing new systems, some from scratch and shooting for a goal that is downright futuristic.

My response: You *are* NASA. Remind me again, why do you exist?

Doodler
2007-Feb-11, 05:50 PM
My response: You *are* NASA. Remind me again, why do you exist?

Don't blama NASA. Tell Congress and the American public to go to Hell when a manned spacecraft goes down or get used to the idea of sticking with a manned program that babysteps forward on proven technology alone.

AtomicDog
2007-Feb-11, 06:44 PM
My response: You *are* NASA. Remind me again, why do you exist?

So when NASA presents you with an extra $5B/year bill for an SSTO development program, you'll be glad to pay it, right?

Drbuzz0
2007-Feb-11, 07:02 PM
So when NASA presents you with an extra $5B/year bill for an SSTO development program, you'll be glad to pay it, right?

Depends on how many years the development takes.

cjl
2007-Feb-11, 07:05 PM
Nobody ever claimed that a space capsul and disposable rocket was an economical way of getting routine robust and simple access to orbit

And yet it is by far the cheapest and simplest way. Look at the cost difference between the shuttle and the soyuz, for example.

Drbuzz0
2007-Feb-11, 07:07 PM
Don't blama NASA. Tell Congress and the American public to go to Hell when a manned spacecraft goes down or get used to the idea of sticking with a manned program that babysteps forward on proven technology alone.

Responses:

Like that is not happening now, with our current manned space program? Amazingly, back in the day, when they were doing completely new and unproven things and inventing technology as they went along, the safeguards in place, such as unmanned tests and escape systems seemed to have a decent test record, since no lives were lost in a mission. (unless you count Apollo one, which was not an actual mission accident, but a practice run. However tragic, the current shuttle makes it look like a small sacrifice, given the 14 who have died in the Columbia and Challenger)


The new CEV uses proven technology, including the shuttle's SRB. If by proven they mean "The current generation has not been directly responsible for complete loss of crew and vehicle" then I suppose that could be true. Von Braun had said many times that it was crazy to put a manned spacecraft on a solid rocket booster, which cannot be shut down and has limited controllability once started.

AtomicDog
2007-Feb-11, 07:46 PM
Depends on how many years the development takes.

The point is, NASA would be glad to restart its SSTO program, if it
A. Was told to, and
B. It had the money. Where is it going to come from?

JonClarke
2007-Feb-11, 09:36 PM
Based on my reading of various SSTOs systems, SSTO vehicles may be incapatible with chemical rocket engines.

It's borderline with chemical engines but impossible with anything else. Economies of scale and advanced materials I suggest will make it possible. I like the ROMBUS concept, but the demand for 500 tonne payloads is rather limited.

In the end it may be better to invest in a space elevator.


What's your take on reusable staged rocket designs like the Kistler K-1 (if they ever actaully launch it)?

Good luck to them! I hope they succeed. Of course Ares I will also be a reusable staged rocket.

Jon

Drbuzz0
2007-Feb-11, 10:07 PM
The point is, NASA would be glad to restart its SSTO program, if it
A. Was told to, and
B. It had the money. Where is it going to come from?

So then the blame rests with congress or the president for his proposals for moon return. It begs the question: Why go to space?

I would argue the reasons are for scientific discovery and to improve technology and develop useful technologies, for example communications satellites, earth imaging data, tactical intelligence satellites (ideally for defensive and diplomatic purposes), navigation, environmental effects data, general science data.

Then the next question is this: Is it more productive toward these goals to return to the moon, using systems derived from current technologies and which will not allow it to be routine and economical (cheaper than reinventing them, but going to the moon will be expensive no matter how you do it),

OR

would the above goals be better served by using the avaliable funds not to go to the moon but to develop launch systems with the goal of making access to space in general more economical and easy, thereby allowing for a greater number of experiments, better support for the space station, cheaper launches for commercial ventures, less time waiting for scientists to get their payload flown ect ect.


I am strongly in favor of the later. If a point can be reached where graduate students can have their experiments flown, where scientists don't have to have years of research riding on a single experiment, which if unsuccessful may never have the chance to be tried again, and where the response to a report of a systems failure on the space station might be "we will send up some replacement parts tomorrow morning." That will be the culmination of the potential which space has.

Granted that is a lofty goal, but it is the direction I would like nasa to head toward, even if making it that far may not happen any time soon.

Larry Jacks
2007-Feb-12, 12:06 AM
A SSTO vehicle is great in science fiction but comes up short when you factor in real world constraints like the rocket equation. Using the rocket equation and applying the best practical propellant combination, it turns out that 90% of the liftoff mass will be propellant. That leaves a whopping 10% for everything else like the vehicle itself, payload, engines, avionics, heat shielding, etc. Scramjets might be able to improve things somewhat but I seriously doubt your propellant mass fraction would drop more than 5 to 10% when all it said and done. Even if you make it work, that's only good to LEO. A spaceplane could be used to commute between the surface and LEO but it carries tons of dead mass for going anywhere else.

In the end, total cost of ownership and flight rates are what matters most. Total cost of ownership includes research & development costs, production costs, infrastructure costs, fixed costs (e.g. personnel) and operations/maintenance cost. A fully reusable ground to LEO vehicle could be made (though probably not SSTO). The R&D costs would be very high but potentially, the operations cost (primarily propellant, crew training, pad refurbishment, etc.) could be quite low. Maintenance costs depend on the design - a vehicle like the Shuttle requires servicing by a cast of thousands.

The true cost per mission would then need to factor in the launch rate. It doesn't matter if the operations cost for flying a mission were only a million dollars if you only fly it a few times a year and the fixed costs are high due to a large workforce like we have today.

The Russian Soyuz is the classic example of a "big dumb booster" (and I mean that in a good way). It's R&D costs are minimal because the design hasn't changed a great deal in 40 years. They were able to build and launch well over 1000 of them with a high degree of reliability. The high launch rates (especially up to the late 1990s when the Soviets were launching over 50 space missions a year, with a high percentage on Soyuz boosters) helped lower the per mission costs radically. While certainly not reusable nor simple, the Soyuz is one of the least expensive boosters out there on a payload to orbit basis. It's very reliable and even man-rated to boot. Any futuristic space plane needs to be compared to the Soyuz when all is said and done. It's hard to argue with success like Soyuz.

Doodler
2007-Feb-12, 05:00 AM
Responses:

Like that is not happening now, with our current manned space program? Amazingly, back in the day, when they were doing completely new and unproven things and inventing technology as they went along, the safeguards in place, such as unmanned tests and escape systems seemed to have a decent test record, since no lives were lost in a mission. (unless you count Apollo one, which was not an actual mission accident, but a practice run. However tragic, the current shuttle makes it look like a small sacrifice, given the 14 who have died in the Columbia and Challenger)

The new CEV uses proven technology, including the shuttle's SRB. If by proven they mean "The current generation has not been directly responsible for complete loss of crew and vehicle" then I suppose that could be true. Von Braun had said many times that it was crazy to put a manned spacecraft on a solid rocket booster, which cannot be shut down and has limited controllability once started.

Quoting Von Braun as an authority on modern rockets would be akin to asking Henry Ford Senior's opinion on the latest model Ford Explorer. Any vehicle carries with it the risk of catastrophe if not designed and operated correctly, that does not imply that technology does not improve over timeor that existing technology cannot be safely used.

FYI, the SRB system on the space shuttle happened to be THE system that killed half the astronauts lost during the shuttle era. As it so happened, the redesign of those SRBs resulted in a safer vehicle with the same roman candle fuel it always used. So, a previously unsafe technology advanced through rather unfortunate circumstances, and is now much more appropriate for human use. As did the Apollo 1 tragedy taught us the dangers of inswinging doors and pure O2 saturated atmospheres, design elements that have never been used again in operational spacecraft.

There are times when we learn by doing, and there are times we only learn by dying.

JonClarke
2007-Feb-12, 07:27 AM
Good post, just a couple of nits.


As did the Apollo 1 tragedy taught us the dangers of inswinging doors and pure O2 saturated atmospheres, design elements that have never been used again in operational spacecraft.

The lesson from Apollo 1 was that inward opening hatches should not be used for crew escape. They continue to be used in many other cases because they save a lot of weight. the LM hatch was just one example. The ISS, Soyouz and Shuttle docking hatches all open inwards.

Pure O2 atmospheres continued to be used on Apollo and, with minor addition of N2, on Skylab. They (or a Skylab like O2-rich atmosphere) are very attractive for Moon and Mars missions. The lesson of Apollo 1 was that they should not be used at Earth surface or greater pressures.

Jon

joema
2007-Feb-12, 02:40 PM
A SSTO vehicle is great in science fiction but comes up short when you factor in real world constraints like the rocket equation....Scramjets might be able to improve things somewhat but I seriously doubt your propellant mass fraction would drop more than 5 to 10% when all it said and done. Even if you make it work, that's only good to LEO...
Exactly right. A SSTO or TSTO using scramjets is a wonderful romantic idea, but it's not feasible.

An airbreathing SSTO must fly a "depressed trajectory" and stay within the atmosphere for much of the ascent. It's like a reentering space capsule but far worse. The heat shielding requirements are far beyond a space capsule or the shuttle.

Scramjets don't work until hypersonic speed. You've ALSO got to have huge turbine engines to haul the entire vehicle off the runway and up to scram jet speed. In actuality no turbojet can go that fast, so you must ALSO have an interim engine to boost from turbojet max Mach no. up to minimum scramjet operational speed.

Then scramjets cannot achieve orbital speed, so you need yet another engine type (generally rockets) to boost from scramjet top speed to orbital speed.

EACH of those systems requires separate fuel, separate structure, separate control systems, and shielding for the return trip.

Someday it may be done, but you don't get extra points for getting to orbit "the hard way", or getting to orbit the "coolest way". The goal is getting to orbit the simplest, safest and cheapest way. Rockets are very good at that, relative to the currently achievable alternatives.

Fine, you say, I'll solve the problem by making a TSTO with an only the 1st stage airbreathing. Sort of like SpaceShipOne, but where the White Knight mothership has scramjets and is hypersonic.

However the math shows it's incredibly challenging, which means expensive. Kinetic energy scales as the SQUARE of velocity, so for the 2nd stage to have enough energy for orbit it must be MUCH bigger than SpaceShipOne. This in turn requires a much bigger mothership -- a vicious cycle.

For a small man-carrying orbiter, (say about like the X-20 DynaSoar, not inc'l 2nd stage propulsion/fuel), the required mothership would be gigantic.

We know that because t/Space is thinking of having Burt Rutan build a gigantic mothership to air launch a man carrying orbital vehicle.

The mothership would be huge -- gross weight of one million lbs, payload 150 tons (3x a 747-400 freighter), wingspan 320 feet (1.5x a 747). It would the largest aircraft ever constructed. See January 2006 Air & Space magazine for details.

Development costs usually increases in proportion to gross weight, so it would be incredibly expensive. The above proposed Rutan mothership isn't supersonic, much less hypersonic. To make it so would be even more expensive.

It's not like launching an X-15 off the back of an XB-70 (max payload about 50,000 lbs). For orbital flight, each vehicle would have to be much bigger, more complex. You'd need something like a supersonic or hypersonic Antonov AN-225: http://en.wikipedia.org/wiki/Antonov_225. Development costs would make the current shuttle look like a model rocket.

joema
2007-Feb-12, 02:55 PM
...FYI, the SRB system on the space shuttle happened to be THE system that killed half the astronauts lost during the shuttle era. As it so happened, the redesign of those SRBs resulted in a safer vehicle with the same roman candle fuel it always used. So, a previously unsafe technology advanced through rather unfortunate circumstances, and is now much more appropriate for human use...
Another point is while the initial SRB joint design was suboptimal, the accident probably wouldn't have happened had the vehicle been operated within the design temperature spec.

The same thing happened with Columbia. The design spec for maximum allowable TPS impact was 0.006 ft-lbs, which is tiny. Yet it was being operated where impacts thousands of times greater frequently happened.

With the shuttle or any future vehicle, whether solid or liquid fueled, you run a risk by operating it outside the specification.

When Ares I finally flies, if it's similarly operated outside the design spec, it can similarly have a catastrophic failure. A launch escape system may save the crew, but it won't save the vehicle, nor will it prevent a possible years-long shutdown to scrutinize the problem.

Doodler
2007-Feb-12, 03:51 PM
Good post, just a couple of nits.



The lesson from Apollo 1 was that inward opening hatches should not be used for crew escape. They continue to be used in many other cases because they save a lot of weight. the LM hatch was just one example. The ISS, Soyouz and Shuttle docking hatches all open inwards.

Pure O2 atmospheres continued to be used on Apollo and, with minor addition of N2, on Skylab. They (or a Skylab like O2-rich atmosphere) are very attractive for Moon and Mars missions. The lesson of Apollo 1 was that they should not be used at Earth surface or greater pressures.

Jon

Corrections noted. :)