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ToSeek
2003-Jul-24, 04:30 PM
That is the question (http://www.spaceflightnow.com/news/n0307/23osp/)

That capsule looks mighty familiar somehow....

Glom
2003-Jul-24, 04:50 PM
Lifting body designs have better hope for reusability, but it always seems that capsules are more efficient at the end of the day.

man on the moon
2003-Jul-24, 05:30 PM
can we use a capsule (cheaper, we could have it "tomorrow" so to speak, but less payload) until an OSP can be built? (the OSP would take more money and time).

if someone were to really be creative, perhaps a capsule could be designed to ride atop a rocket like the Atlas V, with a big payload underneath. sort of like the Apollo set up, but instead of a lander and ascender and rentry module, you would have a payload in a big cylinder sitting on top of the rocket, and the capsule on top of that.

once in orbit the astronauts could access the cylinder portion, do their work...you could even design the cylinder to be built onto the ISS once it has been used. it could be converted into labratory space, quarters, or whatever. then when the astronauts are done, they would get back in the capsule, detach it, and come back to Earth. :-k

it would sort of be like sending the shuttle up, and just coming back with the cockpit. it wouldn't really be like leaving the shuttle body there of course, it would be the used payload cylinder...and it would just be till an OSP could be built in ten or twelve years.

anyway, all these ideas have come to me as i'm typing--off the top of my head you might say--just random thoughts trying to coalesce. it's a new idea and i just want to throw it out there, see what people think.

Doodler
2003-Jul-24, 05:33 PM
if its just a crew ferry, capsules seem just peachy to me... Not just the capsule, but an SM too, could be used as a dual purpose Cargo/Support craft that could do the job of the Progress and the Soyuz for both ISS missions and independant science. Save the shuttles for the big missions that require the heavy cargo lift and brute muscle of its thrusters or the controlled workspace in the cargo bay like the Hubble Telescope or altering the station's orbit substantially

daver
2003-Jul-24, 07:36 PM
Ramblings.

There's probably a mass tradeoff here--above some point wings (or descent rockets) probably makes sense. Below that point, ballistic or semi-ballistic capsules probably make more sense. One of the selling points of the shuttle was that it could bring down large objects; in retrospect, i'm not sure that this was all that useful.

My take is that we really need a ferry as soon as possible. Which means an ELV-launched capsule.. Water recovery would be easiest, land recovery would require some sort of crush zone and landing rocket (and maybe a steerable parachute). It's possible that the steerable parachute idea could be adapted for a fresh-water recovery; the fresh water recovery would be cheaper than an ocean recovery and less stressful than a land recovery (there are obvious complications here, like chasing the rubes away from the lake, and the potential damages if you missed the lake and landed in a church retreat or hotel). Maybe an aerial recovery (with land or water recovery as a backup) is possible, but it seems likely to me that a missed recovery could collapse the parachutes.

I think i'd like to see the first few landings be ocean recoveries; some flexibility for more complicated (and cheaper) recovery mechanisms could be built in. I'd really, really, like to see lots of launches. At least one a month at first. They don't have to be manned, just designed to test out new features (like new recovery mechanisms) or new approach profiles.

I'm not sure how much of the capsule needs to be reusable. It might be that there would be two sections--the living section and a replaceable heat shield/crush-zone/landing rocket section.

Stacking the capsule (and its SM) on top of the payload seems like a reasonable idea. It allows for plenty of flexibility. It might be a reasonable idea to have a variety of SMs available--small ones for going to and from the station, bigger ones for longer duration missions.

After the capsule is flying, NASA would need to start working on the next model of orbiter. Maybe this one would have wings or the capability to bring back payloads.

man on the moon
2003-Jul-24, 07:50 PM
seems like a lot of good ideas here. does anyone know two things:

1) is NASA looking for suggestions/designs

10) how do we contact them

and a third:

11) propose that we continue to bounce ideas off each other, and after a bit, take a consensus and appoint a handful of people to write up an official proposal to send to NASA?

i don't know anything about doing that sort of thing, but it seems like a feasible plan if someone has the expertise. we'd all contribute, and all it would be would be a few people who know how to do official papers, then check it with the others, and send it on it's way. what do you think?

(not that i'm unwilling to help. i can do grammar and the like, i just have no experience writing "official" reports. :-? )

kingneptune8
2003-Jul-24, 08:02 PM
Wouldn't wings make more sense than a capsule?

tracer
2003-Jul-24, 08:11 PM
man on the moon: Numbering your questions in binary, are you?

TinFoilHat
2003-Jul-24, 08:42 PM
Capsules pros:

*Much easier to build - proven designs already exist
*More useful payload per launch mass
*Easier to add a launch escape system to
*Reentry is simpler and more reliable - even in the event of a complete guidance system failure, the capsule can still make a surviveable landing.
*Heat shield is facing downwards during launch, making it less likely to be damaged by debris
*Crew are lying on their backs in launch and reentry, making the G forces easier to endure.

Cons:

*Very little crossrange capability - once you've fired your retrorockets, your landing point is pretty much set
*Can't land with great accuracy; can easily miss the landing target by miles
*Higher G forces during reentry, and a harder landing
*Harder to make reuseable
*Harder to maintain the illusion that the crew are in any way important for piloting the ship during reentry
*People will sneer at it as technologically primitive

Spaceplane pros:

*Significant manueverability means it can land precisely on a runway
*Looks cool, and provides many more aerospace jobs due to greater complexity
*Gentler reentry and landing forces

Cons:

*Far more complex and expensive to build
*Significant weight given over to parts useless in orbit - wings, tail, hydraulic APU system to run control surfaces, and wheels
*Less useable payload per launch weight
*More fragile, and requires complex control system to survive reentry
*Wings create extra stresses during launch, and a crew escape system is harder to implement

I'm in favor of a capsule design, at least as far as a near-term crew transver vehicle is concerned. Mainly because it seems to be a much safer option, and can be developed and working much more quickly.

Emspak
2003-Jul-24, 08:50 PM
Has anyone thought of a spaceplane that could be launched lie a plane as well as landed like one?

Maybe a JATO for the first push, a scramjet kicks in, and a rocket type engine once it gets to orbital speeds for that final oomph out of the atmosphere?

TinFoilHat
2003-Jul-24, 09:04 PM
Has anyone thought of a spaceplane that could be launched lie a plane as well as landed like one?
Horizontal takeoff/Horizontal Landing is very hard to do, might even be impossible with today's technology. Remember that at liftoff any SSTO vehicle is going to be something like 90% fuel. A VTHL vehicle like the shuttle only has to support its dry weight when landed and horizontal - the landing gear and frame don't need to be strong enough to support the liftoff weight. A horizontal takeoff vehicle will need about ten times the strength in its landing gear and lengthwise structural members to support the liftoff weight when taxiing down the runway. All launch vehicles have to support their liftoff weight vertically during liftoff, to survive launch acceleration; making one which can support its liftoff weight both vertically and horizontally adds a huge and unnesseccary weight burden.

man on the moon
2003-Jul-24, 09:08 PM
man on the moon: Numbering your questions in binary, are you?

:D

Glom
2003-Jul-24, 09:15 PM
What about the idea of the two stage space plane? The first stage is a big honkin' lifting body (nuclear of course :wink: ) that takes off from a runway with the orbiter on its back. At the right altitude and speed, it releases the orbiter which goes off into orbit and returns in glider fashion.

Wasn't such an idea explored?

BigJim
2003-Jul-24, 09:23 PM
Horizontal takeoff/Horizontal Landing is very hard to do, might even be impossible with today's technology

TinFoilHat, meet Pioneer Rocketplane. (http://www.rocketplane.com) It's an X-Prize contender, but I think that its basic design has merit as an STS replacement. Pioneer Rocketplane's Pathfinder has more capability than most other near-term designs in several categories. Pathfinder takes off on its own, from a normal runway, using normal, off-the-shelf jet engines. It then fuels its rocket engines from an aerial tanker. This allows it to take off while light, which stops it from having to use schemes like aircraft or balloons to gain altitude, and I think runway takeoffs are ultimately more practical, because then billions of dollars or more in new launch sites do not have to be built. Aerial refueling has been nearly perfected over many years by the Air Force and is done hundreds of thousands of times a year.


The Pathfinder then fires its engines, does a suborbital run, where it can release a payload with a small booster stage (the Pathfinder has a payload bay and a crew cabin) It then lands using its jet engines on a normal runway, eliminating the danger of a dead-stick landing.

Since the Pathfinder can carry crew and payload from normal runways, it can easily be used for fast package delivery, military uses (not that I am in favor of that, but it is suitable), scientific uses (I believe it has a payload range in range of a Pegasus XL), and extremely fast passenger travel, using existing runways and airports. The Pathfinder design cannot reach orbit but larger versions of it can.

But I'm diverging from the point. The debate here is over capsules or winged craft for the OSP design. I support a capsule.Why a capsule?


*More useful payload per launch mass

This is ultimately the most important statistic of the day. A true space access system should have separate designs for each craft, like Mir did. There were Protons for station modules, Progress craft for supplies, Soyuz craft for access. The Shuttle tries to merge all of these into one craft and then make it reusable. However, the STS is remarkably inefficient - over 85% of the weight it lifts is itself. What we need is an Apollo-like design for space access and then a ferry. Putting both in the same craft adds tremendous weight and complexity. The Shuttle was originally designed to complement Apollo and carry supplies to Skylab, not totally replace Apollo and Skylab as its own program.


*Easier to add a launch escape system to

True. And the craft is launched on top of a rocket, which would prevent a Columbia - type disaster caused by things falling on it.


*Much easier to build - proven designs already exist

Soyuz and Apollo are tried and true craft. If we had kept Apollo we would have had the added benefit of being able to continue lunar flights.


*Can't land with great accuracy; can easily miss the landing target by miles


But accuracy is not as important for sea landings.


*Looks cool, and provides many more aerospace jobs due to greater complexity


However, designing something for maximum complexity is the wrong way to do engineering. Designing a system or spacecraft so that everybody gets to do something, like the ISS results in skyrocketing costs and little capability. And looking cool is not a functional benefit.

I think that at the end of the day, payload capability per launch is the most important thing. And the fact that capsules are simpler and have more reliable heat shield systems doesn't hurt, either. So I think that OSP should be a capsule design.


What about the idea of the two stage space plane? The first stage is a big honkin' lifting body (nuclear of course ) that takes off from a runway with the orbiter on its back. At the right altitude and speed, it releases the orbiter which goes off into orbit and returns in glider fashion.

Wasn't such an idea explored?

There were orbiter concepts in which the first stage of the Saturn V was used to boost it. However, these never reached fruition due to budgetary problems. After HTHL, liquid flyback boosters are the next best option for boosting reusable spacecraft. If the Shuttle were boosted by a liquid flyback booster instead of the system it has now, it would be much more efficient.

Colt
2003-Jul-24, 11:58 PM
Right now I would go with a capsule until we can develop a usable and workable spaceplane (I hate that term, it sounds like something you would read from "Big Book of Space for Children"). The Apollo capsule would probably be too small unless you wanted the crew to stay in orbit for a short time. You would need something larger.. Maybe leading to a launch vehicle larger than the Saturn-V. :o The Russians had something like that to launch their manned Lunar missions. I saw it compared to the Saturn-V once.. It was massive. :o Here it is: The N1 (http://www.russianspaceweb.com/n1.html).

Here I discuss an idea I had: Orbiter - Flying gastank booster? (http://www.badastronomy.com/phpBB/viewtopic.php?t=2871&highlight=lob) and specifically what I was talking about: Low Orbital Booster (http://www.geocities.com/wandererofthewastes/LOB.jpg) Really crude sketch but it gets the idea across. -Colt

BigJim
2003-Jul-25, 12:28 AM
Right now I would go with a capsule until we can develop a usable and workable spaceplane (I hate that term, it sounds like something you would read from "Big Book of Space for Children"). The Apollo capsule would probably be too small unless you wanted the crew to stay in orbit for a short time. You would need something larger.. Maybe leading to a launch vehicle larger than the Saturn-V. The Russians had something like that to launch their manned Lunar missions. I saw it compared to the Saturn-V once.. It was massive. Here it is: The N1 .


The Saturn V was larger than the N-1. Plus the N-1 used less efficient propellants, so it only had about 70% of the payload capability.

Keep in mind that the Saturn V could launch an Apollo CSM and LM all the way to the Moon, so you really wouldn't need anything that much larger. Remember that the Saturn IB could launch an Apollo CSM into Earth orbit.

Colt
2003-Jul-25, 08:36 AM
I'm just having visions of the old days coming back. Huge rockets, small capsules. *sigh* The good old days when, if the rocket blew up, it would go like a small nuke.. If I remember correctly, when those N1s failed and exploded it vaporized everything in the area. They had to keep rebuilding the launch platform and that delayed the program. -Colt

Kaptain K
2003-Jul-25, 10:45 AM
Here we go again! :o NASA is going to try to build one new craft to do everything. :roll: They seem to think that one vehicle can be a taxi, delivery van, bus and freight truck. It didn't work with the shuttle and it won't work with the OSP.

Capsule for three or four crew at a time transfers. Later, build a space bus for large scale people moving when it becomes necessary.

Cargo goes up on current boosters. Later, when bigger chunks of hardware need to go up, build an unmanned booster. Maybe a basic box with manuvering jets and mounting points for varying numbers of SRBs depending on the payload.

When your only tool is a hammer, every job looks like a nail.

TinFoilHat
2003-Jul-25, 01:24 PM
I'm just having visions of the old days coming back. Huge rockets, small capsules.
Yeah, those bad old days, when NASA built working vehicles rather than paper studies, and actually achieved their goals.

For the heavy cargo lift and return role, there's another option to consider. It's starting to look like an orbital tether could be easier to develop and build than a heavy cargo spaceplane, and once you have one tether in place it's much easier to build additional tethers.

Donnie B.
2003-Jul-25, 01:24 PM
I've just finished reading Virtual Apollo (a wonderful book, BTW, one that represents thousands of hours of effort with 3-D modeling tools). It seems to me that it wouldn't be too hard to build a capsule that was much more reuse-friendly than Apollo was.

Remember, the CM was designed from the get-go to be a single use spacecraft. Therefore, it incorporated a lot of systems that were expended during flight and couldn't be replaced/refurbished for a second flight. For instance, the attitude control thrusters were ablative designs -- they wore out as they were used. Another example: the CM attached to the SM using straps that were severed by pyrotechnics, as were the umbilical connections between the CM and SM.

If an Apollo-style capsule were designed with re-use in mind, I feel confident that it could be refurbished and flown multiple times. The most obvious items that would have to be replaced would be the heat shields (which, as I should have realized but never did, covered the entire CM, not just the blunt end) and parachutes. But I think most of the rest of the systems could be made reusable.

daver
2003-Jul-25, 07:06 PM
What about the idea of the two stage space plane? The first stage is a big honkin' lifting body (nuclear of course :wink: ) that takes off from a runway with the orbiter on its back. At the right altitude and speed, it releases the orbiter which goes off into orbit and returns in glider fashion.

Wasn't such an idea explored?

Well, once you've gone nuclear, all bets are off.

If you want a horizontal take-off first stage, your most likely scenario is something like a Pegasus launch--climb to altitude, drop the orbiter. The orbiter would be essentially SSTO--it gets altitude from the first stage, but no appreciable velocity. Supersonic and hypersonic release in the atmosphere are too nasty; i think they would likely be avoided in any practical system. You could put rockets on the first stage to get more velocity, but that's adding a lot of complexity--it would likely be cheaper, simpler, and more robust to just add another stage.

A vertical take-off first stage can provide more altitude, more velocity. A flyback stage has the wing problems (weight, aerodynamic loads); some sort of powered landing might be preferable (as in some of Bono's SASSTO proposals). Again, as in SASSTO, you could start off with a disposable first stage, and slowly add features to enable reuse.

As a rough rule of thumb, mixing propulsion modes (turbojets/ramjets, or ramjets/rockets) on a given stage is likely to be a bad idea. Anything involving scramjets is probably a bad idea. Some sort of convertible engine (as in HOTOL (efficient rocket which can be used as an inefficient jet)) might be ok.

That said, there are people who are more knowledgeable than i who think that some of the proposals i've denigrated are worth pursuing.

daver
2003-Jul-25, 07:14 PM
If an Apollo-style capsule were designed with re-use in mind, I feel confident that it could be refurbished and flown multiple times. The most obvious items that would have to be replaced would be the heat shields (which, as I should have realized but never did, covered the entire CM, not just the blunt end) and parachutes. But I think most of the rest of the systems could be made reusable.

I agree. Some guesses would have to be made about flight frequency and the like. If we're only flying four flights a year, it might not make sense to make them reusable. If use-once craft had a longer shelf life than reusable craft, it might make more sense for emergency-vehicles to be disposable. It might be that the best bet for the short term would be to design the capsules with reuse in mind, but only use the first several once (subject them to destructive analysis after recovery to see if the stresses match predictions) (it'd likely be a good idea to continue periodic destructive testing even if they were reuseable, just to see how they age. This also keeps the production lines open).

Colt
2003-Jul-26, 02:13 AM
I agree with all of what you said Daver. :)

Couldn't a converted 747 (modified for high-altitude) do the job of the first stage? They already have two ( I think) which can haul the Orbiter back and forth. This one wouldn't need to travel great distances, just takeoff and circle up to a high altitude before launching. Of course, it could fly closer to the Equator to give more whip to the launch of it's payload. I woudl think that something like this would be much cheaper and more readily buildable than an OSP modeled after the Shuttle.

Realistically, all some people in NASA are wanting to do right now is redesign and update the current Shuttle with more modern technology. They should design something now which works and can supplement the Shuttle. Along the way, they could develop the next, true Orbiter. I've seen a design that is a lifitng body which looks interesting. More cargo room than the Shuttle from the looks of it. There are two launch proposals for it. The first is to accelerate it down a really long EM track and launch it off of an incline (think Maglev Train but cut the rail and stick it on a hill). The other is for it to be fueled and loaded horizontally and then be raised vertical by a cradle and takeoff from there. -Colt

Kaptain K
2003-Jul-26, 10:42 AM
The advantage of a catapult is that the "fuel" for the first stage stays on the ground. No need to lift all that dead weight (tank, fuel, motor, etc.) when you can leave it on the ground where it can be reused.

BTW A 2.5 Km run at 2 Gs will get you just short of the speed of sound. From there, ramjets (or turbojets w/ afterburners) can take you to the edge of space. It wouldn't take a huge booster to reach orbit from there. The second stage can be an unmanned RPV and will fly back home, although if it is a pure ramjet, it will land "deadstick".

Erekose
2003-Jul-26, 12:37 PM
What about the space elevator? It's the most cost-effective way you can possibly get into space and it goes straight to a Geostationary orbit. Of course, it's VERY expensive to build, and the needed material for the cabels have not been developed yet, but in the medium to long term it's the best choice. Spaceplanes are good, but expensive. We should concentrate on capsules in the short term with a goal for the construction of an elevator in 10-15 years. Once constructed, a mars expedition would become substantially easier and we would have a constantly reuseable launch system. NASA would never get the budget, but we can always dream...

Donnie B.
2003-Jul-26, 08:13 PM
Air-breathing stages can give you altitude, but that's not where the real energy expenditure comes. You need speed to get into orbit. 18,000 mi/hr is the canonical orbital speed. That's something like Mach 24. No winged vehicle (other than the Shuttle orbiter) has come anywhere close to that.

The only real advantages of an aircraft-style first stage are that it is reusable, and gets you above a lot of the atmosphere (so you have less aerodynamic stresses to deal with during the rest of your boost). What little velocity it adds is negligible.

Kaptain K
2003-Jul-26, 08:43 PM
What about the space elevator?
The space elevator is an either, or thing. Once it is decided to build one, everything must be cleared out of Earth orbit, all the way to geosynchronous altitude. By everything, I mean all satellites, spent boosters, even "space junk" must be removed to prevent collision with the elevator. :o

TinFoilHat
2003-Jul-26, 10:18 PM
The space elevator is an either, or thing. Once it is decided to build one, everything must be cleared out of Earth orbit, all the way to geosynchronous altitude. By everything, I mean all satellites, spent boosters, even "space junk" must be removed to prevent collision with the elevator. :o
Not nesseccarily true. The High Lift Systems concept ( http://www.highliftsystems.com/ ) anchors the lower end of the tether to a mobile oceangoing platform. Assuming that any debris large enough to endanger the tether can be detected on radar with some warning, it's easy to move the tether out of the way. And there's no need at all to worry about objects in geosynch orbit; the tether is no more in danger from then than another geosynch sattalite would be.

daver
2003-Jul-26, 10:50 PM
The only real advantages of an aircraft-style first stage are that it is reusable, and gets you above a lot of the atmosphere (so you have less aerodynamic stresses to deal with during the rest of your boost). What little velocity it adds is negligible.

I can think of two others. The first is flexibility--you can fly the first stage to wherever is most convenient for launch--no more doglegs, and simplified range safety. The second is an additional advantage to one you've already mentioned--altitude. The exhaust bells of your remaining stages can be designed for low external pressures, yielding some improved efficiencies.

Someone else mentioned a catapult as a 0th stage--this has definite fuel and energy advantages, and if the hill you've built it on is high enough, it can still get above a good chunk of the atmosphere. But it is definitely lacking in flexibility.

Laser launchers were a big hope in the 80's; unfortunately they seem to have gone out of favor.

Kaptain K
2003-Jul-27, 12:42 AM
The space elevator is an either, or thing. Once it is decided to build one, everything must be cleared out of Earth orbit, all the way to geosynchronous altitude. By everything, I mean all satellites, spent boosters, even "space junk" must be removed to prevent collision with the elevator. :o
Not nesseccarily true. The High Lift Systems concept ( http://www.highliftsystems.com/ ) anchors the lower end of the tether to a mobile oceangoing platform. Assuming that any debris large enough to endanger the tether can be detected on radar with some warning, it's easy to move the tether out of the way. And there's no need at all to worry about objects in geosynch orbit; the tether is no more in danger from then than another geosynch sattalite would be.
Emphasis added.

Kinetic energy goes up with the square of velocity. Bits of space debris the size of grains of sand have put some good sized pits in the shuttle's front windows. A half kilo chunk of debris at orbital speed has more K.E. than a fully loaded tractor-trailer rig does at 100 kph!
Also, at orbital speed, the debris is going to be 500 Km away one minute before impact. In one minute, you aren't even going to get the engines running on your "mobile oceangoing platform", much less move it any significant distance.

Erekose
2003-Jul-27, 02:31 AM
The space elevator is an either, or thing. Once it is decided to build one, everything must be cleared out of Earth orbit, all the way to geosynchronous altitude. By everything, I mean all satellites, spent boosters, even "space junk" must be removed to prevent collision with the elevator.

Debris in LEO is a very real problem, I agree. But there will be several hours warning from orbital tracking stations and the tether will be mobile
in order to avoid collisions with satelites, boosters, and larger "space junk".
Some sort of clean up job will probably be necessary, but we will have to do that eventually just to be able to go into orbit

Irishman
2003-Jul-27, 03:26 AM
Colt said:

I'm just having visions of the old days coming back. Huge rockets, small capsules. *sigh* The good old days when, if the rocket blew up, it would go like a small nuke.. If I remember correctly, when those N1s failed and exploded it vaporized everything in the area. They had to keep rebuilding the launch platform and that delayed the program.

And if the Shuttle blew up on the pad, you think it would be different?

Kaptain K, while I respect your comments about needing different vehicles for different purposes, I feel 4 is too small a number. I think the current crew transfer vehicle should be designed around maybe 6 people. I think this amount protects/allows for growth of ISS to closer to full crew complement. Limitations on ISS include emergency crew return capability (Soyuz only carries 3, multiple vehicles adds complexity to evacuation). Since one of the stated roles for this vehicle is to be ISS emergency return vehicle, I think it important to allow for near term expected ISS growth. A later bus in my mind would be for numbers of 20 or 30 or more at a time. YMMV.

TinFoilHat said:

For the heavy cargo lift and return role, there's another option to consider. It's starting to look like an orbital tether could be easier to develop and build than a heavy cargo spaceplane, and once you have one tether in place it's much easier to build additional tethers.

What do you mean by tether? Large scale tether experiments in space have had substantial difficulties. Tethered Space Satellite had two catastrophic failures - one each flight. The first it failed to deploy at all, and the second it deployed and then suffered a burnthrough that severed the tether itself. I think space tethers offer new challenges that we don't have an appreciation for.

Colt said:

Couldn't a converted 747 (modified for high-altitude) do the job of the first stage? They already have two ( I think) which can haul the Orbiter back and forth. This one wouldn't need to travel great distances, just takeoff and circle up to a high altitude before launching. Of course, it could fly closer to the Equator to give more whip to the launch of it's payload.

Flying closer to the equator wouldn't actually be much more help. While you would buy a bit in free velocity to get to orbital speed, you lose orbital inclination - how far north and south you travel. In order to change orbits, you're going to need more fuel than you saved. Now what this might help is allowing a takeoff in Florida and then flying north before you launch, getting your orbit inclination for "free".

Pinemarten
2003-Jul-27, 06:12 AM
The space elevator is an either, or thing. Once it is decided to build one, everything must be cleared out of Earth orbit, all the way to geosynchronous altitude. By everything, I mean all satellites, spent boosters, even "space junk" must be removed to prevent collision with the elevator. :o
Not nesseccarily true. The High Lift Systems concept ( http://www.highliftsystems.com/ ) anchors the lower end of the tether to a mobile oceangoing platform. Assuming that any debris large enough to endanger the tether can be detected on radar with some warning, it's easy to move the tether out of the way. And there's no need at all to worry about objects in geosynch orbit; the tether is no more in danger from then than another geosynch sattalite would be.

Well this has me thinking.

Why do we have to 'tether' to Earth?

If the elevator is in geosync, and a balanced counterweight (mass not length), is attached 'outward'; then all we have to do is place the 'inner' arm of the satellite just 'inside' our atmosphere and move cargo to that point with balloons, high flying aircraft, etc.

Colt
2003-Jul-27, 07:26 AM
I think that that would create problems. What if a storm moves in? It would push the end of the cable around alot. What would happen when something tried to climb it or cargo was put on at the atmosphere side of the line, that adds more mass. I'm tired so I may not be thinking abougt this correctly. -Colt

Pinemarten
2003-Jul-27, 07:34 AM
Go to sleep Colt, your brain is melting.
Storms don't go that high, and the mass thing would be a normal (but tricky) calculation; on any tether.

Colt
2003-Jul-28, 12:29 AM
It is not! :P -Colt

Pinemarten
2003-Jul-29, 11:53 PM
I think that that would create problems. What if a storm moves in? It would push the end of the cable around alot. What would happen when something tried to climb it or cargo was put on at the atmosphere side of the line, that adds more mass. I'm tired so I may not be thinking abougt this correctly. -Colt

The end of the cable wouldn't have to be very far into the atmosphere, and I don't think the air is thick enough to cause any windage problems that high. If it did affect the satellite, it would only move it around, it wouldn't pull it down; you would just have to look around for it.

The satellite would have an opposing tether slung outward with a conterweight on it. As you add mass to the lower end, you just have to extend the length of the outer to maintain the center of gravity, and thus the orbit distance.

I will try and build one this weekend to see if my theory works.

Kizarvexis
2003-Jul-30, 01:23 AM
Tethers Unlimited (http://www.tethers.com/index.html) answers a lot of the tether questions raised so far. Their Hoytether™ (http://www.tethers.com/Hoytether.html) is designed to reduce space debris risks.

Space Elevator (http://www.space.com/businesstechnology/technology/space_elevator_020327-1.html) article on space.com (http://www.space.com). It suggests that a 20 ton capacity cable could be built in 12 years for $10 billion. IF carbon-nanotube tech continues to advance like it has been recenlty.

Wikipedia - The Free Encyclopedia (http://www.wikipedia.org) has an article (http://www.wikipedia.org/wiki/space+elevator) on a space elevator that discusses problems of the elevator failing (i.e. the cables being severed).

And finally, here is an web site (http://www.affordablespaceflight.com/home.html) about an intermediate step for a space elevator. The elevator would not reach to the earth, but into the upper atmosphere. A sub-orbital spaceplane would then dock with the hanging tether.

Kizarvexis

Pinemarten
2003-Jul-30, 06:21 AM
Good links Kizarvexis. Thank you.
If they help my research I will wave from above. :wink:
But all kidding aside; I am pretty sure it is possible, and man can do it.
We just have to straighten out our priorities.

ToSeek
2003-Aug-07, 08:52 PM
More on the capsule vs. plane debate (http://www.thespacereview.com/article/38/1)

mike alexander
2003-Aug-07, 10:46 PM
Mass-to-orbit, near term. Remember the BDB (Big Dumb Booster)? That's the real ticket, mass-to-orbit, and don't forget it.

Spaceplanes are so sexy, and I love 'em. Space elevators are way cool and I loved The Fountains of Paradise.

However.

HOW we do it ain't as important as DOING it. With genuine regret, I have to call the STS a magnificent dead end.

Mass-to-orbit. Come up with the biggest, cheapest reliable booster you can, on a cost per pound (kilos in Canada) basis. Make it as easy and as fast to build as possible. Economy of scale. The cheaper the costs the more you can haul up. Send the baggage separately. The more you can haul up the less pressure on minimizing mass, which leads to relaxed constraints on payload (not having to custom design everything for minimum weight, for example). More off-the-shelf designs with off-the-shelf parts, minimizing costs. Slogan: Haul Mass to Orbit.

People go up in a semireuseable capsule (living section, disposable reentry section, with steerable paraglider for landing), figure about x3 Apollo size. Launches on the same cheap, reliable booster (economy of design).

Forget cool, forget sexy. The goal is to make it ROUTINE. Like we all hoped it would be 30 years ago. Forget egos, forget the right stuff, forget $10/lb. Get the stuff up there and go from there.

As I said, it's time to Haul Mass.

TinFoilHat
2003-Aug-08, 12:50 PM
A quote from the linked article, from someone arguing against a capsule:

“It becomes, in the minds of people here on Capitol Hill, a huge step backwards,” he said. “It means, essentially, that we’re trying to adapt technology that we know how to build.”
I find this quote very revealing about why every launch vehicle NASA has attempted to develop since the Shuttle has failed. Rather than develop a robust and functional transportation system based on proven technology, they'll try and push the bleeding edge past the point of practicality every time. When given a choice between technological options, they'll always pick the one that's harder to develop. Like that Venture-Star fiasco which they chose over the competeing Delta Clipper SSTO, which already had a working sub-scale prototype.

While pushing the edge of technology is always a good thing, you have to seperate the goals of bleeding-edge technology demonstration from developing a reliable transportation system. Can you imagine if the only way to fly cross-country was by X-15? I'm starting to think that the task of developing a reliable crew transportation system should be developed by someone other than NASA - cheap and easy space transportation is not in their political interest.

Hamlet
2003-Aug-08, 01:47 PM
A quote from the linked article, from someone arguing against a capsule:

“It becomes, in the minds of people here on Capitol Hill, a huge step backwards,” he said. “It means, essentially, that we’re trying to adapt technology that we know how to build.”
I find this quote very revealing about why every launch vehicle NASA has attempted to develop since the Shuttle has failed. Rather than develop a robust and functional transportation system based on proven technology, they'll try and push the bleeding edge past the point of practicality every time. When given a choice between technological options, they'll always pick the one that's harder to develop. Like that Venture-Star fiasco which they chose over the competeing Delta Clipper SSTO, which already had a working sub-scale prototype.

While pushing the edge of technology is always a good thing, you have to seperate the goals of bleeding-edge technology demonstration from developing a reliable transportation system. Can you imagine if the only way to fly cross-country was by X-15? I'm starting to think that the task of developing a reliable crew transportation system should be developed by someone other than NASA - cheap and easy space transportation is not in their political interest.

This is a very good point TinFoilHat. Over the years I've come to think that it would be better if NASA was divested of responsibility for developing launchers and the day to day operations needed to support them. I would like to see NASA continue to push the edge of technology and to develop demonstrators, however, I would like to see the private sector develop the transportation system we need for reliable access to space.

It boggles my mind that it has been more than 30 years since the Space Shuttle was designed and we still do not have a viable design for its replacement.

ToSeek
2003-Aug-08, 03:36 PM
A quote from the linked article, from someone arguing against a capsule:

“It becomes, in the minds of people here on Capitol Hill, a huge step backwards,” he said. “It means, essentially, that we’re trying to adapt technology that we know how to build.”
I find this quote very revealing about why every launch vehicle NASA has attempted to develop since the Shuttle has failed. Rather than develop a robust and functional transportation system based on proven technology, they'll try and push the bleeding edge past the point of practicality every time. When given a choice between technological options, they'll always pick the one that's harder to develop. Like that Venture-Star fiasco which they chose over the competeing Delta Clipper SSTO, which already had a working sub-scale prototype.



Former shuttle astronaut had an article in the National Space Society magazine a few years about why the shuttle was so great, and it was all about the cutting-edge technology: tiles that you can pick up by the corners, reusable rocket engines, etc. It kind of sounded like a husband trying to explain to his wife why he bought a Ferrari instead of a Ford pickup: yeah, it's cool, but does it do what you need it to do?

mike alexander
2003-Aug-08, 05:25 PM
And another problem, it struck me, is that people look at launching and recovery as ENDS IN THEMSELVES. Forty years ago this was the case (like the first aircraft: just getting off the ground was important). But it's been FOUR DECADES, folks! The current analogy might be me getting in my car in the morning and feeling FULFILLED because when I turned the key the engine started! So what? I EXPECT that to happen now! Starting is no longer the end point, it's the starting point. I start my car to GO somewhere!

I have an engine that delivers more than the absolute minimum power needed so I don't have to go through excruciating calculations on how much I can carry. Sure, Dear, just toss in another suitcase. I have tires that have gotten much better over the years but are still basically the rubber-impregnated fabric design invented a century ago. The best possible design for transferring power to the road? I really don't know, but they're adequate and get cranked out by the millions. Is there something better than an IC engine? Almost undoubtedly, but it offers, face it, a pretty decent compromise of efficiency, veriable power, and so on at a minimal cost.

Here's another analogy. I just got back from vacation and along the way noticed a few of those hundred thousand dollar-plus mobile home-mansions-buses tooling along. Size of a Greyhound. Man, you have it all: your transportation, your hotel room, your stereo-TV, your kitchen- the whole ball of vacation wax in one stunningly expensive, incredibly unwieldy package. I drove an eight year old van, stopped for lunch or grabbed something out of the cooler and stayed in motels for 50 or 60 bucks a night. For a vacation, unless it's pure vanity, I think my way makes more sense. Plus, someone else makes the beds.

So the question of whether to build a new shuttle (total going from 3 to 4) is pretty much senseless. Don't need another Greyhound on the road. Need more vans.

Colt
2003-Aug-08, 11:49 PM
The current analogy might be me getting in my car in the morning and feeling FULFILLED because when I turned the key the engine started! So what? I EXPECT that to happen now! Starting is no longer the end point, it's the starting point. I start my car to GO somewhere!

We know you really sit in your driveway and rev the Ferrari just to hear it purr. :wink: Of course the Shuttle doesn't really purr and if you stand in its exhaust you won't have to worry about a headache from the fumes. :D

I think that the problem with NASA is that they are NASA. For most of the world they are the space people, the people with stuff so advanced that it will make your head spin. The Russians have their Soyuz. It is not flashy, ver large, or even that good of a spacecraft but it works.
NASA tries to keep up with its image of the best and the brightest that it hurts itself in the process.

I'm still voting for the space capsule. :) -Colt