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tvelocity
2003-Mar-04, 12:15 PM
Hi everybody. I'm new here, and I'd like to start a thread related to all of the noise I'm hearing about whether or not NASA's manned space flight program is worth it. We go through this every time there is an accident, in ANYTHING. Sen. Walter Mondale tried to kill the Apollo program after Apollo 1. The space shuttle program went on hiatus for years after Challenger exploded, while the government debated not only what to do about it, but whether manned space flight should continue at all! Our history is replete with examples of government officials latching on to incidents like this in order to get their names in the news as someone who is "doing something", even if it's the wrong thing. After the Thunderbird's diamond crash, they even tried to do away with ALL air demonstration squadrons, and were even moving towards eliminating military air shows altogether. The point is, someone, somewhere in a position of authority is going to overreact.
My own personal view on the manned space program is of course it should continue! The only question to me is in what form. Now, I'm going to go out on a limb and say this: the Internation Space Station is a black hole orbiting Earth sucking down dollars from NASA's budget. Before you all start flaming me consider this: ISS is a valuable scientific tool, but its true scientific potential is pie-in-the-sky type stuff until a more practical means of transportation to it can be devised. I don't think we are currently ready for ISS. What we are doing with it now is tantamount to draining the ocean to study deep sea life rather than designing a submarine that can reach it. Let's face it, chemical rocket propulsion is simply not practical. NASA's promises of savings provided by the space shuttle have not been realized. Maybe the money spent so far on ISS would be better spent designing a new launch system, such as an electromagnetic launcher (read - The Moon is a Harsh Mistress, Heinlein) In any case, ISS currently supports only three crew members, who spend nearly all of their time on maintenance, and this manning is about to drop to two. Is this any way to run a space station? I don't know. There's very little precedent. Perhaps it's too late to drop the ISS project. There's too much already invested. Why not make the most of it, right? I think that the reality of the problems involved with just getting up there is going to hit NASA and the other space agencies very hard, and ISS might possibly go the way of Skylab and Mir. Don't get me wrong. I think a permanent presence in space is crucial to our future as humans, getting some of our six billion eggs out of this basket so to speak. But I also think we should establish some sort of timeline to this goal, with each step forward in the proper order with the proper priorities. I think we jumped the gun with ISS.
Any thoughts?

David Hall
2003-Mar-04, 02:34 PM
Hi, Tvelocity. Good first post.

I don't think you'll get too much flaming here about ISS. I think a good number of us think that, in it's current form at least, it's a money pit.

My view is that NASA just went about it the wrong way though. Not wanting to go whole hog itself, it decided to make the project a team effort and saddled it with a lot of complications. Also, as you said, they never really designed a decent support system for it. So what we have is a big cluster of tin cans in the sky without the crew or resources to utilize it's full potential. Complaints were already rolling around about how useful science couldn't be done with only 3 crew, and the Columbia tragedy just made it worse, dropping it to two.

The big problem now though, is that the money has been spent and the station is there. Scrapping the project and throwing away what's been accomplished so far would just make things even worse. It could've worked, IMO, and still could, if we just get behind the project fully and start using it the way it was intended, with full crews and lots of science done. This "caretaking" phase is just a waste.

As for manned space exploration generally, I don't think it's going to disappear. We may have setbacks, and we'll always have Mondales fighting against it, but I think space exploration has gained enough momentum to resist them. Just look at what people were saying after Columbia. Hardly anyone at all came out saying we should quit. The general feeling is we should get back out there as soon as possible.

Even if Washington decided to fold up NASA tomorrow, the USA wouldn't stay down for long. There's still the Russian program, and the Chinese about to start up too. There's also the ESA, and Japanese programs, and commercial ventures coming online. There's a kind of international pressure, as well as a feeling of exploring new frontiers, that would be surely push us back out there before too long. And if we don't do it, someone else will.

I'm not too worried.

Thumper
2003-Mar-04, 03:57 PM
Yes, Tvelocity. Welcome to the board.



On 2003-03-04 09:34, David Hall wrote:

My view is that NASA just went about it the wrong way though. Not wanting to go whole hog itself, it decided to make the project a team effort and saddled it with a lot of complications. Also, as you said, they never really designed a decent support system for it

They didn't design a new suppport system for it but couldn't you say the Russian Progress and Soyuz missions along with the US shuttle fleet program was a support system? The reason the station is in maintenance mode with only a three person crew is because there is no on board escape system capable of carrying more than three people. Once they scrapped the 7 person lifepod (can't recall the name of it), the station was doomed to its current condition.

I'm not going to argue the other points that it is a big waste of money or everything was gone about the wrong way. Just that it could have met more of its design goals with the current supply programs if it had the 7 person rescue craft.

David Hall
2003-Mar-04, 04:33 PM
Yes, of course the Progress/Soyuz are part of the support system, but what I said was there never was a decent (read full service) system in place. The scrapping of the 7 man lifeboat was a big part of that. It was, IMO, one of the biggest things they did wrong. In fact, they shouldn't even have gone ahead with the full construction until after such a craft became a certainty.

It's like opening up a retail outlet, but cancelling your order for the trucks needed to ship your products to it from the warehouse. The outlet shouldn't even have opened until the infrastructure was in place. Making due with your friend's minivan just doesn't cut it.

Thumper
2003-Mar-04, 05:16 PM
On 2003-03-04 11:33, David Hall wrote:
It was, IMO, one of the biggest things they did wrong. In fact, they shouldn't even have gone ahead with the full construction until after such a craft became a certainty.


I agree wholeheartedly. It leads to speculation as to why they continued in the first place. Maybe some just wanted to get "something" in orbit before the program was stalled or scrapped. It's alot harder to can it now that it's up there.

daver
2003-Mar-04, 05:41 PM
On 2003-03-04 12:16, Thumper wrote:
It's alot harder to can it now that it's up there.


Hmm. Lots of phrases seem to apply. Camel's nose in the tent. Good money after bad.

I'm embarassed to admit that i was part of the write-in campaign to construct the space station--i even encouraged a few other people to write in. I was anticipating a whole bunch of small, man-tended stations, or maybe a sort of extended mission dock for the shuttle (more room, more power, but not standalone). Instead we got the ISS.

Anyway, i don't see that we would lose all that much if we boosted the station up a couple hundred miles and ignored it until we got a decent space transportation system.

Thumper
2003-Mar-04, 06:20 PM
I wouldn't be embarassed about good intentions. It was speculation on my part. Why would we rush (maybe not a suitable word, how about continue) to construct the space station after the work on making a 7 person escape craft (which would have made the station much more operational) was scrapped?

calliarcale
2003-Mar-04, 07:24 PM
It's worth pointing out that CRV (the 7-man lifeboat) wasn't exactly scrapped. The budget was cut off by Congress. This is a subtle distinction but an important one because what a lot of folks outside the aerospace industry don't realize is that R&D folks don't like to give up their projects. If they lose their source of funding, they'll try to find some way to keep the project alive anyway. CRV is like that. NASA was ordered to cut CRV from the schedule (along with a number of other components, actually) and to focus on "core complete". But they've quietly kept it alive, albeit on extremely limited funding. It was cancelled something like two years ago, but a few months ago NASA actually accepted delivery of the first CRV retropack. Sounds strange, I know, but it had already been paid for. And the parafoil landing tests were completed with the flight analog, along with remote-control guidance tests with a pilot in a virtual reality simulator on the ground while the vehicle was dropped from a B-52. There is not presently funding for the next phase, which is the construction of a real CRV to be carried into orbit by the Space Shuttle and released for an orbital test flight. But if/when that funding materializes, NASA will be quite ready to pick up right where they left off.

RickNZ
2003-Mar-04, 09:15 PM
I agree i think they should hold off on human space flight untill.

a: Theyve studied the effects on humans more vigorously.

b: Theyve exponentially increased specific impulse while also increasing thrust.

c: Some sort of pratical sheilding against radiation and micro-meteors.

Untill then poor the money into research and unmannded probes. Who here wouldnt want to see NASA land a probe on europa with a drill and attached /phpBB/images/smiles/icon_biggrin.gif

Hmmm drilling a hole thru the ice and lowering a passive sonar bouy and hearing the sounds of life /phpBB/images/smiles/icon_biggrin.gif

daver
2003-Mar-04, 10:55 PM
On 2003-03-04 16:15, RickNZ wrote:
I agree i think they should hold off on human space flight untill.

a: Theyve studied the effects on humans more vigorously.



I'm not sure this is necessary. Short term stays aren't that bad. If long term stays were a problem then we could orbit a rotating station. And how are we going to do long term weightless studies without human space flight?




b: Theyve exponentially increased specific impulse while also increasing thrust.



Exponential increase isn't necessary (or defined). Doubling high-thrust specific impulse would make getting into orbit easy. A factor of four (such as Heinlein's Single-H) would make back-yard SSTO's practical.

Chemical rockets already have tons of thrust. High thrust high specific impulse engines are the problem.




c: Some sort of pratical sheilding against radiation and micro-meteors.



Depends on your mission. LEO doesn't have much radiation problem; micro-meteors are an issue, but not that much of one.




Untill then poor the money into research and unmannded probes. Who here wouldnt want to see NASA land a probe on europa with a drill and attached /phpBB/images/smiles/icon_biggrin.gif

Hmmm drilling a hole thru the ice and lowering a passive sonar bouy and hearing the sounds of life /phpBB/images/smiles/icon_biggrin.gif


It'd be really nice if NASA would pour some money into some decent deep-space drives (ion). I don't think there's much that could be done for earth to orbit unless they abandon rockets for at least part of the trip--light gas gun, tether, laser launcher, something along those lines.

Irishman
2003-Mar-06, 06:25 AM
I think it a little unfair to criticize ISS over a problem with shuttle. The current reduction to two crew members vs. three is driven by a concern apart from ISS itself, just the logistics of supporting the crew without Shuttle in the mix. Once Shuttle is back (and it will be back), that problem will ease somewhat.

The "core complete" vs. 7 person version is really a problem with budget control. Large overruns forced NASA to do something to reduce costs on continued build. They did that by canceling parts of the station that hadn't been built yet and could be dropped out of the flow without stopping the flow. You can't just arbitrarily make things cheaper. It doesn't happen. So you find work that hasn't been done yet and you cut that off. The work not done included CRV, hab module, etc. Yes, that does limit current usefulness of ISS, but a buddy of mine has a theory that it was a sly plan. After core complete is finished, there will be incentive to bulk up station back to full complement and 7 person crew. Thus the items chopped (CRV and hab module) will come back into the plan.

Of course there's another ball in the mix. NASA just announced plans on a new crew transfer craft for development by 2010. This vehicle would be launched on an expendable rocket and used for carrying crew. This new crew vehicle could possibly provide some of the function missing with CRV. I'm not sure yet what the full extent of the plan is, but that's another potential workaround.

Also regarding the 2 vs 3 person crew, one of the astronauts on ISS commented that it's not so much that it takes 2 and half people for maintenance, but rather about 85% of the time of who is up there, so with 2 people there would still be that 15% or so for doing science. It's tricky to evaluate without a curve showing amount of time for maintenance vs. number of crew present, but it's probably not linear. Thus a 7 person crew might only take 40% of total time for maintenance, whereas a 2 person crew takes 85%.

I still think ISS is a viable project and a good path. Shuttle will be around for a while longer. We are at least 10 years away from a replacement, and that's from the day we commit to building a replacement. And using or building on existing technology, i.e. rockets. Trying something wholly new (light guns, EM rails, etc) is something for 2 or 3 generations down the road. Begin work on it now, but work on an intermediate to get us there. Venturestar was an idea that didn't work out. The Delta Clipper was a concept that proved single stage vertical takeoff and landing is not economical or practical. An aerospace plane (horizontal takeoff and landing) with a SCRAMJET might be a good approach to consider. But again that's going to take longer.

Given this country's current budget concerns, I just don't see more funding for simultaneous projects in multiple directions.

joema
2003-Mar-06, 08:51 AM
Venturestar was an idea that didn't work out. The Delta Clipper was a concept that proved single stage vertical takeoff and landing is not economical or practical. An aerospace plane (horizontal takeoff and landing) with a SCRAMJET might be a good approach to consider.
I'm not sure Delta Clipper proved much, except the ability of that team to rapidly develop a low performance VTVL prototype. Their approach was "build a little, fly a little", constructing a succession of progressively higher performance vehicles, culminating in the orbital version. By contrast the traditional approach is fully design the final vehicle and (years later) hope it flies.

The Delta Clipper design approach also emphasized simplicity and maximum off-the-shelf component use. Therefore it's likely it would have been more successful sooner than Venturestar, even had Venturstar not encountered its problems. The money was cut for Delta Clipper, not due to technical failure but because it was never a political favorite and the crash gave a pretense for this.

Re an airbreathing aerospace plane, I can't see that working anytime soon, or even not so soon. The technical challenges incurred by achieving near orbital velocity in the atmosphere are immense -- heating, stress, hypersonic combustion, etc. For all that, the *only* thing you get in return is atmospheric oxygen, which is cheap and easy to package anyway (as LOX). It's a fascinating approach, but unfortunately nobody gives you extra points for getting to orbit the hard way, or the "coolest" way. The goal is getting to orbit the cheapest and most reliable way.

-- Joe

daver
2003-Mar-06, 05:55 PM
On 2003-03-06 03:51, joema wrote:

The Delta Clipper design approach also emphasized simplicity and maximum off-the-shelf component use. Therefore it's likely it would have been more successful sooner than Venturestar, even had Venturstar not encountered its problems. The money was cut for Delta Clipper, not due to technical failure but because it was never a political favorite and the crash gave a pretense for this.



I suppose you could claim that Delta Clipper had got as far as it could get with COTS components, and would now need some real development. I don't know, i do know that i was brainwashed early into liking VTVL SSTO and would like to see a bunch more work put into it before it's abandoned.




Re an airbreathing aerospace plane, I can't see that working anytime soon, or even not so soon. The technical challenges incurred by achieving near orbital velocity in the atmosphere are immense -- heating, stress, hypersonic combustion, etc. For all that, the *only* thing you get in return is atmospheric oxygen, which is cheap and easy to package anyway (as LOX). It's a fascinating approach, but unfortunately nobody gives you extra points for getting to orbit the hard way, or the "coolest" way. The goal is getting to orbit the cheapest and most reliable way.

-- Joe


I agree. Thrust to weight of rockets is typically close to an order of magnitude better than that of jets. Scramjets have yet to be proven practical (they've just barely been proven possible). Putting three different engines for three different flight regimes (subsonic, hypersonic, vacuum) doesn't seem very useful for reducing complexity or weight or cost.

On the other hand, some bright people were involved in the British HOTOL plan (but note that HOTOL did not involve a scramjet); it'd be nice to give them a billion or so and see what kind of demonstrator they could come up with.

Irishman
2003-Mar-06, 08:04 PM
Single stage vertical takeoff fully reusable craft have a high coolness factor from our exposure via science fiction. Who wouldn't want to see it? But from a practical standpoint, it won't be cheaper. You're carrying infrastructure to carry fuel that you no longer need. That's why staged rockets are more efficient - you drop the empty fuel tanks as quickly as you can and don't have to carry the dead mass around. VTOL is impressive, but again, wasteful. Why carry fuel to land when you can use aerodynamics? Others have said Delta Clipper proved as much. I wouldn't know, I'm not fully versed on Delta Clipper. I will say that coolness aside, logic doesn't seem to support it for reducing cost to orbit.

SCRAMJETs may not be the way. Maybe it doesn't make sense. I just like to think a fully horizontal takeoff and landing has got to be easier to turn around than a vertical takeoff craft. Maybe I'm wrong. Maybe it's the same situation as with Delta Clipper, or maybe having multiple engines for different regimes is counter productive. But if you're carrying less fuel overall, then for the same weight you're carrying more payload. But are you carrying the same weight? ???

We're stuck in a catch 22. Commercial ventures are going to be hard pressed to research the basic capability, and then develop the application. That's two layers of high risk expenditures. The corporate world doesn't like to function that way. NASA would theoretically be a good way to fund the first level basic research, and then let industry take the research for applications. Practically speaking, the government doesn't appear likely to fund several large scale spaceflight research projects. It would be great to see these ideas playing out simultaneously, as a competition, but the money just isn't there for it.

I don't know what the solution is. Private collective ventures (such as via NSS) to raise capital for projects?

daver
2003-Mar-06, 09:17 PM
On 2003-03-06 15:04, Irishman wrote:
Single stage vertical takeoff fully reusable craft have a high coolness factor from our exposure via science fiction. Who wouldn't want to see it? But from a practical standpoint, it won't be cheaper. You're carrying infrastructure to carry fuel that you no longer need. That's why staged rockets are more efficient - you drop the empty fuel tanks as quickly as you can and don't have to carry the dead mass around.



You pay a high price for staging--you have twice as many pieces to reprocess if you're reusing both stages, twice as many things to inspect. You have to worry about the complexities of stacking and the complexities of separation. If you don't recover the lower stages, you have severe limitations in where you can take off and where you can go.

That said, SSTO is pretty complicated; reusable SSTO is right on the edge of being feasible with chemical drives. If you didn't want reusability, the old Atlas (i think) was theoretically capable of SSTO operation, but never flown that way.




VTOL is impressive, but again, wasteful. Why carry fuel to land when you can use aerodynamics? Others have said Delta Clipper proved as much. I wouldn't know, I'm not fully versed on Delta Clipper. I will say that coolness aside, logic doesn't seem to support it for reducing cost to orbit.



It hasn't been established that vertical landing is more expensive than horizontal landing. The various aerodynamic structures that you need for horizontal landing add up to a lot of weight; the fuel required for a vertical landing may end up being lighter.

On the other hand, the white knuckle factor behind a vertical landing is much higher. Basically, you hold off firing your engines until the last possible moment. If they don't fire, you lithobrake. And, as you alluded to above, your engines have to be throttleable over a very wide range of thrust. So you need high efficiency high thrust restartable throttleable highly reliable engines.




SCRAMJETs may not be the way. Maybe it doesn't make sense. I just like to think a fully horizontal takeoff and landing has got to be easier to turn around than a vertical takeoff craft. Maybe I'm wrong. Maybe it's the same situation as with Delta Clipper, or maybe having multiple engines for different regimes is counter productive. But if you're carrying less fuel overall, then for the same weight you're carrying more payload. But are you carrying the same weight? ???



Oxidizer goes down. Fuel goes up. Engine weight goes up. Structural weight goes up (both because of the extra complexity and because g forces now vary along two axes--down when flying, back when accelerating in rocket mode). Note that HTHL craft have severe differences in weight distribution between takeoff and landing (so do VTVL craft, but weight distribution isn't as important there). That makes wing placement and fuel tank placement very difficult.




We're stuck in a catch 22. Commercial ventures are going to be hard pressed to research the basic capability, and then develop the application. That's two layers of high risk expenditures. The corporate world doesn't like to function that way. NASA would theoretically be a good way to fund the first level basic research, and then let industry take the research for applications. Practically speaking, the government doesn't appear likely to fund several large scale spaceflight research projects. It would be great to see these ideas playing out simultaneously, as a competition, but the money just isn't there for it.

I don't know what the solution is. Private collective ventures (such as via NSS) to raise capital for projects?



NACA used to be a research program--they'd do research into, for instance, wing geometries and the like. It'd be nice if NASA had a similar program--something that would research ion engines for deep space (and stationkeeping), aerospikes for boost phase, LACE, scramjets, super-lightweight conformal hydrogen tanks, whatever. Once the concepts were demonstrated, industry (or another NASA site in the case of deep space probes) could take over.

calliarcale
2003-Mar-07, 03:31 PM
Why is it I so often see people utterly convinced that NASA does not do pure R&D? They do quite a lot of it, actually, although much of it doesn't get into the press because it's all geeky engineering stuff.

daver
2003-Mar-07, 06:30 PM
On 2003-03-07 10:31, calliarcale wrote:
Why is it I so often see people utterly convinced that NASA does not do pure R&D? They do quite a lot of it, actually, although much of it doesn't get into the press because it's all geeky engineering stuff.


I know they do. For a while our library carried NASA Tech Briefs. They do a lot of little stuff.

NASA does have a blue-sky program, where they evaluate the truly wierd stuff (like the gravity nullifiers). I'm not sure how some of this stuff gets on their list, it seems so obviously wacko. I guess they must look at the potential payoff if the stuff happens to work.

I believe NASA has been responsible for VASIMR, which has the potential for doing a lot of the stuff i've been bashing NASA for not doing.

The air bag landing scheme for the various Mars landers is also an example of something radically new and useful that NASA paid for.

My understanding (which has very little basis in reality--i'd be glad if people who have actually been involved would correct my misunderstandings) of the way that NASA evaluates mission proposals is that unless there is a very good reason to do otherwise, that only well proven, tried-and-true technologies need apply. Particularly for mission-critical components such as propulsion and guidance and power. Don't get me wrong--this is as it should be. But the problem is that there is no way to improve the core technology.

I'd like to see NASA cobble together some dummy missions (maybe just a camera and some random components) and launch them. No serious science, just to see if ion drives or inflatable antennaes or whatnot actually work in a space environment. Of course, they could try getting some science out of the missions, but the primary objective would be technology feasibility tests.

And it'd be nice if the people putting together the missions would submit a wish list (such as "we used a magnetic tape data storage device here. we'd like to have used a solid state one, but we don't know if they'd work in a high radiation environment"). NASA could gather the suggestions, see which ones would fit on the next technology demonstrator probe and put together a test package.

This would have a hard time being implemented given the state of NASA's budget, but i feel that it is the type of thing that NASA really should be doing.

Kaptain K
2003-Mar-07, 09:19 PM
That said, SSTO is pretty complicated; reusable SSTO is right on the edge of being feasible with chemical drives. If you didn't want reusability, the old Atlas (i think) was theoretically capable of SSTO operation, but never flown that way.

IIRC At least once, an Alas boosted itself into orbit.

joema
2003-Mar-08, 05:32 AM
On 2003-03-06 15:04, Irishman wrote:
Single stage vertical takeoff fully reusable craft have a high coolness factor....But from a practical standpoint, it won't be cheaper. You're carrying infrastructure to carry fuel that you no longer need....VTOL is impressive, but again, wasteful. Why carry fuel to land when you can use aerodynamics?
This has been studied extensively, and VTHL and VTVL are about equally efficient, depending on the specifics. True with VTVL you carry fuel up and down. With VTHL you carry wings, aerosurface actuators, thermal protection for the wings, aerosurface hydraulics, beefy 200+ kt. landing gear, etc. up and down.

VTHL would seem to have a simplicity advantage on landing -- you'd figure there's less to go wrong on a dead stick landing than a powered landing. OTOH since you can only land at a [long] runway, the approach is critical. With VTVL in theory you could land in a parking lot. However there are lots of possible failure points on both designs. With VTVL the engines must work on landing, but they also had to work on takeoff, and a proper design would include redundancy to tolerate engine out situations on either ascent or descent.

But NASA seems fascinated with wings, so my guess is future manned vehicles will have wings.

tvelocity
2003-Mar-08, 09:53 AM
It seems to me that spacecraft really haven't changed much in the past 50 years. We are still using chemical propulsion to get into orbit. Has any significant improvment to the basic rocket been made during this time? Has specific impulse been improved measurably? How close are we to developing a new type of propulsion that solves the whole thrust/weight ratio problem once and for all? I see some promising technology for deep space missions, such as electric propulsion which was such a success on the Deep Space One mission. But when it comes to dealing with Earth's gravity well, old Isaac Newton still rules with an iron fist. What looks feasible in the near future? I've seen the proposals that NASA is collecting for its next generation space vehicle, and they all look like refinements of the space shuttle concept. Is there anything truly revolutionary within reach?
Here's a quote from the Marshal Space Flight Center concerning the third-generation RLV:

The program's primary emphasis is on technologies for 3rd Generation RLVs that could be operational in a 2025 timeframe. The goal is to develop space transportation systems that would be 100 times cheaper and 10,000 times safer than today's launch vehicles. These true spaceliners of the future could take off from aero-space ports that will accommodate both air and space vehicles.

url: http://std.msfc.nasa.gov/ast/astp.html

So, is it doable? I hope so. I would really like to think I could go rock climbing on the moon after I retire.

here's another url with pictures of some neat concepts for interstellar flight:
http://std.msfc.nasa.gov/gallery/index.html

By the way, daver, is "lithobraking" an actual technical term? Perhaps, the process by which an airborne vehicle might exchange its airspeed energy for a deep well?

Kaptain K
2003-Mar-08, 01:24 PM
I read "lithobraking" as a tongue-in-cheek way of saying "crashing".

daver
2003-Mar-10, 06:01 PM
On 2003-03-08 08:24, Kaptain K wrote:
I read "lithobraking" as a tongue-in-cheek way of saying "crashing".



Yep. In a similar vein as "hard start" and "spontaneous self-disassembly".

daver
2003-Mar-10, 06:07 PM
On 2003-03-08 04:53, tvelocity wrote:

By the way, daver, is "lithobraking" an actual technical term? Perhaps, the process by which an airborne vehicle might exchange its airspeed energy for a deep well?




It might have been coined back in the usenet days in sci.space. My vague recollection is that someone suggested aerobraking asteroids into earth orbit (for mineral extraction), someone else suggested that lithobraking them into the moon might be more practical.

Lexx_Luthor
2003-Mar-11, 04:59 AM
What about not so much wings but lifting bodies.

Maybe with a chute. I know somebody worked on something like that, cos they showed it thumping down on the desert under a chute. What happened to it? Wasn't that a proposed escape vehicle for the ISS?

I would think a much larger lifting body with a chute (or sail I dunno) would be less complex than a delta winged shuttle.

??

Tuckerfan
2003-Mar-11, 08:28 AM
Jack Schmitt on the importance of manned missions. (http://"http://www.space.com/missionlaunches/sts107_vision_030310.html")
"The question raised about whether humans should be in space at all is an old one, usually raised by non-exploration scientists who want NASA money to go to their pet ‘robotic’ projects," Schmitt said.

"I know from history and personal experience on the Moon that during exploration, humans will provide instantaneous observation, interpretation, and assimilation of the environment in which they work and a creative reaction to that environment unavailable from any other source," Schmitt said. Of course, Schmitt could be considered to be a bit biased on the issue.

tvelocity
2003-Mar-11, 09:44 AM
Lifting bodies have very low aspect ratios. This means that they reenter at a steep angle without experiencing bone-crushing deacceleration. The steep angle means a minimum of flight time, and getting back to the surface as quickly as possible. Of course this also means that lifting bodies fall like rocks when they are unpowered, as this NASA lifeboat clearly is. I think this design was the best compromise between "aircraft" and "space capsule", but I wonder just how necessary the "aircraft" aspect of it is. The lifeboat looks pretty, but wouldn't it be cheaper just to rig up two soyuz capsules as emergency lifeboats?

daver
2003-Mar-11, 05:36 PM
On 2003-03-10 23:59, Lexx_Luthor wrote:
What about not so much wings but lifting bodies.



One of the cancelled spaceplanes started out as a lifting body. They did some simulation on stability in various flight regimes, and found they had to add larger stabilizers and control surfaces. More simulation revealed that they needed yet larger ones. By the time of cancellation, the control surfaces were a fair percentage of the size and weight of the wings they had tried to replace.

I'm summarizing from what i remember of a usenet posting--lots of room for error here. If someone has better data please post.

Irishman
2003-Mar-12, 02:10 AM
Lifting body technology is a part of the Shuttle. There's a reason it flies like a brick.

daver said:

My understanding (which has very little basis in reality--i'd be glad if people who have actually been involved would correct my misunderstandings) of the way that NASA evaluates mission proposals is that unless there is a very good reason to do otherwise, that only well proven, tried-and-true technologies need apply. Particularly for mission-critical components such as propulsion and guidance and power. Don't get me wrong--this is as it should be. But the problem is that there is no way to improve the core technology.

I'd like to see NASA cobble together some dummy missions (maybe just a camera and some random components) and launch them. No serious science, just to see if ion drives or inflatable antennaes or whatnot actually work in a space environment. Of course, they could try getting some science out of the missions, but the primary objective would be technology feasibility tests.

Dude, they do that. They flew a mission with an ion drive. They flew a payload on Shuttle with an inflatable ... um, something or other. I think it was an antenna. Heck Tethered Satellite was basically a big experiment in conducting space tethers. (Actually, that was an Italian payload.) It's just the money spent on those is a very tiny fraction of the budget, vs. the money spent on shuttle and station. But experiments do fly to test out new hardware, new technologies, etc. It's probably fair to argue wanting to see higher visibility, and more money spent on those aspects, but they do happen.

tvelocity, the CRV does have advantages over Soyuz, besides the larger return crew capability. Primarily, permanent station keeping without degradation, vs. replacement every 6 months (or whatever).

The "aircraft" part is lifting body technology for reentry, vs. the old ablating heat shields.

ToSeek
2003-Mar-12, 03:55 PM
On 2003-03-07 13:30, daver wrote:

I'd like to see NASA cobble together some dummy missions (maybe just a camera and some random components) and launch them. No serious science, just to see if ion drives or inflatable antennaes or whatnot actually work in a space environment. Of course, they could try getting some science out of the missions, but the primary objective would be technology feasibility tests.



Like this mission? (http://nmp.jpl.nasa.gov/ds1/)

daver
2003-Mar-12, 05:47 PM
On 2003-03-12 10:55, ToSeek wrote:


On 2003-03-07 13:30, daver wrote:

I'd like to see NASA cobble together some dummy missions (maybe just a camera and some random components) and launch them. No serious science, just to see if ion drives or inflatable antennaes or whatnot actually work in a space environment. Of course, they could try getting some science out of the missions, but the primary objective would be technology feasibility tests.



Like this mission? (http://nmp.jpl.nasa.gov/ds1/)



Yes, exactly. Thank you.

ToSeek
2003-Mar-12, 06:26 PM
Mars Pathfinder (http://mars.jpl.nasa.gov/missions/past/pathfinder.html) was also primarily a technology mission, though obviously it was very successful scientifically as well.

johnwitts
2003-Mar-12, 10:55 PM
Why not just land vertically in the sea on parachutes, like Apollo? No wings, no wheels, no control surfaces, just plop in the ocean and get picked up by a passing freighter...

tvelocity
2003-Mar-13, 08:55 AM
It seems that the atmosphere is both an asset and a liability to spaceflight. It presents problems for reentry, but can you imagine technical problems involved with landing on a planet as massive as Earth without any sort of aerobraking? I wonder if it would be possible to set up some sort of manufacturing plant on the moon. Far easier I think to build ship on the moon and launch them, than on Earth. The moon has almost all of the elements that Earth does, which would facilitate production if some sort of convenient method of smeltering could be developed for the environment. Any metalurgists out there who can contribute?

daver
2003-Mar-13, 06:32 PM
On 2003-03-12 17:55, johnwitts wrote:
Why not just land vertically in the sea on parachutes, like Apollo? No wings, no wheels, no control surfaces, just plop in the ocean and get picked up by a passing freighter...


Well, for manned flights, it got to be a bit of a pain to send out a task force to pick up a capsule.

The soviets of course would fire retros just before plowing into the steppes (hopefully not on top of some peasant). Not a very smooth landing. But cheap, reasonably robust.

daver
2003-Mar-13, 06:38 PM
On 2003-03-13 03:55, tvelocity wrote:
It seems that the atmosphere is both an asset and a liability to spaceflight. It presents problems for reentry, but can you imagine technical problems involved with landing on a planet as massive as Earth without any sort of aerobraking? I wonder if it would be possible to set up some sort of manufacturing plant on the moon. Far easier I think to build ship on the moon and launch them, than on Earth. The moon has almost all of the elements that Earth does, which would facilitate production if some sort of convenient method of smeltering could be developed for the environment. Any metalurgists out there who can contribute?


The moon is pretty light on volatiles (you'd like those for fuel for your rocket and life support for your crew). Also on heavy elements. I'd think that there's a good chance that most of the heavy stuff is down towards the center. I don't know if there were any forces acting to concentrate ores the way there were on earth, so your main chance of finding iron and the like may be in prospecting for meteorites.

A good part of our manufacturing and refining relies on water and an atmosphere. There are probably ways to make do without, but they'd have to be developed from scratch.

johnwitts
2003-Mar-13, 11:22 PM
Why did they use a carrier and half the fleet to recover the Apollo crews? Surely a smaller boat would have done?

tvelocity
2003-Mar-14, 01:22 AM
On 2003-03-13 18:22, johnwitts wrote:
Why did they use a carrier and half the fleet to recover the Apollo crews? Surely a smaller boat would have done?


Apollo happened in the '60's, the height of the cold war. Those were pretty paranoid times. I imagine they used Navy SEALs to make contact with the astronauts after splashdown for the same reason.

David Hall
2003-Mar-14, 10:35 AM
I can imagine a few reasons to use an entire fleet. For one thing, there's a large splashdown area, and you never know exactly where the capsule will come down. You'd need several ships to cover the entire area. A carrier is pretty much mandatory because of the recovery aircraft needed. I suppose you could get by with a smaller helicopter ship, but you'd also want chase planes and such as well. Best to have something big. Finally, as pointed out, this was the cold war, so it's best to be prepared. I don't doubt that outside the US fleet there were quite a few "observers" from other countries as well.

I'm sure we wouldn't need as much support if we were doing recovery missions today.

Eric McLoughlin
2003-Mar-14, 06:12 PM
The carriers used on these recovery operations tended to be older 1950s vessels such as USS Intrepid, USS Hornet USS Wasp etc and were relaitvely small by the standards of the main carriers of the day (USS Forrestal, USS Constellation, USS John F Kennedy).

johnwitts
2003-Mar-15, 12:44 AM
Why would you need a helicopter? Pick them up in a boat...

daver
2003-Mar-15, 12:48 AM
On 2003-03-14 19:44, johnwitts wrote:
Why would you need a helicopter? Pick them up in a boat...


Why not use a helicopter. You've got an entire fleet out there, the cost of one copter flight isn't going to change the price significantly.

There are reasons to get to the capsules as quickly as possible. If the floatation bags burst you lose your capsule and your astronauts.

tvelocity
2003-Mar-15, 09:10 AM
Here's a little info on the Apollo recoveries. Note how all of the missions from Apollo 10 onward landed in the Pacific. The Pacific is quite a bit larger and the Soviets didn't have as much of a presence there as they did in the Atlantic. Supposedly they had intelligence collecting ships nearby (though usually not within sight of the battle group) and were scanning the telemetry of the returning command module.

http://navy.memorieshop.com/Kawishiwi/Space/Apollo-Mission.html