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Back to the Future? The Command Module Flies Again?
"Dr. O" dr.o@xxxxx wrote in message .. .
"Brett O'Callaghan" wrote in message ... (Rusty B) wrote: Boeing is using Command Module shaped hardware and an Apollo type escape rocket in some of its recent concept drawings: I guess a good design is a good design, regardless of how old or recycled it is. ;-) Absolutely. The Russians have been using them for years I had hoped that, in keeping with the desire for a simpler entry/descent/landing than the (99% successful) Space Shuttle option, we might have opted for a self-orienting reentry vehicle for the CEV. I am thinking of off-nominal cases when even your entry-attitude rockets might not be working. Mercury and Gemini were self-orienting (Carpenter mentioned Faget's confidence of less than a 60-degree oscillation of the nose during reentry, but I guess it was blunt-end forward, or BEF, on average!), and Soyuz is, too. But the Apollo command module shape had two stable entry attitudes, BEF and nose-forward. The launch escape tower included canards to destablize the nose-forward attitude so the CM would end up BEF for parachute deployment (IIRC). So my question is: what is a good shape (besides sperical, like Vostok and Voskhod) that is self-orienting for re-entry? John Charles Houston, Texas |
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Back to the Future? The Command Module Flies Again?
John Charles wrote:
I had hoped that, in keeping with the desire for a simpler entry/descent/landing than the (99% successful) Space Shuttle option, we might have opted for a self-orienting reentry vehicle for the CEV. I am thinking of off-nominal cases when even your entry-attitude rockets might not be working. Mercury and Gemini were self-orienting (Carpenter mentioned Faget's confidence of less than a 60-degree oscillation of the nose during reentry, but I guess it was blunt-end forward, or BEF, on average!), and Soyuz is, too. But the Apollo command module shape had two stable entry attitudes, BEF and nose-forward. The launch escape tower included canards to destablize the nose-forward attitude so the CM would end up BEF for parachute deployment (IIRC). Mercury had a small spoiler flap attached to its nose to orient it blunt-end forward during re-entry. I think it was designed to put the capsule in that attitude during an abort as well. --Bill Thompson |
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Back to the Future? The Command Module Flies Again?
On 27 Jan 2004 00:03:25 GMT, "Jorge R. Frank"
wrote: Cardman wrote in : They usually are, where Boeing's diagrams do not indicate thick walls. Don't take those "diagrams" seriously. They're concept art, nothing more. That was already my view, but they can only provide assumptions about such technology. Then why bother with inflation if the walls are so thick? As in that case you could just use solid metal or some plastics. Because it's possible to pack a much larger volume into a given launch vehicle shroud. I see. The walls are actually composed of a Kevlar inner bladder surrounded by alternating layers of open-cell foam and Nextel fabric. It was good to see partitioned foam in order to minimise thermal loss. So what about windows on these things? As if you are going to build large structure out of them, then they will be desiring windows. The foam can be packed tight for launch, then inflated along with the rest of the volume. See: http://www0.arch.cuhk.edu.hk/~hall/s...-2002-6105.pdf Yes I see what these are about now. So how these things do in terms of mass? In terms of mass per unit volume, pretty good. Then the big question must be on the feasibility of using TransHab modules on NASA's future Moon Base? As I can only see that doing so would greatly reduce costs. Cardman http://www.cardman.com http://www.cardman.co.uk |
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Back to the Future? The Command Module Flies Again?
In article ,
John Charles wrote: ...But the Apollo command module shape had two stable entry attitudes, BEF and nose-forward. The launch escape tower included canards to destablize the nose-forward attitude so the CM would end up BEF for parachute deployment (IIRC). It was a little more complicated than that. The canards were to ensure base-first orientation during the atmospheric aborts. For an actual reentry, from a high-altitude abort, even they weren't good enough: interaction of the tower shock with the CM produced a weak nose-forward stable position that bigger canards didn't fix. But since stability there was weak, the CM couldn't settle into that position if it was rotating at more than about 2deg/s. So high-altitude abort procedures called for immediately establishing a 5deg/sec pitch rate, ensuring that it would always stabilize base-first. While it is nice to have dependable passive stability on reentry, you do pay a price for it, and the tradeoff needs careful assessment. There is nothing inherently risky about needing active attitude control early in reentry; in many cases you need active attitude control to get to that point anyway. Providing redundant guidance and RCS may be easier, especially given that you probably want those anyway... To quote a comment from a 1990 Aerospace Safety Advisory Panel memo: ...for every failure mode someone can envision, someone else must provide a solution... The proven costs of such solutions are money, schedule delays, and additional unknowns. I believe that many of our solutions to problems create more serious problems through added complication, dilution of effort, and increased time compression on already over-stressed work loads... Unless management and program personnel develop a sense of proportion, we will forever be trying to chase things to the last decimal point, frittering away limited resources on insignificant issues. The author of that, by the way, was an astronaut. -- MOST launched 30 June; science observations running | Henry Spencer since Oct; first surprises seen; papers pending. | |
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Back to the Future? The Command Module Flies Again?
Cardman wrote in
: So what about windows on these things? As if you are going to build large structure out of them, then they will be desiring windows. I confess I haven't dug into the issue of windows. Should be possible, but could be a challenge. Then the big question must be on the feasibility of using TransHab modules on NASA's future Moon Base? As I can only see that doing so would greatly reduce costs. I agree they have the potential. I think it would be smart to test one in LEO first, to see if they can really fulfill that potential. -- JRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. |
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Back to the Future? The Command Module Flies Again?
On Mon, 26 Jan 2004 21:09:49 +0100, "Dr. O" dr.o@xxxxx wrote:
"Cardman" wrote in message .. . On 25 Jan 2004 23:26:36 -0800, (Rusty B) wrote: Boeing is using Command Module shaped hardware and an Apollo type escape rocket in some of its recent concept drawings: Boeing is just trying to cover all options since NASA has not yet clearly defined their CEV needs, even if we all have a good idea what they will require. Think "moon". Got the Delta IV-H in there I see, as well as a Mars craft, a Luna space station, cargo modules, TLI hardware and a Luna Lander. The moon stuff looks pretty viable to me. Maybe so, but I do not think that going with a Luna Space Station and separate CEV and Luna Lander is the way to go. The Mars craft is just rubbish, unless it's for a flyby (very possible, but extremely dangerous because of solar flares). It did look on the small side to me. Well, you know what Boeing's concept drawings are like, when they no doubt had them around for years and just play "mix and match" whenever they suit NASA's latest ideas. So what they come up with in the end would be very different to those. I see that Boeing's designs have changed a great deal in the past year, when beforehand they also presented wing designs, while now they show only capsules. I predicted some time ago (on the basis of some NASA statement which someone posted in this NG) that they would go for a capsule and scrap all winged spacecraft. Well I came to this group about a year ago and clearly pointed out why NASA should use a capsule instead of a wing craft. Some time following they came to that same conclusion, which is why winged concepts were dropped. After all there was a big debate going on at the time if wings or capsules were better. NASA even later on considered increasing their number of crew members on such craft due to the mass savings from not having wings. Not sure if they ever followed through with that idea though. I hereby also predict that the Shuttle will be scrapped BEFORE the 2010 deadline, perhaps as early as 2007. Hey that is my idea. :-] The only problem is that NASA has to find the extra funding in order to increase their Shuttle launch rate. Still, the completion of the ISS early, would allow early scrapping of the Shuttle and it's support systems, which would make the CEV come on-line about 3 years earlier. Then lets not forget that a complete ISS three years early, would allow full station occupation and a good research return. I suppose that they can always beg congress for this money, where they could even pay back this loan in about 2008/9 by delaying the CEV by about a year. Better yet congress could spread out any such loan repayment in the longer term by tapping NASA's budget between 2008 and 2012, when that should not harm CEV construction much. Since it makes sense to me, then they should go do it, if they can get the funding and desire their CEV early. Not to forget landing on the Moon BEFORE 2015, by about 2013 by my estimate. Any person who does not want that to happen must have a job working on the Shuttle, when it is all good news. Anyone wishing to donate a few billion to NASA's Shuttle flight rate is welcome to make offers. How much would about 12 to 15 flights a year cost in total by the way? Cardman http://www.cardman.com http://www.cardman.co.uk |
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Back to the Future? The Command Module Flies Again?
On Mon, 26 Jan 2004 20:20:58 GMT, (Henry Spencer)
wrote: As others have noted, with multi-wall design, this isn't an issue. In fact, inflatables generally score better on debris/meteorite puncture resistance, because the designers of rigid modules have trouble providing adequate spacing between the bumper sheet and the backstop. Wider spacing, to let the debris cloud spread out farther before it hits the backstop, improves protection *much* more than adding mass... but since the bad experience on Skylab, NASA has been afraid of *deployable* bumpers, so added wall depth has to come out of interior space, which discourages wide spacing. But inflatables deploy everything anyway, so they can have quite wide spacings between the layers of their walls. What are the odds of having your moon base using these? Interestingly enough they have not yet considered making a larger rocket better suitable for Moon launches, like with using those RS-84 engines that they are currently developing. The immediate money is going to be for spacecraft, not rockets, and the ability to fly on the existing EELVs is certain to be a requirement. That sounds to me like NASA cutting their own legs off before they learn to walk claiming "we don't need legs when we can crawl". The earlier that they face that fact that one day they will be needing to move a large volume of mass in the general direction of the moon, then the earlier that they will plan on adding a new rocket into their master plan. Not today, not tomorrow, but one day between 2015 and 2020 it will move from an option into a requirement. So this is not a good time to be pushing new rockets. I believe that it is, when doing the Moon on the Delta IV-H is just a bad idea. I have no problems with using the Delta IV-H for taking their CEV into LEO or even GEO (even if others do, due to the no engine out option), but they should realise that if their Moon plans are to work out in any realistic way, then they would either need a new bigger rocket, or a whole LEO assembly space station. Since I doubt that they would be allowed another space station, then doing Lunar orbital work seems like the better option anyway. Now, if they wish to build their CEV first then fine, but at some point shortly following they will be needing their new rocket. I hope that they take this into account, instead of stunting their whole future by building their moon plans around baby rocket IV-H. (They have surely *considered* it, but have decided to put the idea on the shelf for a while -- it's not what NASA wants to hear just now.) I would be under the assumption that they had some kind of "master plan", which defines how everything should go together. That master plan from what I can see should go CEV, CEV's cargo module, the big cargo module, new rocket, moon base. It would be particularly amusing if the rocket in question was an EELV or EELV derivative, since both of those use major foreign components, the "sad losers" being able to do some things better than the Americans can. Certain Russian rocket engines come to mind, where even the Chinese should soon impress you with their space plans advancing in leaps and bounds. Most notably, Atlas V uses Russian engines because no competitive US engine was available. I remember seeing a programme a few years ago, shortly following when the Russians and Americans started working together, where the Americans had a good look at the Russian hardware. One of the first things they noticed was the impressive performance figures for the modern Russian rocket engine, when their pre-burner based design put all comparative US versions to shame. Sure enough the Russians showed then how they came to build these engines, where there was their room with like one hundred rocket engines on the floor. What they had of course been doing was to build a rocket engine, test it, and then to figure out how to make it better. And so they built a new engine in this design, tested it, improved it and so on, until they had their room full of a hundred engines. So that is how that rocket engine came about, where quite simply it would be quite difficult for US companies to do better. LM of course knew that those are good engines, where it will cost them more to make their own copy, not to forget upsetting the Russians. The last thing I recall was how the Americans said that they would have to learn to build their new engines like that. Not yet it seems. (In fact, if one wanted to revive the Saturn V itself right now and didn't have an unlimited budget, one would seriously consider Russian engines for the first stage, True, where in a way that could almost happen. What I mean is that Boeing's LP-1 based RS-84 engines is borrowing this pre-burner idea (and maybe more) from this Russian design, where the higher chamber pressure should produce great performance results. Put five of those engines on your new moon rocket, then you would certainly be able to shift some serious mass. and the obvious choice for the second and third stages is the French Vulcain, which is available off the shelf and has specs broadly similar to the old J-2 except better.) Yes, but don't forget that using the RS-84 instead of those direct Russian engines in the first stage makes for a reusable instead of a disposable first stage. They could even stick on some simple parachutes to have it land safely, even if in the ocean is not the best idea. As the one thing that I do know is that making your Saturn V-b is not the best design idea due to the high cost that helped to end this project in the first place. Cardman http://www.cardman.com http://www.cardman.co.uk |
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Back to the Future? The Command Module Flies Again?
On 27 Jan 2004 05:41:42 GMT, "Jorge R. Frank"
wrote: Cardman wrote in : So what about windows on these things? As if you are going to build large structure out of them, then they will be desiring windows. I confess I haven't dug into the issue of windows. Should be possible, but could be a challenge. The biggest issue seems to be folding up your windows for launch. The actual windows I guess depends on the interface between the window and your TransHab. Then the big question must be on the feasibility of using TransHab modules on NASA's future Moon Base? As I can only see that doing so would greatly reduce costs. I agree they have the potential. I think it would be smart to test one in LEO first, to see if they can really fulfill that potential. Hmmm LEO. I suppose that could be useful for NASA if they wanted their LEO refueling station and needed some other excuse to put it there. The problem I guess is adding many forms of life support to a single TransHab module, which would of course require a noticeable size of solar power. Seems like a lot of effort for testing your TransHab module, when you can test it tons on the Earth, then it should not be too much different to send it to the Moon instead of LEO. I guess it comes down to how much you can trust it, where I cannot see too much hassle in an inflatable. Cardman http://www.cardman.com http://www.cardman.co.uk |
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Back to the Future? The Command Module Flies Again?
Pete Lynn wrote: Looking at the Transhab design, I am still trying to work out why they used foam at all, I can not see that it does anything useful, accept making packing and deploying difficult. It is in a vacuum, foam does not improve your thermal insulation, it hurts it. Nextel is better than foam as an impact barrier and in space, space is cheap, so why use foam as a separating layer? For a permanent base made from such inflatable modules, try this on for size...you land the thing on the Moon- with it inflated with gas. Then, by taking the surface soil and mixing it with self-hardening foam of some sort, you can replace the gas with the foam/soil composite material, and shield the thing with a layer of material that you did not need to bring 9/10's the weight of from Earth...same for Mars... it beats the living daylights out of trying to excavate a hole to put the base module in to protect it from the solar wind. You can do this within a matter of hours after landing. Pat |
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