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#60 by vt_hokie on 18 May, 2006 05:22
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The Russians claim that the lifting body version of Kliper is capable of direct entry from lunar flights.
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#61 by lmike on 18 May, 2006 06:15
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Sigh, again the 'capsule' stigma thread...
So, after reading this thread, I still don't understand what the technical problem is with going the 'capsule' (not a strict technical term) route. Some nebulous conjectures and opinions about how the 'capsules' are not 'cool'. Are we at some fashion convention, or are we talking about a technical means to fulfill a given objective? Anyway, the 'capsule' seems to be all the rage these days. It does work. And RLV has zilch to do with what shape the spacecraft is. As is reusability. Capsules can be made reusable. What more do you need?
The last designed and produced known functional LEO/Moon spacecraft, the Shendzhou is a 'capsule'. Lots of COTs participants use 'capsules', the SpaceX's Dragon, the t/Space's CXV, the SpaceHab's Apex.
The next breakthrough will be not an 'orbital space plane' (what an inane oxymoronic term! I can't believe NASA actually used it as a term for a space system for a decade) , but a new way to propel things to orbital velocity, new propulsion motors, staging schemes, or maybe even tethers. Spacecraft as such need wings like a fish needs a bicycle (now *launch vehicles* may be another story, tbd) I'm willing to allow and in fact, a 'capsule' is a lifting body! Lifting body concepts are at least as old as capsules. Are we now going to argue about the proper amount of the L/D ratio for a craft to be considered as advanced? Wings, tail and wheels are the criterion? That'd be silly.
Oh, and I personally, have no problem with someone trying to design a space system with lifting bodies, wings, balloons, or helicopter rotors... And if they work, great! Why others shun the 'symmetric around the Z axis' lifting body, which is what a capsule is, concept specifically? Rutan engineered some great *one-of-a-kind* aircraft, but man, aircraft are not spacecraft at the fundamental level! -
#62 by vt_hokie on 18 May, 2006 06:40
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Perhaps I'm letting emotions dictate over technical merit despite my engineering background, but I just can't get excited over returning to the "spam in a can" approach to human spaceflight after the remarkable achievements of STS. Something about parachuting back to Earth in this thing just rubs me the wrong way. It's not exactly what I'd call inspiring. After growing up with the space shuttle and the promise of even better things to come, this to me is a major disappointment. And the fact that it will consume the bulk of NASA's human exploration budget for decades means there will be no NASP or VentureStar or anything similarly ambitious and groundbreaking, perhaps for the remainder of my lifetime.
Oh, and I think "Crew Exploration Vehicle" is just as stupid a name as "Orbital Space Plane", personally.
From the article referenced at the beginning of this discussion:
NASA spokesman Dean Acosta said the crew exploration vehicle is a "fiscally responsible" project that achieves the space agency's goal of returning to the moon within its budget constraint.
"If you want sexy, it will cost a lot more money," Acosta said.
Translation: If you want anything good, give us more money. Otherwise, expect the Yugo of spaceflight. -
#63 by lmike on 18 May, 2006 09:35
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I think I understand your point of view. It seems like a deeply held opinion about what constitutes progress and I respect that.
I'd just like to point out that the notion that "the mighty STS is being replaced by the puny CEV" which seems to make its way through these kinds of discussions is INCORRECT.
The fact is, the STS is being replaced by an exploration SYSTEM consisting of: CEV CM, CEV SM, CLV, LES, CaLV, EDS, LSAM, + some miscellaneous lunar base hardware and a host of mission specific technologies, and to top it off the COTS program. Now if we could also add an orbital tug system to this line up. Manned, unmanned, heavy lift, LEO, the Moon, it's all in there. (well, no manipulator arm) All of this for the price of the yearly STS/ISS upkeep plus some inflation compensations. For my money, this ain't half bad. In fact, this is better than we've had for quite some time. Far from perfect, but oh, well... Looking at this bag of goodies and just finding the 'capsule' and poking fun at it, seems a bit off.
Of course, we can prognosticate that the plan won't pan out as planned (but what if the stock market crashes tomorrow, but people must make plans ), and poke holes in it on technical merits, but this exploration SYSTEM is the intent, and work order contracts that are being given out to pursue it. Personally, I hope it works out as planned (although, I do have some reservations about some details of what they plan, mostly in the costs and schedule)
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#64 by GLS on 18 May, 2006 15:05
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I feel we're going back with this CEV thing... OK, a capsule is fine to get from LEO to the moon, but we need *a* shuttle to get to and from LEO... no, not *this* shuttle, it's old and it's not "as good as they wanted", but it was the first. Now we can do better! And now you're asking: "Why do we need a shuttle?" So you can have a couple spacecrafts making LEO-Moon-LEO... and when they need refurbishment you bring them down, work on them and send it back up. I think this is going to be important on the way to mars... How would you go to mars? I wouldn't want to go on anything less big than about half Mir's size, because you'll have to take all your entertainment with you as there's nothing outside for some months! Is it better to built and launch this big spacecraft everytime you go to mars and then scrap it or to bring down the modules (on *a* shuttle) when they need refurbishment?
Now, all this costs money... more than what they are giving.... and this lack of funding forces NASA to kill programs and stuff to go to the moon, and this is wrong! If it keeps going this way, in a couple decades, when they turn to mars, they're going to scrap the moon base because they going to need the money to get to mars!!! To me, all this "Vision for Exploration" is way too narrow.... -
#65 by Jim on 18 May, 2006 15:31
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GLS - 18/5/2006 10:52 AM
It would take too much energy to return anything from Mars other than the crew capsule. There is no talk of reusablity wrt Mars spacecraft. All mars return scenarios have a capsule performing a direct entry while the main vehicle flys pass earth into solar orbit. The energy to brake into earth orbit (or to haul around a shield for aero braking) is too great
I feel we're going back with this CEV thing... OK, a capsule is fine to get from LEO to the moon, but we need *a* shuttle to get to and from LEO... no, not *this* shuttle, it's old and it's not "as good as they wanted", but it was the first. Now we can do better! And now you're asking: "Why do we need a shuttle?" So you can have a couple spacecrafts making LEO-Moon-LEO... and when they need refurbishment you bring them down, work on them and send it back up. I think this is going to be important on the way to mars... How would you go to mars? I wouldn't want to go on anything less big than about half Mir's size, because you'll have to take all your entertainment with you as there's nothing outside for some months! Is it better to built and launch this big spacecraft everytime you go to mars and then scrap it or to bring down the modules (on *a* shuttle) when they need refurbishment?
Now, all this costs money... more than what they are giving.... and this lack of funding forces NASA to kill programs and stuff to go to the moon, and this is wrong! If it keeps going this way, in a couple decades, when they turn to mars, they're going to scrap the moon base because they going to need the money to get to mars!!! To me, all this "Vision for Exploration" is way too narrow.... -
#66 by hyper_snyper on 18 May, 2006 15:36
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Jim - 18/5/2006 11:18 AM
QuoteGLS - 18/5/2006 10:52 AM I feel we're going back with this CEV thing... OK, a capsule is fine to get from LEO to the moon, but we need *a* shuttle to get to and from LEO... no, not *this* shuttle, it's old and it's not "as good as they wanted", but it was the first. Now we can do better! And now you're asking: "Why do we need a shuttle?" So you can have a couple spacecrafts making LEO-Moon-LEO... and when they need refurbishment you bring them down, work on them and send it back up. I think this is going to be important on the way to mars... How would you go to mars? I wouldn't want to go on anything less big than about half Mir's size, because you'll have to take all your entertainment with you as there's nothing outside for some months! Is it better to built and launch this big spacecraft everytime you go to mars and then scrap it or to bring down the modules (on *a* shuttle) when they need refurbishment?
It would take too much energy to return anything from Mars other than the crew capsule. There is no talk of reusablity wrt Mars spacecraft. All mars return scenarios have a capsule performing a direct entry while the main vehicle flys pass earth into solar orbit. The energy to brake into earth orbit (or to haul around an shield for aero braking) is too greatr Now, all this costs money... more than what they are giving.... and this lack of funding forces NASA to kill programs and stuff to go to the moon, and this is wrong! If it keeps going this way, in a couple decades, when they turn to mars, they're going to scrap the moon base because they going to need the money to get to mars!!! To me, all this "Vision for Exploration" is way too narrow....So you would have to build a new Mars Transfer Vehicle every time you want to go to Mars?
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#67 by Jim on 18 May, 2006 15:37
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hyper_snyper - 18/5/2006 11:23 AM
QuoteJim - 18/5/2006 11:18 AM
QuoteGLS - 18/5/2006 10:52 AM I feel we're going back with this CEV thing... OK, a capsule is fine to get from LEO to the moon, but we need *a* shuttle to get to and from LEO... no, not *this* shuttle, it's old and it's not "as good as they wanted", but it was the first. Now we can do better! And now you're asking: "Why do we need a shuttle?" So you can have a couple spacecrafts making LEO-Moon-LEO... and when they need refurbishment you bring them down, work on them and send it back up. I think this is going to be important on the way to mars... How would you go to mars? I wouldn't want to go on anything less big than about half Mir's size, because you'll have to take all your entertainment with you as there's nothing outside for some months! Is it better to built and launch this big spacecraft everytime you go to mars and then scrap it or to bring down the modules (on *a* shuttle) when they need refurbishment?
It would take too much energy to return anything from Mars other than the crew capsule. There is no talk of reusablity wrt Mars spacecraft. All mars return scenarios have a capsule performing a direct entry while the main vehicle flys pass earth into solar orbit. The energy to brake into earth orbit (or to haul around an shield for aero braking) is too greatr Now, all this costs money... more than what they are giving.... and this lack of funding forces NASA to kill programs and stuff to go to the moon, and this is wrong! If it keeps going this way, in a couple decades, when they turn to mars, they're going to scrap the moon base because they going to need the money to get to mars!!! To me, all this "Vision for Exploration" is way too narrow....So you would have to build a new Mars Transfer Vehicle every time you want to go to Mars?
That is the plan -
#68 by GLS on 18 May, 2006 15:53
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Doesn't that sound wrong?
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#69 by mong' on 18 May, 2006 15:56
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If I understand the need for the CEV on lunar missions, I don't understand why you would need it to go the mars.
Because all the mars direct and semi direct plans out there don't call for such a vehicle. except maybe to ferry the crew between earth and the mars transfer stage + Hab.
But why would you want to carry 20+ tons of deadweight ? I could see it integrated at the top of the ERV as the earth reentry vehicle but that's all -
#70 by Jim on 18 May, 2006 16:23
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mong' - 18/5/2006 11:43 AM
If I understand the need for the CEV on lunar missions, I don't understand why you would need it to go the mars.
Because all the mars direct and semi direct plans out there don't call for such a vehicle. except maybe to ferry the crew between earth and the mars transfer stage + Hab.
But why would you want to carry 20+ tons of deadweight ? I could see it integrated at the top of the ERV as the earth reentry vehicle but that's all
It carries the crew to the MTV (not with full load of consumables). It then become alternate command center, safe haven and return entry vehicle.
It is in the ESAS -
#71 by Jim on 18 May, 2006 16:26
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mong' - 18/5/2006 11:43 AM
If I understand the need for the CEV on lunar missions, I don't understand why you would need it to go the mars.
Because all the mars direct and semi direct plans out there don't call for such a vehicle. except maybe to ferry the crew between earth and the mars transfer stage + Hab.
But why would you want to carry 20+ tons of deadweight ? I could see it integrated at the top of the ERV as the earth reentry vehicle but that's all
Mars direct and semi direct do not have crew escape mechanisms. Zubrin made the same mistake as the shuttle, he has no abort system in Mars Direct -
#72 by mong' on 18 May, 2006 17:15
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yes but if you really want crew escape then you can use the CEV to dock to the Hab in LEO, transfer crew, undock and back to earth. that way you don't need to carry the heavy CEV all the way to mars.
Anyway i gotta read that part of the ESAS again, must've missed something -
#73 by Jim on 18 May, 2006 17:21
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mong' - 18/5/2006 1:02 PM
yes but if you really want crew escape then you can use the CEV to dock to the Hab in LEO, transfer crew, undock and back to earth. that way you don't need to carry the heavy CEV all the way to mars.
Anyway i gotta read that part of the ESAS again, must've missed something
You need to carry some sort of small earth entry vehicle. The current CEV SM can be offloaded. The current idea is to dettach the CEV days before earth entry to allow the MTV to deflect away from earth. Also it gives enough time for CEV check out -
#74 by mong' on 18 May, 2006 17:46
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ok I re-read that part of the ESAS and it looks like an awful lot of unnecessary complications.
First it needs 4 launches (!) including 3 HLV's
second, the HAB is supposed to survive for something like 30 months on its own plus 18 with the crew on board. that's a lot for something as critical.
Third, it depends on the development of NTR for the MTV and that is kind of a long shot.
I'm not saying that plan is bad, it's not my place, people much smarter than me have worked their butt on it, I just think that it's taking a lot of chances for just some marginal safety improvements compared to a more direct plan. -
#75 by mlorrey on 24 May, 2006 19:52
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lmike - 18/5/2006 1:02 AM
Sigh, again the 'capsule' stigma thread... snip... Spacecraft as such need wings like a fish needs a bicycle (now *launch vehicles* may be another story, tbd) I'm willing to allow and in fact, a 'capsule' is a lifting body! Lifting body concepts are at least as old as capsules. Are we now going to argue about the proper amount of the L/D ratio for a craft to be considered as advanced? Wings, tail and wheels are the criterion? That'd be silly.
Oh, and I personally, have no problem with someone trying to design a space system with lifting bodies, wings, balloons, or helicopter rotors... And if they work, great! Why others shun the 'symmetric around the Z axis' lifting body, which is what a capsule is, concept specifically? Rutan engineered some great *one-of-a-kind* aircraft, but man, aircraft are not spacecraft at the fundamental level!
There is no doubt that a perfect capsule has symmetric forces around the z axis, but that, even capsule builders admit, is NOT how capsules really reenter, because the g forces would be too high if they augered in straight along their z axis, particularly reentering from a lunar trajectory, would be over 14 g's sustained. Capsules kinda skid/skew their way into the atmosphere, to acheive an L/D over zero, and reduce the g load on passengers. Thus, capsules are, in fact, flying vehicles, whether or not they have wings.
While lmike makes sense that spacecraft that are intended to stay in space, have no need for wings, the primary purpose of the capsule isn't really living and working in space (otherwise, Soyuz would not have separate OM, CM, and SMs, and Apollo would not have separate CM/SM/LMs). Thus, orbital modules, service modules, and lunar lander modules have no excuse to have wings on them, and I think everyone here can agree on that. It is a waste of mass to try to bring back to Earth equipment that has no use on earth, or in returning the crew to earth, unless that equipment is very expensive and can be made reusable.
The primary purpose of a capsule is to fly, both hypersonically and subsonically, and land its crew safely on earth. Therefore, to maximize its capability for returning its crew to earth, it should have as wide a cross range and as great a maneuvering flight regime as possible.
Now, hypersonic flight, the most crucial flight regime, doesn't have the same demands as subsonic or even supersonic flight. Its a whole different ball of wax. There are arguments to be made for having as blunt a leading edge as possible, as that dissipates reentry shock heating over as large an area as possible. That is the route the capsule takes as its primary design parameter. The spaceplane tries to duplicate this by reentering at a high Angle of Attack, to expose as large a cross section as possible to the thin atmosphere. With old TPS materials, that is what we were limited to.
However, with new TPS materials, specifically the SHARP materials (hafnium diboride and zirconium diboride), sharp edged and nosed vehicles don't need to deal with large cross sectional areas, the nose and leading edges can handle all reentry braking, and enjoy a massive cross range maneuverability. Furthermore, the materials, as well as the shock wave they produce, are transparent to radio signals, allowing communication with ground control throughout reentry. -
#76 by imfan on 25 May, 2006 14:53
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Jim - 18/5/2006 10:24 AM
Quotehyper_snyper - 18/5/2006 11:23 AM
QuoteJim - 18/5/2006 11:18 AM
QuoteGLS - 18/5/2006 10:52 AM I feel we're going back with this CEV thing... OK, a capsule is fine to get from LEO to the moon, but we need *a* shuttle to get to and from LEO... no, not *this* shuttle, it's old and it's not "as good as they wanted", but it was the first. Now we can do better! And now you're asking: "Why do we need a shuttle?" So you can have a couple spacecrafts making LEO-Moon-LEO... and when they need refurbishment you bring them down, work on them and send it back up. I think this is going to be important on the way to mars... How would you go to mars? I wouldn't want to go on anything less big than about half Mir's size, because you'll have to take all your entertainment with you as there's nothing outside for some months! Is it better to built and launch this big spacecraft everytime you go to mars and then scrap it or to bring down the modules (on *a* shuttle) when they need refurbishment?
It would take too much energy to return anything from Mars other than the crew capsule. There is no talk of reusablity wrt Mars spacecraft. All mars return scenarios have a capsule performing a direct entry while the main vehicle flys pass earth into solar orbit. The energy to brake into earth orbit (or to haul around an shield for aero braking) is too greatr Now, all this costs money... more than what they are giving.... and this lack of funding forces NASA to kill programs and stuff to go to the moon, and this is wrong! If it keeps going this way, in a couple decades, when they turn to mars, they're going to scrap the moon base because they going to need the money to get to mars!!! To me, all this "Vision for Exploration" is way too narrow....So you would have to build a new Mars Transfer Vehicle every time you want to go to Mars?
That is the planQuoteGLS - 18/5/2006 10:40 AM
Doesn't that sound wrong?
noone said going to mars is easy. U have to build spacestation because there is almost no difference in current ISS stays and mars missions. ah there is one. mars mission is longer.
building new MTV each flight is one option. however I like energia proposal more. they want to build space station with BIG(I mean really BIG) solar array which would give power to ION engine. although it is reusable U will nedd few flights after each mision to get new fuel, bring new lander(I dont suppose these would be reusable) etc. and still U need something to get down to earth-so cev makes sence here -
#77 by vt_hokie on 26 May, 2006 11:31
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imfan - 25/5/2006 10:40 AM
U have to build spacestation because there is almost no difference in current ISS stays and mars missions. ah there is one. mars mission is longer.
Radiation hazards are also much greater.
