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#40
by
nacnud
on 27 Jun, 2006 22:50
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God my spelling sucks, sorry about that.
The Great Eastern, thats the one. It's always hard to draw anaolgies that hold but your description of it does sound a little like everyones favorite space plane, the Shuttle.
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#41
by
Shuttle>CEV
on 29 Jun, 2006 00:47
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I agree, keep the space plane design like the shuttle.
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#42
by
rumble
on 29 Jun, 2006 01:18
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I can only really see a good argument for a space plane if you're going to try to recover stuff from space (besides people). Read as: If you're returning large bulky stuff from space, with size on the order of that of a satellite, a space plane is the way to go.
If almost all your cargo is outbound (with very little returned to earth besides the people), a capsule makes perfect sense. Having a space plane for the rare occasions you're trying to big home some big stuff doesn't make much sense, because you have to keep ground staff trained & vehicle ready for the one launch every year or two.
I remember a comment above about the shuttle being the sexiest launch vehicle we've got, and I'll agree, but WOW! it's an expensive ferry to & from ISS. I'm all for using the right tool for the job, and for round trips to the moon & Mars, capsule gets my vote.
For a long trip, like to Mars, I also think having an additional piece of equipment would be required. Capsule + lander + crew "lounge." There'll need to be a place to live during the long flight.
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#43
by
mong'
on 29 Jun, 2006 01:56
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current plans call for sending the crew in a habitation module (HAB) separate from the earth return vehicle(s)
they should have plenty of place (relatively speaking)
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#44
by
kraisee
on 29 Jun, 2006 19:28
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Rumble, you're spot on with your comments. Mind you, you don't actually *have* to have a winged vehicle for returning payloads to Earth either. I can easily conceive of an automated "capsule" with a bay capable of returning something the size of Hubble to a splash-down in the ocean one day in the future - if required. I actually think such a vehicle wouldn't have to be all that expensive either, and could possibly re-use a number of CEV elements - like the 5m heat shield...
Ross.
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#45
by
mlorrey
on 29 Jun, 2006 20:02
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nacnud - 27/6/2006 5:37 PM
God my spelling sucks, sorry about that.
The Great Eastern, thats the one. It's always hard to draw anaolgies that hold but your description of it does sound a little like everyones favorite space plane, the Shuttle.
Well, think of it this way: The Great Eastern was the only ship of its time big enough to lay the transatlantic cable. Without it, we would not have had telegraph service to England until the turn of the century. She was also used to lay other cables. In that respect, one can compare it to the Shuttle's launch and repeated servicing of Hubble and other space telescopes. If we had no shuttle, if Hubble had been launched unmanned and found to be defective as it was, we would not have had the ability to repair her, and would have written her off, Hubble would have long since reentered the atmosphere and ruined someones barbie in Australia with a many-ton mass mirror. An Apollo type repair effort would have required a rendezvous of Hubble, an Apollo, and an unmanned cargo carrier.
That being said, I'm a huge critic of shuttle. Like the Great Eastern, she was built and operated by financially troubled groups, suffered accidents and deaths. But I'm a critic not because I'm a capsule fan, but because she was an aborted kluge. The only way to build a shuttle is to splurge on the better TPS materials, if not a complete hot structure. We now have the capability to build an air breathing combined cycle shuttle, but would rather go back to the olden days, like space faring wahabbists.
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#46
by
bad_astra
on 29 Jun, 2006 20:18
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Thats's a poor choice of words at the end of your post, IMHO. I agree work should be done on TPS. I don't care if it's a capsule or not, as long as it does the job. For a Lunar program, the Apollo CM shape will be just fine. It was before.
OTOH, if I thought the CEV, Shenzhou, and Soyuz would be all the manned orbital access we'd see for the next few decades, I'd be fairly depressed about that.
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#47
by
mlorrey
on 30 Jun, 2006 17:56
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bad_astra - 29/6/2006 3:05 PM
Thats's a poor choice of words at the end of your post, IMHO. I agree work should be done on TPS. I don't care if it's a capsule or not, as long as it does the job. For a Lunar program, the Apollo CM shape will be just fine. It was before.
OTOH, if I thought the CEV, Shenzhou, and Soyuz would be all the manned orbital access we'd see for the next few decades, I'd be fairly depressed about that.
With the current course of events, CEV, Shenzhou, and Soyuz are going to be all the manned orbital access we'll see until the twenty teens at least, and longer if the private ventures don't find a market.
My choice of words might have been attention getting. How about this: by going back to capsules, we are like space faring Amish. That might make you feel better because the Amish never hurt anybody (as opposed to the Wahabbists), but then again, the Amish have had little to no impact on human history whatsoever. Is that the sort of space program you want?
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#48
by
Jim
on 30 Jun, 2006 18:16
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So what if they are around for twenty years. Just like some airplanes. It not how you get there, it's what you do when you get there. Let the CEV do it's little niche and if someone else wants to develop a different way, let them.
Just remember CEV is not just for LEO, it is for lunar and Mars Return
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#49
by
vt_hokie
on 01 Jul, 2006 20:33
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bad_astra - 29/6/2006 4:05 PM
OTOH, if I thought the CEV, Shenzhou, and Soyuz would be all the manned orbital access we'd see for the next few decades, I'd be fairly depressed about that.
They might be, sadly. Although, if SpaceDev claims it can develop the orbital version of its HL-20 derived "Dreamchaser" for ~$100 million, I say give them the money rather than giving billions of taxpayer dollars to ATK and other contractors to support their porkbarrel Apollo-era capsule design and antiquated shuttle derived launch vehicles.
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#50
by
vt_hokie
on 01 Jul, 2006 20:36
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Jim - 30/6/2006 2:03 PM
Just remember CEV is not just for LEO, it is for lunar and Mars Return
I don't buy the Mars claim, and when humans finally do go to Mars, I doubt the CEV capsule will have anything to do with it. As for returning to the moon, I have yet to hear a compelling reason for doing so, especially given the high costs and low flight rates that the ESAS hardware will result in. Before we can do any meaningful exploration on a significant scale, we need a better, more cost effective means of reaching orbit.
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#51
by
Jim
on 01 Jul, 2006 20:47
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vt_hokie - 1/7/2006 4:20 PM
bad_astra - 29/6/2006 4:05 PM
OTOH, if I thought the CEV, Shenzhou, and Soyuz would be all the manned orbital access we'd see for the next few decades, I'd be fairly depressed about that.
They might be, sadly. Although, if SpaceDev claims it can develop the orbital version of its HL-20 derived "Dreamchaser" for ~$100 million, I say give them the money rather than giving billions of taxpayer dollars to ATK and other contractors to support their porkbarrel Apollo-era capsule design and antiquated shuttle derived launch vehicles.
Their LV is no better and just as antiquated. It just happens to be a hybrid.
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#52
by
hyper_snyper
on 01 Jul, 2006 20:59
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vt_hokie - 1/7/2006 4:23 PM Jim - 30/6/2006 2:03 PM Just remember CEV is not just for LEO, it is for lunar and Mars Return
I don't buy the Mars claim, and when humans finally do go to Mars, I doubt the CEV capsule will have anything to do with it. As for returning to the moon, I have yet to hear a compelling reason for doing so, especially given the high costs and low flight rates that the ESAS hardware will result in. Before we can do any meaningful exploration on a significant scale, we need a better, more cost effective means of reaching orbit.
My understanding on it is that there's no way to brake into Earth orbit on a Mars return... or even a lunar return for that matter. It's not that it's impossible, the propellant needed for the deltaV is prohibitively high. You'd have to carry it all they way to the destination and back. Now the only way you can do a direct entry from those speeds coming back from Mars or the moon is with a blunt body capsule. If you can find a way to do EOI from Mars or the moon than, I think, the major advantage of capsules goes away.
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#53
by
mlorrey
on 02 Jul, 2006 00:07
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hyper_snyper - 1/7/2006 3:46 PM
vt_hokie - 1/7/2006 4:23 PM Jim - 30/6/2006 2:03 PM Just remember CEV is not just for LEO, it is for lunar and Mars Return
I don't buy the Mars claim, and when humans finally do go to Mars, I doubt the CEV capsule will have anything to do with it. As for returning to the moon, I have yet to hear a compelling reason for doing so, especially given the high costs and low flight rates that the ESAS hardware will result in. Before we can do any meaningful exploration on a significant scale, we need a better, more cost effective means of reaching orbit.
My understanding on it is that there's no way to brake into Earth orbit on a Mars return... or even a lunar return for that matter. It's not that it's impossible, the propellant needed for the deltaV is prohibitively high. You'd have to carry it all they way to the destination and back. Now the only way you can do a direct entry from those speeds coming back from Mars or the moon is with a blunt body capsule. If you can find a way to do EOI from Mars or the moon than, I think, the major advantage of capsules goes away.
If you were using chemical thrusters, you'd be right. If you are using electric propulsion, you'd be wrong.
Doing a direct entry with a blunt body capsule would experience MUCH higher G forces than a lifting body. That is the whole point of using the lifting body: the g forces are much more moderate. In fact, the only way to make a capsule do a direct entry in a way that is tolerable for most astronauts would be a very oblique entry that used at least one skip to bleed energy. A single augering in would impose G loads of 10 gs or more.
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#54
by
vt_hokie
on 02 Jul, 2006 00:21
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mlorrey - 1/7/2006 7:54 PM
Doing a direct entry with a blunt body capsule would experience MUCH higher G forces than a lifting body. That is the whole point of using the lifting body: the g forces are much more moderate. In fact, the only way to make a capsule do a direct entry in a way that is tolerable for most astronauts would be a very oblique entry that used at least one skip to bleed energy. A single augering in would impose G loads of 10 gs or more.
Which is why Lockheed Martin originally proposed
this design for the CEV.
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#55
by
Jim
on 02 Jul, 2006 02:24
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vt_hokie - 1/7/2006 8:08 PM
mlorrey - 1/7/2006 7:54 PM
Doing a direct entry with a blunt body capsule would experience MUCH higher G forces than a lifting body. That is the whole point of using the lifting body: the g forces are much more moderate. In fact, the only way to make a capsule do a direct entry in a way that is tolerable for most astronauts would be a very oblique entry that used at least one skip to bleed energy. A single augering in would impose G loads of 10 gs or more.
Which is why Lockheed Martin originally proposed this design for the CEV.
Capsule's use offset GG and with the skip entry negated the need for wings.
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#56
by
shuttle_buff
on 02 Jul, 2006 03:03
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I struggled with the decision of an Apollo-style capsule also until I put a number of technological issues together (and it helps to watch the NASA Channel!).
Originally (around 2002) the plan was to extend shuttle life until 2020 or beyond with the next generation of LEO vehicles being Hyper-X (Scramjet) Technology. We still would have gone back to the moon and mars by 2020 but the moon/maps ship would have been built in space with multiple shuttle flights and probably launched from the ISS.
Well the Columbia accident changed all that.
The fact is we (the USA) need a low-cost, multi-pupose, realiable and safe space ship to get to LEO now and also be used for extended missions in space.
Hyper-X is just not ready today (and it would serve LEO missions only anyway)
The Apollo-style space ship is a stop-gap to get us through 2025.
The next generation space ship will be the Hyper-X.
What do others think?
Shuttle_buff
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#57
by
vt_hokie
on 02 Jul, 2006 03:22
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shuttle_buff - 1/7/2006 10:50 PM
Hyper-X is just not ready today (and it would serve LEO missions only anyway)
The Apollo-style space ship is a stop-gap to get us through 2025.
The next generation space ship will be the Hyper-X.
What do others think?
Shuttle_buff
It never will be ready as long as we're pouring so many billions into legacy systems like this stop-gap CEV that there is no money left for research and development.
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#58
by
lmike
on 02 Jul, 2006 07:58
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cozmicray - 23/6/2006 10:11 AM
Can someone point me to the trade studies or analysis that support the choice of a capsule design?
...
(NASA I presume)
http://www.nasa.gov/mission_pages/exploration/news/ESAS_report.html ? Also, 5 out of 6 COTS finalists propose 'capsule' designs. Search for SpaceX, Andrews Space, t/Space, SpaceHab, Rocketplane Kistler (VTVL, but still the 'dreaded' capsule). The future looks bright for the capsules.
Capsules work great for suborbital, LEO, and beyond. They are cheaper and easier to manufacture. They can be reusable if the economics allow. They can land anywhere with multiple backup controls and abort modes, not just on a couple of multi-billion dollar strips (if the control surfaces still work) like some other designs.
So, why *not* a capsule? What's the alternative anyway? Shooting fragile airplanes into space (if the weather allows)? That's backwards and so last century. Perhaps, you inquire about ground to orbit propulsion methods and confuse it with the shape of the ascent/descent vehicle? Well, that's a different story, and there is no breakthrough on the horizon.
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#59
by
lmike
on 02 Jul, 2006 08:18
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mlorrey - 1/7/2006 4:54 PM
...Doing a direct entry with a blunt body capsule would experience MUCH higher G forces than a lifting body. That is the whole point of using the lifting body: the g forces are much more moderate. In fact, the only way to make a capsule do a direct entry in a way that is tolerable for most astronauts would be a very oblique entry that used at least one skip to bleed energy. A single augering in would impose G loads of 10 gs or more.
Not "MUCH" but higher, you are right. (function of reciprocal of the L/D of the body, angle of attack, air viscosity, ... remember the cpasule is also a lifting body. The optimal lifting body.)
But for shorter duration. Same for the heat loads. Higher amplitude but shorter in duration. Which is better. Plus, the symmetric lifting bodies which is what a 'capsule' is, have less leading edges for the shock wave (==heat) to concentrate on (there is a 'smothering' effect) That all with even being more optimal in terms of weight/volume (see ancient Greeks and that wicked geometry dude -- Pythagoras)
Another thing, the lifting bodies, or winged bodies, still give you nothing but *unpowered gliding* descent. You missed your strip and you're dead. Can't do another approach. This eats into the "better for landing" argument a lot.