CEV Design Q&A |
CEV Design Q&A |
Oct 6 2007, 02:45 AM
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Starting this thread in hopes that we'll all have some detailed insight into the next generation of MSF engineering.
Noble goal, eh? Truth of the matter is that I was just looking at one of the innumerable 'CEV enroute to the moon' artist conceptions, and I realized that the solar arrays as depicted meant that the vehicle almost certainly has to remain in a fixed attitude with respect to the Sun for them to operate at maximum efficiency. IIRC, the Apollos had to spin a bit in order to maintain thermal equilibrium & avoid localized heating and/or freezing. Am I missing something here in terms of trade-offs? Seems unwieldy at best to have the arrays mounted to a sort of slip-ring assembly (with mast articulation) to maintain solar lock while the main body rotates. Likewise, seems as if an extensive--and in terms of power & volatile requirements/risk, expensive--ECS would be needed to avoid the temperature differential problem if the S/C is intended to maintain a continuous power-positive attitude during transit. Sure that there's a simple answer I've missed; would very much like to hear it! (Let me guess: LOTS of heat pipes?) -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Jan 19 2008, 06:27 PM
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
Problem is, the CEV has been redesigned and made smaller once already, based on performance projections for the Stick. We're now at the raw edge of the Stick's current ability to orbit Orion as currently designed. Any reduction in performance will result in a further redesign that will severely limit the CEV's ability to perform its design mission.
I think we may be looking at the potential for changing over to an Atlas V or a Delta IV (in their Heavy configurations) as the first stage for Orion. Any such decision has to be made *very* soon, though. -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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Jan 19 2008, 06:52 PM
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
I don't think the problem can be adressed by changing engine bells, it has to do with oscillations in booster casing volume, pressure and hence burn speed. It's a process that feeds itself and is a natural characteristic of all solid boosters. An analogy might be pogo in liquid fuelled engines, even though the mechanisms at work are different.
I agree with oDoug in that it would be wise to bite the bullet and consider abandoning the Stick altogether. I'm really pessimistic that will actually happen. Rather, billions of dollars might be spent on fixing this issue that came up in the first place because they wanted to use as much Shuttle technology as possible, but that's going too much into politics here. There are obvious problems with switching to the Atlas V - it uses Russian engines so it's probably a big no-no. The Delta IV is more expensive and the Heavy variant produces a rather large fireball during ignition which, although it doesn't pose any significant problems to the payload, does look rather discomforting. There are also things like Ares V using components built for Ares I which then can be scratched off the funding for V, i.e. if you were to cancel the Ares I, Ares V development costs would be seen to rise. It looks like it's going to be a pretty expensive booster even now, I hear. -------------------- |
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