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Post by gwiz on Jan 22, 2008 10:04:59 GMT -4
There's an interesting piece in the current issue of Aviation Week. A group of senior figures in the space business, including astronauts, planetary scientists and a couple of former NASA directors, are frustrated by the lack of funding for the return to the moon and in consequence are meeting next month to discuss alternative missions. Favourites are the L1 and L2 Sun-Earth libration points or a near-Earth asteroid. These missions are claimed to be cheaper than returning to the Moon, while better for gaining the experience needed for a manned Mars mission.
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Post by Jason Thompson on Jan 23, 2008 8:50:45 GMT -4
They'd be better off discussing how they can better sell the idea of manned space exploration to the people who provide the funding: the taxpayers. From what I've seen here in the UK, there's really no incentive for the man on the street to care about going to the Moon or Mars. For every person who thinks it should be done for sound technical reasons, or because of the desire to explore, or the noble goal of increasing knowledge, there are five who want their tax dollars spent on tangible benefits like better health care or cleaner streets. Apollo only got the backing it did because of the collective fear of communism and the desire to show themselves better than the reds. Once the Russians were beaten interest waned rapidly, and funding with it. There is no such collective incentive now, so if NASA wants the funding they need to go all out to convince everyone that they should have it and that going to the Moon and Mars is worthwhile. Otherwise, they'll get no more support for their planned Mars missions than they did in the 70s.
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Post by gwiz on Jan 23, 2008 13:14:49 GMT -4
Well, you could try selling the asteroid mission as testing techniques for dealing with an earth-impact hazard.
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Post by PhantomWolf on Jan 23, 2008 16:06:13 GMT -4
Well if Obama wins then we could easily see the Constellation programme delayed by at least 5 years, if not scrapped.
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Post by JayUtah on Jan 23, 2008 19:07:19 GMT -4
I think the spacefaring industry correctly predicted years ago that lack of funding commitment would likely sink this project.
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Post by Hypersonic on Jan 23, 2008 22:43:04 GMT -4
Problems with the Ares I may sink the whole thing. If it can lift the Orion, it may shake it to pieces.
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Post by PeterB on Jan 24, 2008 10:37:15 GMT -4
Problems with the Ares I may sink the whole thing. If it can lift the Orion, it may shake it to pieces. Urk! Who says that? And where? And why is it so?
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Post by JayUtah on Jan 24, 2008 11:17:13 GMT -4
Problems with the Ares I may sink the whole thing.
Doubtful. The first manned lunar launch vehicle also had early pogo and weight problems too. The whole point of design is to find and fix this sort of thing, so the vehicle is right about where it should be at this stage of design.
This time we're lucky in that we can test designs for this kind of problem without having to build physical articles. Using new FEM tools that combine fluid and structural dynamics, <plug mode=shameless>running on state-of-the-art supercomputers</plug>, we can detect these problems early enough that it's still cheap to fix them.
But it's important to realize that vibration etc. problems are exected to arise during design.
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Post by JayUtah on Jan 24, 2008 11:26:51 GMT -4
Who says that?
NASA and ATK. It's not a secret; it's just being blown out of proportion by the media.
And why is it so?
Adding the fourth segment changed the structural properties of the SRM casing and the fluid-dynamics properties of the original grain configuration.
A solid rocket grain burns from the middle outward. This means that combustion at the top of the rocket produces gas that has to fight its way through midpoint and tail-point combustion processes to the nozzle. In short, you get standing waves in the exhaust gas column that lead to uneven flow through the nozzle. It's not unlike some forms of combustion instability in liquid-fueled thrust chambers, but on a larger scale. The shape of the grain and the flexing of the rocket casing under flight loads affect the behavior of the exhaust gas column, so those are variables you tinker with.
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Post by Hypersonic on Jan 24, 2008 12:07:42 GMT -4
Jay, I hope you're right. Given the reports of the Ares I being underpowered, coupled with the incredible shrinking Orion, I have to wonder if there is enough margin in the design to build a usable system. But like you say, the media, even the areospace media, loves to blow thing out of proportion. Even though I have my doubts, I would love to see NASA prove me, and the media, wrong.
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Post by JayUtah on Jan 24, 2008 12:19:13 GMT -4
Design tools are already well-developed to solve the combustion instability problem.
As for the power and payload problems, those are more difficult. Of course projections made from napkin designs aren't going to stand the test of time. Sometimes actual designs come in less than projected, other times greater. Some of the napkin designs for Apollo were pretty ambitious. A constraint here is to use as much STS technology as possible, which limits the design vocabulary. There may come a time when NASA reluctantly concludes that a jumbo-ized STS SRM won't work. But that time hasn't come yet.
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Post by Czero 101 on Jan 24, 2008 12:25:09 GMT -4
There may come a time when NASA reluctantly concludes that a jumbo-ized STS SRM won't work. But that time hasn't come yet. Should that time come, are there other "off the shelf" type designs they can use / adapt, or would they have to go right back to the drawing napkin... I mean... board? Cz
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Post by Trinitrotoluene on Jan 24, 2008 13:03:54 GMT -4
They should run it on a 486 DX2, it'd be fine
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Post by JayUtah on Jan 24, 2008 13:20:34 GMT -4
Should that time come, are there other "off the shelf" type designs they can use / adapt
None that are human-rated. Since the Titan family was retired, that leaves the Delta and Atlas as existing design lineages that may be candidates for uprating. There is also SpaceX's Falcon, but that's not currently rated for anything, much less for humans. However, it may be at a point in its development where a human-rated variant may be a good design solution.
I don't know offhand whether any of those vehicles will lift Orion.
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Post by Hypersonic on Jan 24, 2008 13:22:23 GMT -4
Should that time come, are there other "off the shelf" type designs they can use / adapt, or would they have to go right back to the drawing napkin... I mean... board? Cz The Delta IV and the Atlas V exist now. The Delta is better developed at this point, but either would require a new upper stage. And human-rating either would take some time. SpaceX really wants its Falcon 9 to become a human booster, and it time it may. But since it hasn't actually flown yet it's probably not an option.
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