Author Topic: When will LOX/LH2 lose its dominance with rocket launches?  (Read 37783 times)

Offline aftercolumbia

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RE: When will LOX/LH2 lose its dominance with rocket launches?
« Reply #60 on: 06/09/2006 02:00 am »
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mlorrey - 5/6/2006  4:22 PM
Keep in mind that the US was perpetually a decade ahead of Russia on computer design, and until the 1980's, US chip makers didn't produce significant quantities overseas. I recall seeing articles in Aviation Leak of captured Soviet I/Cs with photos of the chip design. If Glushko was a decade behind NASA in 1965 in computing power, there is no way they had the computing power to do the necessary CFD and thermodynamic calcs.

Given that Avro Aircraft had started using CFD on the CF-105 Arrow in 1955, that doesn't seem like too much of an excuse either.  I think that it was a conscious choice, probably based on the volume and/or length of the engine.  For an engine of four times as much thrust as an equivalent at the same propellant mix and pressure, you need four times as much exit area to get it done.  Because this scales unfavorably, the engine with four times as much thrust winds up being eight times as big.  Splitting the motor into four gets it a lot closer to being four times as big instead.

Offline aftercolumbia

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RE: When will LOX/LH2 lose its dominance with rocket launches?
« Reply #61 on: 06/09/2006 02:09 am »
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Propforce - 7/6/2006  7:01 PM

But one thing they were not able to solve was the issue of combustion instability.  But why?  Their mathematicians were just as good, if not better, than ours.  Their budget for hardware testing, blow-up, and re-test was far more than ours.  So why couldn't they solve the issue of HC combustion instability issue whereas we could?  

Actually, they didn't have as big a budget.  The main reason why the N1 failed to do the same job as the Saturn V is because literally ten times as much was spent on the Saturn V to ground test and analyse the daylights out of it.  As far as I know the only time it really blew up was two complete S-II stages (which, BTW, had nothing to do with the F-1 engine.)  Also, they licked the hydrocarbon combustion instability better than you might think.  One RD-170 motor is twice as big as an H-1.  Come to think of it, I think one RD-170 would feel quite at home underneath an S-IB.

Offline aftercolumbia

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Re: When will LOX/LH2 lose its dominance with rocket launches?
« Reply #62 on: 06/09/2006 02:15 am »
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It is a good question, could the RD-17x and RD-180 be downrated for significantly cheaper manufacturing techniques and better reliability?

I seriously doubt it...the way the Russian's do things?  What I think might happen is you can downrate them for a reusable stage and have them last longer, but I don't think it would make them much cheaper than they are.

Offline hop

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RE: When will LOX/LH2 lose its dominance with rocket launches?
« Reply #63 on: 06/09/2006 03:26 am »
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The main reason why the N1 failed to do the same job as the Saturn V is because literally ten times as much was spent on the Saturn V to ground test and analyse the daylights out of it.
Indeed, the Soviets tried to stretch their budget by taking shortcuts in testing, and this gamble bit them in a very big way. To their credit, they learned this lesson quite well for Energia/Buran (although they still managed to blow up a few Zenits).

"Challenge to Apollo" has a good recounting of the N1 story.

If you look at the Soviets early rocket development (Proton and R-7 for example), the four failures in a row was only marginally below par. However, with the N1 it was a much bigger cost. Fly and fix things as they blow up is only a valid strategy if you can afford it.

Offline aftercolumbia

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RE: When will LOX/LH2 lose its dominance with rocket launches?
« Reply #64 on: 06/09/2006 04:52 am »
Blow up four times in a row was a single bogey back in the late fifties for both sides.  Atlas has its share of explosions, and there is one other booster to fail four launches in a row: the Atlas-Able Star

Offline Jim

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RE: When will LOX/LH2 lose its dominance with rocket launches?
« Reply #65 on: 06/09/2006 01:51 pm »
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aftercolumbia - 9/6/2006  12:39 AM

Blow up four times in a row was a single bogey back in the late fifties for both sides.  Atlas has its share of explosions, and there is one other booster to fail four launches in a row: the Atlas-Able Star

Able-Star only flew on Thors, it was an Able.  But it doesn't really count separately as a Atlas variant.  It is lumped in with all the other Atlases flying at the time (in a row doesn't count)

Offline cpooley

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Re: When will LOX/LH2 lose its dominance with rocket launches?
« Reply #66 on: 06/19/2006 03:09 am »
The H2 question:   I came into this late, but to comment on the hydrogen question in a general way:

If you are talking about NASA, USAF and others with a lot of money, H2 will continue to be used, but for the new generation of would-be startups (one will succeed someday), H2 and the infrastructure to handle it if very very expensive.   Hydrocarbon or methane ("poor man's hydrogen") makes more sense.  The Russians ge >350 Isp with kerosene.  Their molecules are no better than ours.  With state of art engineering, startups should also be able to have performance good enough to make hydrocarbons the fuel of choice.

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