How different would things have been if.......

[raven]

Would he have been able to solve their metallurgy issue?

What issue was this? I'd be interested to know.

[JayUtah]

The NK-33 debaucle versus the RD-180 suggests a very definite maybe.

[smartcooky]

I watched "Apollo 17: The Untold Story" last night on Nat Geo. Very, very interesting even if the narrator tended to drone somewhat. They brought up an interesting question similar to what has been asked here.

If America had been first to launch a satellite into orbit, and first to put a man in orbit, how would that have changed the space race? Would Apollo have ever even taken place?

[Obviousman]

I have often said that I think it might be possible that Eisenhower deliberately prevented the Juno launch from achieving orbit, in order to allow the Soviets to gain first place. This would have been in response to the 'Open Skies' proposal, which the Soviets rejected. If the Soviets achieved orbit first and then made public hay of it, they would then be forced to either say they violated various countries airspace or that orbit was open to everyone.

[raven]

The NK-33 debaucle versus the RD-180 suggests a very definite maybe.

Could you elaborate, please?

[JayUtah]

The NK-33 blew up in the Antares.  Most likely caused by failure of the turbine casing, which in turn was most likely caused by a metallurgical degradation over time of the "magic" alloys that ordinarily would have kept the hot, oxygen-rich gases from breaching it.

In contrast the later RD-180, another expression of the same high-pressure. oxygen-rich, staged-combustion design, seems to work reasonably well.

[ka9q]

Jay, I know about the oxygen preburners on the NK-33 and RD-180. What I don't understand is why. What is to be gained by creating what is obviously a very difficult materials engineering problem?

The SSMEs used hydrogen preburning, which made perfect sense. The preburners produced a lot of hot, gaseous hydrogen (plus a little steam) to drive both fuel and oxidizer turbines. Sure, the hydrogen mass flow rate is a lot lower than the oxygen flow rate, but the thought of having to develop turbine blades to withstand a torrent of hot oxygen is chilling, er, uh, daunting.

[JayUtah]

The marginal increase in performance -- well, thermodynamic efficiency in a greater power-to-weight ratio -- is apparently enough to motivate designers to shift the complexity of engine design over to exotic and unpredictable materials.  Go figure.

[cjameshuff]

Jay, I know about the oxygen preburners on the NK-33 and RD-180. What I don't understand is why. What is to be gained by creating what is obviously a very difficult materials engineering problem?

The SSMEs used hydrogen preburning, which made perfect sense. The preburners produced a lot of hot, gaseous hydrogen (plus a little steam) to drive both fuel and oxidizer turbines. Sure, the hydrogen mass flow rate is a lot lower than the oxygen flow rate, but the thought of having to develop turbine blades to withstand a torrent of hot oxygen is chilling, er, uh, daunting.

These are LOX/RP-1 engines...an engine with a fuel rich preburner would probably not run long before being choked with coking deposits in the turbine and injectors.

[ka9q]

Ah, good point. Why didn't I realize that? The SSME burns LH₂ so its fuel preburners don't have that problem.

I suspect that even gas-generator-cycle engines burning RP-1/LOX have coking problems since they also have to run fairly rich to keep the turbine temperatures down. Just not as rich as a fuel preburner.

[cjameshuff]

I suspect that even gas-generator-cycle engines burning RP-1/LOX have coking problems since they also have to run fairly rich to keep the turbine temperatures down. Just not as rich as a fuel preburner.

They also have a simpler downstream path...through the turbine and out the exhaust pipe.

[Bob B.]

The Russians also operate the preburners of their hypergolic staged-combustion engines oxygen-rich, such as the RD-253, which burns UDMH and nitrogen tetroxide.  I'm not sure why they choose to do this, unless there just isn't an adequate mass of UDMH to drive the turbopumps (there's more than twice as much N₂O₄ as there is UDMH).

[JayUtah]

These are LOX/RP-1 engines...an engine with a fuel rich preburner would probably not run long before being choked with coking deposits in the turbine and injectors.

Yeah, I wrote something to that effect somewhere on this forum recently.  Coking and sooting are problems even at the gas-generator mixing ratio.  So no, I wouldn't run a hydrocarbon-fueled engine with a fuel preburner unless told to.

[JayUtah]

The Russians also operate the preburners of their hypergolic staged-combustion engines oxygen-rich, such as the RD-253, which burns UDMH and nitrogen tetroxide.  I'm not sure why they choose to do this, unless there just isn't an adequate mass of UDMH to drive the turbopumps (there's more than twice as much N₂O₄ as there is UDMH).

Yeah, those design decisions almost always come down to narrow margins in molecular chemistry and thermodynamics, usually aimed at performance and efficiency.  The advantage of having solved the metallurgical problem of stainless steel exhaust lines to the powerhead that don't themselves erupt in flames under hot, high-pressure oxygen would be that you'll have practically solved it for all propellant formulations that use oxygen.

[ka9q]

I'm not a metallurgist, so I have no real idea how to make metals contain extremely hot, extremely fast streams of nearly pure oxygen. All I can think of is a refractory ceramic coating of some sort, but even if it won't burn or melt you still have to keep it from physically eroding.