Commercial and US Government Launch Vehicles > Blue Origin
Why is BE-4 ORSC instead of FRSC?
hkultala:
Kerosine has coking issues which is the reason kerosine-based SC engines are oxyge-rich,
and also the reasons there are no american SC kerosine engines as US did not previously have knowledge on the metallurgy for ORSC engines?
But BE-4 uses methanes instead of kerosine, with no coking issues?
So it could easily be FRSC?
Why go to ORSC which needs more exotic metallurgy etc.?
kraisee:
Basic question has been covered before, even quite recently in other threads.
Short answer is that Oxy is a heavier molecule than either C or H. By using more of it to drive the turbines in the turbopump, you can drive the turbines that much harder, which delivers higher pressures out of the pump side = higher overall engine performance.
There's more to it (isn't there always) but that's at the core of the whole FRSC/ORSC trade.
And methane fuels still contains Carbon, and some impurities that cause coking, just a lot less than kero. But still some. And coking always gets worse the higher your temperatures and pressures - and the purpose of staged combustion engines is to achieve *really* high temp and pressure. You can guess the rest.
The only fuel I'm aware of that doesn't coke at all, is H2, but its a lot harder to handle.
Ross.
envy887:
Methane does coke, if you get it hot enough. I think around 1300F. There was a discussion on this in the Raptor thread.
gin455res:
Would ammonia coke?
Steven Pietrobon:
--- Quote from: gin455res on 06/15/2018 08:46 pm ---Would ammonia coke?
--- End quote ---
No, as there is no carbon in ammonia. NH3 decomposes into a nitrogen gas The problem is that CHx can decompose into carbon, which is a solid which has a very high melting point of 3727 C.
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