[AR] Re: engine life (was Re: Nozzles for Amateur Solids)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sun, 11 Mar 2018 23:47:10 -0400 (EDT)
On Sun, 11 Mar 2018, Robert Clark wrote:
It's one thing for the melting point to be, say, 1,200 C and the jet
engine to be operating at, say, 1,500 C, and quite another thing for the
melting point to be 1,200 C and the rocket engine to be operating at
3,000 C.
What matters is what temperature the metal is at, and as a factor in that,
what temperature the gas *next to the metal* is at -- if that gas isn't
too hot, then the temperature in mid-flame is entirely irrelevant.
(It's harder to achieve relatively-cool gas next to the wall if the flame
is really hot, but once you've achieved it, the flame temperature just
doesn't matter.)
...can we get the engine to operate at lower temperatures say 1,000 C so
more common metal alloys can be used that are above the operating
temperature? Then we can get thousands of hours of use out of a rocket
engine like for jet engines...
So your idea for making rocket engines that are as long-lived as jet
engines is to do things entirely differently from how the long-lived,
ultra-reliable jet engines do it? This sounds to me like another case of
something I've grumbled about in the past: envying aviation's results and
hoping to match them, while refusing to learn anything about how they were
achieved.
By the way, did you overlook the part about how long-lived rocket engines
already exist? You should at least pay some attention to them, even if
you refuse to learn anything from jet engines.
...Use common metal alloys for the engine but only for the surfaces
exposed to the high temperature, then use insulation around the engine,
then finally use carbon fiber composites for strength to contain the
high pressure.
Good luck finding a "very effective insulation" material that also has
compressive strength high enough to be sandwiched inside a pressure-vessel
wall.
Henry
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