Had a brief thought for all the long lived aluminum chamber rocket motors
people on list have fired...
-george
Sent from my iPhone
On Mar 11, 2018, at 8:47 PM, Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
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
