SSME engines got a lot of cracks in the inside surface of the regen tubes.
It's been reported that similar cracks have been seen in the center of
channels of more modern engines.
But cycling an engine repeatedly is fairly easy; and can be done with high
fidelity on the test stand.
On Sunday, December 27, 2015, David Weinshenker <daze39@xxxxxxxxxxxxx>
wrote:
On 12/27/2015 08:01 PM, Henry Spencer wrote:
On Sat, 26 Dec 2015, I wrote:
However however, there is clearly no great problem in building big
liquid engines for tens of flights, if you try. The F-1 was specified
(and thoroughly tested to verify that it met the spec) for 20 cycles
and 2250s of operation, just to support development adequately.
Addenda: Flight F-1s were fired an average of 12 times before flight.
At the time, folks thought that on a reusable vehicle, an operational
life of 20 flights ought to be straightforward, with a mid-life overhaul
after the first 10.
What's the primary life limit on such engines - creep and distortion
due to repeated heat-cycling of the chamber, I suppose? That sounds
like something that could -probably- be addressed at the design level
if one were determined to do so. (You'd have to make sure you didn't
hit a ductile yield condition under any thermal gradient of startup
or shutdown as well as in steady-state running, I guess!)
-dave w