It has been discussed previously how XCOR (Doug Jones et al) achieved long
engine life particularly with the Saddle Jacket (SJ) engine design -- hundreds
of cycles on a given engine with lots of apparent life left after engine
tear down.
How does a Film Cooled (FC) engine compare to the SJ design in terms of
longevity. Clearly the SJ has a higher Isp all other factors the same. The
FC engine is somewhat simpler in design and fabrication and does not appear
to have the degree of inner surface to outer surface thermal stress that
you get with a traditional regeneratively cooled non SJ engine design.
Is the FC engine chamber and nozzle essentially undergoing the same /
similar lower thermal stress on the inner chamber as the SJ engine and
therefore would have a longlife?
In this case I am choosing to rate longevity as a higher priority over Isp
performance for suborbital flights as opposed to more recently discussed
orbital efforts.
The SJ is somewhat more complex with added failure and maintenance modes
compared to an FC design. Maybe I'm overstating it in the context of the
overall complexity of the full rocket system?? That said, it's never a bad
idea to reduce part count, complexity and failure modes, especially in a
complex system if one can afford the performance drop off.
I appreciate all comments... Thank you.
Cheers
Brian Feeney