Armadillo did a lot of work with film cooling, and seemed to have it
working pretty well for them in some long-life engines. Hard to say how
much technical detail is available at this point, though.
Henry V
On 2/23/2018 4:43 PM, Brian Feeney wrote:
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