On 12/31/2015 02:38 AM, Richard Garcia wrote:
Also what XCOR is doing is here nothing new. A look in the ol' history books
will show many engines made in this way. Even amateur engines like in the
attached picture from the RRI. (now defunct offshoot of the RRS) It happens
to be one of the easiest way to build a regenerative thrust chamber. Although
to XCOR's credit I've never heard of anyone else choosing this form of engine
for the express purpose of increasing fatigue life.
State of the art, high performance, milled channel , nickle backed thrust
chambers can usually get around 100 runs before cracks start showing up from
thermal cycling induced fatigue. (Take a look at "Some Effects of
Thermal-Cycle-Induced Deformation in Rocket Thrust Chambers" by Hannum and
Price on NASA's NTRS) Put a margin on that number and only run 25 times. Lets
say about 10 runs for tests through the lifespan of the engine. That leaves
15 flights. Replacing a thrust chamber every 10th or 15th flight is a heck of
a lot cheaper than replacing it every flight. Thats major savings on
reusability without having to advance the state of the art.
-Richard
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