Rocket Encyclopedia Illustrated Hardcover - 1959 Editor: John W. Herrick
http://www.amazon.com/Rocket-Encyclopedia-Illustrated-John-Herrick/dp/B009BDA40I
It's a pretty interesting book. Being state of the art from 1959 it now doubles
as a history book.
________________________________
From: arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> on behalf of
Lars Osborne <lars.osborne@xxxxxxxxx>
Sent: Wednesday, December 30, 2015 5:43 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: fatigue life (was Re: Re: SpaceX F9 Launch/Update...)
What's the full name of that book?
Thanks,
Lars Osborne
On Wed, Dec 30, 2015 at 5:38 PM, Richard Garcia
<GalaxyNGC1672@xxxxxxxxxxx<mailto:GalaxyNGC1672@xxxxxxxxxxx>> wrote:
Allowing the inner wall to expand may ameliorate the problem but does not
eliminate it. What really matters is the temperature gradient across the wall
itself. The inner portion of the wall grows more that the outer portion of the
wall will let it. The inner wall of a dual wall chamber would eventually crack
even if it never touched the outer wall and could support itself. What would
really help is reducing the thermal gradient across the wall. The best way to
do that would be to make it out of something very thermally conductive (i.e.
copper) and to make it as thin as possible. That thinness is where you start to
run into trouble. Making the thrust chamber walls thinner than some copper
milled wall chambers already are (less that 0.075") will limit what chamber
pressure you can run at, sacrificing performance. I was under the impression
that most XCOR engines ran at low or modest pressures, like 350 psi or so.
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
________________________________________
From: arocket-bounce@xxxxxxxxxxxxx<mailto:arocket-bounce@xxxxxxxxxxxxx>
<arocket-bounce@xxxxxxxxxxxxx<mailto:arocket-bounce@xxxxxxxxxxxxx>> on behalf
of Henry Spencer <hspencer@xxxxxxxxxxxxx<mailto:hspencer@xxxxxxxxxxxxx>>
Sent: Wednesday, December 30, 2015 4:23 PM
To: Arocket List
Subject: [AR] Re: fatigue life (was Re: Re: SpaceX F9 Launch/Update...)
On Wed, 30 Dec 2015, Brian Feeney wrote:
Does the Saddle / Jacket engine design alleviate much of the inner to
outer differential thermal wall stress by way of the inner wall (chamber
/ nozzle) sliding relative to the outer wall.