Need help with a rocket motor ID

On 3 Feb 2007 00:12:02 -0600, jc wrote:

On Fri, 2 Feb 2007 18:38:32 +1030, "Dave Kearton"
wrote:
[snip]



The other thing is the way the fluid lines wrap around the
can looks like preheat to me. That either means a fuel that
doesn't vaporize easily, like kerosene, or a cold soaked
environment. That goes along with the idea that it's
designed for vacuum.

Well, yes. It does preheat the propellant.

But that is not the main idea, or usually isn't.

Almost all liquid propellant rockets are "regen" cooled. That keeps
them from melting down and burning through.

All your usual engines are like thta. Atlas, Delta, F-1, SSME, etc.

American LOX/RP engines use RP cooling. the temp rise is fairly small,
doesn't have much effect on combustion. Note that the engine has to
start so it has to run on "cold" propellant.

It is a bit different with LOX/LH2 engines. In fact, AFAIK, there are
NO "LH2" engines. The hydrogen picks up enough heat in the jacket so
that it enters the combustion chamber as a gas.

One of those engines, the P&W RL-10, the Centaur engine runs the H2
thru a turbine which drives the turbo pump. They call it the "expander
cycle."

At one time, there was a great series of studies of new engine
designs, and P&W was pushing "their" expander cycle. One of the
advantages they claimed was that the expander cycle has "graceful
degradation." Say you get a hot sopt in the jacket and it starts to
burn through (just the inner wall). That cuts the flow to the trubine
which reduces the heat flux and stops the burn through.

That sounded good. As as vehicle design team participant in the study,
I backed them all I could. For my own vested interests.

It turned out that P&W could find no other mode that the expander was
more graceful at than the competing "GG" cycle, And, the GG cycle was
not at all prone to burn thru. So it was something like a protection
agains a problem that you were causing.

P&W and I gracefully degraded, together.

Henry H.



[snip]