SM engine failure?

Did the Apollo SM engine ever fail? When I was at a program at the
Cape in 68, they said that the SM engine had a reliability of 99.99%
(or 99.999 or 99.9999%). Late in the program I *thought* I heard that
it failed one time, but I'm not sure about that report or my memory.
Did it ever fail on a flight?

"Jan Philips" wrote in message
...
Did the Apollo SM engine ever fail? When I was at a program at the
Cape in 68, they said that the SM engine had a reliability of 99.99%
(or 99.999 or 99.9999%). Late in the program I *thought* I heard that
it failed one time, but I'm not sure about that report or my memory.
Did it ever fail on a flight?


I suppose it depends what you mean by 'SM engine' (i.e. which associated
systems does one include?) and 'failure' (is it any off-nominal event or are
we talking about a completely inert system?).

Apollo 16 experienced an unstable yaw gimble as CMP Ken Mattingly attempted
the circularisation(?) burn - that's the best I can come up with.

DK
-
Dave Kenworthy
-----------------------------
Changes aren't permanent - but change is!

Dave Kenworthy wrote:
"Jan Philips" wrote in message
...

Did the Apollo SM engine ever fail? When I was at a program at the
Cape in 68, they said that the SM engine had a reliability of 99.99%
(or 99.999 or 99.9999%). Late in the program I *thought* I heard that
it failed one time, but I'm not sure about that report or my memory.
Did it ever fail on a flight?



I suppose it depends what you mean by 'SM engine' (i.e. which associated
systems does one include?) and 'failure' (is it any off-nominal event or are
we talking about a completely inert system?).

Apollo 16 experienced an unstable yaw gimble as CMP Ken Mattingly attempted
the circularisation(?) burn - that's the best I can come up with.

Definitely a matter of defintions. As I recall, this was a failure
in one side of the gimbal servo loop (no rate feedback?).

Brett

There were no in-flight failures of the thrust portion of the SPS. You've
already heard about the gimbal failure. However, during early development
there was an issue with combustion instability that was solved by "burping"
the engine early in the mission.

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In article ,
says...
There were no in-flight failures of the thrust portion of the SPS. You've
already heard about the gimbal failure. However, during early development
there was an issue with combustion instability that was solved by "burping"
the engine early in the mission.

Yeah, that was a problem that only occurred when you started a burn with
both legs of the SPS fuel/oxidizer plumbing. The fuel and oxidizer
injection system was redundant, the fluids passed through two sets of
ball valves each. The engine could be operated at full thrust on either
bank. The early problem was that if you just opened Bank A and Bank B on
both the fuel and the oxidizer side at the same time, you could get a
"hard start" which could blow out your engine. I believe the problem was
finessed out of the system after Apollo 8, but that flight required a set
of pre-planned midcourse burns, designed to cancel each other out, to
"wet" the engine with each bank separately prior to the planned two-bank
LOI burn.

There was one other SPS-related failure during Apollo. The Apollo 15 CSM
had a glitch in its panel wiring which caused SPS Bank A (if I'm
remembering correctly) to open up as soon as you armed the engine. The
behavior that told them they had this problem was that the SPS thrust
light came on in the cabin spuriously, while the SPS was NOT in use.
They got around this problem by waiting to arm Bank A until after the
computer had auto-started a burn on Bank B, and then disarming Bank A a
few seconds before auto cut-off. The fix worked just fine.

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