[AR] Re: thinking big once more
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Fri, 30 Sep 2016 12:39:06 -0400 (EDT)
On Fri, 30 Sep 2016, Daniel Rocha wrote:
That suggests that a design priority for rocket with
many less-than-perfectly-reliable engines should be
that the failures involve an engine that stops running,
rather than one which explodes and destroys the rocket.
Was it ever accomplished?
Many times. It's the usual outcome of a liquid-rocket engine failure.
Most conspicuously, a Saturn I stripped the gears in a turbopump, Apollo 6
lost two engines due to ruptured igniter fuel lines (and a third due to a
wiring error), and Apollo 13 lost one due to violent Pogo oscillations...
and all three made orbit.
(You might remember me referring to *four* Saturns surviving losing
engines; this is not a miscount. :-) The fourth was a deliberate engine
shutdown on an earlier Saturn I, as a test of engine-out behavior.)
There was also one Shuttle flight which lost an engine late in ascent, but
that was a false alarm, shutdown due to a sensor malfunction. (It did an
Abort To Orbit, more or less completing its mission -- "more or less"
because the orbit was lower than planned and this messed up a few
experiments, although the press releases never mentioned that. :-) )
There have also been a number of cases where a failing engine was
successfully shut down, or safety interlocks prevented startup, but the
rocket was unable to complete its mission due to the performance
shortfall. (And in vehicles without intact-abort capability, that
generally meant loss of vehicle and payload.) Apollo 6's mission was
successfully completed only because the spacecraft had enough performance
reserve to make up for the shortfall caused by the final engine failure.
Henry
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