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From: brettvs@blake.u.washington.edu (Brett Vansteenwyk)
Newsgroups: sci.space,sci.space.shuttle
Subject: Re:  New Shuttle Engines
Message-ID: <11236@milton.u.washington.edu>
Date: 16 Nov 90 06:42:14 GMT
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My impression was (especially from reading Feynman's book) that the SSMEs were
virtually rebuilt after each launch--the component parts going into a system
of inspection and repair such that when a given engine was rebuilt, many
of the pieces in the new build came from other engines that were also in the
rebuild process at the time--the original engine's parts by and large would
not find one another again, except for statistical chance.  It seemed that
each engine was disassembled into some pretty small pieces, where they could
be inspected, repaired, etc., and that the rebuild was as involved as building
a new engine.  Cracked turbine blades were a big item here.  Anyway, this is
what I referred to as the "enormous refurbishment cost".  If this sort of
undertaking is no longer as extensive as I have described, then it would
seem that these engines have come quite a way, and would be quite happy
to hear of it.

I am curious as to how much of a design difficulty it is to have an engine
operate (well or otherwise) at both sea level and in the vacuum (just a matter
of ambient pressure or much more?).  If this is a heavy constraint, why light
the SSMEs at sea level at all when it would seem that you could replace
that thrust (1/6 or so of the total) by adding another booster and then
lighting them high up at, say, the booster separation?  I realize that there
is a certain reluctance to tacking on an SRB, but if LRBs get developed,
could this become a viable option?

By the way, I remember that there is some consideration (or ongoing effort)
to adapting the RL-10 to operate at sea level.  Is this a good example of
this sort of design "difficulty"?

[Really random question]  Aside from the weight consideration, how close do
automobile turbochargers come to the operating conditions of their
counterparts (with a stretch of the imagination) in some of the lower
performance rocket engines?

		--Brett Van Steenwyk