Path: utzoo!attcan!uunet!ogicse!unicorn!milton!brettvs@blake.u.washington.edu
From: brettvs@blake.u.washington.edu (Brett Vansteenwyk)
Newsgroups: sci.space.shuttle
Subject: re:  Launch Question
Message-ID: <7671@milton.u.washington.edu>
Date: 17 Sep 90 06:45:58 GMT
Sender: news@milton.u.washington.edu
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Organization: University of Washington, Seattle
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Regarding gimbaling of the SSME's, sometimes the cameras will focus in on these
just as they light up--the adjustment between quiescent and 100% (plus
structural loading) you see a LOT of gimbaling.  It is interesting to watch
(though you only get to see 2-3 seconds).

The shuttle flies "upside down" to minimize aerodynamic stress on the ENTIRE
system--mostly the external tank (which, ironically enough, was originally
considered one of the weakest links of the shuttle system).  I think this was
mentioned before, and while it would be hard for me to explain without doing
a lot of drawing (I'm not good at ASCII-art), you can consider the following
notion:  in the "shuttle down" position, the SSME's are more underneath the
c.g. of the entire vehicle, thus less of an angle of attack.  The cross-
sectional area of the SRB's is considerable, at least comparable to that of
the wings on the shuttle, thus minimizing the angle of attack is very desirable.
The tank connects the SRB's and the shuttle into the whole system--it would
seem reasonable that the largest stresses are here.  And to think that this
remarkable piece of engineering is the only part of the shuttle system that
is thrown away!
				--Brett Van Steenwyk