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From: jcp@brl-tgr.ARPA (Joe Pistritto <jcp>)
Newsgroups: net.columbia,net.space
Subject: Re: Discovery a lightweight?
Message-ID: <4492@brl-tgr.ARPA>
Date: Sat, 8-Sep-84 18:29:27 EDT
Article-I.D.: brl-tgr.4492
Posted: Sat Sep  8 18:29:27 1984
Date-Received: Sun, 16-Sep-84 08:42:36 EDT
References: <540@sequent.UUCP>
Organization: Ballistics Research Lab
Lines: 24

Yes Discovery is lighter than either of the first two orbiters (which
are approximately the same weight).  Some of the weight reduction
was made by replacing the silica 'tile' surface in some areas with
thinner, larger molded plates made of metal and/or composite
materials.  (test plates of this material were flown earlier on
Challenger).  The upper surface of Discover (white area) has quite
a bit of this.  Also, the wing structures have a few less internal
struts, in non-critical areas.  Some weight reduction has also been
achieved thru use of different materials for the OMS pods, I believe.
The total weight reduction of the orbiter is on the order of 1500 lbs.
Of course, all shuttle missions recently have used the lightweight
external tank, (unpainted), which shaved off 3000lbs all by itself.
The idea is to increase launch payload.  For instance, only Discovery
and the next orbiter (Endeavor?) will be able to launch the max
payload capacity ~70K lbs.  The first Discovery flight had a payload
of ~45K lbs I believe.  (Three satellites, which didn't come back down,
plus the extensible solar array assembly, which did).  Also, the flight
instrumentation for Discovery is simpler, (the development instrumentation
having never been installed).  I believe Discovery has 'head-up' displays
for the commander and pilot, (the 'pilot' sits in the right seat), unlike
the previous orbiters, which are being retrofitted for this.  (Challenger
will have them on the next mission, I believe)

							-JCP-