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From: rjnoe@ihlts.UUCP (Roger Noe)
Newsgroups: net.columbia
Subject: Re: Challenger's tight fuel budget
Message-ID: <420@ihlts.UUCP>
Date: Wed, 11-Apr-84 10:35:46 EST
Article-I.D.: ihlts.420
Posted: Wed Apr 11 10:35:46 1984
Date-Received: Fri, 13-Apr-84 01:20:54 EST
References: <1191@sdccs7.UUCP>, <2701@alice.UUCP> <161@homxa.UUCP>
Organization: AT&T Bell Labs, Naperville, IL
Lines: 28

>	So the MMU's fuel reserve was OK, but not the shuttle's.
>	What good is the shuttle then?
>	Orlando Sotomayor-Diaz     ihnp4!homxa!osd7

The shuttle is being expected to do a number of extraordinary things
this mission.  In the first place, there was a very massive (22100 lbs.)
satellite that had to be carried up to an altitude of 250 nautical miles.
Already this is much higher than any shuttle had been before; STS-4 only
went up to 175 nm and with no significant payload mass.  I think this
is also one of the biggest payloads the shuttle is expected to carry,
although Spacelab might have been more.

Once LDEF was deployed the shuttle had to increase apogee to 265 nm
to reach SMM's present orbital altitude.  Then all the station-keeping
done with RCS (reaction control subsystem) takes more fuel.  Not to
mention how much must be kept in reserve for the event of an astronaut
on EVA needing to be scooped up.

But this still isn't all that the OMS (orbital maneuvering subsystem) is
expected to do this mission!  Plans before launch said they would go up
to 285 nm with SMM still in the payload bay and redeploy it there.  Of
course, the OMS always has to have enough left for the deorbit burn.

I think it's fantastic that the shuttle can even make it up to 300 miles,
never mind all that maneuvering, orbit changing, and satellite carrying.
With the exception of the TPAD, I'm very impressed with the people and
the machines involved in this mission.
	Roger Noe		ihnp4!ihlts!rjnoe