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Path: utzoo!kcarroll
From: kcarroll@utzoo.UUCP (Kieran A. Carroll)
Newsgroups: net.space
Subject: Shuttle External Tanks and Space Stations
Message-ID: <6205@utzoo.UUCP>
Date: Thu, 5-Dec-85 17:19:58 EST
Article-I.D.: utzoo.6205
Posted: Thu Dec  5 17:19:58 1985
Date-Received: Thu, 5-Dec-85 17:19:58 EST
References: <8512011611.AA12940@s1-b.arpa>, <6196@utzoo.UUCP>
Organization: U of Toronto Zoology
Lines: 50

*
   While it maight be insuperably difficult to
make a shuttle's external tank into a functioning
space station (requiring all sorts of extra thermal
control, attitude and orbit control, power supply
and conditioning equipment, etc.), I don't believe
that it'd be too difficult (or expensive) to carry
one into orbit to be a >>part<< of a space station.
Provided with (a) an airlock at the top,
(b) a hatch between the oxygen and hydrogen tanks, and
(c) a simple vent, for discarding LH2 and LO2 as they
vaporize, an ET could be attached almost immediately to
the habitable portion of an already-existing
space station.  Extra thermal insulation might have to
be sprayed on the outside before launch, in order for the
ET not to become too cold (or hot!) on-orbit; this would
involve a mass penalty, as would the airlock, hatch and vent.
However, for the resulting >>small<< mass penalty
(maybe a total of 1 ton, or two?), a >>vast<< amount
of habitable volume would be added to the station!
While this volume would not initially contain any useful
equipment, I'm sure that uses would soon be found for it, 
enormously off-setting the initial investment.
If nothing else, it could be used as a relaxation area by the
crew (who, after all, will be spending 3 months at a time
in a space the size of 5 house-trailers strung together).
   It seems to me that the arguments against bringing the ETs
to orbit are based on the assumption that it'll have to
serve many functions at once, and that it'd be too expensive
to make it do that.  If you don't make it perform any other function
than providing "attic space" for the station, tho',
it can be provided essentially for free (in fact, bringing it
up to orbit may allow the shuttle to >>increase<< its
to-orbit payload, since the fuel previously used in the
ET-jettison manoeuvre won't have to be expended, and this may
offset the mass penalty of the extra ET-attached hardware).
I think that by requiring too much performance of the ET
as a space station component, its cost can of course be forced
(literally) sky-high; the same is true of >>any<< part of
a spacecraft.  Why not just bring up a few tanks empty,
at a very low cost, and find out what they're good for up there,
before adding performance requirements to them and raising their
cost?  (These people are not only looking a gift horse in the
mouth, they're sending it back because with a rating of only
1 horsepower, it's makes a lousy sportscar....)
   Any comments?
-- 

     Kieran A. Carroll @ U of Toronto Aerospace Institute
     {allegra,ihnp4,linus,decvax}!utzoo!kcarroll