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From: calius@SU-STAR.ARPA (Emilio Calius)
Newsgroups: net.space
Subject: Re: Re: Shuttle external tanks
Message-ID: <8512012228.AA13706@s1-b.arpa>
Date: Sun, 1-Dec-85 17:13:00 EST
Article-I.D.: s1-b.8512012228.AA13706
Posted: Sun Dec  1 17:13:00 1985
Date-Received: Mon, 2-Dec-85 03:46:24 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: Emilio Calius <calius@su-star>
Organization: The ARPA Internet
Lines: 47


	I think that most everybody agrees that the effort required to carry
the ET to LEO is fairly trivial. Why hasn't it been done? I don't know, but I
can't help thinking that somebody in NASA made a political decision.

        However, once you've got it in orbit, there are several issues to be
resolved:
	1) How much does the Shuttle orbit change from one mission to the next?
That will determine how much delta V is required to assemble several tanks in
to a space station, a tank farm, a scrap yard, or whatever you have in mind.
Would 1 or 2 dedicated missions be sufficient for this purpose or do we have to
wait for the OMV?.
Note that big Coke can is a navigational hazard and also should have a limited
lifetime in the low orbits where it's likely to end up. How do we avoid a repeat
of the Skylab circus?

	2) Once you've got them where you want them, there remains the question
of adapting them for whatever purpose you have in mind. This is likely to 
require a fair amount of 0g shop work in which the US seems to be lagging behind
the USSR. For example, if you want to convert the tank into workshop/hangar
space, you will have to add a lot of local strengthening to the basic pressure
vessel structure, as well as adding all the services you require (electricity,
air, fluids, thermal control, etc.), airlocks (if you are making a hangar, you
have to figure out how to make one end into a door), and installing and checking
out your equipment. Contrast this with sending up space station modules pre-
configured and checked out on the ground. Even if you just want to use the tank
as a tank you will have to figure out how to modify it so that you can fill &
empty it in 0g (remember that its present plumbing is designed to be used once,
at longitudinal accelerations >= 1g).

	3) If you're going to have humans routinely working inside in a "shirt-
sleeve" environment for longer than a few days, I am not sure wether the single
skin design of the ET is acceptable without some sort of escape mechanism. I
would feel much more confortable with a second skin and a self-sealing medium
in between. So maybe you have to coat the tank with some kind of foam and add
a shield or "bumper".

	Maybe all of the above issues have already been resolved. If that is so
I would like to hear about it. Anyway, I still think that throwing away the ET
and its residual fuel is still a waste of a potentially very useful resource.
Just think of the residual contents of the tanks and refuelling the orbit
control systems of satellites as well as the OMV.

Emilio P. Calius
Dept. of Aero/Astro
Stanford Univ.
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