Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: space news from Aug 15 AW&ST
Message-ID: <1988Sep17.222225.9422@utzoo.uucp>
Organization: U of Toronto Zoology
References: <1988Sep12.032459.25617@utzoo.uucp> <972@netxcom.UUCP> <776@etive.ed.ac.uk> <1631@daisy.UUCP>
Date: Sat, 17 Sep 88 22:22:25 GMT

In article <1631@daisy.UUCP> wooding@daisy.UUCP (Mike Wooding) writes:
> Presumably before moving into the ET, some modifications
> would be required? The tanks are designed to seperate and
> contain LOX and LH, and are presumably short on access
> portals and life support systems. Would such modifications
> be feasible in orbit?

It's a significant problem.  First, one must stabilize the tank -- it
has no attitude control of its own.  Then, one has to get into it.
The tanks do have access hatches, although one would have to cut the
sprayed-on insulator off the hatches first.  The hatches are not as
large as one would like, but they are adequate.  If one is going to
keep the tank pressurized, one must supply it with a "meteor bumper"
shield against space debris -- the tank walls are not that thick.
The shield can also help keep tank-produced debris under control:
the sprayed-on insulator will outgas in space, and there will probably
be some "popcorning" as a result, which will throw off bits of debris
unless there is something to catch them.  Temperature control will
also be simplified by putting an outer shield on.  Lastly, one needs a
highly reliable solution to the reboost/de-orbit problem -- NASA is
paranoid about a repetition of Skylab.

All the above looks feasible.  The people who are working on turning
an ET into a gamma-ray telescope -- this is the only NASA-funded ET
project at the moment -- have to do all this, and they say "no big deal".

To use the tank as a space station, obviously more work is needed.
A lot of equipment needs to be moved in.  The tank's own internal frames
are well suited for attaching stuff, but there is some worry about the
overall structural strength -- during launch, the tank is stiffened to
a considerable extent by high internal pressure.  By itself, it's weaker
than you'd like.  One might like to have more than one hatch into the
tank, for safety reasons.  (NB all of this considers mostly use of the
hydrogen-tank portion, which is several times the size of the LOX
section, but that doesn't alter the issues much.)  It would be better
to strip the insulation off entirely, since the space station would
prefer to minimize outgassing (it's a big enough problem already).
Temperature control becomes more critical.  Life support will need to
be moved in.  Internal partitions, preferably sound-absorbing ones, will
be needed.  And so on.  There is potential there, but it's not quite as
simple as one would like.  Note especially that *any* modifications to
the tank before launch are going to have to be approved as safe for
flight, which is a massive headache.
-- 
NASA is into artificial        |     Henry Spencer at U of Toronto Zoology
stupidity.  - Jerry Pournelle  | uunet!attcan!utzoo!henry henry@zoo.toronto.edu