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From: karn@jupiter..bellcore.com (Phil R. Karn)
Newsgroups: sci.astro,sci.space,sci.space.shuttle
Subject: Re: Stopping Space and Light Pollution.
Message-ID: <1379@thumper.bellcore.com>
Date: 2 Nov 88 22:06:59 GMT
References: <8811011709.AA02398@decwrl.dec.com>
Sender: news@thumper.bellcore.com
Reply-To: karn@jupiter.UUCP (Phil R. Karn)
Organization: Bell Communications Research, Inc
Lines: 65


The note on stopping space pollution is interesting, but one of
the proposed solutions is, shall we say, a bit impractical.

First of all, the main problem isn't intact payloads. The real problem is
with the numerous small fragments in long-lived orbits, and these are not
easily reached from the Shuttle.  Debris, large or small, that *is* in a
typical Shuttle orbit (about 300 km) re-enters within a few months anyway,
so there's not much point in going up to get it.

Second, there are so *many* small bits of debris, in so many different
orbits, that even if you could reach them with the Shuttle you'd have to
expend enormous amounts of fuel chasing them all.

Third, the Shuttle itself generates a not-insignificant amount of debris
through such things as waste dumps and loose parts. This would largely
offset whatever debris it could pick up.  I remember seeing the first
on-orbit TV of the payload bay sent to earth during STS-1; clearly visible
was a small piece of loose hardware spinning across the field of view, off
into the blackness.

If you're seriously interested in the space pollution problem, I believe
you should advocate the following PREVENTIVE approaches:

1. An international treaty prohibiting deliberate collisions between or
explosions of objects in earth orbit above a certain altitude, say 500 km.
This would include both Soviet and American SDI and ASAT tests. Much
existing orbital debris is the result of Soviet ASAT tests. The reduction of
space debris is only one of many reasons that a complete ban on all ASAT
testing would be to our mutual advantage.

2. An international treaty requiring launch agencies to vent excess liquid
fuel from spent upper stages to render them incapable of exploding.  Much
existing orbital debris has come from upper stages that explode some time
after deploying their payloads.  This can happen in a cryogenic stage when
the fuel vaporizes (e.g., the Ariane 3rd stage that launched SPOT-1) or it
can happen in a hypergolic stage when the fuel and/or oxidizer corrode
through the bulkhead and mix (e.g., some Delta 2nd stages). I believe that
most launchers now vent as standard operating procedure, so it shouldn't be
much of a burden to make this a formal requirement.

3. International guidelines for the design of orbital missions missions such
that the fewest possible non-payload objects are deployed in long lived
orbits. This would consist of several aspects:

a. The use of short-lived transfer orbits whenever possible. For example, a
standard Ariane geostationary transfer orbit has a perigee of about 200 Km.
Spent Ariane third stages generally last in this orbit for a few years or
so.  intermediate earth orbits with "direct ascent" launches are the real
problem, since the upper stage goes into the same orbit as the payload. If
at all possible, spent stages should be designed to de-orbit themselves
after deploying their payloads.

b. Methods to control the amount of debris generated in long-lived orbits,
with emphasis on payload deployment operations. Clamp bands, springs,
fasteners, explosive bolt cutters and the like should be captive, i.e., they
should be tethered so they don't go floating off on their own after
separation.  This is already standard procedure on most Western launches; it
should be an international requirement.

c. Integrity standards for external coatings on all objects deployed in
long-lived orbits. The white paint used on Delta upper stages has been
traced as the cause of some small craters found on Shuttle windows.

Phil