Xref: utzoo sci.astro:2991 sci.space:8025 sci.space.shuttle:1854
Newsgroups: sci.astro,sci.space,sci.space.shuttle
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Stopping Space and Light Pollution.
Message-ID: <1988Nov4.214749.25328@utzoo.uucp>
Organization: U of Toronto Zoology
References: <8811011709.AA02398@decwrl.dec.com> <1379@thumper.bellcore.com>
Date: Fri, 4 Nov 88 21:47:49 GMT

In article <1379@thumper.bellcore.com> karn@jupiter.UUCP (Phil R. Karn) writes:
>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.

In fact, even if you had propulsion suitable to the job -- I once took a
cursory look at the idea of a tiny satellite with electrodynamic propulsion,
specifically as a garbage retriever -- the sheer size of the problem is
just plain excessive.  It's not the two-ton lumps that are the real
problem:  they are (relatively) few in number and collisions with them
are fairly unlikely.  The bad part of the problem is the coin-sized bits.
They're too small for any practical retrieval scheme, too numerous to
just trust to luck, too small *and* too numerous to just track and avoid,
and too massive to just disregard.  The best we can do is to protect major
facilities against them and try hard to avoid creating more!

>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...

An alternative that is worth exploring for some types of object is photo-
degradeable materials.  De-spin weights, for example, *have* to be cut
loose, but I would suspect that they and their cables could be made out
of some plastic that would break down in sunlight, so eventually you'd
have nothing but organic gas left.

>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.

Those who are enthusiastic about using shuttle external tanks in orbit
should note that the insulation on the tanks is likely to "popcorn" in
vacuum as it outgases.  The folks working on turning a tank into a
gamma-ray telescope (the only NASA-funded external-tank work) plan to
put an outer casing around the tank, partly to contain the debris.  (The
other reason for the casing is as a classic "meteor bumper" against both
natural meteorites and space debris.)
-- 
The Earth is our mother.        |    Henry Spencer at U of Toronto Zoology
Our nine months are up.         |uunet!attcan!utzoo!henry henry@zoo.toronto.edu