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From: gcb1@ukc.UUCP (G.C.Blair)
Newsgroups: net.physics,net.space,net.research
Subject: Star-Wars/Space Telescopes
Message-ID: <384@ukc.UUCP>
Date: Thu, 14-Nov-85 17:40:59 EST
Article-I.D.: ukc.384
Posted: Thu Nov 14 17:40:59 1985
Date-Received: Sun, 17-Nov-85 06:20:46 EST
Organization: U of Kent at Canterbury, Canterbury, UK
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Xref: linus net.physics:3300 net.space:3226 net.research:296

I consider myself fairly well up-to-date with the current advances in
the so-called "Star Wars" technology & research, but I realised something
today which had never occurred to me before:

We all know how you can make a parabolic mirror by stretching a thin
film of aluminised plastic over a ring of metal or some other such
material, then using a vacuum pump to suck the film into the shape of
a parabola, but has this actually been achieved in space (ie en vacuo)?
Surely the principle demands that the pressure on the front surface is
greater than the pressure from the back? So in a vacuum, the pressure
would be equal from both sides, even with the vacuum pump, thus the
sheet of plastic would not deform into the required shape. Does this
then mean that the telescope would require a closed volume of gas in
front of the mirror, supplying a pressure, but also re-introducing
an absorbing medium for the light? This latter argument is certainly
one that I have never heard propounded. Does anyone know of any
experiments that have been carried out in a vacuum on this topic?

			Grant C. Blair

[Is anyone out there willing to sponsor me to do Stars Wars research? Please?]