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From: bane@umcp-cs.UUCP
Newsgroups: net.space
Subject: Re: Better solar sails? - (nf)
Message-ID: <3510@umcp-cs.UUCP>
Date: Tue, 1-Nov-83 14:26:06 EST
Article-I.D.: umcp-cs.3510
Posted: Tue Nov  1 14:26:06 1983
Date-Received: Fri, 4-Nov-83 02:19:18 EST
References: <532@ucbcad.UUCP>
Organization: Univ. of Maryland, Computer Science Dept.
Lines: 23

I first heard about the perforated solar sail idea at a talk by Robert
Forward at Constellation in September.  I forget whether he claimed the
idea was his or not.  The big win here is not that the sail gets lighter,
but rather that the sail will now let gas pass through it so it can be
used much closer to bodies with atmospheres; the holes are large enough
that gas molecules can get through, but smaller than the wavelengths of
most sunlight.  This will allow neat tricks like geosynchronous satellites
away from the plane of the equator (the satellite is a solar sail thrusting
along the earth's axis).

There were many other strange propulsion ideas thrown out at that talk;
Forward had just finished preparing a report for the Air Force on the
future of propulsion for space.  The one that had me gaping was not the
perforated sails, though.  Forward mentioned the possibility of the existence
of a form of helium created at enormous energy cost which:
1) Would be a solid up to about 300 degrees C.
2) Could turn back into helium gas with an energy release of about
   10 times the best possible chemical fuels.

Anybody out there know more about this stuff?
-- 
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