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From: peterb@pbear.UUCP
Newsgroups: net.space
Subject: Re: Light Sail Deployment
Message-ID: <61@pbear.UUCP>
Date: Mon, 25-Feb-85 05:30:53 EST
Article-I.D.: pbear.61
Posted: Mon Feb 25 05:30:53 1985
Date-Received: Thu, 28-Feb-85 01:21:06 EST
Lines: 51
Nf-ID: #N:pbear:27600001:000:2296
Nf-From: pbear!peterb    Feb 22 15:05:00 1985


	Regarding light sails,

	I don't know if mylar is the best, but I  think  that  it
will work quite well.

	When building a  light  sail,  there  are  a  few  design
 problems  that  have  to be overcome, such as weight (obviously)
 rigidity, ease of deployment,  and  resistance  to  damage  from
 micro  meteors.   I  remember  a  story called "Sun Jammer" that
 described an earth to moon race by solar yachts.   These  varied
 in  design,  and  the  story  described  quite  a  bit about the
 problems of solar sails.

	One of the problems is how do you deploy a sail that is a
few miles in surface area, and then once deployed how do you keep
it in shape.

	One of the obvious ideas it to  spin  the  sail  and  use
centrifical  force  to  keep  the sail in place while it is being
deployed.  This is assuming that the sail has been  packed  in  a
tube  with  the shrouds to be released first and then as the tube
rotates the rest of the sail pulls it self out.  Also  the  speed
of  rotation  would  drop as more and more sail is released until
the entire sail is released.

	Once released and spinning the sail would form  a  circle
with  a  depressed  center  (from  photon pressure) and has to be
strutted in order for it to keep its shape for  a  few  millenia.
One  idea  I  thik  would  work is to us an foaming agent that is
released into mylar tubes that are bonded to the  sail  (backside
so as not to interfere with the mirror).  As the foam expands, it
would  rush  to  the  extreme  end of the tube that is exposed to
vacuum.  Also the centrifical force would help  it  on  its  way.
Then  the foam would vacuum cure and become rigid.  This may be a
little messy, but it would be quite simple in design.   Also  the
tubes would not have to worry about crimping since the foam would
expand  slightly  as  it  cured and cause the tubes to assume the
largest volume (a circle).

	The tubes can all be connected to a central valve at  the
apex  of  the  sail  and  once the foam is injected and cured the
deploment tube can jus cut itself away and the sail  would  start
on its journey.

	Steering the sail would be difficult, and  I  don't  have
the  answers to that one.  I would wish someone would pick up the
idea and bounce it around.

					Peter Barada
					ima!pbear!peterb