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From: derek@uwvax.UUCP (Derek Zahn)
Newsgroups: net.space
Subject: Re: Light Sails
Message-ID: <133@uwvax.UUCP>
Date: Wed, 27-Feb-85 13:25:26 EST
Article-I.D.: uwvax.133
Posted: Wed Feb 27 13:25:26 1985
Date-Received: Sun, 3-Mar-85 03:33:23 EST
References: <722@mordor.UUCP>
Organization: U of Wisconsin CS Dept
Lines: 18

> In the talks I have heard on solar sails by the experts, it was stated
> that the pressure of sunlight is in the range of a thousand to a million
> times that of solar wind particles.  

Got time for a dumb question?  Too bad.  I can't figure how the energy of
photons from the sun is going to be converted into motion of the light sail.
I jus' don't get it.  If the photon is reflected, there can be no change in
momentum of the sail (momentum being conserved), unless the photon loses
energy.  In this case, what is the mechanism that causes the transfer of
momentum, and how efficient could it possibly be?  If the photon is absorbed,
it seems much more likely that the energy would be converted to heat.
Somebody help, for I is baffled.

derek
-- 
Derek Zahn @ wisconsin
...!{allegra,heurikon,ihnp4,seismo,sfwin,ucbvax,uwm-evax}!uwvax!derek
derek@wisc-rsch.arpa