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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.space
Subject: Re: Laser Launch
Message-ID: <6301@utzoo.UUCP>
Date: Sat, 18-Jan-86 20:42:27 EST
Article-I.D.: utzoo.6301
Posted: Sat Jan 18 20:42:27 1986
Date-Received: Sat, 18-Jan-86 20:42:27 EST
References: <8601170304.AA18252@s1-b.arpa>
Organization: U of Toronto Zoology
Lines: 18

> I have the feeling that the advances in phase conjugate lasers have just
> solved the most difficult of the engineering problems in [laser launchers]

Last I heard, there was near-universal agreement that by far the most
difficult engineering problem of the laser launcher was on the receiving
end of the beam, not in the beam optics:  how to efficiently use the beam
energy to heat exhaust mass.  Nobody has more than vague notions for the
design of the beam receiver, I believe.

Incidentally, I believe Kantrowitz's proposals generally envisioned having
the vehicle carry the exhaust mass in tanks, rather than scooping up air
for the purpose.  The extension to using air results in a prettier system
with potentially higher performance, but makes the beam-receiver design
still harder.  A "first generation" system probably would avoid the extra
complexity and accept the lower performance.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry