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Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.space
Subject: Re: Orbital Artillery
Message-ID: <3577@utzoo.UUCP>
Date: Sat, 25-Feb-84 21:01:59 EST
Article-I.D.: utzoo.3577
Posted: Sat Feb 25 21:01:59 1984
Date-Received: Sat, 25-Feb-84 21:01:59 EST
References: <16648@sri-arpa.UUCP>, <3562@utzoo.UUCP>
Organization: U of Toronto Zoology
Lines: 28

Kieran asks:

      Has anyone else on the net, upon hearing O'Neill's idea for using
   mass-drivers throwing away tiny pellets of reaction mass ( say little
   buckets of lunar dirt) as a high-efficiency rocket-engine, had the thought,
   "Good Lord, who wants to fill the solar system up with billions 
   more meteorites, especially around what will eventually be a crowded 
   shipping region, the earth-moon region? Won'rt the probability
   of hulling your ship increase dramatically?"

Actually, O'Neill thought of this.  The first part of the answer is
that there is so much natural debris around that it's hard for human
activities to increase it much.  The second part is that there are
fairly easy ways to handle the problem, which should probably be used
to prevent a problem developing in the long term.  Specifically...

The mass-driver's big virtue is that it can use most anything as
reaction mass.  So you can choose something that will be relatively
inoffensive.  Early on, the choice of propellant will be constrained
by what's available, such as aluminum dust from ground-up shuttle
external tanks.  The problem can be minimized by spraying a static
charge onto the dust as it leaves the mass-driver; this will make
the dust particles disperse.  Later, the propellant of choice is
liquid oxygen extracted from lunar/asteroidal rock.  The LOX simply
boils off into vacuum after release, leaving no debris at all.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry