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From: eder@ssc-vax.UUCP
Newsgroups: net.space
Subject: Re: Lunar landings, cold mining, launchings
Message-ID: <755@ssc-vax.UUCP>
Date: Mon, 16-Jan-84 15:25:55 EST
Article-I.D.: ssc-vax.755
Posted: Mon Jan 16 15:25:55 1984
Date-Received: Fri, 20-Jan-84 01:12:54 EST
References: <15313@sri-arpa.UUCP>
Organization: Boeing Aerospace, Seattle
Lines: 22

From Dani Eder at Boeing Aerospace
16 January 1984

     Another method of getting stuff to and from the lunar surface is a
rotating cable.  Since the Moon is much smaller than the Earth, material
strengths can be lower for cable type systems.  For example, suppose you
have a cable orbiting the Moon at 1650 meters/sec.  It is spinning so that
it's outer tip is moving at lunar escape velocity (2333 meters/sec),
and its inner tip is moving at a corresponding amount slower(966 meters/
sec).   
     On your way from Earth, you come in at escape velocity, grab on for
half a rotation of the cable, then let go.  You have reduced your velocity
from 2333 meters/sec to 966 meters/ sec.  You do the rest with rockets.
Compared with pure rockets, you have to do only 41% as much velocity
change.  If you are using LOX-Hydrogen rockets your fuel use goes from
.677 times landed weight to .239 times landed weight, only 35% as much
fuel.  You don't have to have any special facility on the lunar surface.
     On the way up, you drop off some oxygen or aluminum to feed an ion
thruster or  mass driver at the center of the cable.  This is required
to balance any net momentum change if the payload to the moon does not
equal the payload from the moon.