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From: dietz%usc-cse%USC-ECL%SRI-NIC@sri-unix.UUCP
Newsgroups: net.space
Subject: Lunar landings, cold mining, launchings
Message-ID: <15313@sri-arpa.UUCP>
Date: Wed, 11-Jan-84 14:03:00 EST
Article-I.D.: sri-arpa.15313
Posted: Wed Jan 11 14:03:00 1984
Date-Received: Sat, 14-Jan-84 04:05:12 EST
Lines: 38

Last month I sent a message describing an idea by Krafft Ehricke to
land payloads on the lunar surface.  It involved skidding the payloads
on a long strip of lunar soil at orbital velocity (about 1650 m/sec).
A difficulty is sifting the lunar soil to remove rocks from the top
1/2 to 1 meter.  But this may not be necessary.  The rocks could be
removed by a special vehicle.

The vehicle would have pipes that would be extended several meters into
the lunar soil.  Around the outside of the vehicle is a gas-tight skirt
that would be anchored in the soil.  Gas would be injected into the
lunar soil through the pipes.  Sufficient gas flow would liquify the
soil, causing large objects such as rocks to sink.  Smaller soil
particles would be buoyed by the gas flow.  Gas would be collected
under the skirt for recirculation.  Care must be taken not to let the
vehicle sink.  Subsurface lunar soil is quite cold, so the gas will
have to reheated, probably with sunlight.  Or, the cold gas could be
used as a heat sink to increase the efficiency of solar powered heat
engines.

Another way to sift the soil would be to give the soil particles
electrical charges.  The particles repel one another, allowing large
rocks to sink.  This suggest a novel form of earth moving possible only
in a vacuum:  spray the soil to be removed with an electron beam while
giving a soil collector a positive charge.  Lack of moving parts should
help reliability.

I previously proposed using an aluminum strip to levitate rockets for
lunar launches.  Samarium-cobalt magnets should be sufficiently light
to make the scheme practical.  For extra efficiency, high launch
accelerations could be used (10 gee's, say), and the strip could be
covered by a gas-tight tunnel ~14 km long.  The rocket would use lunar
oxygen and imported hydrogen as fuel; the water produced by combustion
would be trapped in the tunnel, recovered and the hydrogen recycled.
The tunnel would have gas tight doors on the east end which would
close after launch to trap the water.  This scheme will help keep a
lunar atmosphere from developing.