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Path: utzoo!linus!philabs!seismo!hao!hplabs!sri-unix!dietz%usc-cse%USC-ECL@SRI-NIC
From: dietz%usc-cse%USC-ECL%SRI-NIC@sri-unix.UUCP
Newsgroups: net.space
Subject: GEO vs lunar delta-vees
Message-ID: <14926@sri-arpa.UUCP>
Date: Mon, 26-Dec-83 13:41:00 EST
Article-I.D.: sri-arpa.14926
Posted: Mon Dec 26 13:41:00 1983
Date-Received: Thu, 29-Dec-83 01:04:35 EST
Lines: 31

Of course I meant going to lunar orbit, not to the lunar surface.

One figure you didn't mention is the delta-vee for returning from GEO.
Retrofire to put you into an atmosphere skimming orbit for aerobraking
will take about as much delta-vee as the orbit circularization burn
(maybe a little more).  Perhaps a better (albeit more time consuming)
maneuver would be to boost into an elongated orbit that passed near the
moon, which would then put the vehicle onto an earth-intersecting orbit.

I read somewhere that someone (Krafft Ehricke?) has proposed landing
payloads on the moon by sliding them on a flat strip of lunar soil
(sifted to remove rocks).  Energy would be dissipated by heating and
accelerating the loose sand-like material, which would be smoothed over
before the next landing.  Orbital velocity at the lunar surface is
around 1650 m/sec, so this sounds semi-plausible.  Deceleration at 10
gee's would mean a strip 14 km long.

A more refined scheme could use a solid aluminum strip for magnetic
flight.  The incoming vehicle would have magnets for repulsive magnetic
levitation.  The vehicle could be decelerated by eddy currents in the
strip, by coils in the strip (which could deliver usable power to a
launch system) or by shooting gas derived from lunar soil (oxygen or
argon) at the front of the vehicle.  After being decelerated to less
than 100 m/sec the vehicle would use wheels.  Such a scheme could also
make rocket lift-off from the lunar surface more efficient by
eliminating the need for the rocket to support the mass of the vehicle
against lunar gravity -- all thrust would go into increasing the
orbital velocity of the vehicle.  Of course, the mass of the magnets
would probably negate any advantage gained.