Aucbvax.6112
fa.space
utcsrgv!utzoo!decvax!ucbvax!space
Mon Feb 8 03:20:13 1982
SPACE Digest V2 #101
>From OTA@S1-A Mon Feb 8 03:02:10 1982
SPACE Digest Volume 2 : Issue 101
Today's Topics:
half-time power from the moon
NASA budget
"horseshoe" orbits
Horseshoe Orbits
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Date: 7 February 1982 06:19-EST
From: Jerry E. Pournelle <POURNE MIT-MC AT>
Subject: half-time power from the moon
To: KING at KESTREL
cc: SPACE at MIT-MC
Not if they are at the poles they don't.
(that's the answer; the question was, don't lunar power
stations cease to function two weeks of the month?)
Of course a non-polar lunar colony would indeed need
either a good energy storage system, or a good generation
system; if you put it up in a large whack, say by ORION, then a
small nuclear power plant would probably be the right thing to
have for a colony.
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Date: 7 February 1982 06:21-EST
From: Jerry E. Pournelle <POURNE MIT-MC AT>
Subject: NASA budget
To: DIETZ at USC-ECL
cc: SPACE at MIT-MC
There are other developments; and some private work on Big Dumb
Boosters, and the like. But Single Stage to Orbit technology is
indeed very important, and somewhat overlooked. It may,
nowever, get funding directly from DOD.
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Date: 7 February 1982 06:22-EST
From: Jerry E. Pournelle <POURNE MIT-MC AT>
Subject: "horseshoe" orbits
To: LRC.SLOCUM at UTEXAS-20
cc: SPACE at MIT-MC, knutsen at SRI-UNIX
I gather that two objects "in the same orbit" actually share an
orbit that NEITHER of them is actually in?
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Date: 8 February 1982 03:35-EST
From: Robert Elton Maas <REM MIT-MC AT>
Subject: Horseshoe Orbits
To: Tavares.WFSO at MIT-MULTICS
cc: SPACE-ENTHUSIASTS at MIT-MC
The two satellites are in almost identically the same orbit, thus the
one in the lower/faster/smaller orbit very very slowly overtakes the
other over a period of many orbits. If they were of zero mass, they'd
simply bump into each other as they pass, and be diflected in some
semi-random direction like particles in a sub-atomic accellerator.
But they have enough mass that as they get close to each other they
pull on each other slightly. The one ahead in orbit (the higher/slower
one) is pulled backward, causing it to lose energy and spiral down to
a lower orbit. The one behind in orbit (the lower/faster one) is
pulled forward, causing it to gain energy and spiral up to a higher
orbit. Eventually they are in exactly the same orbit, one behind the
other, and they don't get any closer because the one behind is no
longer traveling faster than the one ahead. But they are still close
together, in fact they are at their closest point now, and they continue
to attract each other. The one ahead continues to lose energy and spiral
into a lower and lower orbit, and the one behind continues to gain energy
and spiral into a higher and higher orbit. The one ahead, being now in
a lower orbit, races ahead, and the behind, being now in a highe orbit,
lags behind. They thus slowly drift apart, the one in front in a lower
oribit and the one behind in a higher orbit, until they are far enough
away to no longer effect each other significantly.
Many many orbits later, their difference in orbits has caused the one
ahead&faster to get nearly a whole orbit ahead of the one behind, and
they start to effect each other but with roles reversed (the one that
was slightly ahead is now almost a full orbit ahead, thus is slightly
behind, and is in the lower/faster orbit on approach; the one that was
slightly behind is now almost a full orbit behind, thus slightly ahead,
and is in the higher/slower orbit on approach).
(I hope this explanation satisfies everybody.)
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End of SPACE Digest
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