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From: David.Smith@cmu-cs-ius.arpa
Newsgroups: net.space
Subject: Intersecting orbits
Message-ID: <489@sri-arpa.UUCP>
Date: Sat, 31-Mar-84 10:10:03 EST
Article-I.D.: sri-arpa.489
Posted: Sat Mar 31 10:10:03 1984
Date-Received: Sat, 7-Apr-84 01:46:52 EST
Lines: 26


	Also, a minor point.  The vast majority of all satellites go in more
	or less the same direction.  The reason is straightforward.  If you
	launch East you get up to 1000 miles/hour free velocity from the
	Earth's rotation.  If you launch west you have to overcome up to
	1000 miles/hour before you get any forward motion at all.
	This blurb is in response to someone who thought satellites go
	every which way and could easily be set into head on collisions.

Perhaps most satellites are launched in more or less the same direction
(eastward), but that doesn't mean they are travelling in more or less
the same orbit.  If you launch two satellites eastward from Cape Canaveral
(28.5 degrees north latitude) twelve hours apart, their orbits will have
a 57 degree difference in inclination.  If each travels at 17,500 mph,
then their closing speed is 16,700 mph.  That should be enough to crack
up a satellite.

The fact is, satellites do go every which way.  We launch satellites from
28.5 degrees north, the Soviets launch from around 55 degrees north, and
we both launch into polar orbits.  Maybe nobody launches straight west,
but the US launches satellites south-southwest from Vandenberg.

This, by the way, makes me skeptical about the claim that the space station
would be useful as a base for satellite repair.

		David Smith