Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site decwrl.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!harpo!decvax!decwrl!rhea!dvinci!fisher
From: fisher@dvinci.DEC (Burns Fisher, MRO3-1/E13, 231-4108)
Newsgroups: net.space
Subject: Orbital mechanics
Message-ID: <7506@decwrl.UUCP>
Date: Mon, 30-Apr-84 08:58:28 EDT
Article-I.D.: decwrl.7506
Posted: Mon Apr 30 08:58:28 1984
Date-Received: Tue, 1-May-84 08:18:31 EDT
Organization: DEC Engineering Network
Lines: 24


>  I'm surprised that a 2% change in velocity can bring them down...

Yes...the small delta-v just lowers the altitude at the opposite side of
the orbit from the burn so that it is in the atmosphere.

Do a sanity check:

    Columbia is orbiting at (very) roughly 4000 miles from the center of the
earth.  A altitude change of 2% is about 80 miles.  Most STS missions are
orbiting at an altitude (from the surface) in the vicinity of 150 miles.
Lowering part of the orbit by 80 miles brings it to 70 miles, well within the
range of atmospheric friction.  I make no representation that velocity change
is linear with altitude (in fact I am sure it is not); this is just a quick
very rough sanity check to help make my assertion plausible to unbelievers.


Burns

	UUCP:	... {decvax|allegra|ucbvax}!decwrl!rhea!dvinci!fisher

	ARPA:	decwrl!rhea!dvinci!fisher@{Berkeley | SU-Shasta}