Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site allegra.UUCP
Path: utzoo!linus!philabs!seismo!harpo!eagle!allegra!karn
From: karn@allegra.UUCP (Phil Karn)
Newsgroups: net.space
Subject: GEO vs lunar delta-vees
Message-ID: <2132@allegra.UUCP>
Date: Thu, 22-Dec-83 00:18:20 EST
Article-I.D.: allegra.2132
Posted: Thu Dec 22 00:18:20 1983
Date-Received: Fri, 23-Dec-83 01:49:43 EST
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 31

Someone mentioned the relative delta-vee requirements needed to get to
geostationary orbit as compared to to the moon.  I did some research
and calculations to get some real numbers.

Apollo 11 (a representative moon trip) started with a 192 x 190.6 km
parking orbit. Trans-lunar injection required 3182 m/sec from the S-IVB,
while lunar orbit insertion required only 889.2 m/sec.  However, landing
required 2,065 m/sec and liftoff 1,850; you can see the advantage of the
separate LM approach.  The return to earth required 999.4 m/sec.

Here's the numbers for a typical geostationary satellite launch from the
shuttle.  Assume a 28.5 deg inclination 300 x 300 km parking orbit.
The PAM (payload assist module) perigee kick motor produces about 2579.7
m/sec to put the spacecraft into a 23.5 deg elliptical transfer orbit.  About
170 m/sec of this burn is used to reduce the inclination by about 5
degrees. (I don't know why they do this, it should be more efficient
to change the plane out at apogee.)

At one of the following apogees, the kick motor on the satellite itself
produces 1879 m/sec.  Most of this circularizes the orbit at
geostationary altitude, while 231.6 m/sec goes toward making the
inclination zero.  Now when comparing these figures you have to take
into account the different initial parking orbits, but this is enough to
give the general idea.  Note the big difference, though, between getting
to lunar orbit and getting to the lunar surface.

192 km LEO to lunar orbit: 4071.2 m/sec
192 km LEO to lunar surface: 6136.2 m/sec
300 km LEO to GEO: 4458.7 m/sec

Phil