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Path: utzoo!watmath!clyde!burl!ulysses!allegra!mouton!karn
From: karn@mouton.UUCP
Newsgroups: net.space
Subject: Re: More on Satellite Retrieval
Message-ID: <198@mouton.UUCP>
Date: Sun, 28-Oct-84 22:32:16 EST
Article-I.D.: mouton.198
Posted: Sun Oct 28 22:32:16 1984
Date-Received: Mon, 29-Oct-84 03:28:09 EST
References: <11810@sri-arpa.UUCP>
Organization: Bell Communications Research, Inc
Lines: 28

My understanding is that the hydrazine thrusters originally intended
for station keeping were used to drop the two satellites into lower orbits
for retrieval.

While I don't have specific information on Palapa or Westar, I do have
a "NASA Facts" sheet on Galaxy I, which is also a Hughes HS-376 design.
The spacecraft plus unfired apogee kick motor weighs 1,218 Kg, of which
135 Kg is hydrazine.  Assuming a specific impulse of 150 sec (I don't
have the exact number but monopropellant hydrazine thrusters aren't
very efficient), that gives a delta V capability of 172 m/sec.
However, if the AKM has been fired this would get rid of about 585 kg
of solid propellant, increasing the delta V capability to 353 m/sec.

Depending on the apogee of the bad orbit, dropping the satellite back into
a 300 km circular orbit is well within the capability of these thrusters.
For example, 83.5 m/sec is required for a 600 km apogee, and 189 m/sec
for a 1000 km apogee. I don't know many of the actual figures involved;
if anyone could send them to me I'd appreciate it as I'd like to do
these calculations again with greater precision.

The thing that interests me is how they will be able to match the planes
of the Palapa-B and Westar-6 while still meeting the launch window
constraints of the two other satellites the shuttle is taking up.
Anybody have current orbital elements?

Phil