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From: eder@ssc-vax.UUCP (Dani Eder)
Newsgroups: net.space
Subject: Re: More on Satellite Retrieval
Message-ID: <174@ssc-vax.UUCP>
Date: Mon, 29-Oct-84 11:53:52 EST
Article-I.D.: ssc-vax.174
Posted: Mon Oct 29 11:53:52 1984
Date-Received: Wed, 7-Nov-84 00:45:52 EST
References: <11810@sri-arpa.UUCP>
Organization: Boeing Aerospace Co., Seattle, WA
Lines: 39

> While we're all wondering about some details of the satellite recovery
> schedule for the next shuttle mission, I'd like to add my own wonders:
> 
> What are the constraints on the rendezvous?  According to the PBS show,
> the satellites are in quite an elliptical orbit.  I got the impression
> 
     The satellites were placed in elliptical orbits by the first of 
two solid motors that were to be used in their original delivery.  The
second, smaller, motors were fired months ago, and placed the satellites
about 600 km high (if memory serves me).  The Hughes model 376 satellites
carry fuel used to keep them in position or move about in GEO.  This
fuel was recently used to move the satellites down to an altitude
the Shuttle Orbiter can reach.

> How dangerous is all this?  

     Probably less dangerous than the delivery of the new satellites which
will also occur on this mission.  The new ones carry 8000 lbs of very
energetic propellants each.  The old satellites have burnt out their
motors, which means no fuel is left.

     Someone in another article asked why the RMS is being used to recover
the satellites rather than the astronauts directly, and whether the satllites
are spinning fast.  The satellites mass 1000 lbm each.  Even though they
'weigh' nothing, that mass still has to be pushed around.  The nearest
equivalent I can think of is pushing a boat around a dock by hand.  At
low speeds this is nearly frictionless in two dimensions.  The astronauts
are in these bulky suits, too boot.  While it could be done, it is much
easier to use the electrically powered RMS.  

     The satellites will have been spun down to less than one RPM before
the astronauts get to them.  Once the stinger is firmly attached to the
satellite, the astronaut merely pushes the 'stop' button on his Manned
Maneuvering Unit.  The MMU calculates which thrusters to fire to stop the
residual spin.

Dani Eder / Boeing Aerospace Company / ssc-vax!eder /(206)773-4545

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