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From: fisher@dvinci.DEC
Newsgroups: net.space
Subject: Apollo 13
Message-ID: <2263@decwrl.UUCP>
Date: Sat, 18-May-85 18:26:39 EDT
Article-I.D.: decwrl.2263
Posted: Sat May 18 18:26:39 1985
Date-Received: Tue, 21-May-85 00:12:40 EDT
Sender: daemon@decwrl.UUCP
Organization: DEC Engineering Network
Lines: 26


A bit more about the problem (this is from a NASA book called something like
"The Apollo Missions to the Moon".

It seems that the heater's acceptable current rating had been upped, but
this information had not been circulated to everyone concerned, specifically
the folks concerned with the cutoff thermostat in series with the heater.
It also seems that at one point, the tank was dropped, fixed back up, and
then reinstalled.  During a ground test, the tank was filled, and then they
tried to empty it.  It seemed to take to long (did the drop cause this?),
so they cranked up the current in the heater to the (new) max to boil off the
oxygen..  Unfortunately, the thermostat had not been upgraded to the new
current rating, and when it opened, it arced and welded.  None of this was
noticed. 

During the flight, the heater was merrily doing its thing, and when the
thermostat was supposed to open and cut it off, it could not.  Thus overheating
and explosion as mentioned in another posting.

Burns

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