Apur-ee.161
net.columbia
utzoo!decvax!pur-ee!davy
Wed Nov  4 10:15:00 1981
Mission Scrubbed
       Shortly before T -31 seconds before liftoff this morning,
Shuttle Control detected a problem with the LOX pressure in the
fuel tanks for the APUs (Auxilliary Power Units).  The pressure,
which should have been 800 lbs./sq.in. (?) was approximately one
p.s.i. below the launch criterion.  George Page, Launch Director,
decided to go ahead with the launch, however, when the attempt was
made to switch over to the shuttle's onboard computers, a problem
arose which caused the clock to stop at T -31 seconds.
       It turns out that a "software management problem" with the
programs in the onboard computers prohibited the onboard computers
from taking over.  Basically, what happened is someone didn't write
the code to let the computers take over when an "acceptable" discrep-
ancy arose (the pressure problem).
       The clock was re-set to T -9 minutes, and then to T -20 min.
At 9:35 EST this morning, the clock was due to begin countdown again,
this would have included a built-in 10 minute hold at T -9 minutes.
This would have set liftoff time at roughly 10:05 EST.  However, at
9:45 EST, the mission was "scrubbed" for today.
       Another problem discovered, was that the lubrication oil pressure
in two of the three APUs was too high.  Officials did not know what
caused this, but decided to scrub the mission.  This means that the
earliest takeoff time is at least 48 hours away.  The reason for this
48 hour delay is that the fuel tanks must be drained of the cryogenic fuel
(LOX) in order to avoid rupturing the insulation.  The process of
drainiing, temperature conditioning, and reloading the tanks will
take 48 hours.  This is the EARLIEST time for takeoff, and weather
reports indicate that it may be even later.

--Dave

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