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From: tc@amd.UUCP (Tom Crawford)
Newsgroups: net.columbia
Subject: Abort to Orbit
Message-ID: <1605@amd.UUCP>
Date: Tue, 6-Aug-85 09:46:48 EDT
Article-I.D.: amd.1605
Posted: Tue Aug  6 09:46:48 1985
Date-Received: Sat, 10-Aug-85 20:30:35 EDT
Organization: AMD Applications, Santa Clara, CA
Lines: 54

Here are paragraphs from an article in Aug 5 Aviation Week.  These are
reproduced without permission.

Abort-to-Orbit Incident Will Intensify Shuttle Engine Procedure Reviews

Johnson Space Center-  The premature shutdown of one of the shuttle
orbiter Challenger's main engines that forced an abort to orbit last
week was caused by a temperature sensor failure in the Rocketdyne engine
rather that an actual problem with the propulsion system, shuttle managers
believe.

...

Lead ascent flight director Cleon Lacefield said a reexamination of data
indicates that, had the second engine failed at a time when abnormal
sensor readings were occurring in it, Challenger could still have 
achieved a safe but tenuous orbit.  A second engine failure, however, would
have caused the shuttle's 39-ton Martin Marietta external tank to fall on
populated areas of Europe somewhere along a line stretching across central
France, Switzerland, south of Milan or near Athens.
...


5 min. 55 sec.  Fullerton, piloting Challenger, rotated a switch on the 
instrument panel to the abort ATO position, then pushed an ajoining
abort command button.  This told the orbiter's computers that ATO
procedures were now required.  It immediately ignited Challenger's
two Aerojet orbital maneuvering engines to dump 4,400 lbs. of OMS
propellant so the remaining main engine thrust could be used more
efficiently.

6 min - For 106 sec. Challenger's two OMS engines fired along with the
two remaining main engines.  The OMS engines provided an additional
12,000 lb. of thrust, but this was incidental to the abort situation.
The requirement was to dump OMS propellant to lighten the load.

......

8 min. 12 sec.  Howard at the booster console saw sensors on the right
main engine, one of two still firing, start to act improperly.  She
first saw the B-side fuel pump temperature sensor fail on the right
engine, the same failure that started the center engine's problems....

8 min 45 sec  Lacefield had Richards radio Challenger, "Main engine
limits to inhibit," an emergency call to prevent the second engine
from failing if the temperature sensor data climbed higher.  Fullerton
immediately flipped a switch on the console, canceling out the
protective circuitry in the engines that could have shut down the
engines.



			Tom Crawford
			...amd!tc