From: yee@trident.arc.nasa.gov (Peter E. Yee)
Subject: Tether investigation status report 1 (Forwarded)
Apparently-To: sci-space-news@ames.arc.nasa.gov
Followup-To: sci.space
Organization: NASA Ames Research Center, Moffett Field, CA
Date: Fri, 28 Aug 1992 20:33:01 GMT

Mark Hess
Headquarters, Washington, D.C.                        August 28, 1992
(Phone:  202/453-4164)

TETHER INVESTIGATION STATUS REPORT 1

	The Tethered Satellite System (TSS) Investigative Board
today presented an interim status report to Space Flight Associate
Administrator Jeremiah Pearson.

	Board Chairman Darrell Branscome reported the team is focusing
on 5 problems that occurred during the deployment of the Tethered
Satellite System on Space Shuttle mission STS-46.  Those problems are:


o Failure of the No. 2 umbilical to retract from the tethered satellite
o Failure of the satellite to deploy on the first "flyaway" attempt
o The unplanned stop of the satellite at 179 meters
o The unplanned stop of the satellite at 256 meters
o Inability to either deploy or retrieve the satellite at 224 meters.

	The tethered satellite has been removed from the orbiter Atlantis
and placed in a checkout stand in the Operations and Control facility
at the Kennedy Space Center, Fla.  The Board had its first look at TSS
hardware this week.

	Detailed inspection of the tether reel assembly provided evidence
that the unplanned stops at 179 and 256 meters were due to a mechanical
obstruction.  

	Visual evidence and preliminary analysis point to a 1/4-inch
diameter bolt which prevented part of the reel mechanism from freely
traveling back and forth.  The level wind mechanism, which operates
similar to the way a fishing reel feeds out line, contacted the end of
the bolt preventing it from moving all the way out to its stopping
point.

	The bolt is part of a structural modification that was installed
on the reel assembly earlier this year.  The modification was required
following the final computer analysis which is done for every Shuttle
mission to verify that all structural connections between the payload
and orbiter will withstand the rigors of launch and landing.

	Engineers require that attach points such as these be at
least twice as strong as necessary to pass stringent safety criteria.
Analysis indicated the margin of safety was less than that for some
fasteners at the point where the reel assembly was mounted to its
specially adapted support structure.  The modification strengthened the
mounting area to provide the required factor of safety.

	Testing of the flight hardware is planned to verify that this
mechanical obstruction was the cause of the jamming of the deployment
reel and the subsequent unplanned stops of the satellite at 179 and 256
meters.

	The Board believes that even without the problems with the
umbilical and the jamming of the tether at the upper tether control
mechanism, this problem would have prevented full deployment of the
tethered satellite.

	Branscome said the board is continuing work to identify causes
for the other anomalies:  the umbilical problem; the first "flyaway"
attempt; and the jamming at 224 meters.  The next interim report is
expected to be complete in about a month.
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