ARRL

ARRL Satellite Bulletin ARLS009 (1996)

SB SPACE @ ARL $ARLS009
ARLS009 Ariane 501 report

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QST de W1AW
Space Bulletin 009  ARLS009
From ARRL Headquarters
Newington, CT  July 26, 1996
To all radio amateurs

SB SPACE ARL ARLS009
ARLS009 Ariane 501 report

A board of inquiry has blamed a software glitch for the June 4
failure of the Ariane 501 launcher after some 40 seconds of flight.
The Ariane 502 launcher was scheduled to carry the Phase 3D Amateur
Radio satellite aloft this fall. The board's findings could delay
that schedule, however, since it's not certain at this point how
long it will take to correct the problems and test the revised
systems.

The board determined that the rocket's inertial guidance system
stopped ''talking'' to the engines, and the thrust nozzles responded
by shifting abruptly to an ''extreme position.'' This caused the
rocket to veer off at a wild angle. Auto-destruct occurred seconds
later.

''The failure of Ariane 501 was caused by the complete loss of
guidance and attitude information 37 seconds after start of the main
engine ignition sequence (30 seconds after liftoff). This loss of
information was due to specification and design errors in the
software of the inertial reference system,'' the board concluded.
''The extensive reviews and tests carried out during the Ariane 5
development programme did not include adequate analysis and testing
of the inertial reference system or of the complete flight control
system, which could have detected the potential failure.''
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