Remarks by Maj.
Gen. Robert C. Hinson, Accident Investigation Board President
Sept. 2, 1998 Press Conference, Cape Canaveral
Titan IVA-20 lifted off from Space Launch Complex 41
at 7:30:01 Eastern Daylight Time on August 12, 1998.
At liftoff the vehicle weighed just over 1.9 million
At T+39 seconds we witnessed our first indication of
At 41 seconds after liftoff, at an altitude of
17,000 feet, a down range distance of 4400 ft, and a speed of .95 Mach, the Titan IVA
pitched down and yawed right of its planned trajectory. This exceeded the structural
design of the launch vehicle.
The north Solid Rocket Motor separated from the core
booster and began its built-in self-destruct sequence.
This automatic destruct sequence resulted in the
destruction of the core vehicle, then the southern-most Solid Rocket Motor and the Centaur
At 45 seconds, 4 seconds after the automatic
destruct sequence, the Mission Flight Control Officer sent command destruct signals to the
To date, we have reviewed factual data that
indicates the launch vehicle experienced an electrical anomaly at T+39.4 seconds, which,
in turn, affected the Guidance Computer and the Inertial Measurement Unit. These are the
systems which guide the rocket. We suspect this electrical interruption caused the rocket
to lose its attitude frame of reference.
When power was restored, the Guidance Computer
issued a maximum pitch down command, and, at approximately 15 degrees pitch down and 4
degrees yaw right, the vehicle began to aerodynamically breakup.
Solid Rocket Motors are steered by a Thrust Vector
Control System which injects N204 into the thrust chamber of each Solid Rocket Motor.
The brightness of the exhaust plumes during the
pitch down indicate that the steering system responded to the command of the Guidance
At T+41.3 seconds the vehicle began to break apart
as a result of forces exerted on it by its high angle of attack and speed.
Facts show that the Inadvertent Separation Destruct
System worked as designed, and all of the debris fell well within the computed impact
boundaries. Additionally, the debris pattern and associated plume created by the rocket
was dispersed and dissipated at sea.
We are still evaluating data and supporting analyses to identify
exact root causes of the electrical interruption and subsequent failure.