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September 2, 1998


Remarks by Maj. Gen. Robert C. Hinson, Accident Investigation Board President

Sept. 2, 1998 Press Conference, Cape Canaveral AS, Fla.

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 pounds.

At T+39 seconds we witnessed our first indication of an anomaly.

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 Upper Stage.

At 45 seconds, 4 seconds after the automatic destruct sequence, the Mission Flight Control Officer sent command destruct signals to the vehicle.

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 Computer.

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. 


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