Titan IVA-20 Accident Investigation Board releases results
Released: 19 Jan 1999
PETERSON AIR FORCE BASE, Colo. (AFPN) -- Electrical shorts likely caused a Titan IVA rocket to self-destruct shortly after launch Aug. 12.
According to an Air Force Space Command accident investigation board report, electrical shorts in the vehicle power supply wiring harness most likely caused the vehicle to catastrophically fail 41 seconds into powered flight from Cape Canaveral Air Station, Fla. The shorts originated in the second stage of the core vehicle.
The board found evidence that a wire with damaged insulation -- undetected during pre-launch inspections and tests -- intermittently shorted as vehicle vibration increased after liftoff.
The shorts within the VPS wiring harness momentarily caused a power outage of the missile guidance computer, resulting in the loss of the synchronization signal to the inertial measurement unit. This electrical interruption caused the rocket to lose its attitude frame of reference.
When the intermittent shorting subsided and power was restored, the MGC came back on line, responded to an incorrect attitude reference from the IMU, and issued a pitch down and yaw right command. The resulting pitch caused an aerodynamic angle of attack in excess of the structural design limits.
At this point, one of the vehicle's solid rocket motors separated from the core vehicle, leading to vehicle breakup. Once this occurred, the vehicle's self-destruct system activated in order to prevent uncontrolled flight.
The booster was the last Titan "A" model scheduled for launch in the Air Force's inventory. The "B" model will continue to provide unmanned heavy lift capability until 2002, when the Evolved Expendable Launch Vehicle is scheduled to become operational.
The cost of the Titan IVA-20 mishap is more than $1 billion. Costs include the launch vehicle, a classified National Reconnaissance Office satellite and range support. The Air Force, in concert with the Space and Missile Systems Center and Lockheed Martin Astronautics, has taken actions to address the findings of the investigation. (Courtesy of Air Force Space Command News Service)