Forty-three launches took place from 1966 to 1972 with two complete failures and one partial. The launch of a
KH-4A photo reconnaissance satellite on May 9, 1967, malfunctioned when the Thor's first stage failed to cut off on schedule and continued burning until
LOX depletion, thus putting the satellite into an incorrect orbit that seriously reduced its image quality. The first total failure was the launch of a
Nimbus weather satellite on May 5, 1968, when control of the Thor failed during launch and it was destroyed by
Range Safety action at T+120 seconds. The satellite carried a pair of isotopic power generators known as SNAP (
Systems For Nuclear Auxiliary Power). As the possibility of a launch failure had been considered during their design, the power generators were equipped with a robust casing to prevent their radioactive contents from escaping into the environment. After the destruction of Nimbus-B's launch vehicle,
Navy crews began an extensive search for the SNAP generators. On September 27, the Nimbus satellite was located in 300 feet of water near the
Santa Barbara Islands with the SNAP units nearby. They were successfully fished out of the ocean two weeks later and their protective casings found to be intact. The fuel inside them was removed and reused in a subsequent Nimbus launch. As part of the investigation, parts of the Thor were recovered and examined. It was discovered that the yaw gyro was installed improperly and had missing alignment pins, apparently because a pad technician had mistakenly broken them off during installation. Without the pins, the gyro rotated out of position with the effect that the booster lost control almost as soon as the pitch and roll sequence started. The other total failure was the attempted launch of a
KH-4B photo-reconnaissance satellite on February 17, 1971. A technician mistakenly added too much lubricant to the Thor's fuel system, the result being that the excess fluid formed a frozen plug in a section of plumbing. The booster lifted and flew normally until the start of the pitch and roll program about 20 seconds after liftoff at which point the turbopump gearbox disintegrated due to loss of lubricant. Flying debris tore up the Thor's thrust section, causing total loss of thrust. With the main engine being the only source of attitude control, the launch vehicle tumbled uncontrollably and exploded 30 seconds after launch, the debris impacting in
Bear Creek Canyon a quarter mile from the launch complex. == Gallery ==