The crew was sitting on the pad awaiting fueling of the
Soyuz-U booster to complete prior to liftoff. Approximately 90 seconds before the intended launch, a bad valve caused nitrogen pressurisation gas to enter the RP-1 turbopump of the Blok B strap-on. The pump began spinning up, but with no propellant in it, the speed of rotation quickly exceeded its design limits which caused it to rupture and allow RP-1 to leak out and start a fire which quickly engulfed the base of the launch vehicle. Titov and Strekalov could not see what was happening outside, but they felt unusual vibrations and realized that something was amiss. The
launch control team activated the escape system but the control cables had already burned through, and the Soyuz crew could not activate or control the escape system themselves. The backup radio command to fire the LES required two independent operators to receive separate commands to do so and each act within five seconds, which took several seconds to occur.
Explosive bolts then fired to separate the descent module from the service module and the upper launch
payload shroud from the lower portion, then the escape system motor fired, which dragged the
orbital module and
descent module, encased within the upper shroud, free of the booster with an acceleration of 14 to 17
g (137 to 167 m/s²) for five seconds. According to Titov, "We could feel the booster swaying from side to side. Then there was a sudden vibration and a jerking sensation as the LES activated". Just after the escape tower pulled the descent module away, the booster exploded. Its remains burned on the pad for nearly 20 hours. Four
grid fins on the outside of the shroud opened and the descent module separated from the orbital module at an altitude of , dropping free of the shroud. The descent module discarded its
heat shield, exposing the
solid-fuel landing rockets, and deployed a fast-opening emergency parachute. Touchdown occurred about from the launch pad. The two crew members were bruised badly after the high acceleration, but were otherwise in good health and did not require any medical attention. Upon being greeted by recovery crews, they immediately asked for cigarettes to steady their nerves. The cosmonauts were then each given a tumbler of
vodka to help them relax. The
KH-11 reconnaissance satellites returned photos of the damaged Site 1 in several runs during late 1983 and early 1984. The descent module was refurbished and later used for
Soyuz T-15. The failure's immediate result was the inability to replace the ageing
Soyuz T-9 return capsule attached to the Salyut 7 space station. This resulted in dire reports in the western media about the cosmonauts remaining aboard Salyut 7 (which had arrived several months before in the Soyuz T-9) being 'stranded' in space, with no ability to return. Official reports by the Soviet news agency
TASS gave few details, merely saying that there had been a pad accident and the cosmonauts were rescued by the LES. It was not until several years later during
glasnost that the full story of the accident was revealed to the outside world. Years later, in an interview with the United States
History Channel regarding the flight, Titov claimed that the crew's first action after the escape rocket fired was to deactivate the spacecraft's
cockpit voice recorder because, as he put it, "We were swearing". == See also ==