Soyuz 7K-ST - Launch-Abort

Soyuz 7K-ST No. 16L, September 26, 1983 The crew were 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 pressurization 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 LES could be activated by radio command, but it required two launch personnel in a building some distance away to press two buttons within 5 seconds of each other after receiving a code word. This procedure took 20 seconds to perform, by which time the entire booster and pad were in flames. Explosive bolts fired to separate the descent module from the service module and the upper launch payload shroud from the lower. Then the escape system motor fired, dragging the orbital module and descent module, encased within the upper shroud, free of the booster with an acceleration of 14 to 17g (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 650 meters (2132 feet), 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 four kilometers (2.4 miles) from the launch pad. The two crew members were badly bruised 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 given shots of vodka to help them relax. The explosion and fires severely damaged LC-1 (the same pad used by Sputnik 1 and Vostok 1), which cost an estimated 300 million USD to repair.[citation needed] Official records claim that the LES activated a mere six seconds before the booster exploded, but some estimates put the time as low as two seconds. Source: https://en.wikipedia.org/wiki/Soyuz_7...