Soyuz T-10-1, a mission scheduled to visit Salyut 7, the space station occupied by the Soyuz T-9 crew, exploded on the launch pad, September 26, 1983. Miraculously, cosmonauts Vladimir Titov and Gennady Strekalov survived via the launch escape system.
While waiting for fueling of the booster to finish, a bad valve allowed pressurized nitrogen gas into a pump with no propellant. The pump ruptured and started a fire which consumed the base of the launch vehicle. The crew, realizing something was very wrong, could not initiate the escape system. The launch control team could activate it but the control cables were already destroyed by the fire.
The LES was activated by two launch personnel, but the procedure required them to press two buttons within 5 seconds of each other after receiving authorization. It took 20 seconds to perform the operation and the booster and pad were in flames by that time. The orbital module was separated from the lower part of the rocket by explosive bolts and then the escape system motor fired, breaking the crew free from the booster, which exploded just after.
The cosmonauts landed badly bruised from the sudden acceleration but alive and well, four miles away. They asked recovery crews for cigarettes to calm their nerves and were given shots of vodka to help them relax.