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 descent module discarded its heat shield, exposing the solid-fuel landing rockets, and deployed a fast-opening emergency parachute.

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.

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".