Launch from Baikonur. Soyuz 18a was intended
to be the second mission to take cosmonauts to the Soviet Salyut 4 space
station for a 60-day mission.
The launch proceeded according to plan
until T+288.6 seconds at an altitude of 145 kilometres (90 mi), when the second
and third stages of the booster began separation. Only three of the six locks
holding the stages together released and the third stage's engine ignited with
the second stage still attached below it. The third stage's thrust broke the
remaining locks, throwing the second stage free but putting the booster under
unanticipated strain that caused it to deviate from the proper trajectory. At
T+295 seconds, the deviation was detected by the Soyuz's guidance system, which
activated an automatic abort program. As the escape tower was long gone by this
point, the abort had to be performed with the Soyuz's own engines. This
separated the spacecraft from the third stage booster and then separated the
orbital and service modules of the Soyuz from the re-entry capsule.
the time when the safety system initiated separation the spacecraft was already
pointed downward toward Earth, which accelerated its descent significantly.
Instead of the expected acceleration in such an emergency situation of 15 g
(147 m/s²), the cosmonauts experienced up to 21.3 g (209 m/s²).
Despite very high overloading, the capsule's parachutes opened properly and
slowed the craft to a successful landing after a flight of only 21
The capsule landed southwest of Gorno-Altayska (50° 50' N,
83° 25 E). The capsule landed on a snow-covered slope and began rolling
downhill towards a 152 m (499 ft) sheer drop before it was stopped by the
parachutes' becoming snagged on vegetation.
Having landed in chest-deep
powder snow and a local temperature of -7 °C (19 °F), the cosmonauts
donned their cold-weather survival clothing. As the cosmonauts were uncertain
if they had landed in China, they quickly destroyed documents relating to a
military experiment planned for the flight (this was at a time when Sino-Soviet
relations were extremely hostile). Soon, the crew was in radio contact with a
rescue team in an approaching helicopter, who confirmed their landing point was
in the Soviet Union, near the town of Aleysk. The deep snow, the high altitude,
and the terrain meant the rescuers had great difficulty in making contact with
the cosmonauts. It was the next day before they were safely air-lifted
Initial Soviet reports stated the men had suffered no ill effects
from their flight. Vladimir
, the Director of Cosmonaut Training, reported they
were fit to fly another mission. However, subsequent reports claimed that
was injured by the high acceleration of re-entry.
The Soyuz 18A flight has been the only case of a manned booster
accident at high altitude. The exact landing site of the capsule had been a
subject of debate amongst space historians in subsequent years.