Soyuz 11


Soyuz 11 was the first successful visit to the world's first space station, Salyut 1. However the mission ended in disaster when the crew capsule depressurised during preparations for re-entry, killing the three-man crew. This accident resulted in the first and to date only astronaut deaths to occur in space (not in high atmosphere). The cosmonauts aboard Soyuz 11 were Vladislav Volkov, Georgi Dobrovolski and Viktor Patsayev.

The Event
The Space Shuttle Challenger disaster occurred on January 28, 1986, when Space Shuttle Challenger broke apart 73 seconds into its flight, leading to the deaths of its seven crew members. The spacecraft disintegrated over the Atlantic Ocean, off the coast of central Florida, United States at 11:39 a.m. EST (16:39 UTC).
Disintegration of the entire vehicle began after an O-ring seal in its right solid rocket booster (SRB) failed at liftoff. The O-ring failure caused a breach in the SRB joint it sealed, allowing pressurized hot gas from within the solid rocket motor to reach the outside and impinge upon the adjacent SRB attachment hardware and external fuel tank. This led to the separation of the right-hand SRB’s aft attachment and the structural failure of the external tank. Aerodynamic forces promptly broke up the orbiter.
The crew compartment and many other vehicle fragments were eventually recovered from the ocean floor after a lengthy search and recovery operation. Although the exact timing of the death of the crew is unknown, several crew members are known to have survived the initial breakup of the spacecraft. However the shuttle had no escape system and the astronauts did not survive the impact of the crew compartment with the ocean surface.
The disaster resulted in a 32-month hiatus in the shuttle program and the formation of the Rogers Commission, a special commission appointed by United States President Ronald Reagan to investigate the accident. The Rogers Commission found that NASA’s organizational culture and decision-making processes had been a key contributing factor to the accident. NASA managers had known that contractor Morton Thiokol’s design of the SRBs contained a potentially catastrophic flaw in the O-rings since 1977, but they failed to address it properly. They also disregarded warnings from engineers about the dangers of launching on such a cold day and had failed to adequately report these technical concerns to their superiors. The Rogers Commission offered NASA nine recommendations that were to be implemented before shuttle flights resumed.

Shortly after Soyuz 11 undocked from Salyut 1 and made an initial retro fire, communication was lost with the crew far earlier than normal. The capsule descended and was recovered on June 29, 1971 23:17 GMT. When the hatch was opened it was discovered that the crew was dead.

Root Cause

After an apparently normal re-entry of the capsule of the Soyuz 11 mission, the recovery team opened the capsule to find the crew dead. It quickly became apparent that they had suffocated. The fault was traced to a breathing ventilation valve, located between the orbital module and the descent module, that had been jolted open as the descent module separated from the service module. The two were held together by explosive bolts designed to fire sequentially, but in fact, they fired simultaneously. The force of this caused the internal mechanism of the pressure equalization valve to loosen a seal that was usually discarded later, and normally allowed automatic adjustment of the cabin pressure. The valve opened in space, and the gradual loss of pressure was fatal within seconds. The valve was located beneath the cosmonaut's couches, and was impossible to locate and block before the air was lost. Flight recorder data from the single cosmonaut outfitted with biomedical sensors showed death occurred within 40 seconds of pressure loss. By 935 seconds after the retrofire, the cabin pressure was zero.

Lessons Learned

The Soyuz spacecraft was extensively redesigned after this incident to carry only two cosmonauts. The extra room meant that the crew could wear space suits during launch and landing. A Soyuz capsule would not hold three cosmonauts again until the Soyuz-T redesign in 1980, which freed enough space for three cosmonauts in lightweight pressure suits to travel in the capsule.