June 30, 1971 - Soyuz 11
Soyuz 11 was the first and only manned mission to board the world's first space station, Salyut 1. The mission arrived at the space station on June 7, 1971 and departed on June 30, 1971. The mission ended in disaster when the crew capsule depressurized during preparations for re-entry, killing the three-man crew. This accident resulted in the only human deaths to occur in space (as opposed to high atmosphere). The crew members aboard Soyuz 11 were Vladislav Volkov, Georgi Dobrovolski, and Viktor Patsayev.
On June 30, 1971, 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 asphyxiated. 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, 723 seconds after retrofire. The two were held together by explosive bolts designed to fire sequentially; 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 at an altitude of 168 kilometers (104 mi), and the gradual loss of pressure was fatal within seconds. The valve was located beneath the seats and was impossible to find and block before the air was lost. Flight recorder data from the single cosmonaut outfitted with biomedical sensors showed cardiac arrest occurred within 40 seconds of pressure loss. By 935 seconds after the retrofire, the cabin pressure was zero, and remained there until the capsule entered the Earth's atmosphere.
