Three cosmonauts died in space during the Soyuz 11 mission due to a faulty valve, a tragedy that reshaped space safety protocols.
Soyuz 11 mission tragedy
Three cosmonauts died during the Soyuz 11 mission on June 30, 1971, at an altitude of 168 kilometers. The incident occurred when a pressure equalization valve opened prematurely, causing the cabin to lose all its air within seconds.Cause of the fatal decompression
A 16-millimeter pressure equalization valve opened at 168 km, emptying the cabin of air and killing the cosmonauts within about thirty seconds. The valve was meant to open only a few kilometers from the ground but triggered too early due to a mechanical impact.Medical findings after the incident
Autopsies of the cosmonauts, Georgy Dobrovolsky, Vladislav Volkov, and Viktor Patsayev, revealed cerebral hemorrhage, ruptured eardrums, and pulmonary injuries. These injuries are typical of explosive decompression, with no signs of burns or impact.Mission background and communication loss
The cosmonauts had completed a record 23-day stay aboard the Salyut 1 station. Radio communications cut off abruptly around 22:35 GMT on June 29, 1971, before the separation of the modules.Recovery and investigation
The descent module landed normally in Kazakhstan, and recovery teams found the three lifeless bodies within a minute of opening the hatch. A Soviet investigation concluded that decompression of the descent module was the most probable cause.Design flaw and safety changes
The pyrotechnic charges used for module separation caused the valve to open prematurely, a design flaw not previously detected. The Soyuz spacecraft was later modified to a two-person configuration to allow for the use of pressurized Sokol suits, a safety measure still in effect today.Recent space station incident
On June 5, 2026, NASA ordered five astronauts to take shelter in a Crew Dragon spacecraft due to an aggravated air leak in the Russian segment of the International Space Station. The flow rate increased from about one pound of air per day to two pounds.Legacy of the Soyuz 11 tragedy
The incident served as a chilling reminder of the risks of decompression in space. Dobrovolsky, Volkov, and Patsayev remain the only humans to have died in space beyond the Karman line, which marks the boundary between Earth's atmosphere and outer space.
