Deadliest spaceflight disaster

The deadliest incidents in the history of crewed spaceflight were the destruction of the Space Shuttles Challenger and Columbia on 28 January 1986 and 1 February 2003, respectively, both of which resulted in the deaths of all seven crew.

While both of these incidents occurred during orbital missions, neither actually took place above the 100-km (62-mile) Karman Line - the accepted definition of the boundary between Earth and space. Challenger was destroyed when its rocket failed during launch, while Columbia broke up during re-entry into Earth's atmosphere at an altitude of around 60 km (37 miles). To date, the only fatal accident to have occurred in space is the failure of the Soviet Soyuz 11 capsule on 30 June 1971, which killed three cosmonauts.

The Soyuz 11 capsule suffered a malfunction while returning to Earth from the Salyut 1 space station. A ventilation valve that was supposed to open on landing instead opened shortly after the separation of the service module. The cabin rapidly depressurized at an altitude of 168 km (104 mi), killing the crew. The capsule made an otherwise normal re-entry and landed in Kazakhstan.

Owing to the secrecy of the Soviet Union, and the propaganda utility of the space programme, the Soviet Union minimized the tragic aspects of the Soyuz 11 mission and celebrated its pioneering feats. NASA would not learn the cause of death of the cosmonauts for two years but as a result of the disaster both NASA and the Soviet space programmes would adopt the wearing of pressure suits during any stage where depressurization could occur.