Salyut 1

Salyut 1 (DOS-1) (Салют-1) was the world's first space station launched into low Earth orbit by the Soviet Union on April 19, 1971. The Salyut program followed this with five more successful launches of seven more stations. The final module of the program, Zvezda (DOS-8), became the core of the Russian segment of the International Space Station and remains in orbit. Salyut 1 was modified from one of the Almaz airframes, and was made out of five components: a transfer compartment, a main compartment, two auxiliary compartments, and the Orion 1 Space Observatory. Salyut 1 was visited by Soyuz 10 and Soyuz 11. The hard-docking of Soyuz 10 failed and the crew had to abort this mission. The Soyuz 11 crew achieved successful hard docking and performed experiments in Salyut 1 for 23 days. However, they were killed by asphyxia caused by failure of a valve just prior to Earth reentry, and are the only people to have died above the Kármán line. Salyut 1's mission was later terminated, and it burned up on reentry into Earth's atmosphere on October 11, 1971. Salyut 1 originated as a modification of the Soviet military's Almaz space station program that was then in development. After the landing of Apollo 11 on the Moon in July 1969, the Soviets began shifting the primary emphasis of their crewed space program to orbiting space stations, with a possible lunar landing later in the 1970s if the N-1 rocket became flight-worthy. Leonid Brezhnev canceled the lunar landing program in 1974 after four catastrophic N-1 launch failures. One other motivation for the space station program was a desire to one-up the US Skylab program then in development. The basic structure of Salyut 1 was adapted from the Almaz with a few modifications and would form the basis of all Soviet space stations through Mir. Civilian Soviet space stations were internally referred to as DOS (the Russian acronym for "Long-duration orbital station"), although publicly, the Salyut name was used for the first six DOS stations (Mir was internally known as DOS-7).