Soyuz 24

The Soviet Union launches the Soyuz 24 mission to the Salyut 5 military space station. Cosmonauts Viktor Gorbatko and Yuri Glazkov carry special breathing gear to protect them from toxic fumes reported to have been the cause of the hasty exit of the crew of Soyuz 21 in 1976. They vent the entire atmosphere of Salyut 5 into space and replenish it, taking up residence for 18 days, during which they perform their own science and Earth surveillance experiments. They leave the station habitable for a visit by another crew, but Salyut 5’s fuel will be exhausted before that mission can take place.