The Soviet Union launches Soyuz 9, a long-endurance mission which becomes the longest space flight in human history to date, lasting 18 days. Biomedical measurements are taken of cosmonauts Andrian Nikolayev and Vitaly Sevastyanov throughout their two-and-a-half-week stay in orbit, and Soyuz 9 is seen as a trailblazer for the Soviet space program’s new focus of long-term crewed space stations. Both cosmonauts suffer from muscle loss during their flight, as the Soyuz capsule isn’t big enough to allow for exercise.
