Soyuz 21 was a Soviet space mission launched on July 4, 1976. The mission's primary objective was to dock with the Salyut 5 space station, where the crew conducted scientific experiments and gathered data on the effects of long-duration spaceflight. The crew consisted of two cosmonauts, Viktor Gorbatko and Yuri Malyshev. The mission lasted 7 days, 22 hours, and 16 minutes, concluding on July 12, 1976. During their time aboard Salyut 5, the crew successfully completed various tasks, including Earth observation and medical research. Soyuz 21 contributed valuable insights into human spaceflight and the challenges of extended missions.