Apollo-Soyuz Test Project

Mission Profile

Apollo-Soyuz Test Project (ASTP) was the first crewed spaceflight jointly conducted by the United States and Soviet Union, with Apollo 18 docking with Soyuz 19 in Earth orbit on 17 July 1975 during the height of Cold War political détente. The mission required development of a special docking module with an androgynous docking mechanism that could interface with both spacecraft, solving the incompatibility between their atmospheres (pure oxygen for Apollo, nitrogen-oxygen mix for Soyuz). The crews of Thomas Stafford, Vance Brand, and Deke Slayton (US) and Aleksei Leonov and Valeri Kubasov (USSR) conducted joint experiments, exchanged gifts, and shared meals during two days of docked operations. ASTP marked the end of the Space Race era and established the international cooperation that later defined the Space Shuttle-Mir program and International Space Station.