Forty years ago a great adventure took place. It was one that changed the course of history. In the middle of a forty-year the Cold War between the United States and the Soviet Union the heads of the two rival states agreed to undertake the first international human space flight in history. Symbolizing the deténte between the United States and the Soviet Union during the mid-1970s, the Apollo-Soyuz Test Project (ASTP) specifically tested the compatibility of rendezvous and docking systems for American and Soviet spacecraft.
In essence, ASTP opened the way for international space rescue as well as future joint human flights. To carry out this mission existing American Apollo and Soviet Soyuz spacecraft were used. The Apollo spacecraft was nearly identical to the one that orbited the Moon and later carried astronauts to Skylab, while the Soyuz craft was the primary Soviet vehicle used for cosmonaut flight since its introduction in 1967. A universal docking module was designed and constructed by NASA to serve as an airlock and transfer corridor between the two craft.
The actual flight took place between 15 and 24 July 1975 when astronauts Thomas P. Stafford (1930- ), Vance D. Brand (1931- ), and Donald K. Slayton took off from Kennedy Space Center to meet the already orbiting Soyuz spacecraft. Some 45 hours later the two craft rendezvoused and docked, and then Apollo and Soyuz crews conducted a variety of experiments over a two‑day period.
After separation, the Apollo vehicle remained in space an additional six days while Soyuz returned to Earth approximately 43 hours after separation. The flight was more a symbol of the lessening of tensions between the two superpowers than a significant scientific endeavor, taking 180 degrees the competition for international prestige that had fueled much of the space activities of both nations since the late 1950s. It was the beginning of possibilities for cooperative efforts in the post-Cold War era between the U.S. and Russia.