Image: The Apollo-Soyuz test project: An orbital partnership is born

(Phys.org) -- On July 17, 1975, something momentous happened: two Cold War-rivals met in space. When their respective spacecraft rendezvoused and docked, a new era of cooperative ventures in space began.

For more than a decade, American astronauts and Russian cosmonauts have been regularly living and working together in Earth orbit, first in the Shuttle-Mir program, and now on the International Space Station. But, before the two Cold War-rivals first met in orbit in 1975, such a partnership seemed unlikely. Since Sputnik bleeped into orbit in 1957, there had been a Space Race, with the U.S. and then-Soviet Union driven more by competition than cooperation. When President Kennedy called for a manned moon landing in 1961, he spoke of "battle that is now going on around the world between freedom and tyranny" and referred to the "head start obtained by the Soviets with their large rocket engines."

But by the mid-70s things had changed. The U.S. had "won" the race to the moon, with six Apollo landings between 1969 and 1972. Both nations had launched space stations, the Russian Salyut and American Skylab. With the space shuttle still a few years off and the diplomatic chill thawing, the time was right for a joint mission.

The Apollo-Soyuz Test Project would send NASA astronauts Tom Stafford, Donald K. "Deke" Slayton and Vance Brand in an Apollo Command and Service Module to meet Russian cosmonauts Aleksey Leonov and Valeriy Kubasov in a Soyuz capsule. A jointly designed, U.S.-built docking module fulfilled the main technical goal of the mission, demonstrating that two dissimilar craft could dock in orbit. But the human side of the mission went far beyond that.