This mission involved a docking of ships between the American Apollo and Russian Soyuz to develop techniques for emergency rescues, as well as to perform some experiments. This was the first international space mission.
The Apollo-Soyuz mission began on July 15, 1975 with the launch of the Russian Soyuz, followed by the launch of the American Apollo that same day. This was the first manned spaceflight conducted jointly by two nations. This mission aimed to benefit both countries by developing space rescue techniques for emergencies that in future manned missions. Mission objectives included transferring crew from one vehicle to another through rendezvous, the process of bringing two spacecraft together. The two crews then conducted a series of experiments together.
The docking, or coupling together, was through a specially-built adapter that was built on the Apollo for the Soyuz. On July 17, 1975, the historic handshake between the commanders of the two spacecraft took place. Commander of the Apollo was Tom Stafford, and with him were command module pilot Vance Brand and docking module pilot Donald " Deke" Slayton. Alexei Leonov was captain of the Soyuz, and with him was flight engineer Valery Kubasov.
When the Apollo crew was re-entering, they inadvertently left the reaction control system on during descent. As a result, the crew was exposed to nitrogen tetroxide gas. They were then given pure oxygen in a recovery vessel and fully recovered. The mission was a great success, and it increased public-relations between Russian and America.