page_title: Apollo–Soyuz
section_title: Background
hierarchical_section_title: Apollo–Soyuz / Mission summary / Background
caption_attribution_description: English: Liftoff of Soviet Soyuz launch vehicle from Baykonur Cosmodrome in Kazahstan carrying Soyuz 19 spacecraft for the Apollo–Soyuz Test Project. This picture was reproduced from a frame of 35 mm film furnished by the USSR in an exchange of photography taken during the mission. Deutsch: Eine Sojus-Rakete mitsamt Sojus 19 Raumfahrzeug hebt im Kosmodrom Baikonur ab.
context_page_description: Apollo–Soyuz was the first international space mission, carried out jointly by the United States and the Soviet Union in July 1975. Millions of people around the world watched on television as a United States Apollo module docked with a Soviet Union Soyuz capsule. The project, and its memorable handshake in space, was a symbol of détente between the two superpowers. It is generally considered to mark the end of the Space Race, which had begun in 1957 with the launch of Sputnik 1.
  The mission was officially known as the Apollo–Soyuz Test Project. In contrast, the US vehicle was unnumbered, as it was left over from the canceled Apollo missions; it was the last Apollo module to fly.
  The three United States and two Soviet Union astronauts performed both joint and separate scientific experiments, including an arranged eclipse of the Sun by the Apollo module to allow instruments on the Soyuz to take photographs of the solar corona. The pre-flight work provided useful engineering experience for later joint American–Russian space flights, such as the Shuttle–Mir program and the International Space Station.
context_section_description: The ASTP entailed the docking of an American Apollo command and service module (CSM) with a Soviet Soyuz 7K-TM spacecraft. Although the Soyuz was given a mission designation number (Soyuz 19) as part of the ongoing Soyuz programme, its radio call sign was simply "Soyuz" for the duration of the joint mission. The Apollo mission was not a numbered mission of the Apollo program, and similarly bore the call sign "Apollo". Despite this, the press and NASA have referred to the mission as "Apollo 18", but this should not be confused with the canceled lunar mission.
  The Apollo spacecraft was launched with a docking module specially designed to enable the two spacecraft to dock with each other, used only once for this mission. The Saturn IB launch vehicle and CSM were surplus material. Like the Apollo Lunar Module, the docking module had to be retrieved from the S-IVB upper-stage of the Saturn rocket after launch. The docking module was designed as both an airlock — as the Apollo was pressurized at about 5 pounds per square inch (34 kPa) using pure oxygen, while the Soyuz used a nitrogen/oxygen atmosphere at sea level pressure (about 15 pounds per square inch (100 kPa)) — and an adapter, since the surplus Apollo hardware used for the ASTP mission was not equipped with the APAS docking collar jointly developed by NASA and the Academy of Sciences of the Soviet Union for the mission. One end of the docking module was attached to the Apollo using the same "probe-and-drogue" docking mechanism used on the Lunar Module and the Skylab space station, while its other end had the APAS docking collar, which Soyuz 19 carried in place of the standard Soyuz/Salyut system of the time. The APAS collar fitted onto Soyuz 19 was releasable, allowing the two spacecraft to separate in case of malfunction.
  The Apollo flew with a three-man crew on board: Tom Stafford, Vance Brand, and Deke Slayton. Stafford had already flown into space three times, including within eight nautical miles of the lunar surface as Commander of Apollo 10, and was the first general officer to fly into space. He was a brigadier general in the United States Air Force at the time of the flight; he would retire with three stars in 1979. Slayton was one of the original Mercury Seven astronauts selected in 1959, but an irregular heartbeat grounded him until 1972. He became head of NASA's astronaut office and, after a lengthy medical program, selected himself for this mission. At the time, Slayton was the oldest person to fly in space and the one with the longest gap between selection as an astronaut and first flight into space. Brand, meanwhile, had trained with the Apollo spacecraft during his time as a backup Apollo 15 command module pilot, and had served two stints as a backup Skylab commander. The closest he had come to flying prior to ASTP was as commander for the Skylab Rescue mission mustered to potentially retrieve the crew of Skylab 3 due to a fuel leak on that mission's Apollo CSM.
  The Soyuz flew with two men: Alexei Leonov and Valeri Kubasov. Leonov became the first man to walk in space on Voskhod 2 in March 1965. Kubasov, who flew on Soyuz 6 in 1969, ran some of the earliest space manufacturing experiments. Both were to have flown on the ill-fated Soyuz 11 in 1971 (Leonov as commander, Kubasov as the flight engineer), but were grounded because Kubasov was suspected of having tuberculosis. The two-man crew on the Soyuz was a result of the modifications needed to allow the cosmonauts to wear the Sokol space suit during launch, docking, and reentry.
  The ASTP-class Soyuz 7K-TM spacecraft used was a variation of the post-Soyuz 11 two-man design, with the batteries replaced by solar panels enabling "solo" flights (missions not docking to one of the Salyut space stations). It was designed to operate, during the docking phase, at a reduced nitrogen/oxygen pressure of 10.2 pounds per square inch (70 kPa), allowing easier transfers between the Apollo and Soyuz. Six ASTP-class Soyuz spacecraft were built in total, including the one used. Before the actual mission, two craft were la
caption: A Soyuz-U launch vehicle lifts the Soviet crew into orbit.
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