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Apollo–Soyuz
The Apollo–Soyuz Test Project (ASTP) flew in July 1975. It was the last Apollo mission, the first joint U.S./Soviet space flight, and the last manned US space mission until the first Space Shuttle flight in April 1981.
Though the mission included both joint and separate scientific experiments (including an engineered eclipse of the Sun by Apollo for Soyuz to take photographs of the solar corona) and provided useful engineering experience for future joint US/Russian space flights such as the Shuttle-Mir Program and the International Space Station, its primary purpose was symbolic. ASTP was a symbol of detente that the two superpowers were pursuing at the time, and it ended the tension of the Space Race.
This was astronaut Deke Slayton's only flight. He was chosen as one of the original Mercury Seven in April 1959 but had been grounded until 1972 for medical reasons.
The Apollo–Soyuz Test Project (ASTP) entailed the docking of an American Apollo spacecraft with then-Soviet Soyuz spacecraft. Whilst the Soyuz was given a mission designation number (Soyuz 19) as part of the ongoing Soyuz program, it was referred to simply as "Soyuz" through the duration of the joint mission. The Apollo mission was officially not numbered, though some sources refer to it as "Apollo 18".
To dock the two spacecraft together, the Apollo command module launched with a docking module, designated APAS-75, and like the Apollo Lunar Module on the lunar flights, had to be retrieved from the S-IVB upper-stage of the Saturn IB rocket after launch. Designed as an adapter (the Apollo and Soyuz had different docking mechanisms) and as an airlock (the Apollo was pressurized at 5.0 psi using pure oxygen, while the Soyuz used a nitrogen/oxygen atmosphere at sea level), the docking module was attached to the Apollo using the same docking mechanism ("probe and drogue") used on the Lunar Module and the Skylab space station, while the other end had the APAS design feature, which Soyuz 19 carried in place of its standard Soyuz/Salyut system at the time. The APAS fitting with the Soyuz 19 was releasable, allowing the two spacecraft to separate.
The Apollo flew with a three-man crew on board: Tom Stafford, Vance Brand and Deke Slayton. Stafford had already flown three times into space, including within eight miles of the lunar surface, and was the first General Officer to fly into space (Stafford was a brigadier general in the USAF at the time of the flight; he would retire with three stars in 1979). For Slayton, it was a personal milestone in his life; he was one of the original Mercury 7 astronauts selected in 1958 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 flight into space. Brand had trained with the Apollo Spacecraft used for this mission during his time as a backup Apollo 15 command module pilot as well as multiple stints as a backup Skylab commander. The closest he came to actually flying prior to ASTP was as commander for the Skylab Rescue mission mustered to possibly retrieve the crew of Skylab 3 due to a fuel leak on that mission's Apollo CSM.
On the Soviet side, the Soyuz flew with two men: Alexey Leonov and Valery Kubasov. Leonov was the first man to walk in space in 1965 on Voskhod 2. Kubasov, who flew on Soyuz 6 in 1969, ran some of the earliest space manufacturing experiments. Both were slated 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 to have 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.
Although the equipment developed for ASTP was only of use as a one-off, the program allowed NASA to maintain a manned space focus following the end of the Apollo and Skylab missions. The Apollo's Saturn IB launcher and CSM were all surplus material. The Soyuz used was at the time, a variation of the post-Soyuz 11 two-man design with the incorporation of solar panels instead of batteries for "solo" flights (those not destined to the civilian Salyut or military Almaz space stations). Two ASTP-class Soyuz spacecraft were built, the primary, which flew the actual ASTP mission, and a backup, which was later used on the last "solo" Soyuz flight in 1976, but with the APAS docking adapter replaced with a battery of astrophysics experiments. The ASTP-class Soyuz 7K-TM spacecraft were also designed to operate, during the docking phase, at a reduced nitrogen/oxygen pressure of 10.2 psi, allowing easier transfers between the Apollo and Soyuz.
The Soyuz and Apollo flights launched within seven and a half hours of each other on July 15, and docked on July 17. Three hours later the two mission commanders, Stafford and Leonov, exchanged the first international handshake in space through the open hatch of the Soyuz. NASA had calculated that the historic handshake would have taken place over the British seaside resort of Bognor Regis, but a delay resulted in its actual occurrence being over the town of Metz in France.
While the two ships were docked, the three Americans and two Soviets conducted joint scientific experiments, exchanged flags and gifts (including tree seeds which were later planted in the two countries), signed certificates, visited each other's ships, ate together, and conversed in each other's languages. (Because of Stafford's pronounced drawl when speaking Russian, Leonov later joked that there were actually three languages spoken on the mission: Russian, English, and "Oklahomski.") There were also docking and redocking maneuvers during which the two spacecraft reversed roles and the Soyuz became the "active" ship.
After 44 hours together, the two ships separated, and maneuvered to use the Apollo to create an artificial solar eclipse to allow the crew of the Soyuz to take photographs of the solar corona. Another brief docking was made before the ships went their separate ways. The Soviets remained in space for five days, the Americans for nine, during which the Apollo crew also conducted experiments in Earth observation.
The mission was a great success, both technically and as a public-relations exercise for both sides. The only serious problem was due to an Apollo crew mistake during re-entry preparations that resulted in a very rough landing and entry of noxious gas into the spacecraft. The reaction control system was inadvertently left on during descent and highly toxic nitrogen tetroxide was sucked into the spacecraft as it drew in outside air. Brand briefly lost consciousness, and Slayton reported suffering nausea. As a precaution, the three astronauts were hospitalized for two weeks in Honolulu, Hawaii. In his autobiography, Slayton reported that the crew received doses of nitrogen tetroxide approaching the level that would cause death. The three upright bags in the nosecone were designed to upright the command module capsule if necessary after splashdown. These upright bags partially failed leaving the capsule upside down on the ocean's surface awaiting rescue by navy divers. This is the only time this situation occurred during the entire Apollo program. During the post mission hospitalization, a lesion was discovered on Slayton's left lung, not believed to have been caused by the fumes. A biopsy determined it was benign.
This was the final flight of an Apollo spacecraft. Immediately after the launch of the Apollo spacecraft, preparations began to convert Launch Pad 39B and the Vehicle Assembly Building at Kennedy Space Center for use by the Space Shuttle, the United States' next manned spacecraft program. Launch Pad 39A had already been closed after the launch of Skylab.
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