It was launched, initially unmanned, by a modified Saturn V rocket, and weighed about 77 metric tonnes in orbit by itself. Three manned missions to the station, conducted between 1973 and 1974 by an Apollo Command/Service Module (CSM) atop the smaller Saturn IB, each delivered a three-astronaut crew. During that time, an additional Saturn IB was on standby for rescuing those in orbit.
During Skylab’s operational life, numerous scientific experiments were conducted aboard it, and crews were able to confirm the existence of coronal holes in the Sun.
Thousands of photographs of Earth were taken, and records for human time spent in orbit were extended.
Plans were drawn up to refurbish and reuse Skylab, using the Space Shuttle to boost its orbit and repair it; however, in 1979, before the shuttle was ready, Skylab reentered Earth’s atmosphere and disintegrated, with debris striking portions of Western Australia.
After Skylab’s demise, the focus shifted to the reusable Spacelab module, an orbital workshop that could be deployed from the Space Shuttle and returned to Earth.
The next American space station project was Space Station Freedom, which was never completed, although it eventually led to the construction of the US Orbital Segment of the International Space Station, starting in 1998. Shuttle-Mir was another project, and led to the U.S. funding Spektr, Priroda, and the Mir Docking Module in the 1990s.
Skylab included the Apollo Telescope Mount (multi-spectral solar observatory), EREP, Multiple Docking Adapter (with two docking ports), Airlock (with EVA hatches), and the Orbital Workshop in the main body of the station, which housed much of the supporting systems.
Power came from a solar array as well as fuel cells in the docked Apollo CSM. The rear of the station included a large waste tank, tanks for maneuvering jets, and a heat radiator.
Apollo–Soyuz Test Project
The Apollo–Soyuz Test Project (ASTP) (Eksperimantalniy polyot Soyuz-Apollon) 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.
The mission included both joint and separate scientific experiments (including an engineered eclipse of the Sun by Apollo to allow 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; the ASTP was a symbol of the policy of détente that the two superpowers were pursuing at the time.
The ASTP was US astronaut Donald “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 the 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” for 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 was launched with a docking module, designated APAS-75. Like the Apollo Lunar Module on the lunar flights, the APAS had to be retrieved from the S-IVB upper-stage of the Saturn IB rocket after launch.