Skylab

Skylab was the United States' first space station launched by NASA, occupied for about 24 weeks between May 1973 and February 1974. It was operated by three trios of astronaut crews: Skylab 2, Skylab 3, and Skylab 4. The manifestation of the Apollo Applications Program, Skylab was constructed from a repurposed Saturn V third stage (the S-IVB), a dry workshop, and took the place of the stage during launch. Operations included an orbital workshop, a solar observatory, Earth observation, ten spacewalks, and hundreds of experiments. NASA's station concept had competed with the Department of Defense's Manned Orbiting Laboratory concept from 1963 to 1969. Skylab was the world's second space station, after the Soviet space program's Salyut 1. Its pressurized volume of over 350 m3 was not rivalled until the completion of the first modular space station, Mir, in 1996; the central Orbital Workshop, at 270 m3, dwarfed subsequent station modules, including the largest on the International Space Station (ISS), Kibō, at 150 m3. A successor station, Skylab B, was concurrently constructed in 1970 and considered for integration with Salyut and Soyuz, but cancelled in 1973. Plans for Skylab to be boosted and reused with the Space Shuttle were abandoned after it became clear that the shuttle would not be ready by 1979. Skylab's orbit eventually decayed and it disintegrated in the atmosphere on July 11, 1979, scattering debris across the Indian Ocean and Western Australia. Unity became the second US-built space station element, joining the ISS in 1998.