Skylab was the first United States space station, launched by NASA, occupied for about 24 weeks between May 1973 and February 1974. It was operated by three separate three-astronaut crews: Skylab 2, Skylab 3, and Skylab 4. Major operations included an orbital workshop, a solar observatory, Earth observation, and hundreds of experiments. Unable to be re-boosted by the Space Shuttle, which was not ready until 1981, Skylab's orbit eventually decayed, and it disintegrated in the atmosphere on July 11, 1979, scattering debris across the Indian Ocean and Western Australia. Overview Skylab was the only space station operated exclusively by the United States. A permanent station was planned starting in 1988, but its funding was canceled and U.S. participation shifted to the International Space Station in 1993. Skylab had a mass of with a Apollo command and service module (CSM) attached and included a workshop, a solar observatory, and several hundred life science and physical science experiments. It was launched uncrewed into low Earth orbit by a Saturn V rocket modified to be similar to the Saturn INT-21, with the S-IVB third stage not available for propulsion because the orbital workshop was built out of it. This was the final flight for the rocket more commonly known for carrying the crewed Apollo Moon landing missions. Three subsequent missions delivered three-astronaut crews in the Apollo CSM launched by the smaller Saturn IB rocket. Configuration Skylab included the Apollo Telescope Mount (a multi-spectral solar observatory), a multiple docking adapter with two docking ports, an airlock module with extravehicular activity (EVA) hatches, and the orbital workshop, the main habitable space inside Skylab. Electrical power came from solar arrays and fuel cells in the docked Apollo CSM. The rear of the station included a large waste tank, propellant tanks for maneuvering jets, and a heat radiator. Astronauts conducted numerous experiments aboard Skylab during its operational life. Operations For the final two crewed missions to Skylab, NASA assembled a backup Apollo CSM/Saturn IB in case an in-orbit rescue mission was needed, but this vehicle was never flown. The station was damaged during launch when the micrometeoroid shield tore away from the workshop, taking one of the main solar panel arrays with it and jamming the other main array. This deprived Skylab of most of its electrical power and also removed protection from intense solar heating, threatening to make it unusable. The first crew deployed a replacement