First U.S. space station .
Launched into Earth orbit in 1973 on a Saturn V rocket, it used as its main habitat the vehicle's third stage, which had been outfitted as a workshop. Its apparatus included a powerful solar telescope and equipment for Earth-and materials-sciences research and for studies of the human body's adaptation to weightlessness. Three successive astronaut crews conducted research aboard Skylab for a total of 171 days in 1973–74. Because its thermal shielding was damaged during launch, its first crew took up and installed an improvised sunshade to prevent the station from seriously overheating. Although plans called for Skylab to be reused, increased solar activity caused its orbit to degrade faster than expected. In 1979 it entered Earth's atmosphere and broke up, with debris spreading over the southeastern Indian Ocean and a sparsely populated section of Western Australia.