was the first space station the United States launched into orbit, and the second space station ever visited by a human crew. The 75 metric ton station was in Earth orbit from 1973 to 1979, and it was visited by crews three times in 1973 and 1974. It included a laboratory for studying the effects of microgravity and a solar observatory.
Two flight-quality Skylabs were built. The first was de-orbited and crashed in Western Australia in 1979; the second, a backup, is on display at the National Air and Space Museum in Washington, DC. A full scale training mockup once used for astronaut training is located at the Lyndon B. Johnson Space Center visitor's center in Houston, Texas. Another full scale training mockup is now kept at Huntsville, Alabama, made from spare parts. It is currently being restored.