U.S. space exploration history on U.S. stamps also the only space station NASA launched alone. The 100-ton space station was in Earth's orbit from 1973 to 1979 and it was visited by crews three times in 1973 and 1974. Circling 50 degrees north and south of the equator at an altitude of , Skylab had an orbital period of 93 minutes. There were a plethora of UV astronomy experiments done during the Skylab lifetime, as well as detailed X-ray studies of the Sun. The station was active until July 11, 1979, when it fell out of orbit. The 10-cent Skylab commemorative stamp first day of release took
Bigelow Commercial Space Station with the first module to be launched no earlier than 2016. The CSS Skywalker (Commercial Space Station Skywalker) was a 2005 concept for the first "space hotel" by Bigelow Aerospace. The Skywalker was designed to be composed of multiple Nautilus (B330) habitat modules, which would be inflated and connected upon reaching orbit. An MDPM (Multi-Directional Propulsion Module) would allow the Skywalker to be moved into interplanetary or lunar trajectories. In short, CSS Skywalker was "an effort to build the planet's first orbiting space hotel, [with a projected] room rate of USD$1 million per night", and a hoped-for launch date for