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
Space architecture On July 12, 2006 the "Genesis I" experimental space habitat was launched into low Earth orbit. "Genesis I" demonstrated the basic viability of inflatable space structures, even carrying a payload of life science experiments. The second module, "Genesis II", was launched into orbit on June 28, 2007 and tested out several improvements over its predecessor. Among these are reaction wheel assemblies, a precision measurement system for guidance, nine additional cameras, improved gas control for module inflation, and an improved on-board sensor suite. While Bigelow architecture is still modular, the inflatable configuration allows for much more interior volume than rigid modules.