Humans don’t like to be cramped, but it’s always been hard to fit large spacecraft or station modules on top of narrow rockets. In the 1960s NASA flew a satellite made of a flexible material that folded up tightly on top of the launcher. In orbit, the satellite was inflated to a diameter of over 30 meters. That could have become the basis for space station designs, but the concept fell by the wayside.
NASA revived the idea in the 1990s, when it was looking for ways to build a crew dormitory for the International Space Station. The agency hoped to build an inflatable shell made of layers of advanced materials, including Kevlar, packed together for insulation and strength; the result would protect against micrometeorites and space debris at least as well as a traditional metal module. Development was cancelled in 2000, but in 2004 Bigelow Aerospace bought exclusive rights to the technology, and two years later it launched an unmanned prototype habitat. It is still in orbit, collecting data on the module’s long-term viability. Another prototype was launched in 2007. The company plans to start building a commercial space station made from inflatable modules in 2014, and it has a partnership with Boeing to provide transport to and from the station.
While Bigelow’s development program continues, NASA is researching and testing designs suitable for human missions to the moon or Mars.