TransHab was a concept pursued by NASA in the 1990s to develop the technology for expandable habitats inflated by air in space. Specifically, TransHab was intended as a replacement for the already existing rigid International Space Station crew Habitation Module. When deflated, inflatable modules provide an 'easier to launch' compact form. When fully inflated, TransHab would expand to 8.2 meters in diameter.
History
The name of the project is a contraction of Transit Habitat reflecting the original intention to design an interplanetary vehicle to transfer humans to Mars. Considerable controversy arose during the TransHab development effort due to delays and increased costs of the ISS program. In 1999, the National Space Society issued a policy statement recommending that NASA continue R&D of inflatable technologies while ceasing development of a TransHab ISS module. Finally in 2000, despite objections from the White House, House Resolution 1654 was signed into law banning NASA from conducting further research and development of TransHab. An option to lease an inflatable habitat module from private industry was included in the bill. Since that time, the private companyBigelow Aerospace has purchased the rights to the patents developed by NASA and is pursuing a similar scheme for a private space station design. The company has launched the Genesis I, Genesis II, and BEAM pathfinder spacecraft, with plans for additional experimental craft culminating in their BA 330production model and the Bigelow Commercial Space Station.
Technology
The TransHab design called for a hybrid structure that combines the packaging and mass efficiencies of an inflatable structure with the advantages of a load-bearing hard structure.
Multi-Layer Inflatable Shell
TransHab's inflatable shell consisted of multiple layers of blanket insulation, protection from orbital and meteoroid debris, an optimized restraint layer and a redundant bladder with a protective layer. TransHab's foot-thick inflatable shell design had almost two dozen layers. The layers were fashioned to break up particles of space debris and tiny meteorites that might hit the shell with a speed seven times as fast as a bullet. The outer layers protect multiple inner bladders, made of a material that holds in the module's air. The shell also provides insulation from temperatures in space that can range from plus 121 degrees Celsius in the Sun to minus 128 degrees Celsius in the shade. The key to the debris protection in the design and prototype units was successive layers of Nextel, a material commonly used as insulation under the hoods of many cars, spaced between several-inches-thick layers of open cell foam, similar to foam used for chair cushions on Earth. The Nextel and foam layers cause a particle to shatter as it hits, losing more and more of its energy as it penetrates deeper. Many layers deep in the shell was a layer of superstrong woven Kevlar to hold the module's shape. The air was held inside by three bladders of Combitherm, a material commonly used in the food-packing industry. The innermost layer, forming the inside wall of the module, was Nomex cloth, a fireproof material that also protected the bladder from scuffs and scratches.
