This week, NASA announced that crews aboard the International Space Station will soon test an inflatable space module in orbit. The "balloon-like" module prototype will be manufactured by Las Vegas-based Bigelow Aerospace and it's scheduled for a 2015 launch aboard a SpaceX cargo run to the station.
The technology certainly has exciting implications – imagine being able to launch a full habitat to the moon on a single rocket! - but it's not a novel idea. The Bigelow Aerospace design has its roots in the inflatable NASA concept TransHab developed (and ultimately canceled) for living on the space station, but designs for inflatable space habitats go even further back than that. NASA's Langley research center originally considered an inflatable space station as a jumping off point for lunar missions in 1959.
In the late 1950s, most proponents of space exploration was an Earth orbiting station as a necessary step on the way to deep space missions. Engineers at the Langley research center were no exception, formally entering the space station game in the spring of 1959. On April 1, NASA created a Research Steering Committee for Manned Space Flight led by Harry Goett. The Goett Committee as it became known included representatives from all NASA centers who met to discuss the agency's future on May 25. Representatives from Langley wasted no time, jumping into a presentation on the merits of a space station.
Called the Advanced Man in Space – AMIS – program, Langley's vision proposed a station with a type of shuttle vehicle that could take astronauts to distant points in the solar system. The station itself would help NASA study the psychological and physiological effects of extended spaceflight on astronauts and at the same time train crews for future demanding missions. It would also be a test bed for the new technology the space agency would no doubt have to develop to explore the Cosmos.
After a series of concept studies, Langley engineers settled on a self-deploying inflatable design for its space station. Noninflatable configurations had been systematically passed over: a cylindrical module attached to a booster's upper stage was dynamically unstable; a modular concept would need too many launches; and hub-and-spoke designs, basically big orbiting Ferris wheels, were expected to have disorientating and nauseating effects on a crew.
Langley's winning design was an inflatable torus - astronauts would basically live inside a giant orbiting doughnut – designed with the Goodyear Aircraft Corporation. Properly called the Erectable Torus Manned Space Laboratory, Langley's ideal torus was a flat design 24 feet in diameter that could be packed snugly inside a rocket for protected on its ride through the atmosphere to orbit. Once inflated, the inner habitable volume could provide astronauts with varying strengths of artificial gravity anywhere between O and 1 G, and ports on the outside of the torus could accept incoming and launch outgoing shuttles.
But there was one major problem with the inflatable aspect – it was extremely vulnerable. Meteorites and micrometeorites posed the greatest and most immediate danger, but it wasn't the only worry. Some engineers worried that astronauts moving vigorously inside the torus could somehow rip through the structure and shoot themselves out into space. Goodyear built a research model out of a lightweight three-ply nylon cord held together by butyl elastome, a sticky, rubber-like material. This strengthened the torus, but it wasn't enough. It would still be vulnerable during a meteoroid shower.
Stability issues cropped up, too, again from the crews' expected vigorous movements. Some engineers thought it was possible for astronauts to move around with enough force that the torus would start wobbling. A wobble, even a slight one, could make the station an unstable (and nauseating) place to be.
To address these strength and stability problems head on, Langley built a 10-foot-diameter elastically scaled model of the torus. The model was finished and ready for testing in the summer of 1961. But by then the torus was out of fashion, passed over in favor of a more rigid hexagonal design, also lightweight and foldable, and also from Langley.
But the bigger problem facing the space stations was NASA's new commitment to the moon. Benefits of spending the time in orbit to prepare men for the two-week trip from to the moon couldn't outweigh the need to get there first. Space stations, both inflatable models and their more rigid offshoots, were shelved.