It slides into view, slowly filling the frame: a giant spaceship, bristling with nacelles, antennas and other devices of unknown purpose. A deep rumbling pushes your sound system’s bass response to the limit. After a length of time, as determined by a complex interplay between how much awe or menace the director is trying to convey and the size of the special effects budget, a collection of glowing engines finally passes into view.
By comparison, Earth’s current mega-space project, the International Space Station, is puny. When (and if) completed, the ISS’s spindly conglomeration of modules, trusses and solar panels will be 361 ft long and mass of about 460 tons. (For comparison, 361 feet is the supposed width of one of Battlestar Galactica’s flight pods.
The reason we don’t have anything even approaching, say, the wheeled space stations envisioned in the 1950’s, let alone the giant spacecraft of science fiction movies, is because building large structures in space is tough. In the absence of fully-equipped orbital shipyards, spacecraft and spacestations have to be built on Earth, and then lofted into orbit atop a rocket. America’s Skylab and Russia’s series of Salyut space stations were built all in one piece and then launched into orbit, but the limit of how big such a space station can be was quickly reached in the 1970’s. The next logical step was to build larger structures by plugging together prefabricated modules launched separately, and the Soviet Union pioneered this technique with the Mir space station, which grew from a single core module launched in 1986 to a 7 module complex by the time Mir was deorbited in 2001.
The same approach of stringing modules together to build a larger structure is being used to build the ISS, which began construction in 1998. But the individual modules are still limited by severe size constraints dictated by the rockets used to launch them and as a result, most of the ISS modules are no more than 15 ft in diameter and between 18 and 28 feet long. Building up a large habitable volume to live and work in using such relatively small building blocks requires lots of expensive launches, which is part of the reason why the ISS still has quite a ways to go before it is completed.
Engineers have been thinking about better ways to build large space structures, and in the last few years, have turned to an old idea made new: inflatable modules. The idea of building spacestations out of modules that are launched as compact bundles and then inflated on-orbit to provide a large living and working space goes back at least as far as the 1940’s, when rocket pioneer Werner von Braun used it in his super-hard-science fiction novel Project Mars: A Technical Tale. By 1961, Goodyear was even building a prototype of an inflatable spacestation for NASA. But inflatables fell out fashion, perhaps because engineers (and astronauts) simply felt more secure with trusting solid metal walls when it came to coping with hazards such as micrometeoroids, radiation and the temperature extremes of outer space.
In the 1990’s, a team of NASA engineers revived the inflatable approach with a proposal for a module that would house the astronaut living quarters onboard the ISS. Called TransHab, it was hoped that the technology could also be used when building Mars-bound spacecraft. It was demonstrated that an inflatable module could actually offer improved protection from the space environment as compared to a rigid, metal-walled module, because the inflatable design allowed for much thicker walls with multiple protective layers. The TransHab module would have had a diameter almost twice that of rigid ISS module. The TransHab team built and ground tested some prototype hardware, but then NASA cancelled the program due to budgetary problems.
The story doesn’t end there though—a Las Vegas real estate tycoon and space enthusiast called Robert Bigelow saw potential in the technology and decided to go into the space station construction business. He founded Bigelow Aerospace in 1999 and licensed the TransHab technology from NASA. Since then, progress has been rapid, with Bigelow actually launching a one-third-scale unmanned prototype in 2006, dubbed Genesis I. A year later, the second prototype, Genesis II, was orbited. Due to the success of these test flights, Bigelow has accelerated his schedule and plans to launch a human-rated protoype module in 2009 or 2010, with even larger production modules to follow that would be 45 feet long and 22 feet wide. (Each of these modules would have an internal volume of 330 cubic meters, as compared to the 75 cubic meters afforded by the recently launched European ISS laboratory module, Columbus)
Will Bigelow’s super-sized space station get off the ground? I hope so—and maybe then we can think about building some really big spaceships.