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But the team faced a dilemma: Since the advent of the space shuttle in the early '80s, NASA has been limited in what it can send into space by the size of the shuttle's cargo bay, a mere 15 feet in diameter. Aluminum modules, such as the ones being built for the International Space Station, must be smaller than that to fit inside. Once fully outfitted with research and life-support hardware around the perimeter, these "hard habs" become the extraterrestrial equivalent of shotgun shacks, seven-foot by seven-foot corridors without enough room to accommodate the supplies, let alone the psychological needs, of astronauts on long missions.
An inflatable module like Transhab, on the other hand, could be launched as a cylindrical core of hardware wrapped in what is basically a deflated balloon. Once out of the cargo bay, Transhab would be inflated with attached air tanks; the balloon around the core would expand to three times the packed volume, 12,000 cubic feet, the equivalent of a 1,500-square-foot house on earth. In other words, NASA could put a module the size of Skylab into space with just one launch. Adams likens the idea to the earth-based evolution of exoskeletal to endoskeletal biology: The hard hab is like an oyster, with its skeletal structure on the outside. Transhab is like a human -- a more advanced life form that's mushy on the outside with its skeleton underneath.
The risk of Transhab seems obvious: Wouldn't an inflatable structure pop? Both NASA and the Russian space program have been experimenting with inflatables since the late '50s and early '60s, but until now fabric technology wasn't advanced enough to accommodate the idea. Transhab's outer shell is a foot thick and made up of 20-some layers. The structure itself combines ancient craft with modern technology: a basket-weave of super-strong Kevlar. (A mock-up was actually hand-stitched by 400 local union garment workers.) A food-packing material called Combitherm keeps the air inside, and successive layers of Nextel and simple foam keep the micro-meteoroids out. According to NASA, it's better than bulletproof.
But the shell isn't the only watershed design element on Transhab. This balloon is the closest thing astronauts have ever seen to a home in space. When the module is inflated, the core of the structure folds out -- a little bit like umbrella struts -- to make three floors. To create the illusion of even more room, openings in the floors lend Transhab an atrium effect, and two 20-inch-diameter windows give the astronauts a view of earth far below. The top floor is the exercise and health care area, with a treadmill and resistance equipment to keep the astronauts' muscles from atrophying in microgravity. The bottom floor is the kitchen, including a table that seats 12 -- enough for the entire crew plus its replacements. NASA has discovered that eating dinner together is as important for astronauts as it is for families. The separation of kitchen and exercise room is no coincidence: "Sweat floats," Adams says. "It's really gross." It seems like common sense, but most spacecrafts put the treadmill and the food preparation area right on top of each other.
The middle level holds six individual crew quarters, each with a sleeping bag, personal storage space and a computer entertainment system. This level is also important because it is completely surrounded by water storage tanks that protect the crew from radiation. Radiation is a numbers game: A little exposure is okay, a lot is not. In this design, astronauts would lower their exposure time by at least sleeping in a safe environment. Plus, the area would serve as something like a cellar in the event of a solar storm. The current design for the International Space Station includes nothing of this kind.
In 1998, the Transhab team presented its design to NASA management. "They said, 'Wow! This is such an incredible idea. I want you to consider proposing this as the habitation module on the space station,' " project manager Donna Fender remembers. Transhab was originally conceived for a potential mission to Mars, but now it had a much more immediate purpose. NASA gave the team a year and a little bit of money to prove that it would work. Within that year, Transhab went from a concept on paper to a reality. "Within that one year," Fender says, "we about killed ourselves."
They built a full-scale model, inflating and deflating it in a huge vacuum chamber that simulates the conditions of space. They fired larger and larger aluminum pellets at panels of its layered shell. Eventually the pellets got so large that they broke not the balloon's material but the hypervelocity guns used to shoot them. The team even tested the Kevlar-weave structure to a safety factor of four times the standard-operating pressure inside the shell. If you blow up a balloon with too much air, it pops. But in this test, to everyone's amazement, not a single stitch broke.
"Every time they gave us a hurdle," says Fender, "we leaped the hurdle -- with room." The Transhab team even passed the toughest test of all: astronauts. Dr. Shannon Lucid, who earned the American record for the most consecutive time in space with 188 days aboard the Russian space station Mir, has given the project her endorsement. "Look at it like this," she says. "Think of yourself with your family, and you are living inside a recreational vehicle but you can't open the door. And you're gonna live inside this RV with your family for six months. And then think about the importance of the living space .I was really hoping that the project would continue to be funded."