Skintight spacesuits may look good in the recent Star Trek movie, but they don't fit NASA's future plans—not yet, anyway. The space agency has its sights set on a new spacesuit for astronauts returning to the moon within the next decade or so—a more traditional design that will seek to balance protection and mobility.

The revision comes 40 years after Apollo astronauts first hopped and skipped across the lunar landscape. Now NASA wants more flexible garb that can also endure longer moon missions.

"We want someone in our suit to have the mobility of a geologist on Earth," says Raul Blanco, deputy manager of the EVA (Extravehicular Activity) systems project for Constellation, NASA's current program aimed at sending humans beyond low Earth orbit. His team is "picking the brains" of former Apollo spacesuit designers and looking at current suits worn by shuttle astronauts to prepare for a preliminary design review in 2010.

All spacesuit designs must protect humans from the grim effects of depressurization, which occurs during sudden exposure to a vacuum. Under such conditions trapped air can expand and tear fragile tissues in the lungs' air sacs. And water or other fluids vaporize into gases that cause bodily swelling, interfere with blood circulation, and cool the mouth and airways to dangerously low temperatures as they escape the body.

NASA continues to rely on so-called full-pressure spacesuits that encase astronauts in an oxygenated environment. The suit permits astronauts to draw a normal breath and also wraps them in a layer of pressurized, temperature-controlled air that protects the body from the unpleasant effects of exposure to the vacuum and thermal extremes of a space environment.

A downside of full-pressure suits is that they create resistance for every movement, which becomes physically tiring during lengthy spacewalks or other activities. Harrison Schmitt, the only geologist to ever walk on the moon, recalled his forearms becoming weary after half an hour in the Apollo spacesuit.

That has forced NASA engineers to strike a balance. Current spacesuits are pressurized to 4.3 pounds per square inch (psi)—well below the usual atmospheric pressure on Earth (14.7 psi at sea level), but still providing a pressurized environment that also allows astronauts to move around.
"If you were in a suit at 14.7 psi, it would get so stiff that you couldn't move," says Chris Gilman, chief designer for Orbital Outfitters, a company contracted to work on the shoulder component of the Constellation spacesuit.

Some designers have also looked at another type of spacesuit that could give astronauts much greater freedom of movement. The counterpressure, or "squeeze," spacesuit would provide pressurized oxygen to the helmet but would otherwise rely on tight bands squeezing the body at certain points to counteract the lack of pressure outside.

But Gilman and other experts say formfitting spacesuits are unlikely to soon replace NASA's full-pressure suits. Donning a skintight suit in microgravity would be more difficult and time-consuming than trying to wriggle into a wet suit on Earth. Slim-cut spacesuits would also come with a higher price tag, because each would have to be carefully custom-fitted to fit each space traveler's body.

Even the best fitting counterpressure suits have yet to overcome the discomfort that arises when every part of the human body wants to swell outward in the vacuum—including the tiny follicle pits in the skin where human hairs grow.

"Where there's less pressure, you get edema and swelling that gets uncomfortable very quickly," Blanco notes, having personally tested counterpressure gloves in NASA's vacuum chambers. Problems also run the other way: The pressure bands can cause chafing on the skin.

The counterpressure suit is really a locomotion suit, says Dava Newman, an aerospace engineer at the Massachusetts Institute of Technology. As such, it is most appropriate for walking on the moon—or, perhaps, one day on Mars. She explains that full-pressure suits are fine for spacewalks because leg movement is less necessary.

Constellation's redesigned full-pressure suit is slated to come in two flavors: Astronauts will use the trimmer configuration for launch and landing as well as during spacewalks. For activities both inside and outside the crew capsule, a tether system would connect the astronaut to life-support systems on the spacecraft.

A second, bulkier outfit for strolling on the moon will feature additional considerations such as an electrostatic system that can protect the suit against the abrasive lunar dust. The Constellation team also wants to implement smaller life-support systems in this second style of suit. For instance, large canisters that absorb carbon dioxide on existing spacesuits could give way to a rapid-cycling system that eventually vents the waste gas out of the suit.

"We've never had a suit that we've imposed so many requirements on," Blanco says. But he and other spacesuit designers may welcome the burden of puzzling out engineering challenges now, if it permits future astronauts to tread more lightly.