(FORTUNE Magazine) - Two years ago several members of the Discovery space shuttle crew faced their first big decision: whether to summit Wind River Peak. After a four-day hike carrying 50-pound bags through a snowstorm, they were exhausted. The weather was stormy, visibility poor. But they forged ahead and climbed to Chimney Rock, 500 feet short of the top.

There, after pausing to assess their options, they turned around.

It fell to Cmdr. Steven Lindsey to make the final decision to cut short the climb - but he also consulted the crew. "A person who is less comfortable might have just said, 'We're turning around. Let's go,'" notes Darran Wells, one of the two National Outdoor Leadership School instructors who accompanied the group.

But that person might not have been able to maintain the esprit de corps necessary for a team to thrive on a space mission. The teamwork at Chimney Rock is just the kind of thing NASA wants to inculcate.

For the past five years NASA has been making a systematic effort to teach astronauts to work in teams. Mostly it is done by putting them in the kind of environments where they need to do just that: trips in the wilderness and on NEEMO (NASA Extreme Environment Mission Operations), an undersea research craft half the size of a school bus.

The conditions are tough, but the intention is not to weed out anyone. Instead, the idea is to model the human aspects of space flight the way flight simulators replicate the technical ones.

"You train people to thrive in adverse conditions by putting them into adverse conditions to prepare them," says astronaut John Grunsfeld. "It's a good analogue for space flight, where the environment provides leadership opportunities and life-or-death consequences."

Flying any spacecraft is a group effort; it requires the crew to feed one another the right information at the right time. "If they didn't have this time," says Jon Kanengieter, director of NOLS professional training, "they'd be going through all that up on the shuttle."

Team development is only a few weeks out of several years of training, but there is no doubt that NASA takes it very seriously. "You can dial up the stress a little bit, and maybe different personality traits come out that you have to work on," says Kent Rominger, chief of the astronaut office. "It sends the message from NASA that teamwork is so important we're sending you somewhere for two weeks to work on it."

Psychologically, the most accurate simulation of a space mission is probably a voyage in NEEMO, which requires crew members to work on a cramped craft in an alien environment - in this case 60 feet under. "It gives you a sense of the physical and psychological stress of space," says Bill Todd, who runs the NEEMO project.

Once the boosters ignite, human dynamics and the ability to cope with pressure are as important as individual competence.

"You could be the best pilot, scientist, or astronaut in the world," says astronaut Ron Garan, "but if you can't work as part of a team or live with people for six months, you're no good to NASA."