Spacewalkers' dance of derring-do

Astronauts preparing for an EVA train in a huge pool that boasts submerged mock-ups of space-station modules and the shuttle. Each hour an astronaut spends on a spacewalk has an average of seven hours of pool training behind it, Lutz says. That training covers every step of a planned spacewalk.

Because of the hiatus in shuttle flights after the Columbia disaster in 2003 and the loss of foam debris during last year's first "return to flight" mission, Mr. Fossum and Dr. Sellers have put in additional training time – up to 15 hours in the tank for each hour of their three spacewalks, adds Lieutenant Colonel Fincke, a member of Sellers's astronaut class.

For all the training, the little things can still throw astronauts a curve.

On Saturday's 7-1/2-hour spacewalk, Fossum and Sellers spent 20 minutes with mission controllers trying to figure out why Fossum's retractable tether wouldn't take up slack as he moved back toward its reel. The solution: Release the reel's rewind brake.

In the end, it was a minor glitch in a spacewalk that gave NASA "fantastic results" from experiments to see how well an extension to the shuttle's robotic arm could perform as a crew platform for repairing shuttle tiles in space, notes Tomas Gonzales-Torres, lead EVA officer for the mission.

On EVAs, the timeline is king – even when things go a bit haywire.

Fincke recalls that during his stay on the space station, he and cosmonaut Gennady Padalka were in the midst of their third spacewalk when they noticed the Earth had dramatically changed position in the night sky from their vantage point. The system that controls the station's orientation with respect to the sun and Earth (the attitude-control system) had failed, and the station was slowly tumbling. And the duo had lost contact with mission control in Houston as well.

"There wasn't much we could do about it, and we were coming within range of Russian ground stations, so we kept working," he says. Sure enough, about 8 minutes later, Russian ground controllers called up to warn the two to keep clear of the station's thrusters so they could nudge the station into the right attitude.

Once the shuttle program ends, NASA is likely to put much less focus on mission-specific EVA training. Instead, it will probably put more emphasis during training on generic skills that spacewalking astronauts can apply to a wider range of situations than, say, repairing the Hubble Space Telescope, Fincke suggests.

"These EVAs are an important investment," he continues. "We're starting to help ourselves with some of our maintenance tasks by having more-enhanced robotics. The new Canadian robotic arm is going to have something called 'Dexter,' which will be able to handle some fine-scale tasks and change out some boxes" on the station's exterior.

"But we still need humans in the loop," he maintains. "The things we learn about our spacewalking, how to train for it, and how to maintain our spacesuits on orbit will be applicable" for a range of future missions.

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