When he was a kid, Discovery astronaut Steve Robinson pestered his parents until they bought him flying lessons for his 14th birthday. He exhausted the money in a couple of weeks, but his appetite lingered -- worse than ever -- so he built himself a hang glider.

"Foolhardy?" Robinson mused, when asked earlier this year about the dangers of flying aboard a 21-year-old spaceship with 2.5 million parts, the vast majority of them designed during the previous century.

"Foolhardy is when I jumped off a cliff on a hang glider when I was 15," he said. "This isn't even close."

Wednesday Robinson, a 49-year-old bachelor with a doctorate in mechanical engineering from Stanford University, will make history by dropping over Discovery's side to perform the first in-space shuttle repair ever attempted.

Judging from Robinson's remarks during an on-board news conference early Tuesday, plucking two hanging "gap fillers" from the bottom of Discovery doesn't measure up to hang gliding.

"The main tools are right here," Robinson said, waving his fingers in the air. "I plan to reach out with my right hand and pull out the little piece of material from the belly of the orbiter.

"It won't be too complex."

Mess it up, though, and the consequences could be disastrous during reentry, when the shuttle's underside tiles endure temperatures well over 2,000 degrees Fahrenheit.

The trick is to get rid of the gap fillers without touching the tiles, a task requiring steely nerves and know-how, and Robinson has plenty of both. "Conceptually simple," he said of the job, "but it has to be done very delicately."

Stephen K. Robinson, an expert in turbulence physics at NASA's Ames Research Center in California, became an astronaut in 1994. Discovery is his third shuttle flight and his first as a spacewalker. He served as payload commander on the shuttle that took Sen. John Glenn (D-Ohio), a former astronaut, back to space in 1998.

Perhaps the most whimsical of the Discovery crew, Robinson stashes his tools in a "Tom Corbett Space Cadet" lunchbox that he takes with him on every voyage. It will not accompany him on Wednesday's spacewalk.

He can also discourse at length on the difficulties of whistling in a spacesuit (impossible), trying to play the guitar during a spacewalk (ditto) and his own guitar proficiency.

"It never sounds good no matter where I play," he said earlier this year, probably a lie as he plays lead guitar for the NASA rock band Max Q and could be observed serenading the rest of the Discovery crew during breakfast before launch last week.

But he is also deadly serious about his work. On Earth he goes to the gym every day to stay in shape for spacewalks that can last as long as seven hours and leave spacewalkers exhausted.

He is also keenly aware that a spacesuit makes a person 30 percent bigger, a key consideration during Wednesday's spacewalk: "You bump into a lot of things" during training, Robinson said. "We learn not to do that."

Astronaut Steve Robinson will repair Discovery.