Oct. 28: Astronaut Scott Parazynski works on the exterior of the international space station.
Oct. 30: The evident damage to a solar array which ripped as it was being unfurled by astronauts aboard the international space station.
Oct. 29: Astronauts Doug Wheelock, left, and Scott Parazynski float near the galley on the middeck of space shuttle Discovery.
Oct. 26: Astronaut Doug Wheelock prepares for his spacewalk, with spacewalking partner Scott Parazynski's foot visible over Wheelock's head.
Oct. 25: International space station commander Peggy Whitson, right, welcomes Discovery commander Pam Melroy aboard.
Oct. 23: Space Shuttle Discovery lifts from Pad 39A at the Kennedy Space Center, Fla., on a mission to the International Space Station.
The crew of shuttle mission STS-120, set to launch aboard shuttle Discovery Oct. 23.
The astronaut chosen to make emergency repairs Saturday on the space station's ripped solar wing — a dangerous and unprecedented electrical job — is actually an emergency medical doctor and mountaineer whose specialty at NASA just happens to be spacewalks.
What is more, Scott Parazynski is 6-foot-2 (1.8 meters) and has long arms, a lucky stroke since he will be working alongside a damaged electrical generator with hot wires possibly exposed.
"We have a bunch of challenges ... but the beauty of having Scott available to us is that it's one piece that you don't worry about," flight director Derek Hassmann said Friday. "I cannot overstate the significance of his experience and just his approach to the job."
To save the solar wing, Parazynski needs to clear whatever snagged the panels and caused the wing to tear while it was being unfurled Tuesday. He will not know what he is up against until he sees the damage up close.
As it is now, the wing poses a structural hazard for the international space station. The damage could worsen and the wing could become unstable, quite possibly forcing NASA to cut it loose and lose a vital power source for future laboratories.
That is why NASA is willing to undertake this riskier and trickier than usual spacewalk before shuttle Discovery undocks from the space station in just another few days.
Complicating matters for NASA is a malfunctioning solar rotary joint on the opposite side of the space station. It's needed to turn another set of solar wings toward the sun, but is gummed up with steel shavings and, for the most part, unusable.
But the torn wing is the priority, and the joint work has been scrapped for now. Also put off was a demonstration of a high-tech caulking gun and goo for mending shuttle thermal tiles, a technique that Parazynski helped develop.
It will be Parazynski's fourth spacewalk this mission and the seventh of his 15-year astronaut career.
Parazynski, 46, who is married with a 10-year-old son and 8-year-old daughter, became an astronaut three years after graduating from Stanford Medical School. He said earlier this week that every spacewalk is, by nature, dangerous.
"You're in your own personal spacecraft and you are relying upon the spacesuit hardware and on your own physical abilities," he said.
Parazynski and his spacewalking partner, Army Col. Douglas Wheelock, will wear partial mittens over their gloves for extra protection. Wheelock pierced the outer layer of a glove near the end of Tuesday's spacewalk; it was the third time in less than a year that a spacewalker tore a glove on something sharp at the space station.
As for the electrical hazards, all of the metal parts on Parazynski's spacesuit have been covered with insulating tape — triple-taped, in fact — as have all the tools that he'll carry with him.
The solar panel will be teeming with more than 100 volts of electricity, possibly as much as 160 volts.
"It's not the kind of thing that would burn you, but we could get conduction through the heart, let's say, or mild shocks," said David Wolf, the spacewalk branch chief for the astronaut office.
The astronauts got an early start Saturday, receiving a wakeup call from Mission Control around 1:38 a.m EDT (0538 GMT). The song, dedicated to Parazynski, was the theme to "Star Wars." Parazynski has a son named Luke, who shares a first name with Luke Skywalker, the main character from the "Star Wars" movies.
"That was a great, great way to wake up," Parazynski said before launching into an impression of "Star Wars" villain Darth Vader. "I just have to say: Luke, I'm your father. Use the force, Luke."
Before calling it a day Friday, Parazynski asked for another hookup with spacewalking experts at Mission Control, saying he still had questions. Controllers told him they could not come up with a wire on board for him to practice a fraying technique he may need Saturday.
Parazynski told them not to worry, that he's pretty good at fraying wires "having done a lot of home wiring projects myself."
"Just use your magic on this one the same way," Mission Control replied.