A spacewalking astronaut wrapped up emergency surgery on a ripped space station solar energy panel today, and the crew began extending the wing to its full length.

Scott Parazynski installed homemade braces on the torn wing and clipped the snarled wires that ripped the wing in two places as it was being unfurled Tuesday.

"Looks really good," Mission Control said.

Astronauts inside slowly extended the wing, watching closely for problems as it inched toward its full 35m length. The wing was about three-quarters unfurled when the crew noticed the damage on Tuesday.

"If you see anything abnormal, I want you guys to call an abort," station commander Peggy Whitson told Parazynski and fellow spacewalker Douglas Wheelock.

Perched at the tip of a robotic arm and boom extension, Parazynski worked at the far left end of the linked shuttle-station complex. It's about half a football field away from the pressurised compartments where the astronauts work and live.

The ugly snag involved a guide wire, two hinge wires and two grommets. Parazynski first clipped a hinge wire near the larger tear, using a special tool that looked like a hockey stick to make sure the panel didn't spring back and hit him.

The solar panel captures sunlight to generate electricity, and is alive with more than 100 volts of electricity, possibly as much as 160 volts.

"It's a bit of a reach here," Parazynski said as he stretched to cut part of the guide wire.

"It's what those monkey arms are for," Melroy said, referring to Parazynski's 6ft 2in height.

As soon as Parazynski cut the guide wire, the approximately 30m stretch of it recoiled all the way down into a reel where spacewalker Douglas Wheelock was controlling and monitoring it. To everyone's relief, it retracted smoothly. "Beautiful. Nicely done," Parazynski reported.

Parazynski's helmet camera sent close-up pictures of the damage to Mission Control and the space station, allowing the astronauts and experts on the ground to discuss the best way to tackle the damage on the gold-colored wing.

To reduce the risk of Parazynski being shocked by the electricity generated by the panel, all of the metal parts on his space suit were covered with insulating tape — triple-taped, in fact — as were all his tools.

Wheelock also kept a close eye on Parazynski and his tools, guiding him to lean back when he got a bit too close to the swaying wing.

Without repairs, the wing poses a structural hazard for the international space station. The damage could worsen and the wing could become unstable, possibly forcing NASA to cut it loose and lose a vital power source for future laboratories.

It was Parazynski's fourth spacewalk this mission and the seventh of his 15-year astronaut career.

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