NASA officials say one of the problems must be solved before any more shuttles can fly to the orbiting outpost. The space agency is focusing on the wing because further damage could force officials to junk the important and expensive piece of equipment.
The agency hopes to send veteran spacewalker Scott Parazynski to conduct the repairs Saturday.
It will be a difficult and potentially dangerous mission for Parazynski, who runs the risk of being shocked as he tries to fix the damaged panel.
Parazynski also will be farther from the safety of the station than NASA would like, increasing the chances of problems such as glove tears or spacesuit malfunctions.
The safety concerns led the space agency to delay the outing a day to give experts on the ground more time to analyze every detail. Astronauts aboard the linked shuttle-station complex were spending Friday studying the plans and preparing equipment.
Engineers believe the 115-foot (35.1-meter) wing snagged on a guidewire or guidewire support as it was being unreeled Tuesday. Until Parazynski gets close to the damage, NASA can only theorize what he'll need to do to fix it.
The partially deployed solar wing is producing power, and there is no way to turn it off, flight director Derek Hassmann said. Parazynski has been warned not to touch the electricity-generating solar cells that cover virtually the entire wing. If the metal of a tool he was holding melted, it could burn a hole into his glove.
The metal parts of Parazynski's spacesuit will be covered with insulating tape, as will his wire cutters, pliers and other tools.
Astronaut David Wolf, who heads the spacewalking branch in Houston, acknowledged that it's conceivable but extremely unlikely that Parazynski could be electrocuted. But he said the agency has done everything reasonable to keep that from happening.
"We're upward of over 100 volts DC power on that array," Wolf said. "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.
"This is not going to happen. We have very good techniques to insulate and control the array."
The other problem is the long distance between the damaged wing and the pressurized compartments where the astronauts work and live. NASA normally likes to keep spacewalkers no more than 30 minutes away from the cabin hatch in case of an emergency, but Parazynski could be up to an hour away.
The station's residents will delve into the other power problem after Discovery leaves. That involves a malfunctioning rotary joint that controls the solar wings on the right side of the station. A spacewalking astronaut found steel shavings in the right joint last weekend, the apparent result of grinding parts.
The torn wing is on the opposite side of the station.
The shuttle is to undock Monday and land Wednesday.
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