HOUSTON - NASA mission managers today announced a risky new plan to fix an injured solar wing at a distant end of the International Space Station (ISS).
The solar wing, which tore Wednesday during its remote deployment, is generating plenty of power, but engineers fear that it is structurally unstable. NASA officials decided to make the repair their top priority after scrapping previous plans to inspect worrisome gears at the other end of the orbital laboratory.
To remedy the problem, spacewalker Scott Parazynski will ride out to the damaged area on the end on the space shuttle's 50-foot (15-meter) extension boom, which the space station's Canadarm2 will grapple - a first in spaceflight history.
"Right now the crew on orbit is kind of wrapping their brains up around this new option that we've thrown out there," said Derek Hassmann, lead ISS flight director for the STS-120 space shuttle mission. "We're going to work hard to get there and be ready on Friday."
Hassmann said the spacewalk - the fourth of up to five planned for the mission - could be pushed back to Saturday morning if teams on the ground need more time to devise a specific plan of action. Whatever the case, space shuttle and station crews said they are ready to help.
Suffredini said the fix will "detour" physical stress around the 2.5-foot (0.76-meter) tear in the solar wing. The wing itself is one of two anchored to a mast projecting off of the Port 6 (P6) solar array truss segment.
"The objective is to carry the load around the tear," Suffredini said.
Parazynski, who has six spacewalks under his belt, will thread homemade "cufflinks" through holes that helped secure the arrays during launch seven years ago. Astronauts on board the space station will fashion the straps out of wire before the 6.5-hour spacewalk.
"There could be as many as seven cufflinks all the way across the wing," Suffredini said, as there are seven hole-containing lines running the 115-foot (35-meter) length of the solar wing.
Astronaut Doug Wheelock will venture outside of the space station to monitor Parazynski's handiwork, as well as help reel in a guide wire that snagged and ultimately caused the tear. Parazynski will clip the troublesome wire while on fully extended on the end of the boom-arm combination.
Complicating the spacewalk is the delicateness of the solar array material - about as thick as a vinyl shower curtain but stronger and sturdier - and the dangerous amount of electricity running through it.
"There's a lot of power running through this whole thing," Suffredini said. "So part of our challenge is we don't want to touch the array, we don't want to bump into the array."
Suffredini said all the tools used by Parazynski to make the fix will be coated in non-conductive Kapton tape. Astronaut Dan Tani, who will operate the space station's robotic arm during the spacewalk, will keep Parazynski at a safe distance from the orange-and-black solar wing.
"We want to everything at arm's reach if we can," Suffredini said, noting that Parazynski will bring something other than 39 hours and 46 minutes of spacewalking experience to the table. "One of the advantages of Scott is that he has long arms. It just gives you a little more reach."
NASA expects the space shuttle and Discovery and its seven-astronaut crew to return to Earth on Nov. 7, but mission managers said there are enough supplies on board to last another two days docked with the space station, should they need the time. The shuttle's original 14-day mission has already been extended once to 15 days.
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