AP News, December 18th, 2006
Two Discovery astronauts set out Monday on the shuttle mission's fourth spacewalk to unstick a jammed solar panel array on the International Space Station.
U.S. astronaut Robert Curbeam has been on all four of the flight's spacewalks, a record for the most spacewalks conducted on a mission by a single crew member.
Swedish crew mate Christer Fuglesang, who also paired up on two earlier spacewalks, was to assist as Curbeam attempted to loosen stuck grommets that have prevented the 115-foot solar panel array from folding up so it can be stowed out of the way.
The pair started their latest foray into space at 2 p.m. EST, as their orbit was carrying them over the southern Pacific.
NASA managers hoped the spacewalk could be completed within 4 1/2 hours, but the astronauts could go for two hours longer if needed.
NASA added Monday's spacewalk to the schedule on Saturday after several attempts to fully fold the solar array were unsuccessful, stretching Discovery's mission to 13 days.
Earlier, Mission Control awakened Discovery's crew members with the Beach Boys hit "Good Vibrations" to get them ready for trying to shake the array loose.
"Good morning, Discovery," Mission Control astronaut Shannon Lucid radioed up. "We sort of thought that the wake-up music this morning summed up our hopes for the day."
NASA began retracting the accordion-like structure on Wednesday to make room for new solar arrays that must rotate to face the sun in order to generate electricity. The old panels must be folded out of the way before the new arrays can rotate fully.
Reconfiguring the orbiting space lab's interim power system to the new permanent electricity grid was a primary goal of the Discovery mission.
On the last scheduled spacewalk, which took place Saturday, Curbeam and Sunita Williams went to the array after completing their main tasks, and spent about two hours shaking the array, trying to free the problem grommets. They partially succeeded and other astronauts were able to command the array to retract several degrees more. But more grommets got stuck and the spacewalking duo's time was up.
Asked by a reporter how important is it to get the arrays retracted, crew member Joan Higginbotham, who will be operating a crane-like robotic arm during the spacewalk, offered this assessment: "It's very important from a personal standpoint," she said. "I think we're all very Type A personalities _ I think my crew would agree with me there _ so we always like to accomplish the task that we are given."
The array could safely be left in its current configuration for a couple of months, but NASA managers decided to take advantage of the extra hands on deck and the flexibility in their time schedule to try and resolve the problem now.
Discovery is set to land on Friday, having left the space station with a 2-ton, $11 million addition installed and the new power system. They'll leave Williams on the space station as its newest resident and bring back her predecessor, German astronaut Thomas Reiter.
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