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Station solar wing retraction aborted BY WILLIAM HARWOOD STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION Posted: December 13, 2006 In a make-or-break first step in an ambitious mission to re-wire the international space station, the Discovery astronauts today began retracting a huge solar array to clear the way for a complicated electrical upgrade. But the venetian blind-like blankets on one side developed kinks and folds that forced the astronauts to abort the procedure.
"Houston, Discovery on the big loop," astronaut Sunita Williams called down to mission control in Houston. "Going to retract... ready, ready, now." A few seconds later, she reported "one bay is in... two bays in... three bays, hitting the abort button now." After stopping the retraction, the astronauts inspected the complex collapsible mast and the folding blankets that make up the P6-4B solar wing to make sure all the linkages in the mast were in good shape and that the solar blankets were folding as expected. The P6-4B solar array features two solar blankets to either side of a central mast that fold up like the slats in venetian blinds. The open-framework mast extends 31 40-inch bays and is designed to collapse from the base as a motor pulls the moveable linkages down into a storage canister. Television views from space showed a slight kink in a crease between to slats of the blanket at one end that appeared to be folding in the wrong direction. "OK, Terry, the only thing that I see ... is if you look at the zenith most array and from the blanket box you count maybe one, two, three folds, right there in the middle, it kind of looks like it's popped out a little opposite of the way it's going to fold," commander Mark Polansky radioed Houston. "I don't think it's a problem. ... if you want to look further, let me know." The astronauts continued a detailed photo survey while flight controllers assessed the health of the system. "So far, it looks great," astronaut Terry Virts radioed a few minutes later from mission control. "We have a small change to the plan. We're going to ask you to retract two more bays and while you do that, keep one of the cameras pointed at that area of interest. We think it's not going to be a problem, we think it's going to retrtact fine. We just want to verify that." Williams then sent commands to continue the retraction, stopping after two more bays of the mast collapsed into its canister. "That's four bays... five bays, hitting the abort button now," Williams reported. Video showed generally smooth folding in the body of the array, but slats toward the bottom, where the mast retracts into its storage canister, appeared misaligned and not folding smoothly. Engineers did not appear overly concerned, but they wanted to be sure they understood the situation before proceeding. The array must be retracted at least 40 percent to permit a newly installed set of arrays - P4 - on the left end of the station's main power truss to rotate as required to track the sun. The flight plan calls for that rotation to begin later today, a requirement before the astronauts can stage a spacewalk Thursday to switch the station from it's temporary to its permanent power system. After discussing the situation, flight controllers gave the astronauts permission to continue the retraction to the point where just two bays extended from the storage canister. The original plan called for retracting all the way to one bay, but engineers decided to double that to provide additional safety margin. "Ready, ready, now," Williams radioed at 2:05 p.m. Moments later, after three or four more bays retracted, she aborted the procedure. Video showed major kinking in the aft blanket toward its base, raising questions about whether or not the blanket would, in fact, fold up. "The part on the forward array cleared itself almost immediately," Polansky reported, referring to one of the two blankets. "On the aft array, however, there was a lot of oscillation going on. "It looked a couple of times like it was going to fold correctly, but then it started kind of bowing out in a nadir direction and we just got uncomfortable." Flight controllers told the astronauts to hold off any additional retraction while engineers assess the situation. Polansky suggested re-extending the blankets and then trying another retraction. "OK, thanks for the words," Virts replied. "The options you were just talking about are exactly what we're talking about on the ground." "I mean, the best analogy I can give is ... it's kind of like folding a map up," Polansky said. "You have the fold in the paper and if you start folding it and the fold's going the wrong way, you try a little bit but you get to the point where it bows out and there's nothing you can do but pop it back in place or unfold it and try again."
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