Astronauts Successfully Furl ISS Solar Wing in Extra Spacewalk
STS-116 mission specialist Robert Curbeam works with a solar array during the fourth spacewalk of the STS-116 mission.
CREDIT: NASA TV.
This story was updated at 11:59 p.m. EST.
HOUSTON -- A reluctant solar wing is finally furled atop the International Space Station (ISS) after two spacewalking astronauts poked and prodded it with tape-covered tools.
Veteran spacewalker Robert Curbeam and crewmate Christer Fuglesang spent just over six and one half hours freeing snags on the half-furled array as, bit by bit, its two solar blankets folded into their storage boxes.
"You guys are doing very great work today," Discovery pilot William Oefelein, who choreographed the unplanned extravehicular activity (EVA) from the shuttle's flight deck, told the spacewalking astronauts. "We're not even going to eat you're lunches."
Applause rang out across the communications link between Mission Control, Discovery and the spacewalking duo as the stubborn array's boxes closed for the first time in six-years at about 6:54 p.m. EST (2354 GMT).
"Yes!" Curbeam said just before the applause.
But the solar wing played one last card: some guide wires failed to reel in completely during the retraction, forcing Curbeam to move in and gently tug them with a pair of spaceworthy needle nose pliers. The pliers and other tools used were insulated from electric shocks by the liberal application of translucent orange Kapton tape [image 1, image 2].
"Robert Curbeam, you do good work," NASA astronaut Steve Robinson in Mission Control said when the guide wires were cleared.
About 30 minutes later, the solar array boxes were latched and locked.
"Congratulations," Fuglesang radioed down to flight controllers here at NASA's Johnson Space Center.
Today's six-hour, 38-minute spacewalk began at 2:00 p.m. EST (1900 GMT) [image].
Curbeam set a new shuttle record during the EVA as the first astronaut to make four spacewalks in a single orbiter flight. Today's EVA marked Curbeam's fourth of the STS-116 mission and his seventh overall, hurling him from 13th to fifth place in the annals of total spacewalking time with 45 hours and 34 minutes of spacesuit-ed work.
Fuglesang, who participated in three of the four STS-116 spacewalks, racked up 18 hours and 14 minutes while his fellow astronaut Sunita Williams performed in one for a total of seven hours and 31 minutes.
Solar wing showdown
Monday's solar array showdown began Dec. 13, when astronauts aboard Discovery and the ISS first attempted to retract the portside member of two wings extending from the mast-like Port 6 (P6) truss some 90 feet (27 meters) above the station [image].
The 115-foot (35-meter) solar wing, designated as P6-4B, repeatedly folded improperly as it was pulled in remotely for the first time since its December 2000 installation [image]. Snags between guide wires and the metal eyelets, or grommets, they thread through were cited as the source.
Attempts to wiggle the snags free by moving the solar array, as well as sending vibrations up through the ISS by a vigorously exercising astronaut, failed though physically shaking the wing using two spacewalkers' hands and a bit of elbow grease met with some success on Saturday [image].
It was then that mission managers officially added today's unplanned spacewalk to the STS-116 mission.
"The entire EVA was put together over a course of a couple of days," said Tricia Mack, NASA's lead STS-116 spacewalk officer, adding that not only had Curbeam never trained to work from the ISS robotic arm on this flight, but that mission controllers scrambled to come up with a safe and doable plan. "Normally we train for a year and a half, is a typical flow."
The P6 solar arrays must be retracted before the massive station segment is hauled from its current location to the portside edge of the orbital laboratory's main truss next year [image]. Mission managers were also concerned that leaving the P6-4B array half-furled could leave the wing's mast open to damage during future ISS reboost maneuvers.
While Fuglesang floated freely at the base of the P6-4B array, shaking it at times to free snags. Curbeam flicked stuck grommets with his ad hoc tools from the tip of the space station's robotic arm [image], which was controlled by Williams and STS-116 mission specialist Joan Higginbotham.
"There is just no replacing eyeballs and hands in space," Curry said.
Shuttle departure delayed
Monday's spacewalk delayed Discovery's undocking from the ISS by a full 24 hours and led mission managers to give up one of two spare days typically reserved in case weather or glitches prevent an on-time landing.
Initially slated to undock today, Discovery and its seven-astronaut crew will now depart the ISS Tuesday at 5:09 p.m. EST (2209 GMT) with landing set for Friday, Dec. 22.
Phil Engelauf, NASA's mission operations representative, said Discovery will undock from the ISS slightly later than typical orbiter departures to give the STS-116 crew additional time to ferry all the spacewalking equipment used today into the orbiter.
The shuttle astronauts, meanwhile, said they hoped to find some time during their additional day to soak up their orbital surroundings.
"The extra day is just wonderful," Higginbotham told television reporters Sunday. "Maybe I'll have a little more free time to look out the window."
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