A pair of spacewalkingastronauts will work on the oldest U.S. solar arrays of the International SpaceStation on Saturday, taking care to safeguard themselves against the remotechance of electric shocks near the orbital power plant.
NASAastronauts Steven Swanson and Joseph Acaba plan to float outside the spacestation at about 12:43 p.m. EDT (1643 GMT) to work near the batteries for a pairof 8-year-old solar wings on the outpost?s port-most edge. The chore is one of severalto prime the station for future construction and comes one day after Discoveryshuttle astronauts unfurled apair of new solar arrays on the outpost?s starboard side, completing itsbackbone-like main truss.
But before thespacewalkers exit the station today, they will carefully wrap some of the metalconnecting rings on their spacesuits with insulating tape to protect against anyslight electrical shocks near their portside worksite, which can be prone toarcing from the surrounding plasma environment.
?With thesuits as designed, we believe we have sufficient protection,? space stationflight engineer Kwatsi Alibaruho told reporters late Friday.?We?ve just appliedsome additional factor of safety to drive the probability of a problem absolutelyas low as we could.?
Alibaruhosaid the risk an astronaut receiving even a mild electric shock is extremelyremote, and the voltage and currents involved are very small. But NASA rulescall for an immediate end to any spacewalk if any shock ? no matter how small -should one occur, he added.
Spacewalkingastronauts rely on their spacesuits functioning properly, including onboard electronics,while working outside a spacecraft.
Busyspacewalk on tap
Today?sspacewalk is the second of three for Discovery?s13-day mission, but has been revamped after launch delays prompted NASA cuta planned fourth excursion in order to complete the shuttle flight before thearrival of a Russian Soyuz spacecraft ferrying a new station crew next week.
Thespacewalk will be the fourth for Swanson and the first for Acaba, a formerschoolteacher who is making his first spaceflight. It will send them to variouslocations across the space station?s metallic backbone, a massive truss that islonger than a football field.
?They?reready to go,? Discovery skipper Lee Archambault told Mission Control lateFriday. ?We?re very much looking forward to another day on orbit.?
Swanson andAcaba will loosen bolts on the portside solar wing batteries so future spacewalkerscan replace them later this year. They also plan to prepare the station toreceive two future cargo carriers, take infrared photographs of a damagedradiator and install a new navigation antenna to help Japan?s first unmannedcargo ship - the H-2 Transfer Vehicle - dock at the orbiting lab later thisyear.
While thespacewalkers work outside the station, astronauts inside are expected to begintesting repairs to part of the outpost?s urinerecycling system. The device, a distillation assembly, is part of a largersystem to recycle condensation, astronaut urine and sweat back into pure waterfor drinking, food preparation, bathing and other uses. It has been brokensince December.
AstronautSandra Magnus removed the brokendistillation gear on Friday and plans to test its replacement in a dry runlater today. If successful, the urine recycler will then be used to purify abatch of water late in Discovery?s mission so new samples can be returned toEarth.
?We have a considerableabout of urine in storage containers,? Alibaruho said, adding that the urine isusually discarded aboard disposable Russian cargo ships. ?We?ll take some ofthat ?and attempt to process into clean water.?
NASA wantsto revive the space urine recycler in order to restore the station?s full recyclingsystem and certify that the water it produces is fit for astronaut consumption.
Recyclingwater aboard the station is key to plans to boost the outpost?s crew size up tosix people later this year. It would allow an extra 15,000 pounds (6,803 kg) ofcargo and other supplies, weight that was previously reserved for waterdeliveries, to be launched to the station, NASA has said.
Discoveryand its shuttle astronaut crew launched toward the station on Sunday and aredue to land on March 28.
SPACE.comis providing continuous coverage of STS-119 with reporter Clara Moskowitz andsenior editor Tariq Malik in New York. Click here for missionupdates, live spacewalk coverage and SPACE.com's live NASA TV video feed. Live spacewalk coverage begins at 11:45 a.m. EDT (1545 GMT).
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