Space Station Astronauts Prepare for Aug. 3 Spacewalk

ISS Expedition 13 astronauts Jeffrey Williams (left) and Thomas Reiter ready their U.S.-built spacesuits for an Aug. 3 spacewalk inside the station's Quest airlock CREDIT: NASA TV.

Two astronauts aboard the International Space Station (ISS) will don NASA spacesuits Friday to rehearse an upcoming spacewalk that will prepare their orbital laboratory for future construction.

ISS Expedition 13 astronauts Jeffrey Williams and Thomas Reiter will step into their U.S.-built Extravehicular Mobility Units (EMUs) as practice for an Aug. 3 spacewalk to ready the station's primary cooling system for activation during an upcoming NASA shuttle mission.

Russian cosmonaut Pavel Vinogradov, mission commander for Expedition 13, will assist the spacewalkers as they don their orbital work clothes, NASA said, adding that next week's six-hour spacewalk will begin at 9:55 a.m. EDT (1355 GMT).

"This EVA consists of many maintenance tasks...most of those are in support of the upcoming STS-116 mission, which is the flight after next," said Dana Weigel, NASA's extravehicular activity (EVA) flight director, during a Thursday mission briefing.

NASA's STS-116 shuttle flight is set to launch toward the ISS aboard the Discovery orbiter on Dec. 14, just over three months after the planned Aug. 28 liftoff of its predecessor STS-115 aboard Atlantis, the space agency has said.

Kirk Shireman, NASA's deputy space station program manager, said the Aug. 3 spacewalk is the first of no less than eight EVAs dedicated to support ISS construction between visiting shuttle missions.

"This EVA next week is very important to put us into a position to conduct all those flights," Shireman said of the 15 or so remaining shuttle missions to complete the ISS by 2010, when NASA's three-orbiter fleet is retired.

Williams, a NASA astronaut who arrived on the ISS with Vinogradov on April 1, will serve as EV-1 during the upcoming spacewalk and don a red-striped spacesuit.

Reiter, the first long-duration ISS astronaut for the European Space Agency and Germany, will wear an all-white spacesuit as EV-2. He arrived at the station aboard NASA's shuttle Discovery on July 6.

Critical cooling

Of the numerous tasks planned for Williams and Reiter during their upcoming spacewalk, the most critical are the installation of a new motor and replacement of a broken control box for three radiators mounted to a swivel platform on the station's starboard side.

A duplicate radiator platform sits on the station's port side, though only one radiator on either system is currently unfurled, NASA said.

The new motor to be installed is one of two that allow the radiators' platform to rotate independently of the ISS as the station orbits Earth. The control box- a replacement for a unit that failed in 2004 - will regulate radiator deployment and the valves for the vital liquid ammonia that transports waste heat to the radiators themselves.

Weigel said the spacewalkers will also install a temporary cooling fluid line - known as a shunt jumper - to the starboard radiator system during the EVA.

"We want to make sure the system is functioning properly," Weigel said of the station's independent starboard and port cooling systems, adding that only then can the radiators be filled with liquid ammonia.

A busy spacewalk, a larger crew

In addition to working on orbital cooling systems, Williams and Reiter will mount a new device - known as a Floating Potential Measurement Unit - to the Earth-facing end of the station's Starboard One (S1).

"This is going to provide a great view for the crew," said Paul Boehm, NASA's lead spacewalk officer for Expedition 13.

The new device will monitor the voltage potential that builds up as the outpost's solar arrays generate power. A previous probe was tossed into space last year after astronauts noticed that bolts securing it to the ISS were loosening, prompting debris concerns.

Williams and Reiter will also install a pair of materials exposure experiments to the space station's hull and test an infrared video camera's ability to detect shuttle heat shield damage during their spacewalk, Boehm said.

If time permits, they could retrieve a balky global positioning system antenna, set up a new light outside the ISS or install a vent for use during future experiments inside NASA's Destiny laboratory, he added.

Next week's EVA will mark the third career spacewalk for both Williams and Reiter, but will be the first in more than three years to leave an ISS astronaut inside the orbital laboratory.

ISS crew size reductions following NASA's 2003 Columbia accident forced two-astronaut teams to leave the space station empty, its internal hatches shut and systems monitored by flight engineers on Earth.

Reiter's arrival earlier this month returned the ISS to its three-person crew size.

"Now we have an extra body to help the crew get into and out of the suits, as well as someone inside in case we have work that we need them to do during the spacewalk," Weiger said.

NASA will provide a live broadcast of the ISS Expedition 13 crew's Aug. 3 spacewalk on NASA TV beginning at 9:00 a.m. EDT (1300 GMT). You are invited to follow the spacewalk using SPACE.com's NASA TV feed, which is available by clicking here.

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