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Space Station Crew Performs Spacewalk Work, Added Duties

By | August 7, 2006

      Astronauts on the International Space Station (ISS) are moving ahead with their work in weightless conditions.

      ISS crewmen Jeff Williams and Thomas Reiter worked quickly through scheduled spacewalk tasks last week, then completed three get-ahead jobs, or extra tasks, and were ready for more.

      Mission Control assigned two more jobs, which the astronauts also completed.

      Williams and Reiter wrapped up their 5-hour, 54-minute excursion and began repressurizing the Quest airlock.

      Then the astronauts left the airlock in U.S. spacesuits.

      Station Commander Pavel Vinogradov helped them with spacewalk preparations and getting into their suits.

      It was the first time in more than three years a third crewmember had been available for those tasks on the orbiting laboratory.

      Williams, designated lead spacewalker, or EV1, wore the U.S. spacesuit with red stripes. Reiter, EV2, wore the all-white suit.

      Astronaut Steve Bowen acted as spacewalk intravehicular officer and coached the astronauts from the International Space Station Flight Control Room in Houston’s Mission Control Center.

      Williams and Reiter quickly got ahead of their timeline. First, they installed the Floating Potential Measurement Unit. The device measures the electrical potential of the station so procedures can be devised to minimize arcing hazards, or the jumping of current from a conductor to a ground, as the station grows.

      Their second job was to install two containers for MISSE, the Materials on International Space Station Experiment. The suitcase-like containers are left open to evaluate the long-term effects of space exposure on a variety of materials.

      The idea is to identify optimal materials for use in future spacecraft. MISSE 3 went on one of the high-pressure tanks around the crew lock, while MISSE 4 was installed on Quest’s outboard end.

      The two astronauts then went on to separate jobs. Williams installed a controller for a thermal radiator rotary joint on the S1 truss, while Reiter replaced a computer on the truss.

      Williams then began installing a starboard jumper and spool positioning device (SPD) on the S1 truss. Reiter inspected a radiator beam valve module SPD site where one device was already installed and installed an additional one. He then moved on to install an SPD on a port cooling line jumper. The jumpers are designed to improve the flow of ammonia through the radiators once that coolant is installed.

      Williams began setup for the final major scheduled task, a test of an infrared camera designed to detect damage in a shuttle’s reinforced carbon carbon (RCC) thermal protection. The camera highlights damage by showing variations in temperature between clean and damaged RCC test sections. Reiter operated the experiment while Williams went on to one of the additional tasks.

      Damage to a shuttle orbiter vehicle can occur if foam insulation on the external fuel tank rips loose and hits the orbiter. For example, a large chunk of foam insulation broke free from the tank and hit the Space Shuttle Columbia orbiter wing, punching a hole in its leading edge. The damage was undetected, and when Columbia began its return to Earth, the fiery gases of reentry filled the inside of the wing, causing structural failure. The crew was lost.

      That is why orbiter vehicles reaching orbit now are inspected for damage.

      During the latest spacewalk, the first task was installation of a light on the truss railway handcart to help future spacewalkers. Williams then removed a malfunctioning GPS antenna. After Reiter finished the infrared camera experiment, he installed a vacuum system valve on the U.S. laboratory Destiny for future scientific experiments.

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