The space walk also was the first to be supported primarily from the space station Flight Control Room in Houston, and the first demonstration of a new pre-breathing protocol that uses vigorous exercise to help purge nitrogen bubbles from the space walkers' bloodstreams and prevent what is known as "the bends."

Mission Specialists Mike Gernhardt and Jim Reilly exited the new airlock at 11:35 p.m. CDT Friday and were back inside by 3:37 a.m. Saturday. Working in tandem with the station's Canadarm2 operator and Expedition Two Flight Engineer Jim Voss and shuttle arm operator and Atlantis Commander Steve Lindsey, the space-age construction workers attached a nitrogen supply tank to the airlock's shell. This completed the installation of two nitrogen and two oxygen tanks that will be used to pressurize the airlock and resupply space suits. Atlantis Pilot Charlie Hobaugh and Station Commander Yury Usachev coordinated the space walk from inside, while Flight Engineer Susan Helms supported station arm operations.

Depressurizing the airlock took longer than expected – about 40 minutes instead of the anticipated 7 minutes. Flight controllers and engineers have not yet identified what caused the pressure equalization valve on the Crew Lock's hatch to react so slowly, but are continuing to evaluate data and reports from the crew.

During the mission's third spacewalk, Gernhardt and Reilly also moved hand-over-hand up the station's solar array truss to take a look at a gimbal assembly mechanism that allows the arrays to swivel with the Sun. They reported no visible signs that could account for high-current readings being witnessed by flight controllers on the ground.

The successful construction foray brings the total time for space station-based walks to 4 hours, 21 minutes. There have been 24 space walks devoted to station assembly, a combined total of 155 hours, 39 minutes.

The crews will go to bed at 8:04 a.m., and awaken at 4:04 p.m. to begin preparations for an undocking at 11:54 p.m. CDT Saturday. The Atlantis and Expedition Two crews will say good-bye and close the hatches at 8:59 a.m.

The JSC Newsroom will close at 7:30 a.m. CDT Saturday, and reopen at 3:30 p.m. The next mission status report will be issued about 6 p.m. Saturday or as events warrant.

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