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7 p.m. CDT, Saturday, Aug. 11, 2007
Mission Control Center, Houston, Texas
STS-118 MCC Status Report #07
First-time spacewalkers Rick Mastracchio and Dave Williams added a two-ton, 11-foot-long spacer to the International Space Station’s backbone today during the mission’s inaugural spacewalk.

With the addition of the new spacer, nicknamed “Stubby” by the STS-118 crew, the station’s truss is now 246 feet long.

The two Endeavour mission specialists ventured outside the station to attach the Starboard 5 (S5) segment of the station’s truss and to retract the forward heat-rejecting radiator from the station’s Port 6 (P6) truss. The retraction was the final step needed before the P6 truss can be relocated to its permanent place at the end of the port truss during the STS-120 mission in October.

The spacewalk began at 11:28 a.m. CDT, and Mastracchio and Williams were back inside by 5:45 p.m. The truss was officially installed by 1:26 p.m. Total duration of the spacewalk was 6 hours, 17 minutes. The spacewalkers stayed ahead of schedule, and after finishing the planned tasks completed some extra jobs that advanced the station’s assembly.

Mission Specialist Tracy Caldwell guided the spacewalkers as they eyed clearances for station arm operators Charlie Hobaugh and Clay Anderson. The shuttle pilot and station flight engineer moved the truss segment into place and engaged automatic latches, and then the spacewalkers fastened the primary structural bolts that will hold it in place.

With the new starboard truss section in place, the crew is ready to move on to the next spacewalk. On Monday, Mastracchio and Williams will venture outside again to replace a faulty control moment gyroscope. At least two more spacewalks are scheduled, and a fourth may be added if mission managers decide to extend the mission to 14 days.

While the spacewalk was under way, the station’s primary U.S. Command and Control computer shut down unexpectedly at 2:52 p.m. The redundant system reacted as designed and the primary backup computer took over, and the third computer moved into the backup slot. The shutdown did not affect the spacewalk. With two computers working normally, station flight controllers are troubleshooting the cause of the third’s shutdown.

Meanwhile, mission managers continued to evaluate imagery gathered on the first three days of the flight as they awaited additional information from a focused inspection of the shuttle’s underbelly that is planned for Sunday.

The crew is scheduled to go to sleep at 10:06 p.m. tonight and awaken Sunday for flight day five at 6:06 a.m.

The next STS-118 status report will be issued Sunday morning or earlier if events warrant.