Four of the arms belonged to space walkers Mike Gernhardt and Jim Reilly. Two robotic arms also were called into service - the shuttle's Canadarm and its big brother, the station's Canadarm2. Station Flight Engineers Susan Helms and Jim Voss were at the station arm's controls, while Mission Specialist Janet Kavandi guided the shuttle limb.
The space walk got off to a slightly delayed start at 10:04 p.m. CDT Tuesday after the station's primary Command and Control computer had to be restarted. The computer, needed to guide the station arm as it lifted the high-pressure oxygen and nitrogen tanks out of the shuttle cargo bay and into position alongside the new airlock, was back in business shortly after 8 p.m., allowing first motion of the arm by 9 p.m.
Gernhardt and Reilly, supported by their six colleagues inside the shuttle and station, latched the first two dog house-shaped tank assemblies into place without difficulty, so shuttle and station Flight Directors Paul Hill and Mark Kirasich decided to move ahead with installation of the third tank at 1:41 a.m.
The second space walk of the mission concluded at 4:33 a.m. CDT Wednesday. It was the 66th space walk in shuttle program history, and the 23rd devoted to International Space Station assembly. So far, STS-104 space walks have lasted 12 hours, 28 minutes.
The crews will have an extra day to prepare for the third and final planned space walk of the flight, which now is scheduled for Friday. Mission managers decided Tuesday to add the additional docked day to give the joint crew adequate time to ready the new airlock for its first use.
The two crews are about half a day behind schedule due to a small water leak that occurred when the astronauts were linking the new airlock to the station's Moderate Temperature Loop. The crews will resume troubleshooting a leaky air valve in an Intermodule Ventilation (IMV) unit on the rear, right side of the station's Unity node after wakeup scheduled for 4:04 p.m. today.
With the space walk complete, STS-104 Commander Steve Lindsey and Pilot Charlie Hobaugh, who also was the inside coordinator for the space walk, began another hour-long series of automated steering jet firings to reboost the station's altitude.