NASA officials say the complex S-Zero truss is now ready to handle future assembly plans, which include attaching eight more segments to the truss to create a keel that will be as long as a football field including both end zones.The space station's major power and cooling utilities eventually will come from the hardware attached to that beam and run along wiring and plumbing through the S-Zero truss for distribution to the rest of the multinational complex.
Atlantis astronauts Jerry Ross and Lee Morin -- both grandfathers who were dubbed the "Silver Team" by crewmate Steven Smith -- spent seven-and-a-half hours working outside the station during the second of four planned spacewalks schedule for Atlantis' week-long stay at the frontier outpost.
About half that time was spent bolting a pair of tripod-shaped struts to what, in effect, are studs along the outside skin of the $1.4 billion U.S. Destiny science laboratory.
They also spent time connecting a set of power, data and video cables to the $190 million Mobile Transporter that is attached to the truss.
Essentially the world's first space-based railroad car, the transporter is a platform capable of moving along a pair of rails built into the side of the entire length of the truss. Connected to that platform, when needed, will be the station's Canadian robot arm, which can then slide down the beam to extend the arm's reach.
The rest of the time the spacewalkers were occupied with removing and storing four metal braces that were used to help keep the truss firmly locked in place inside Atlantis' cargo bay during launch.
Two bars and two "V-shaped" keel pins were unbolted from the truss and then re-attached along an unused outer wall of the truss. They had to be moved because they would have been in the way of the Mobile Transporter's rail.
Saturday's spacewalk was Morins' first and Ross' eighth, and the veteran made sure the rookie took in all of the sights as they cruised at 17,500 mph some 240 miles above the planet.
Several times Morin asked his crewmates where they were over Earth as he was moved around at the end of the station's robot arm.
"What city are we passing over now Steve?" Morin asked Smith, who was inside Atlantis helping the spacewalkers keep track of their movements and timeline.
"I think we're coming up to the southern coast of Australia, probably Melbourne." Smith replied.
"There's some big thunderstorms down there," Morin observed, and then a moment later looked up at the Russian spacecraft docked a few dozen yards away: "It looks like you can just almost reach out and touch the Soyuz."
Begun a few minutes early at 10:09 a.m. EDT (1409 GMT), the second spacewalk of the mission ended at 5:39 p.m. EDT (2139 GMT).
Less than an hour later the shuttle took control of maneuvering the station and began an orbit raising exercise to increase the station's altitude by about 1.25 miles (2 kilometers). Two additional firings are planned before Atlantis is scheduled to undock with the station on Wednesday.
Meanwhile, the next major mission event is set for Sunday when the first spacewalking team of Smith and Rex Walheim will return outside to continue working on setting up the Mobile Transporter, which in turn is to lead to the first on orbit test of the railroad system on Monday.
Atlantis remains scheduled to return to Earth on Friday.
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