Shuttle en route, building project starts Tuesday

Construction at the space station to resume – after a four-year hiatus – with arrival of Atlantis.

Astronauts aboard the space shuttle Atlantis face the most challenging spacewalks in the history of manned spaceflight this week, following Saturday's picture-perfect launch from the Kennedy Space Center in Florida.

After nearly two weeks of delays triggered by a lightning strike on the launchpad, a tropical storm, and two puzzling hardware miscues, Atlantis arced skyward late Saturday morning. The mission in effect drapes a "hard-hat area" banner across the International Space Station, raising the curtain on what shuttle program manager Wayne Hale has called the heart of the station's construction tasks.

If all goes well, by the end of the day Monday, the crew will have plucked a 17.5-ton segment of girders, control boxes, and folded solar panels from the payload bay and gingerly handed it to the space station's robotic arm. On Tuesday, the arm will connect it to one end of the station; then astronauts will conduct three spacewalks between Tuesday and Friday to complete the installation.

"These are the most complicated spacewalk and assembly tasks that have ever been done before," Mr. Hale noted during a prelaunch briefing.

The new hardware constitutes a $372 million solar-power plant capable of generating enough electricity to run 30 average-size homes. Solar panels unfold from one end of a new 45-foot section of truss, part of the space station's "backbone." The panels are attached to a mount that slowly spins them, like a windmill, to allow them to track the sun. Once the solar arrays reach their full extension, they will stretch 240 feet from tip to tip. Their arrival is expected to double the station's electricity-generating capacity.

This flight is the first of six aimed at beefing up the station's ability to host additional laboratory modules contributed by international partners. Europe's Columbus lab module, for example, is slated to arrive at the station in October 2007. Little wonder then that shortly after the launch NASA's associate administrator for space operations, William Gerstenmaier, received a flurry of congratulatory e-mails from overseas.

"Our partners are pretty excited," he says.

The mission marks the first since late 2002 dedicated to space-station construction – a hiatus triggered by the loss of the shuttle Columbia and its seven-member crew in February 2003. The accident occurred during reentry. It was traced to foam from the shuttle's external fuel tank, which broke off shortly after launch and damaged key sections of the orbiter's protective heat-shedding tiles.

The tank and its foam insulation have been modified since the Columbia accident. More changes are under way. Thus, the launches, including that of Atlantis, receive intense scrutiny from ground-based cameras, radar, and images taken from the shuttle to gauge the effects of the changes.

Atlantis's launch looked clean, Hale says, cautioning that a full analysis will take several days. But a first look at the images was reassuring, he said during a weekend briefing. Engineers counted five instances of debris loss, and Atlantis appeared to take hits from the debris at least twice. But the losses occurred on the doorstep of space, where there isn't enough air rushing past to accelerate the debris they saw to dangerous speeds.

"We saw nothing of any consequence before four minutes and seven seconds" into the flight, Hale said. "And anything that comes off that late is of no consequence" either.

"Not only am I not alarmed, I'm at ease" after looking at the video, he said. "This tells us that we have a really good tank here," and that engineers are getting a much better understanding of the timing and size of foam losses. "Both bode well for safety."

Indeed, Mr. Gerstenmaier notes, operating lessons from shuttle roll-backs, filling and emptying the fuel tanks, and myriad other activities are being fed to people designing and planning operations for the new crew exploration vehicle (CEV), which will replace the shuttle. NASA announced Aug. 31 that it had awarded the contract for the CEV, now called Orion, to an aerospace team led by Lockheed Martin Corp.

"They kind of look at me cross-eyed," Gerstenmaier says, when he peppers his exploration colleagues with detailed questions drawn from the shuttle's operating experience. But it's a unique chance to build requirements for the next generation vehicle from actual events, he concludes.

Atlantis's much-delayed launch also gave mission planners an opportunity to hone their space traffic-control skills. Ordinarily, planners try to avoid having a shuttle at the station when Russia launches a Soyuz resupply mission. But the launch delay made that inevitable. In addition, a Russian Progress capsule, currently docked at the station, will need to be moved to make way for the Soyuz craft. Managing several vehicles within relatively close proximity is a skill planners will have to hone for missions to the moon and Mars, suggests Gerstenmaier.

"We'll have a lot of spacecraft in orbit around there to keep track of" at the end of the mission, he says. "These kinds of skills – operating multiple vehicles in space and doing rendezvous and proximity operations – are going to be critical" for future exploration activities.

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