U.S. astronauts are on another spacewalk to finish bolting a massive girder to the international space station. Their task includes wiring a cable to the world's first space railway.
Space shuttle Atlantis crewmen Jerry Ross and Lee Morin are making the second of four spacewalks to complete the attachment of the girder to tripod-like struts on the station's U.S. laboratory.
An alternate team fastened it on one side after the station's crane mounted it Thursday.
It is the centerpiece of a truss that will ultimately span 100 meters to support solar energy panels and cooling radiators for future research laboratories.
The two crewmen are also connecting cables to power a railway flatcar attached to the girder. The rail car will ferry the station's crane across the completed span during future construction efforts.
Jerry Ross, 54, is on his eighth career spacewalk, a U.S. space agency record. He and his 49-year-old partner are affectionately called the shuttle's silver team because they are the first grandfathers to walk in space.