CAPE CANAVERAL, Fla. -- Two astronauts of the shuttle Atlantis zipped around the spacecraft's bay for the second day in a row yesterday, testing possible equipment and techniques for construction of an orbiting space station later this decade.
It looked more like play than work during the six-hour spacewalk. Taking turns, the astronauts glided back and forth on a cart running on a monorail along one side of the shuttle's 60-foot-long cargo bay.
They were trying out different manual, mechanical and electrical prototype systems for scooting about safely and efficiently in weightlessness.
Several times, the two astronauts worked hand pedals to generate electricity for a motor driving the cart, as if they were riding a bicycle upside down in an ethereal high-wire act.
"Boy, this thing glides slick, it really does," Dr. Jerome Apt, one of the spacewalkers, exclaimed as he rode the rail.
Lt. Col. Jerry L. Ross of the Air Force agreed, saying, "This is the way to travel around the world."
Space agency officials said the spacewalk should provide valuable data for developing equipment for use by builders of the $30 billion Freedom space station, which the United States plans to assemble in orbit later this decade.
"What we are seeing today may be the ancestors of what we will see on Freedom," said Kari Fluegel, the NASA commentator at Mission Control.
On Sunday, the astronauts ventured into the open cargo bay to make an emergency repair that allowed deployment of the Gamma Ray Observatory, the shuttle's principal payload.
Controllers at the Goddard Space Flight Center in Greenbelt, which is directing the observatory's mission, said that the 17-ton, $600 million satellite was traveling in an orbit ranging from a high altitude of 287 miles to a low of 280 miles.
They said the satellite's main antenna, solar-power panels and navigation systems were functioning normally. It should be at least a month before the observatory begins regular operations.
Astronomers are looking to the observatory to conduct the first comprehensive survey of the sky to map the sources of the high-energy gamma rays. The rays are believed to carry clues to some of the most violent phenomena in the universe, such as exploding stars.
The flight of Atlantis is scheduled to end tomorrow morning with a landing at Edwards Air Force Base in California.