CAPE CANAVERAL, Fla. -- The first railway in outer space was ready to roll on Sunday after astronauts from the space shuttle Atlantis prepped it for its inaugural run, reports a wire service.

The rail car, installed outside the International Space Station on the crew's first spacewalk, will have a top speed of just one inch per second. And ground controllers said they may not open it up all the way in their first test on Monday.

The rail car is part of the 44-foot-long S-Zero truss, the centerpiece of what is to be a 360-foot girder that will support an acre of solar panels generating power for use throughout the space station.

In a spacewalk lasting more than six hours, astronauts Steve Smith and Rex Walheim, the same team that mounted the new truss segment onto the station on Thursday, released launch restraints on the rail car, which rode to space in the shuttle's cargo bay.

NASA said the Mobile Transporter, as the rail car is officially known, was ready for its first test on Monday.

“As far as speed in concerned, it's probably going to be in the fractions of an inch velocity -- on the order of a tenth of an inch per second,” Ben Sellari, the launch package manager at Mission Control, said of Monday's test speeds.

The small trolley is designed to roll the station's giant robotic arm from one construction site to another as work progresses on the station over the next several years.

The Big Arm, as it is known, is 58-feet long and able to heft entire station modules out of shuttle cargo bays.

The two spacewalkers also rewired the Big Arm so it could draw power through the S-Zero truss.

Eight more truss segments will be added on future missions. And a handcar will be added to the rail system so astronauts can move more easily along the truss, which will be longer than a football field.

It was night as the astronauts began their work outside the station.

“Where are we in the world right now, Lee?” Smith asked Lee Morin, part of a spacewalking team with Jerry Ross that alternates with Smith and Walheim.

“Just passing over the northern coast of Australia,” Morin replied from the shuttle's flight deck.

Later, with the sunlit Earth looming beneath him, Walheim said, “Beautiful place we live.”