Two teams of astronauts installed a new entryway on the international space station Sunday, then swung open the hatch with a ceremonial flourish and floated inside.
Applause erupted in Mission Control as the commanders of the shuttle Atlantis and space station Alpha cut a white paper ribbon stretching across the inner threshold of the $164-million air lock for spacewalks, named Quest.
To NASA's relief, the space station's robot arm worked well during its first construction job, exhibiting none of the problems that temporarily crippled it after its own installation three months ago and delayed Atlantis' flight.
Space station astronaut Susan Helms used the 58-foot mechanical arm to lift the 6 1/2-ton air lock from Atlantis' cargo bay and attach it to the space station. Spacewalking shuttle astronauts Michael Gernhardt and James Reilly II helped her line it up for a perfect fit.
Lead flight director Paul Hill was thrilled with Helms' crane-operating skills and the performance of Canada's billion-dollar arm.
"We made history today," Hill said. "The international space station reached into the Atlantis payload bay using its own arm and pulled a cargo element out and installed it and voila! Station now has a brand new module."
It marked the end of a major phase of assembly for the 2 1/2-year-old space station and the start of a whole new spacewalking era.
Once oxygen and nitrogen tanks are attached to the air lock later this week, Americans living aboard the space station will be able to go out on spacewalks at any time wearing their own suits. And once Russian hoses and other gear arrive this fall, residents will be able to leave the air lock in Russian suits too.
Until now, U.S. station occupants have had to rely on Russian spacewalking suits and a Russian exit. NASA's suits are incompatible with Russian station systems.
Gernhardt and Reilly spent six hours on the first of three spacewalks planned for this mission. They removed covers from the air lock, then waited at a distance while Helms hoisted the chamber.
As soon as the air lock was bolted in place, the spacewalkers hooked up its electrical supply.
The aluminum air lock, 18 feet long and 13 feet in diameter at the widest point, added a fifth room to the space station, or a fifth and sixth, counting both compartments.