Air Lock Installed During Spacewalk

Two astronauts floated out of space shuttle Atlantis late Saturday to install a $164-million passageway for spacewalkers on the international space station.

Michael Gernhardt and James Reilly II got started an hour late on their spacewalk, which followed a successful dress rehearsal of the big event. “There we go,” Gernhardt said, popping open the hatch. “Coming out.”

Everyone in orbit and Mission Control were relieved to see the space station robot arm step through all its paces earlier in the day without any of the problems exhibited in recent months. The dry run, conducted soon after the two spacecraft docked late Friday night, cleared the way for Saturday night’s lengthy spacewalk to hook up the new air lock.

Paul Hill, the lead flight director, expected space station Alpha’s arm to work “just fine.”

“I have almost no doubt--I hate to say I have no doubt just because flying in space is kind of a tricky business,” Hill said. “But we haven’t really left any stone unturned.”

Atlantis carried up the 6 1/2-ton air lock in its cargo bay. Because the shuttle’s 50-foot robot arm cannot reach the attachment point on the international space station, the station’s 58-foot robot arm was assigned the lifting.

The Canadian-built station arm had a variety of start-up problems after it was installed during the last shuttle flight in April. Hundreds of engineers in the United States and Canada spent weeks trying to understand and solve the difficulties. A bad computer card was to blame for the most serious and persistent trouble, involving the shoulder joint, and ended up delaying Atlantis’ flight one month.

Space station astronaut Susan Helms operated the station robot arm during Saturday morning’s dry run and again Saturday night for the real event, while shuttle astronaut Janet Kavandi steered Atlantis’ robot arm, needed to transport the spacewalkers around the complex.

The dress rehearsal was crucial given that the eight space travelers had not worked together since early this year. (The three station residents have been in orbit since March.)

Three spacewalks are planned during Atlantis’ weeklong visit. The second and third outings, on Tuesday and Thursday night, will feature the attachment of four high-pressure gas tanks to the air lock.

The air lock, a two-room chamber, will enable Americans living aboard the space station to wear their own spacewalking suits.