CAPE CANAVERAL, Fla. -- Shuttle Atlantis crept up onto its Kennedy Space Center launch pad Thursday, paving the way for the stalled construction of the International Space Station to start-up again in mid-July.
Outfitted with a 15-story external tank and twin solid rocket boosters, the $2 billion spaceship arrived at launch pad 39B about 10 a.m. EDT (1400 GMT) after an overnight move from KSC's 52-story Vehicle Assembly Building.
Delayed two weeks due to problems with the station's new robot arm -- and then again Wednesday by a Central Florida lightning storm -- the trip out to the pad set the stage for a three-week push toward launch of the next major component of the frontier outpost.
"The schedule looks pretty good," said KSC spokesman Joel Wells. "We have a couple of extra days in the (work schedule) and we're continuing to press forward."
Atlantis and a crew of five astronauts are scheduled to launch at 5:04 a.m. EDT (0904 GMT) July 12 on a mission to deliver a $164 million airlock to the station.
Now scheduled to be loaded into the shuttle's cargo bay next week, the 6.5-ton airlock will serve as a staging area for spacewalking work to be conducted outside the outpost.
Fleeting problems with the shoulder joint of the station's new $600 million Canadian robot arm prompted NASA managers earlier this month to postpone the Atlantis move and consider a launch delay until September.Delivered to the station in April, the 57.7-foot (15.5-meter) robot arm is required to mount the airlock to the starboard side of the outpost's U.S. Unity Module.
Shorter shuttle robot arms are not long enough to do that job. Consequently, any problem with the station arm could leave the airlock stranded at the end of the crane during its installation.
The shoulder joint problems cropped up during tests in May and early June, delaying scheduled station assembly activities for the first time since last summer.
A half dozen station construction missions were launched aboard shuttles between July 2000 and this past April. Five Russian re-supply missions and the first two resident station crews also were launched during that time, and a fresh lifeboat was delivered to the complex.
Engineers earlier this week traced the arm problem to a suspect computer chip in an electronic unit that enables its shoulder to maneuver. A software patch designed to bypass the chip and allow the arm to operate as intended is to be beamed up to the station next week.
A dress rehearsal for the airlock installation job was under way aboard the station as Atlantis made its way to the pad. The test called for astronauts Susan Helms and Jim Voss to put the arm through the same maneuvers that will be required to install the airlock.
An initial dry run was conducted last Thursday and the arm's shoulder joint worked without problems during that test.
Countdown to the Atlantis flight is scheduled to pick up July 9 and an on-time launch would lead to a July 23 landing here at NASA's coastal Florida spaceport.
Shuttle Discovery, meanwhile, remains scheduled to launch Aug. 5 on a mission to ferry a new crew to the station and return to Earth with Helms, Voss and outpost commander Yuri Usachev.
Discovery is scheduled to roll out to KSC's launch pad 39A next Wednesday.
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