CAPE CANAVERAL, Fla. -- Shuttle Atlantis will be rolled back into its assembly building for extra inspections to a critical rocket booster-separation system, delaying launch of the International Space Station's first science lab until early February.
The 18-story shuttle and its four-man, one-woman crew now are tentatively scheduled to launch February 6 on a mission to deliver the U.S. Destiny lab to the outpost, which currently is occupied by U.S. astronaut William Shepherd and two Russian cosmonauts.
The all-important station construction flight had been slated for launch Friday but was postponed after new concerns cropped up with a system whose failure could lead to a catastrophic explosion in flight.
"The system is associated with the separation of the solid rocket boosters, which means that it is a 'Criticality 1' system," said Kennedy Space Center (KSC) spokesman George Diller.
"That means if we have a question about it, we don't launch. And we have a question about it," he added. "We're out of the business of taking avoidable risks."
In NASA parlance, a Criticality 1 system is one whose failure could lead to the loss of a $2 billion shuttle and its astronaut crew.
The Atlantis astronauts had been scheduled to fly to KSC Monday evening, and a three-day countdown had been slated to pick up at 5:45 a.m. EST (10:45 GMT) Tuesday.
Senior shuttle program managers, however, scrapped those plans Monday night after engineers discovered faulty separation system cables during weekend inspections.
Fleetwide inspections of all separation system cables were ordered after a serious glitch cropped up during the November 30 launch of shuttle Endeavour on a station construction mission.
On that flight, a pyrotechnic cable designed to separate the shuttle's left-hand solid-fuel rocket booster from its 15-story external tank failed to fire. A backup worked normally and the booster separated cleanly.
Had that backup failed, however, the shuttle and its five-man crew likely would have been lost in a Challenger-like explosion.
NASA subsequently ordered extensive inspections to the separation system cabling on Atlantis. The inspections forced NASA to delay the shuttle's move from its assembly building to an oceanside launch pad from mid December until early January.
New concerns cropped up over the weekend when four out of several thousand cables from NASA's fleetwide inventory failed so-called "wiggle tests." The tests simulate the ability to relay crucial booster separation signals when the wires are subjected to vibrations.
The suspect cables already had passed X-ray examinations, but signal transmissions were intermittent during the weekend electrical tests, raising new concerns about the integrity of Atlantis' separation system. The Atlantis cables also underwent X-ray examinations but were not put through "wiggle tests," Diller said.
Atlantis, as a result, will be moved from launch pad 39A back to KSC's 52-story Vehicle Assembly Building on Friday. The 16-ton Destiny lab will be removed from the shuttle's cargo bay Thursday and stored in a payload changeout room at the pad.
Additional tests to the separation system cabling on the shuttle's twin solid-fuel rocket boosters will be conducted on Saturday, Sunday and next Monday, January 22. As it stands now, Atlantis is to be moved back to the launch pad January 25 for launch on February 6.
Considered crucial to the $60 billion International Space Station construction project, the Destiny will serve as the nerve center and the scientific heart of the outpost, which is a joint project of space agencies in the U.S., Russia, Europe, Japan, Canada and Brazil.
With no replacement waiting in the wings, an identical copy of $1.38 billion lab would take 2.5 years to build. What's more, an intricately orchestrated station construction project would screech to a halt if Destiny were lost in a launch accident.
Unclear late Monday was whether the delay in the Atlantis flight would have a ripple effect in NASA's shuttle launch schedule.
Discovery is slated to launch March 1 on a mission to ferry a fresh crew up to the international station. The current crew -- which includes Russian cosmonauts Yuri Gidzenko and Sergei Krikalev -- is due to return to Earth March 14.
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