CAPE CANAVERAL, Fla. -- The International Space Stations first full-time tenants brushed off NASAs latest shuttle launch slip Tuesday, saying they are prepared for a long haul aboard the orbiting outpost.

Flying high above Earth now for 75 days, U.S. astronaut Bill Shepherd and two Russian cosmonauts -- Yuri Gidzenko and Sergei Krikalev -- had planned to roll out the welcome mat this week for a visiting crew aboard shuttle Atlantis.

This view shows two of the critical attach points between the solid rocket boosters and the external tank. Click on the NASA image to see an expanded view showing workers about to mate Discovery to the shuttle stack.

The 18-story shuttle and its four-man, one-woman crew had been slated to blast off Friday on a mission to deliver the $1.38 billion U.S. Destiny lab -- which will be the stations first science research facility -- to the growing complex.

Those plans, however, were dashed late Monday when new concerns cropped up with a critical shuttle rocket booster-separation system, prompting NASA managers to delay the Atlantis launch until Feb. 6 at the earliest.

The Atlantis postponement, meanwhile, likely will delay by at least a few days Shepherd and companys return to Earth, which already had been pushed back two weeks to March 14 so technicians could fix faulty jet thrusters on their ride home: Space Shuttle Discovery.

Shepherd, however, took the news in stride.

"Just pass on to the Atlantis crew that it doesnt matter if they launch the lab this week, this month or this year," the station commander told fellow astronaut Dan Burbank during a radio chat with flight controllers in NASAs Mission Control Center in Houston. "We are in space to stay."

"Okay, well pass that along," Burbank replied. "Im sure theyll be anxious to get up and see you, though."

Led by veteran astronaut Ken Cockrell, the Atlantis crew was set to fly to Kennedy Space Center (KSC) Monday evening for the planned start-up early Tuesday of a three-day launch countdown.

Senior shuttle program managers, however, cancelled both the flight and the countdown after engineers discovered a quartet of faulty rocket booster-separation system cables during weekend inventory inspections.

Extensive examinations of thousands of separation system cables both at KSC and at shuttle manufacturing plants were ordered after a serious glitch cropped up during the Nov. 30 launch of Endeavour on a station construction mission.

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On that flight, a pyrotechnic cable designed to separate the shuttles 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, Endeavour and its five-man crew likely would have been lost in a Challenger-like explosion.

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The close call on the Endeavour flight prompted extensive inspections on separation system cables hooked up to Atlantis twin solid-fuel rocket boosters, delaying a planned mid-December move to the launch pad. Atlantis ultimately was given a clean bill of health and rolled out to KSCs launch pad 39A on Jan. 3.

New concerns cropped up Saturday when spare cables from NASAs fleetwide inventory failed tests designed to simulate the ability to relay crucial computer commands when separation system cables are subjected to launch vibrations.

The suspect cables already had passed X-ray examinations, but signal transmissions were intermittent during weekend "wiggle tests," raising new concerns about the integrity of Atlantis separation system.

The Atlantis cables also underwent X-ray examinations but were not put though "wiggle tests," KSC spokesman George Diller said.

Atlantis, as a result, will be moved back to KSCs Vehicle Assembly Building Friday so that additional inspections -- which cannot be done at the launch pad -- can be performed on the shuttles separation system cabling.

The 16-ton Destiny lab will be removed from the shuttles cargo bay Thursday and stored at the pad. Additional inspections and "wiggle tests" will be performed on the Atlantis cables Saturday, Sunday and next Monday, Jan. 22.

As it stands now, Atlantis is to be moved back to the launch pad Jan. 25 for launch on Feb. 6.

Considered crucial to NASAs $60 billion station construction project, 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.

NASA has no replacement for the lab, and an identical copy would take 2.5 years to build. Whats more, an intricately orchestrated station construction project would screech to a halt if Destiny were lost in a launch accident.