With Tropical Storm Ernesto breathing down their necks, NASA managers gave up on a Tuesday space shuttle launch and prepared to move Atlantis indoors.

The National Hurricane Center's late Monday morning forecast put Ernesto's track on or just slight east of Kennedy Space Center late Wednesday or early Thursday. The center listed a 60 percent chance of tropical storm force winds just south of the cape.

"We're even more concerned about Ernesto now," Kathy Winters, shuttle weather officer, said Monday morning.

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Unless the storm changes course, NASA aims to start moving Atlantis back to the Vehicle Assembly Building Tuesday morning, said Mike Leinbach, shuttle launch director.

The move would mean a minimum delay of eight days once Atlantis could be rolled back out to the pad. If NASA can avoid moving the shuttle, Atlantis could launch this weekend.

"It's clear in our minds that we're rolling back per plan unless something really extraordinary happens," Leinbach said.

Mission Control informed astronaut Jeff Williams, floating 220 miles above Earth, about the delay in the launch of the six visitors to his home at the international space station.

"Sounds like everyone's got a lot of replanning to do," Williams said. "We're flexible."

NASA is caught between two competing interests: a tight launch schedule to get Atlantis into orbit and a need to avoid storm damage to the multibillion-dollar shuttle. NASA rules say the shuttle should not be outside in winds of more than 45 mph. Tropical storms have sustained winds of at least 39 mph.

It takes nearly two days of preparations to get Atlantis from the launch pad into its massive Vehicle Assembly Building.

The first step was the delicate removal of Atlantis' fuel. After that, NASA removes the explosive devices on the shuttle, its external fuel tank and twin rocket boosters. The slow-moving crawlers take nine hours to get the shuttle safely indoors.

Moving Atlantis off the pad would put the space agency in a time crunch, and a delay of Atlantis' launch could threaten the space agency's short-term goal of finishing construction of the international space station and its long-term goal of returning people to the moon, space experts say.

NASA wants to launch by Sept. 7 so the shuttle's visit to the international space station doesn't interfere with the trip of a Russian Soyuz in mid-September, but a shuttle rollback would make that impossible, said mission management team chairman LeRoy Cain.

The launch window for the mission is also tight, running only through Sept. 13. NASA wants to launch the shuttle to the space station during daylight so it can photograph the shuttle's external fuel tank, where insulating foam has fallen off during previous launches, though that requirement could change, Cain said. The shuttle Columbia was doomed after breakaway foam hit a wing.

Liftoff originally was set for Sunday, but it was delayed to give engineers time to figure out if a lightning strike Friday damaged the spacecraft's systems. NASA cleared its solid rocket booster system late Sunday for launch.

Part of the Atlantis mission is to add a key construction truss to the space station. Fourteen later shuttle flights until 2010 — the agency's self-imposed construction deadline — depend on its success.

"This flight has to work for the next flight to occur and the next flight to occur and the next flight to occur," NASA space station program director Mike Suffredini said Friday.

And that means NASA's long-term goal of returning to the moon also depends on Atlantis and subsequent flights getting off somewhere close to on schedule.

"They're in a bad situation," said Syracuse University technology professor W. Henry Lambright. "If any one flight gets pushed back and the time frame gets cramped, that raises risk ... That's the bind they're in. It's very tight."

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