The enormous crawler-transporter vehicle has been tested in case it’s needed to move the space shuttle indoors, and crews have made room inside the Vehicle Assembly Building to accommodate Atlantis if needed.

Preparations were under way to move the space shuttle out of the way of Tropical Storm Ernesto, but NASA was waiting until early yesterday before making a final call on whether to move Atlantis indoors or try to launch today. There was a 30 percent chance that weather would prohibit a launch today, and the forecast worsened as the week progressed.

Moving Atlantis back to the Vehicle Assembly Building would challenge NASA’s ability to launch Atlantis before a September 7 deadline. The space agency wants to launch before then so the shuttle’s visit to the international space station doesn’t interfere with the trip of a Russian Soyuz in mid-September. But NASA doesn’t want the shuttle on the launch pad if winds are greater than 45 mph. Crews need two days to safely move the shuttle, and weather forecasters predicted the storm could be anywhere from the eastern Gulf near the Florida panhandle to the western Bahamas by tomorrow.

It would take at least nine or 10 days to move Atlantis from the launch pad to Vehicle Assembly Building and back to the pad and then launch, even though the fastest time NASA has done something like that is 11 days in 1999.

Liftoff originally had been set for Sunday afternoon, but it was delayed until today to give engineers more time to figure out if a lightning strike Friday damaged the spacecraft’s solid fuel rocket boosters and other systems. NASA cleared the solid rocket booster system for launch late Sunday. The launch window for this mission only goes through September 13 because 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. The shuttle Columbia was doomed after foam hit a wing, causing a breach that allowed hot gases to penetrate during its return to Earth.

NASA hoped to launch Atlantis before September 7 to prevent a traffic jam at the space station since a Russian Soyuz vehicle is set to blast off in mid-September carrying two new station crew members and a space tourist. If NASA launches later, it will have to persuade the Russians to change their launch date and land at night – something the Russians do not want to do because they have a new private firm handling capsule recovery.