The oil slick threatening the Gulf Coast is throwing a wrench into NASA's plans to transport a new shuttle fuel tank from Louisiana to Florida this week.

Usually towed by one of NASA's solid rocket booster recovery ships, the external tank barge will be pulled from port near New Orleans using commercial tugs Monday at around 9 p.m. EDT.

The external tank is loaded inside the Pegasus barge in Louisiana. Credit: Lockheed Martin

NASA's Freedom Star vessel sailed from Kennedy Space Center to Gulfport, Miss., where it will meet the Pegasus tank barge after it leaves New Orleans.

Lockheed Martin builds shuttle fuel tanks at the Michoud facility just east of New Orleans. Technicians completed manufacturing the tank, called External Tank No. 137, last week and rolled it into the Pegasus barge Saturday.

High winds at Michoud delayed the tank's departure from the weekend, according to Lockheed Martin.

Officials changed the tank shipment plan because the growing oil spill in the Gulf of Mexico blocks the barge's normal deep-water route from Louisiana to the Florida Space Coast.

"Because of the oil spill, the path they would normally take, which is a deep-water path, is not available," said John Shannon, the space shuttle program manager.

The oil spill began April 20 with the explosion of an oil rig off the coast of southeast Louisiana. The U.S. government estimates about 210,000 gallons of crude oil per day are leaking from damaged pipe on the floor of the Gulf of Mexico.

Freedom Star is not equipped to steam into an alternate shallow-water approach to New Orleans, so NASA has procured commercial vessels to tow the barge for the first leg of its 900-mile journey.

"They will use commercial tugs to deliver the barge through shallow water to meet up with Freedom Star," Shannon said.

The barge is scheduled to rendezvous with Freedom Star Tuesday morning, allowing the towboat to begin tugging Pegasus in daylight.

Shuttle fuel tanks are towed around the southern tip of Florida and up the peninsula's East Coast to the Kennedy Space Center, where the tanks are offloaded and moved inside the Vehicle Assembly Building.

The external tank measures 154 feet long and nearly 28 feet diameter. The tanks are covered in burnt orange foam insulation because it holds super-cold liquid hydrogen and liquid oxygen propellants.

The European Space Agency's Envisat satellite took this image of the Gulf of Mexico oil spill with a radar instrument on Sunday. Credit: ESA

ET-137 will be used by the shuttle Discovery on its final scheduled flight in September. The tank would also fly on a rescue mission for Atlantis' upcoming voyage to the International Space Station, if necessary.

Endeavour's last flight, which was scheduled for July, was originally supposed to use ET-137. But last week's delay of the Endeavour mission to November will trigger a swap of external tanks and solid rocket boosters for the shuttle program's final two flights, according to Shannon.

Stacking of the solid rocket boosters for Discovery's flight should begin this week.

If the tank barge leaves Michoud Monday night, the ship should arrive at KSC around May 9.

Discovery's launch is slated for Sept. 16 to carry a modified Italian-built cargo module to be permanently installed on the space station.

Endeavour's STS-134 mission, currently the final scheduled shuttle flight, will launch no earlier than November with another set of supplies and an international cosmic physics experiment.

The final external tank scheduled to launch, ET-138, will be finished and ready for shipment next month, according to Lockheed Martin. Another tank will be completed and shipped to Florida to fly on a potential rescue flight for the last shuttle mission, but it is not currently slated to launch.