A new external tank arrived this morning at Port Canaveral, positioning NASA managers for a decision that will determine whether shuttle Atlantis is slated to launch in May or June.

The 154-foot-long tank now is scheduled to fly with the orbiter Endeavour on an International Space Station assembly mission later this year.

But managers might decide during a meeting next Tuesday to use it to replace shuttle Atlantis' tank, which sustained significant damage during a Feb. 26 hail storm. The launch of Atlantis then would be delayed until mid-June.

The other option would be to continue repairs to the damaged tank, a course of action that would enable NASA to try to launch Atlantis prior to a May 21 deadline.

"That's certainly not out of the realm of possibility," said Kyle Herring, a spokesman for NASA's Johnson Space Center in Houston. "The desire is to stay on that tank."

In any case, NASA managers have decided to remove Atlantis' three main engines so engineers can inspect propellant lines within the orbiter. Four small pieces of silicon rubber recently were found in lines on Discovery, and managers want to make certain there are no contaminants in Atlantis' lines.

NASA uses the silicon material before and after flights to make impressions of any small blemishes or cracks within the propellant lines. Engineers then can determine whether any minor defect enlarges.

Debris in a propellant line could degrade engine performance or, in a worst case, lead to a catastrophic failure in flight.

The new tank arrived at Port Canaveral after a 850-mile trip from the Michoud Assembly Facility in New Orleans.

Mounted on a wheeled transport platform, the tank was rolled onto the 225-foot-long barge from a test and assembly facility last Sunday. The barge departed the factory the next day under tow from the NASA Solid Rocket Booster retrieval ship Freedom Star.

The trip took the ship and the barge down the Mississippi River Delta, out into the Gulf of Mexico and then around the southern tip of Florida. With the barge trailing about a quarter-mile behind it, the ship then hugged the east coast of Florida, entered the locks at Port Canaveral and made its way up the Banana River toward the turn basin just east of the Kennedy Space Center Vehicle Assembly Building.

NASA had planned to launch Atlantis and six astronauts on March 15, but its tank was peppered with hail the size of golf balls during a brief-but-violent thunderstorm. The agency is facing a May 21 deadline to get the shuttle off the ground.

Atlantis can't launch between that date and June 8 because sun angles will be such that the station's solar wings would not be able to generate enough electricity to support joint operations with a visiting shuttle.

A switch to the new tank would delay launch until around June 16 or June 17.

• NASA: Some Atlantis Shuttle Fuel Tank Repairs Complete, New Vessel Due Friday
• NASA Delays Shuttle Launch Date Decision to April
• NASA Eyes Fuel Tank Damage for March Shuttle Launch

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