Last Wednesday, after a full day of testing, the outer skin on one of the four metal-composite panels on the starboard tank peeled away from the tank's inner structure. The failure was similar to a problem that surfaced last December when one of the tank's metal skins came off while being "bonded" with high heat to the rest of the tank. Last week's problem occurred when the tank was extremely cold.

Test crews noticed last week's setback while testing both the pressure and the load-bearing ability of the tank. As technicians drained the tank of liquid hydrogen, a fuel that must be kept at 423 degrees below zero Fahrenheit, frost naturally formed on the tank's surface.

"Most of the crew had gone home for the evening," the Lockheed spokesman said. "As they were collecting data, one of the technicians saw frost shaking off the tank and falling to the ground."

The technicians searched the tank area with remote-controlled video cameras and discovered damage to "lobe skin one" -- the upper-left panel of the hydrogen tank.

"I think it's logical that there will be a delay, but how long a delay is yet to be determined," the spokesman said on condition of anonymity.

NASA headquarters had no official comment on the tank failure's impact on the program. Administrator Dan Goldin has asked the test failure investigation team at Marshall Space Center in Alabama for a "recovery plan," NASA spokesman Jim Cast said.

A report by the General Accounting Office, the investigative arm of Congress, said the delays are costing the federal government. The government's share of the cost is fixed in its agreement with Lockheed-Martin.

Starting Tuesday, a joint Lockheed-NASA team will begin their investigation by erecting a scaffold around the tank to avoid further damage.