Cape Canavarel, Fla. ? Denying that it is yielding to “go fever,” NASA still plans a Fourth of July launch of shuttle Discovery despite the reappearance of the same type of problem that doomed Columbia – defects in the fuel tank’s insulation.

Bill Gerstenmaier, the agency’s associate administrator for space operations, said engineers concluded that a crack in the foam insulation and the loss of a tiny piece of foam did not endanger the ship or the seven astronauts who will board it.

“We’re go to continue with the launch countdown,” he said Monday night. “There’s plenty of margin with the remaining foam.”

Liftoff from the Kennedy Space Center remained scheduled for 1:38 p.m. CDT today. Forecasters predicted a 60 percent chance that weather would cooperate.

At the very least, outside experts said, the development suggested that NASA still does not have a complete understanding of the insulation – a critically important component of a space program that is now 25 years old.

John Logsdon, director of the Space Policy Institute at George Washington University, called it “a really intractable problem.”

This photo composite released by NASA on Monday shows where a piece of foam insulation from a strut fell off where it attaches to the external fuel tank of the space shuttle Discovery at the Kennedy Space Center in Cape Canaveral, Fla.

“Nobody has come up with a way of avoiding this yet,” he said. “And it certainly is not from inattention. For over three years now, foam shedding has been a focus of very intense scrutiny.”

NASA engineers conceded the point and said they will continue studying the issue. “We want to make sure we understand all the considerations that caused this,” said John Chapman, the agency’s shuttle tank manager.

Ominous sign

The latest problem appeared in the insulating foam covering a bracket that holds a fuel line to the huge external fuel tank.

The crack is four to five inches long and an eighth of an inch to a quarter of an inch wide, NASA said.

In addition, a 3-inch-long, triangular-shaped scrap of insulation fell off the tank, according to John Shannon, the shuttle program’s deputy manager. He said it weighed .0057 pounds.

That might seem ominous, given the shuttle fleet’s recent history, but Shannon said it probably was not.

“It is less than half the size that can cause damage,” Shannon said.

Three years ago, a 1.67-pound chunk of foam peeled off Columbia’s external tank and punched a hole in that shuttle’s left wing.

As Columbia returned to Earth at the end of its mission, hot atmospheric gases penetrated the spaceship and caused it to disintegrate, killing all seven astronauts aboard.

Despite more than $1 billion in modifications, smaller pieces of foam also struck Discovery last July during NASA’s first post-Columbia shuttle launch.

Engineers went back to the drawing board, but they predicted that the tank would continue to shed very small – and harmless – pieces of foam.

NASA Associate Administrator Bill Gerstenmaier holds up the piece of foam that fell from the space shuttle Discovery at the Kennedy Space Center in Cape Canaveral, Fla., Monday. NASA officials have rescheduled the launch for today.

No ‘go fever’

Shannon bristled during a Monday afternoon news conference when a reporter mentioned the term “go fever,” a phenomenon that some worry could encourage enthusiastic managers to authorize a launch against their better judgment.

He said NASA engineers were applying proven analytical techniques to resolve any concerns.

Still, the bracket in question is in a particularly sensitive spot, about one-third of the way down the tank and facing the orbiter itself. That would enhance the possibility of damage to the airplane-like component that carries the crew.

The tanks are manufactured by Lockheed Martin at the company’s Michoud facility near New Orleans. Company officials issued only terse comments Monday.

“We will be supporting them to fly as safely and as soon as we can,” said Marion LaNasa, a Lockheed Martin spokesman.

NASA technicians discovered the flaws Sunday night, during a routine inspection following two weather-related launch postponements over the weekend.

Shannon said the defects might have been caused by the double-barreled filling and emptying of the tank over the weekend, a process that causes the tank to flex.

The delays cost NASA about $2 million in overtime pay and fuel costs.