Engineers designing the new U.S. moon rocket said Thursday they plan to cover part of it with the same type of foam that doomed Columbia and has been a problem throughout the space shuttle program.

The dense, brittle foam will likely fall off the new rocket just like it has from the shuttle's external fuel tank, they said. But NASA doesn't expect it to pose any safety concerns.

Used as insulation for tanks that hold super-cold rocket fuels, foam has been falling off the shuttle's huge, orange tank since the earliest flights.

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A piece of foam the size of a briefcase hit one of Columbia's wings during liftoff in 2003, causing a hole that resulted in the orbiter burning up on re-entry and killing seven astronauts. Foam also came off during the subsequent flight of Discovery.

Part of the new manned rocket, called Ares I, will include a section similar to the shuttle's external tank. So it, too, needs the foam, according to upper stage project manager Danny Davis.

But unlike with the shuttle, astronauts will ride in a six-person capsule that sits atop the rocket. That means any falling foam won't hit the crew compartment, said Don Krupp, chief of the vehicle analysis branch at Marshall Space Flight Center.

"This is a different application," Krupp said. "If we have any foam debris, it falls away from the astronauts. They're ahead of it."

Davis said engineers working on Ares assume that the spacecraft will shed foam.

"But it just won't matter," he said.

Davis and Krupp were among NASA managers who met with reporters during an open house for the media at Marshall, which manages the shuttle's rockets and is designing propulsion systems for the new lunar spacecraft.

Engineers developed the Apollo spacecraft in the 1960s using slide rules and handmade models, but Ares is being designed on computers. Engineers can test their ideas on virtual models, letting them know quickly which designs won't work.

Built in stages, Ares I will be stacked atop a single solid-rocket booster larger than the ones that lift the space shuttle into orbit.

Ares will fly higher and faster than the shuttle during the moments right after launch, making it subject to more stress. But with a cylindrical design, it won't have the shuttle's wings, tail or delicate heat-shielding tiles.

That difference should make the new rocket less susceptible to launch delays because of bad weather at Cape Canaveral, Krupp said.

"We are trying to design this vehicle to fly in any weather," he said. "Our goal is to not let weather constrain our launch window."

The Ares rocket will include concepts used in both the Apollo and shuttle programs, but Krupp said every piece that goes into the new spacecraft will be tested as if it were brand new.

"I do not want to have another Challenger or Columbia on my watch. We do not want to lose another astronaut," he said.