NASA is grounding the U.S. space shuttle fleet after a large piece of insulating foam broke off from the fuel tank of the Discovery during Tuesday's launch. A similar malfunction was responsible for the disaster of the space shuttle Columbia in February 2003, which put America's manned space flight program on hold for 2 1/2 years, until this week's Discovery mission.

Cameras captured the image of a sizable chunk of insulating foam as it fell away from Discovery's hydrogen fuel tank during lift off on Tuesday.

The insulation is designed to protect the orbiter from excessive heat upon reentering the earth's atmosphere.

In 2003 during the ill-fated Columbia mission, a protective heat tile flew off and struck the shuttle during lift off. That caused a breach in the orbiter that led to the disintegration the space shuttle as it attempted to land killing all seven Astronauts on board.

Mission managers say at this point, it doesn't appear the insulating foam damaged Discovery in any way. However, some of the images appear to show that the flying debris may have caused at least one divot, or pit, in another tile.

"Until we're ready, we won't go fly again. Now, I don't know when that might be. So, I'll just state that right up front. We're just in the beginning of this process of understanding. This is a test flight," said Bill Parsons, manager of the space shuttle program.

Mission controllers say high-resolution cameras aboard the International Space Station will take pictures of the underside of the Discovery as it nears the outpost for docking on Thursday. The images should give engineers on the ground a closer look at any potential damage to the heat tiles, according to mission deputy manager Wayne Hale.

"Are we concerned about this? We are treating it very seriously. Are we losing any sleep over it? Not yet," he said.

Mr. Hale says NASA officials will spend the next few days coming up with a plan either to have the astronauts try to repair the heat tiles, or to return to Earth with things the way they are.