The BBC reports that NASA is investigating two cases of apparent debris seen falling from the space shuttle Discovery as it blasted off:
In one case, a heat shield tile seems to have been affected on the underside of the shuttle.
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John Shannon, STS-114 mission operations representative, pointed out video frames apparently showing a piece of heat shield tile breaking off from the underside of the shuttle.
This has left a one-and-a-half inch white spot near the nose landing gear doors.
"We're very interested in that," he told reporters, "that's something we're going to get better pictures of on flight day three."
Mr Shannon said it could simply be that part of the black covering on the orbiter's underside was damaged exposing the heat shield tile.
But he added that it was equally possible the tile itself had been dented or sheared.
The missions operations representative also showed journalists video footage of a dark object falling from the external tank.
Experts cannot yet determine its size, but it did not appear to hit the shuttle, they said.
California Yankee first posted about the debris, including a picture, in the update to this post.
UPDATE: The New York Times offers some perspective about Discovery's possible debris damage:
The more NASA looks for damage, engineers and other experts say, the more it will find. And the risks of overreaction to signs of damage while the shuttle is in orbit may be just as great as the risks of playing them down.
"How do you distinguish - discriminate - between damage which is critical and damage which is inconsequential?" asked Dr. David Wolf, an astronaut who spent four months aboard the Russian space station Mir. "We could be faced with very difficult decisions, in part because of all this additional information that we will be presented with."
The shuttle program has lived with damage from debris from the very first flight, in 1981; in 113 missions the orbiters have been hit by debris some 15,000 times, mostly on liftoff. The National Aeronautics and Space Administration replaces about 100 insulating tiles after every flight and repairs many more than that, Stephanie S. Stilson, the vehicle manager for Discovery, said Monday.
Now, though, it will be far easier to spot such damage while the shuttle is still in orbit. Thanks to a $15 million laser camera system developed by a Canadian company, Neptec, for example, NASA can detect a crack of just two-hundredths of an inch, the width of two business cards pressed together. On the leading edge of the orbiter's wing, such a crack could admit dangerous amounts of superheated gas during re-entry. A similar crack elsewhere might not.
It was a large hole in the left wing's leading edge, caused by impact with a 1.67-pound piece of insulating foam during the launching, that led to the Columbia disaster.
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The intense scrutiny of the Discovery's mission is an effort to make up for decades of ignorance. Until the Columbia accident, NASA officials generally believed that something as light as insulating foam could not harm the shuttle. The disaster sent the space agency into a two-year struggle to learn just how fragile the craft's thermal protection system is and how to detect damage to it.