pound (760-gram) piece of foam that broke free from an external fuel tank at launch. The foam pierced a hole in the ship's left wing and as the spacecraft re-entered the Earth's atmosphere, searing gases melted the wing from the inside, causing the ship to break apart. All seven astronauts aboard were killed. NASA officials' excitement over Discovery's return to space was dampened by video that showed a nearly 1-pound (400-gram) chunk of foam _ reminiscent of the one that doomed Columbia _ breaking free from Discovery's external tank shortly after liftoff. The foam did not strike Discovery. The agency quickly grounded future flights, saying that more work must be done, despite spending hundreds of millions of dollars to redesign the tank. Despite the setback, NASA says Discovery's flight has taught important lessons and overall been an «incredible» success. «We've shown that we've been able to return the vehicle back to safe operational flight,» astronaut Andrew Thomas said Sunday aboard Discovery. «There's a lot of success that goes with this mission that I think is going to be important for the long-term future and well-being of this flight program.»
