NASA halts shuttle flights over tank foam problem

HOUSTON (Reuters) - NASA grounded its space shuttle fleet on Wednesday after learning that large chunks of insulating foam broke off Discovery's external fuel tank during launch, an echo of the problem that doomed sister ship Columbia and its crew 2 1/2 years ago. 

The seven Discovery astronauts were not in danger and the falling debris does not appear to have hit or damaged their ship, which took off on Tuesday on a 12-day mission to the International Space Station, deputy shuttle program manager Wayne Hale said.