In late December, the space shuttle Discovery trundled from the launch pad back to NASA's Vehicle Assembly Building at the Kennedy Space Center in Florida amid tests and inspections after cracks were found in its massive external fuel tank--the big orange cylinder to which the shuttle clings. Just this week, engineers at the space agency said they believe they've determined what caused the cracks, and space shuttle management gave the go-ahead for repairs. ?
?The goal is to get Discovery ready for a launch now set for February 24, on a mission to the International Space Station. The shuttle has been delayed since an initial expected launch date in the latter half of 2010.