A cracked hinge in a fuel line door could force NASA to delay the shuttle Discovery's planned March 9 takeoff, but agency officials say they are hopeful the ship can be repaired at the pad and launched on schedule.

In the meantime, engineers at the Kennedy Space Center pressed on with plans to start a two-day practice countdown Tuesday, a major milestone in a shuttle's launch processing.Discovery is tentatively scheduled to take off at 3:49 a.m. EST March 9 to kick off an eight-day "Star Wars" research mission, the first of seven flights on tap in 1991.