US: The US space shuttle Discovery is poised for launch today for what Nasa engineers hope will be an uneventful mission, knowing that another accident could doom the shuttle programme and deflate ambitions for future space exploration.
The shuttle is flying without the approval of Nasa's top safety officer, who voted "no-go" at the final flight readiness review because of concerns that unacceptably large pieces of foam insulation could break away from the external fuel tank during launch.
The flight is the second since Columbia disintegrated over Texas in February 2003, because of damage caused by insulating foam breaking away from the external fuel tank. Further foam loss during Discovery's first post-Columbia flight last summer prompted Nasa to ground the shuttles again until now.