Inspectors found no damage to the Space Shuttle Discovery or to its external reserve tanks after a thin multi-piece measuring tool fell during repair work, Nasa said.

The accident has not compromised Discovery’s February 24 mission to the International Space Station, said Allard Beutel, spokesman at the Kennedy Space Centre in Florida.

A feeler gauge – a 13-part metal tool about as thick as a piece of paper held together by a retainer screw – came apart late on Wednesday and fell from the launch pad, Mr Beutel said.

The accident took place as technicians changed a seal at the ground umbilical carrier plate, or GUCP, on the shuttle’s external fuel tank.

“Engineers have identified minor foam damage to the backside of the external tank, which will not need repair. All components from the gauge have been located,” Nasa said in a statement.

The shuttle was initially set to launch on November 5 but the attempt was scrubbed after hydrogen leaks were detected.

Discovery’s 11-day mission with its all-American crew of six is to deliver a pressur-ised logistics module called “Leonardo” to the International Space Station, which will be permanently attached to the space station to provide more storage space.

The three US shuttles – the other two are Atlantis and Endeavour – are due to become museum pieces once the final shuttle mission takes place.

Endeavour is set for take-off on April 19 and Atlantis is scheduled for June 28, after which the famed fleet will be retired.