Shuttle deemed safe to launch

Nasa has given the space shuttle Discovery permission to launch.

The decision was taken after cracks were found on a spare part similar to some on board the craft.

The on-board components have been ruled safe.

Engineers say there is no risk to the craft or its crew.

At one point, officials were considering replacing the hydraulic power units on the left-hand solid rocket booster as a precaution.

Engineers are now confident the on-board units, responsible for steering the rockets after lift-off, are crack-free, reports Spaceflight Now.

Countdown to Thursday's planned launch is now underway. Blast-off is scheduled to take place just after 10.30pm Irish time.

The main aim of the mission is to take a replacement crew to the International Space Station and bring the current team home.