Discovery set for final countdown

US space shuttle Discovery is poised to make its last flight.

The launch countdown is in its final hours, with fuelling set to begin, and this time Nasa is confident that no hydrogen gas will leak and no cracks will develop in the fuel tank.

Both those problems cropped up during the initial countdown in November, with repairs taking almost four months to complete.

Discovery will head to the International Space Station with a crew of six, as well as supplies and a humanoid robot.

This will be the 39th flight for Nasa’s oldest surviving shuttle. Discovery first blasted off in 1984 and has since logged 143 million miles.

Nasa expects 40,000 guests in Florida to watch Discovery’s farewell launch.