Space Shuttle Discovery Poised for Final Liftoff

CAPE CANAVERAL, Fla. — Space shuttle Discovery is poised to make its last flight.

The launch countdown is in its final hours, with fueling set to begin shortly after sunrise Thursday.

This time, NASA is confident 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. The repairs took almost four months.

Discovery will head to the International Space Station with a crew of six, as well as a load of 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 on hand in Florida for Discovery's farewell launch.