NASA says Discovery is now scheduled to take off (1903 UTC) Friday afternoon. Mission managers will meet early Friday to re-evaluate the weather conditions at the site of the launch, Florida’s Kennedy Space Center.
The launch, which was originally scheduled for Monday, has already been delayed by electrical problems and gas leaks.
When the 11-day mission finally begins, the shuttle will carry six American astronauts to the International Space Station, and deliver a final module for the U.S. portion of the orbiting laboratory.
The shuttle will also carry the first humanoid robot into space, Robonaut 2 (R2).
With human-like arms, a powerful-looking torso and a gold-helmet head, R2 looks something like a comic book superhero.
Once aboard the space station, the robot will become a permanent resident, where, initially, it will do little more than hold tools. NASA envisions R2 will eventually assist astronauts during spacewalks.
On its return to Earth, Discovery will be retired along with shuttles Atlantis and Endeavour after a final mission by Endeavour in February. Discovery has completed 38 missions in 26 years. It is the oldest of the three shuttles.
After NASA retires its shuttle fleet, partners in the space station will use Russian and private rockets to send crew and supplies to the orbiting laboratory.
Some information for this report was provided by AP, AFP and Reuters.