Nasa will attempt to launch space shuttle Discovery next week following a four-month delay.
Discovery’s final lift-off is set for Thursday afternoon, with senior managers voting unanimously on the new launch date.
Discovery has been grounded since the beginning of November. Cracks in the external fuel tank were discovered following a launch attempt that was foiled by leaking hydrogen gas.
Discovery will carry six astronauts and a humanoid robot, along with a full load of supplies, to the International Space Station. One of the human crew is a substitute, replacing an astronaut who was injured last month in a bicycle crash.
NASA opted for a Thursday lift-off, even though a European cargo vessel will be docking at the space station that morning. Officials normally prefer more time between arriving spacecraft, but they want to get Discovery flying as soon as possible given its lengthy delay.
The shuttle launch will be put off if anything goes wrong with the docking of the European freighter.
As for the cracks in Discovery’s external fuel tank, engineers traced the problem to inferior material combined with assembly issues. The cracking was confined to some of the aluminium alloy struts in the centre of the tank, which holds instruments but no fuel. The damaged struts were patched, and the others reinforced as a precaution.
Nasa feared that the underlying cracks could have caused foam insulation to break off the tank and slam into Discovery, as it did during Columbia’s doomed mission in 2003.
Another problem cropped up last week: A measuring gauge broke at the launch pad, and one of the falling pieces gouged a tiny slit in the fuel tank foam. No repairs were necessary because of the location on the bottom back side of the tank.
This will represent the end of Discovery’s flying career. Nasa is retiring the three remaining shuttles this year, leaving orbital trips to private companies so it can focus on interplanetary travel. Until the private sector can take over crew transportation, Nasa will have to pay millions of dollars to Russia for astronaut trips to and from the space station.