NASA has found four more cracks in the Discovery shuttle's fuel tank, but says it believes it can repair them in time to launch on February 3 as planned.
An X-ray analysis of the tank showed a further four small cracks on three stringers on panel 6, on the opposite side of the tank from Discovery. They're smaller than those found in panel 2, at between two and a half and four inches long.
The launch was originally scheduled for November 5, but was cancelled at the last minute after a hydrogen fuel leak which was traced to a 21-inch crack in the tank's foam insulation. Further investigation uncovered cracks in the tank's support beams, or stringers.
The new cracks weren't found at the time, as they weren't accessible from the launchpad. But after the rollback of Discovery's STS-133 stack to the Vehicle Assembly Building on December 22, NASA was able to examine all 108 stringers on the outside of the external tank’s intertank section.
NASA managers believe they can repair the new cracks in the same way as those discovered during the November 5 launch attempt. The work should take two or three days, they say, and can be carried out within the Vehicle Assembly Building.
NASA says it still doesn't know what caused the cracks. It's considering installing special splints on the stringers which experience the most stress during fueling and launch.
The next available launch date is Thursday, February 3, with a launch window continuing until February 10. The preferred launch time on February 3 is 1:37 am EST, says NASA.
The 11-day mission will deliver spare parts to the International Space Station, along with a humanoid robot and an external platform to hold large equipment.