NASA said Thursday it has found four more small cracks on the metal supports of the shuttle Discovery's external fuel tank, as the aging shuttle undergoes X-ray testing before its final space mission next year.
Repairs would be made to the cracks in a similar fashion to the cracks discovered after the November 5 launch attempt, the National Aeronautics and Space Administration said in a statement.
The space agency said it was still too early to determine if the new cracks will delay the Discovery's February launch with six astronauts to the orbiting International Space Station.
Repairs of the newly discovered cracks will take an estimated two to three days, NASA said.
"Any further work will be evaluated thoroughly early next week after additional data is reviewed," it added.
The Discovery has been plagued with setbacks since its initial launch attempt last month. It was moved from its launch pad at the Kennedy Space Center in Florida to the Vehicle Assembly Building on December 22 for evaluation and repairs.
Engineers are trying to figure out why a pair of "stringers" -- 21-foot-long (6.5 meter) U-shaped aluminum brackets -- cracked during the countdown for the shuttle's last voyage into space.
Discovery's final mission has been delayed until a launch window from February 3-10. If the launch cannot occur at that time another window will open from February 27 to March 3.
"The next available launch date is Thursday, February 3 at the opening of a window that extends through February 10," NASA said Thursday.
The current preferred launch time on February 3 is 1:37 am (0637 GMT), the agency added.
Another shuttle, Endeavour, is set to take off in April in what will be the last official shuttle launch scheduled for the US program.
A third shuttle launch could take place in the summer before the entire fleet is retired for good.
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