Cape Canaveral, Fla. -- Engineers repairing the shuttle Discovery found another crack in the spacecraft's external fuel tank Monday, jeopardizing its launch date, U.S. officials said.
There are now four known cracks in two vertical beams called stringers that give the tank strength and rigidity, WESH-TV, Orlando, reported.
Engineers say they're not sure how they'll be able to repair Discovery in time for its upcoming seven-day launch window that begins Nov. 30.
There are a total of 180 stringers, and more may be found to be cracked as workers cut into the tank's foam insulation.
NASA officials said they hope to cut out and replace the cracked metal, after which new foam insulation could be applied that would take four days to cure.