NASA says a switch box removed from the space shuttle Endeavour has a blown circuit, which could complicate efforts to track down the glitch that forced a launch postponement last week.
The repair work is taking longer than expected. That means Endeavour's launch on the next-to-last shuttle flight may face yet another delay. NASA currently is targeting a launch for next Tuesday at the earliest.
Endeavour was supposed to lift off last Friday. But fuel-line heaters did not turn on during the final part of the countdown. The problem was traced to the switch box. A replacement was installed Wednesday, but more testing is needed.
NASA said the fact that fuses were blown inside the box might have been the result of an external short circuit that has yet to be identified. But it's still possible that the short is contained inside the old box, which would make the fix simpler and keep the launch team on track for a launch on Tuesday.
Endeavour's final voyage is under the command of Mark Kelly, husband of wounded Rep. Gabrielle Giffords. She plans to return to Florida once the launch is rescheduled.
During the two-week mission, the shuttle will deliver a $2 billion particle-physics experiment and a storage platform to the International Space Station, plus tons of additional supplies. Four spacewalks have been scheduled for space station maintenance.
After Endeavour returns to Earth, it's slated to be prepared for exhibit at the California Science Center in Los Angeles. Atlantis is due to take on the 30-year space shuttle program's final flight in late June, but if Endeavour's flight is delayed much more, NASA will have to push Atlantis' launch date into July.
This report includes information from The Associated Press and msnbc.com.