NASA delayed Discovery's planned launch at least 24 hours to allow more time to troubleshoot a problem on one of the orbiter's main engine controllers.
Engineers detected voltage irregularities in the back up controller on Main Engine No. 3. Each of the shuttle's three liquid-fueled main engines have primary and back-up controllers that effectively are the electronic brains of the engines.
Liftoff had been scheduled for 3:52 p.m. Wednesday.
The earliest Discovery could launch now would be 3:29 p.m. Thursday. Weather conditions don't look good for that launch window, however. There is only a 30 percent chance that weather would cooperate.
The same back-up controller exhibited some circuitry trouble during routine prelaunch checkouts earlier in the countdown, but switch throws in the shuttle's cockpit cycled power on and off, clearing the problem. NASA Test Conductor Steve Payne said that problem was considered to be resolved.
Stay tuned for a news conference at 6:30 p.m. Click on the screen on the right to watch.