NASA wants nightly Space Shuttle launch

Launching at night limits the view of airborne debris, which can smash into the ship as it lifts off. NASA has more than 100 cameras near the launch pad and on the spacecraft to monitor liftoff, but they won't work as well in the dark.

"We'll learn more on a day launch about where a piece (of debris) may have come off, there's no doubt about it," NASA safety chief Bryan O'Connor says. "But we also have benefits to launching at night, and we're trying to weigh those."

Since the Columbia accident in 2003, all shuttle astronauts have been required once they reach orbit to inspect the ship with sensors, separate from those used during launch, that can detect cracks as tiny as 0.02 inches long. So every crew should see any damage to the ship and either fix it or wait at the space station to be rescued.