Another Discovery Delay

Launch of space shuttle Discovery has been delayed again, to at least February 22, as NASA engineers try to make sure a fuel valve problem is under control.

Delays have been a hallmark of the shuttle program. It's an extremely complex craft, of course, and making sure everything is in working order takes time. That complexity is the reason the shuttle never came close to fulfilling its original promise of perhaps 50 launches a year. That said, the space shuttle will go down in aviation history as a remarkable technological achievement.