Editorial: Back to the Drawing Board

While everyone can be thankful that the large chunk of insulating foam that shook loose from the Space Shuttle Discovery’s external tank during liftoff July 26 did not strike the orbiter, the incident proves that NASA officials still do not understand their vehicle. That revelation raises serious new questions about how many shuttle flights NASA will be able to conduct between now and 2010, the date the agency intends to retire all three remaining orbiters.