The next space flight accident: How do we prevent it?

I recently watched NESC Deputy Director Mike Kirsch stand before a roomful of engineers at the Langley Research Center and tell them that with every passing day, NASA breaks a record: the longest stretch without a major accident in the nation's human spaceflight program since the Space Shuttle Columbia disintegrated during reentry on February 1, 2003. NASA's challenge, he told them, was to make sure the record keeps being broken.