Here's some disturbing background to the Columbia crash, courtesy of whistleblower Don Nelson, a 36-year veteran of the space program who helped design the original shuttle. If his charges pan out, a lot of officials at NASA may soon face bad news of a different kind.
Here's Nelson's website.
Here he is two years ago, telling the AP that we'll "lose another crew someday. And we will. The warning signs are all there."
A prescient voice in the wilderness, or a fretter whose fears finally happened to come true? I don't have the engineering knowhow to say, and I invite anyone who does to post their thoughts on the comments page.