[Mmmike]

I have another question about the tiles: Is it impractical to use two layers of tiles so that a damaged outer layer can be cast off and be replaced by the inner layer?

[Chad Fairbanks]

Think of how much weight that would add, in theory...

[ThinkingMan]

I would think that the weight added by another set of tiles would be extremely restrictive.

The space program is not without it's inherent risks. It is a testimony to the brilliance of our scientists and engineers that this type of thing does not happen more frequently. Think about the apathy that this country normally has regarding space flight. (This from a nation that thinks Survivor and Joe Millionaire is exciting.) It shows that those involved with NASA have reduced the risks to the point that it is no longer "exciting" for most people.

Yes this is a tragedy, but it can also be a valuable learning experience for NASA. A lot of safety regulation is unfortunately written in blood. We cannot stop exploring because "someone might get hurt". All that we can do is learn our lesson, put it to use, and move on to a bolder and brighter future in space.