In which I finally get up the nerve to write what I really think. It's here.

My bottom line on the meaning of the Columbia crash:

A newspaper colleague compared the shuttle astronauts to Lewis and Clark, but that is bad metaphor. Lewis and Clark were the vanguard for a huge wave of settlers who followed. The astronauts have been nothing more than a vanguard for a bunch more little Lewis and Clark-like expeditions.

(updated to include free link)