I agree that the term hero is loosely defined because of its overuse. My thought is that a hero is someone that acts on someone else's need at great cost to him/her self. Unquestionably setting the right example for all of us. Courage and moral/ethical solidity is what sets the stage. I cannot take anything away from the Columbia crew, I admire and appreciate what they do so very professionally and with tremendous bravery. However I struggle to consider them heroes, at least on the level of the 9-11 firemen. They saved lives where I can't say the same for the astronauts. Yes, their deaths were a terrible loss and all the world agrees, so much so that I don't really oppose them being called heroes given the benefit of my doubt.
I am simply saying that the better definition (by example) of a hero would be the people who attacked the terrorists mid-flight or the firemen at the WTC. Maybe it (for me) hinges on protection, or the attempt to save someone's life, which doesn't (to me) apply to the Columbia crew..even as much as I respect them.