Suppose that on STS-26, the post-Challenger Return to Flight mission, something occurs (say, a catastrophic SSME turbopump failure, "the most serious accident to have never happened") which results in the destruction of Discovery and the loss of crew and mission. What happens?
Obviously, NASA, despite very carefully going over STS-26 prior to flight, has now lost two orbiters and their crews in a row, and on "routine satellite deployment" missions. That's going to look...bad is not the word for it. I'd be surprised if Shuttles were flying in 1995, let alone 2011.