Joe Sutter did a lecture on the Shuttle disaster investigation at the University of Washington shortly after leaving the committee. He gave a memorable explanation of the risks of flying the Space Shuttle, which he described as an experimental vehicle with 700 flight safety-critical parts [1]. "Safety-critical" means that if the part fails you lose the aircraft.

Sutter claimed that thanks to redundant design the 747 had zero flight safety-critical parts. I have never been able to confirm this independently but it has stuck with me ever since. Anyway, he instantly cut through the prevailing NASA propaganda that the shuttle was the beginning of regular travel to low-earth orbit. It was a great talk by a great engineer.

[1] http://www.faa-aircraft-certification.com/faa-definitions.ht....