On this day in 1986 Ronald McNair, Ellison Onizuka, Judith Resnick, Dick Scobee, Michael Smith, Greg Jarvis, & Christa McAuliffe lost their lives in the Challenger space shuttle (STS 51-L).
Look here for an independant view on the reliability of the shuttle done by Richard Feynmen after the loss of the Challenger shuttle. I believe that he was asked to do this as part of the official investigation, but when it turned out to be so damning, they refused to use it in the report.