It was a cold January morning in 1986. Too cold, worried engineer Bob Ebeling whose company built the rocket boosters for Space Shuttle Challenger. He knew the shuttle's rubber O-rings, used to seal booster joints at ignition, could become brittle in frigid weather. Tragically, he was right. Seventy-three seconds after liftoff, the shuttle broke apart, killing its seven crew members, including teacher Christa McAuliffe. #NASA #challenger #spacelaunch #engineer