This Day in History: br Challenger Disaster January 28, 1986 Seventy-three seconds after br its 11:38 a.m. launch, NASA's br space shuttle exploded, killing br all seven crew members. Among the crew was Christa McAuliffe, br a 37-year-old high school social br studies teacher from New Hampshire. McAuliffe had won a br competition that earned br her a place on the Challenger. Millions witnessed br the tragedy on live television. In the aftermath, President Ronald Reagan br appointed a special commission to br determine what went wrong with Challenger. The investigation determined br the disaster was caused by br the failure of an “O-ring” seal br due to cold weather. It would be two br years before NASA sent br astronauts into space again.