At 11:38 a.m. EST, the space shuttle Challenger lifts off from Cape Canaveral, Florida. Onboard was Christa McAuliffe, who was on her way to becoming the first U.S. civilian to travel into space on a non-scientific mission. McAuliffe, a 37-year-old high school teacher from New Hampshire, won a competition that earned her a place among the seven-member crew of the Challenger. She underwent months of shuttle training, and then, beginning on January 23, was forced to wait six long days as the Challenger's launch countdown was repeatedly delayed due to weather and technical problems. Finally, on January 28, the shuttle lifted off. Seventy-three seconds later, hundreds of spectators on the ground, including Christa's family, stared in disbelief as the shuttle exploded in a forking plume of smoke and fire. Millions more watched the wrenching tragedy unfold on live television. There were no survivors. A presidential commission appointed to investigate the accident determined that the explosion was caused by the failure of an O-ring seal in one of the two solid-fuel rockets. The elastic O-ring did not respond as expected because of the cold temperature at launch time, which began a chain of events that lead to the massive explosion. As a result of the tragedy, NASA did not send astronauts into space for more than two years as it redesigned a number of features of the space shuttle.