STS-51-L was the twenty-fifth flight in the American Space Shuttle program, and marked the first time a civilian had flown aboard the Space Shuttle. The mission used Space Shuttle "Challenger", which lifted off from launch pad 39B on January 28, 1986, from Kennedy Space Center, Florida. The mission ended in disaster following the destruction of "Challenger" 73 seconds after lift-off, because of the failure of an O-ring seal on "Challenger"'s right solid rocket booster, which led to the rapid disintegration of the shuttle stack from overwhelming aerodynamic pressures. The seven-member crew was killed when the crew compartment hit the Atlantic Ocean at 207 miles per hour, after two and a half minutes of freefall.