On this day in 1986, at 11:38 AM, EST, the space shuttle Challenger lifted off from Cape Canaveral, Florida. Among the crew aboard was Christa McAuliffe, a high school teacher who was about to become the first US civilian to travel into space. The Challenger's launch countdown had been delayed repeatedly because of weather and technical problems.

Liftoff. The shuttle finally lifted off. Seventy-three seconds later, as the world watched, the shuttle exploded. There were no survivors.

Book of Records. The Columbia was the only the aircraft-like shuttle entered into orbit around Earth. It was launched by two solid-rocket boosters and an external tank. When the mission was completed, the shuttle fired engines to reduce speed. After traveling down through the atmosphere, it landed like a glider.

Why a Shuttle? Early shuttles took satellite equipment into space and carried out various scientific experiments.

The Eve of Destruction. The Challenger disaster was the first major shuttle accident. After, a special commission was appointed to determine what went wrong with Challenger, and to prevent future disasters. The commission was headed by former secretary of state William Rogers, and included former astronaut Neil Armstrong and former test pilot Chuck Yeager. (see Today Only October 14).

A Tiny Part. A Huge Tragedy. The investigation determined that the explosion was caused by the failure of an O-ring seal in one of the two solid-fuel rockets. Because of the cold temperature at launch time, the elastic O-ring did not respond as expected. The O-ring seals were intended to prevent hot gases from leaking through the joint during the propellant burn of the rocket motor. That triggered a chain of events that resulted in the explosion. As a result of the explosion, NASA did not send astronauts into space for more than two years. By then, various shuttle features had been re-designed.