40 years ago this morning, the unthinkable happened: the Space Shuttle Challenger exploded 73 seconds after liftoff, killing all 7 astronauts on board, including Christa McAuliffe, who was supposed to be the first teacher in space. School children watched in horror as the tragedy happened. This is original coverage from the Eyewitness News vault. | ABC7NY

35 YEARS LATER: On this day in 1986, the Space Shuttle Challenger exploded after liftoff, killing all seven astronauts on board. The Challenger broke apart at 11:39 a.m., falling into the Atlantic Ocean. Investigators would later discover the disaster was caused by the failure of an “O ring” seal in one of the two solid-fuel rockets. As a result of the horrific accident, NASA did not send astronauts into space for more than two years as it redesigned a number of space shuttle features for improv