The STS-1 mission launched NASA astronauts John W. Young and Robert Crippen into space for a 54.4 hour, 36 orbit test flight of Space Shuttle Columbia on April 12, 1981. | Space.com

The NASA space shuttle Challenger exploded 40 years ago, on January 28, 1986, just 73 seconds after liftoff. The disaster claimed the lives of all seven astronauts aboard, including Christa McAuliffe, a teacher from New Hampshire who would have been the first civilian in space. “The crew of the space shuttle Challenger honored us by the manner in which they lived their lives,” President Regan said in an address to the nation that night. “We will never forget them, nor the last time we saw them,