Other than the national tragedy of the Apollo 1 command capsule fire that took the lives of astronauts Gus Grissom, Ed White and Roger Chafee on Jan. 27, 1967 during a launch rehearsal at Cape Kennedy, NASA's darkest hour up to that point occurred 19 years later when the space shuttle Challenger exploded 73 seconds after launch on Jan. 28, 1986, causing the deaths of all seven astronaut aboard.
