The Challenger is trending on the 25th anniversary of NASA's first space shuttle disaster.
On Jan. 28, 1986, 73 seconds into its flight and about 9 miles off the coast of Florida, the Challenger broke apart after an O-ring seal in its right solid rocket booster failed. Seven astronauts were killed, including Christa McAuliffe, the first member of the Teacher in Space project.
President Reagan addressed the nation that night: "I know it's hard to understand, but painful things like this happen. It's all part of taking a chance and expanding man's horizon." Space shuttle flights were halted for 32 months following the Challenger accident.