Click the arrow to watch NASA's video on the 25th anniversary of the Challenger accident.
The accident of Space Shuttle Challenger, mission 51-L, interrupting for a time one of the most productive engineering, scientific and exploratory programs in history, evoked a wide range of deeply felt public responses. There was grief and sadness for the loss of seven brave members of the crew; firm national resolve that those men and women be forever enshrined in the annal of American heroes, and a determination based on that resolve and in their memory, to strengthen the Space Shuttle program so that this tragic event will become a milestone on the way to achieving the full potential that space offers to mankind.
— Preface to the Report of the Presidential Commission
on the Space Shuttle Challenger Accident
Space Shuttle flights in the early 1980s lost their sequential numbering. STS-51L meant the mission was scheduled for 1985, hence the "5". The "1" meant it would launch at Kennedy Space Center, while a "2" meant it would launch at Vandenberg Air Force Base in Southern California. And the "L", the 12th letter of the alphabet, meant it was the 12th scheduled launch for that "51" moniker in 1985.
The flight suffered repeated delays, and frustration with those delays led to NASA management ignoring the warnings of contract engineers that it was too cold to launch. Seventy-three seconds after liftoff, a right solid rocket booster failure detonated its external tank and the Space Shuttle was destroyed.
The Shuttle would fly again, but NASA learned a lesson that can only be taught by hubris. That lesson would be taught again on February 1, 2003.
The loss led to the creation of the Challenger Center network of space education facilities. To quote their web site, "Our network of Challenger Learning Centers, diverse classroom programming, and community outreach programs, excite students' natural curiosities and encourage them to learn."
The Challenger accident was a loss of innocence, yet it also inspired a generation of teachers to fulfill the vision of the first Teacher in Space, Christa McAuliffe.
Click here to watch CNN's live coverage of the launch and aftermath.