On January, 28, 1986, the Space Shuttle Challenger exploded 73 seconds after lifting off from launch pad 39B at Kennedy Space Center in Cape Canaveral, Florida.
The shocking accident - broadcast live on television - claimed the lives of all seven crew members, including Christa McAuliffe, a Concord, N.H. school teacher who had been selected to inaugurate NASA's highly publicized Teacher In Space Project.
(Story continues below slideshow.)
Challenger Disaster Anniversary
Later that day, President Reagan returned to the airwaves to console a grieving nation. He reserved a few words specifically for the schoolchildren who had been watching.
"I know it is hard to understand, but sometimes painful things like this happen," he said. "It's all part of the process of exploration and discovery. It's all part of taking a chance and expanding man's horizons. The future doesn't belong to the fainthearted; it belongs to the brave. The Challenger crew was pulling us into the future, and we'll continue to follow them."
The shuttle program was grounded for almost three years following the accident. During that time investigators worked to pinpoint and correct the causes of the explosion - notably a failed "O-ring" gasket in the shuttle's booster rockets that allowed superheated gases to ignite fuel inside an external tank.
Twenty-six years have passed since Challenger disintegrated over the Atlantic Ocean, and the shuttle program itself is now history. But those who watched the disaster can never forget seeing the shuttle's elegant arc abruptly give way to twisted white contrails and falling debris. And even now few events loom as large in the nation's space lore.