Riding the Stack
One year ago this week, the world watched with horror as the Challenger space shuttle and its crew of seven disappeared in a fireball.
Before the accident, risk was a dirty word in NASA. But to the shuttle's crews and to its designer, Maxime Faget, it was, and still remains, an experimental rocket plane.
Attitudes have changed, and now NASA allows the astronauts themselves to reveal, with unprecedented frankness, the long-term risks of Riding the Stack.
Reporter James Reston Jr Film editor RICK SPURWAY Producers WILLIAM CRAN and STEPHANIE TEPPER for WGBH Boston
Horizon editor ROBIN BRIGHTWELL