Forty years after the Challenger disaster, NPR explores the engineers' last-minute efforts to stop the launch, their decades of guilt and the vital lessons that remain critical for NASA today.

WASHINGTON — It's been 39 years since the Challenger space shuttle explosion, one of NASA's most devastating tragedies. NASA's Challenger shuttle exploded 73 seconds after lifting off on Jan. 28, 1986 ...

Both the 2003 Columbia and 1986 Challenger space shuttle disasters, which resulted in fatalities, received the "Type A mishap ...