Seventy-three seconds into flight, a failed O-ring seal in the right solid rocket booster let hot gas escape, igniting the external fuel tank. Challenger disintegrated over the Atlantic before a live television audience that included schoolchildren watching McAuliffe, the first teacher chosen for spaceflight. The disaster grounded the shuttle program for 32 months and prompted a sweeping investigation into NASA's safety culture.
Millions of American schoolchildren tuned in that morning because Christa McAuliffe, a New Hampshire social studies teacher, had won a nationwide competition to become the first ordinary citizen in space. Instead they watched the shuttle's twin contrails suddenly fork into a chaotic plume, and confused NASA commentary continued for agonizing seconds before anyone confirmed a catastrophe.
The Rogers Commission, which included physicist Richard Feynman, traced the cause to a rubber O-ring in the right solid rocket booster that lost its elasticity in the unusually cold Florida morning, just 36 degrees Fahrenheit at launch. Feynman famously dunked a piece of O-ring material into a glass of ice water during a televised hearing, demonstrating how it stiffened and lost its seal. Engineers at booster manufacturer Morton Thiokol had warned managers the night before against launching in such cold, but their concerns were overridden.
All seven crew members died, including commander Dick Scobee, and the cabin was later found largely intact, having survived the initial breakup before slamming into the ocean. The tragedy forced NASA to redesign the boosters, create an astronaut office with more independent safety authority, and confront how schedule pressure had eroded engineering caution.