3.1M Commanders on Instagram: "On January 28, 1986, millions watched live as the Space Shuttle Challenger lifted off from Kennedy Space Center—only to disintegrate 73 seconds later. All seven crew members were lost, including Christa McAuliffe, the schoolteacher chosen to be the first civilian in space. The event left her students and viewers nationwide devastated. Investigators traced the disaster to a failed O-ring in one of the solid rocket boosters, a flaw worsened by the unusually cold temp