1986 – Space Shuttle program: STS-51-L mission: Space Shuttle Challenger disintegrates after liftoff, killing all seven astronauts on board. On January 28, 1986, Space Shuttle Challenger broke apart 73 seconds into its flight, killing all seven crew members aboard. The spacecraft disintegrated 46,000 feet above the Atlantic Ocean, off the coast of Cape Canaveral, Florida, at 16:39:13 UTC (11:39:13 a.m. EST, local time at the launch site). It was the first fatal accident involving an American spacecraft while in flight. The mission, designated STS-51-L, was the 10th flight for the orbiter and the 25th flight of the Space Shuttle fleet. The crew was scheduled to deploy a commercial communications satellite and study Halley's Comet while they were in orbit, in addition to taking schoolteacher Christa McAuliffe into space under the Teacher in Space Project. The latter task resulted in a higher-than-usual media interest in and coverage of the mission; the launch and subsequent disaster were seen live in many schools across the United States. The cause of the disaster was the failure of the primary and secondary O-ring seals in a joint in the right Space Shuttle Solid Rocket Booster (SRB). The record-low temperatures on the morning of the launch had stiffened the rubber O-rings, reducing their ability to seal the joints. Shortly after liftoff, the seals were breached, and hot pressurized gas from within the SRB leaked through the joint and burned through the aft attachment strut connecting it to the external propellant tank (ET), then into the tank itself. The collapse of the ET's internal structures and the rotation of the SRB that followed propelled the shuttle stack, traveling at a speed of Mach 1.92, into a direction that allowed aerodynamic forces to tear the orbiter apart. Both SRBs detached from the now-destroyed ET and continued to fly uncontrollably until the range safety officer destroyed them. The crew compartment, containing human remains, and many other fragments from the shuttle were recovered from the ocean floor after a three-month search and recovery operation. The exact timing of the deaths of the crew is unknown, but several crew members are thought to have survived the initial breakup of the spacecraft. The orbiter had no escape system, and the impact of the crew compartment at terminal velocity with the ocean surface was too violent to be survivable.
