The Challenger's Explosion explained

Short Explanation: an "O-Ring" that was on the srbs "Solid Rocket Boosters"
was frozen, which caused the shuttle to explode

Long in-depth Explanation

On January 28, 1986, the Space Shuttle Challenger broke apart 73 seconds into its flight, killing all seven crew members aboard. The spacecraft disintegrated 46,000 feet (14 km) above the Atlantic Ocean, off the coast of Cape Canaveral, Florida, at 11:39 a.m. EST (16:39 UTC).
It was the first fatal accident involving an American spacecraft while in flight. The mission, was the 10th flight for the orbiter and the
25th flight of the Space Shuttle fleet. The crew was scheduled to deploy a 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 program. The latter resulted
in a higher-than-usual media interest 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 redundant O-ring seals in a joint in the shuttle's
right 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