Why did the space shuttle challenger exploded?

Answer 1

Damaged seals on a joint in one of the solid rocket boosters made the booster separate from the rest of the vehicle causing a massive explosion.

Answer 2

The breakup of the space shuttle Challenger was caused by the failure of two O- rings in the aft joint in the right solid rocket booster (SRB's) to properly seal due to the cold weather. There had been problems with the seal on other missions, but it is thought that the decision to launch in near-freezing temperatures contributed to the failure, making the seal rigid and unable to seal properly.

It is interesting to note that the rings, manufactured by Thiokol, are just one of a number of synthetic rubbers developed in Germany during the 1930's and their physical/chemical properties are/were well documented in manuals out for decades: the engineers were well aware of the elasticity/resilience failure of Thiokol at low temperatures and advised their superiors of the potential disaster. Unfortunately, the administrators were unwilling to call off the launch. Some believe this was politically motivated. The seal failure led to a catastrophic chain of events. Hot gases escaped through the right Solid Rocket Booster aft field joint, followed by a flame, damaging the clamp securing the SRB, and burning through the external fuel tank causing the tank to disintegrate. The forces created caused the orbiter to disintegrate (it did not explode) before the debris crashed into the ocean.