the space shuttle challenger disaster occurred on january 28, 1986, when the nasa's  broke up 73 seconds after liftoff. all seven crew members were killed. it was the 25th flight of a space shuttle. the cause of the explosion was a part called an o-ring that broke in the right solid rocket booster. during the flight, hot gases escaped from the o-ring and made it break apart. shuttles stopped flying for two and a half years.