ENCORE: Challenger Disaster | What Really Happened

On January 28, 1986, the Space Shuttle Challenger exploded 73 seconds after liftoff, killing all seven astronauts on board. The disaster was witnessed by millions on live television, including schoolchildren. In the hours before the launch, engineers at Morton Thiokol, the contractor that built the shuttle’s solid rocket boosters, had pleaded with NASA to delay. They presented data showing that the thin rubber O-rings sealing the booster joints were unsafe to use below 50 degrees Fahrenheit. The temperature at launch was barely above freezing. The decision makers went forward anyway. In the days and weeks that followed, a Presidential Commission uncovered not just a mechanical failure, but a systematic breakdown in decision-making, a cover-up, and a culture at NASA that prioritized schedule over safety.

The First Evidence and a Leaked Memo

The day after the disaster, Thiokol engineer Al McDonald viewed high-resolution film of the launch that had not been released to the public. It showed puffs of gray smoke escaping from a joint on the right booster just after ignition—smoke that McDonald recognized as burned rubber from an O-ring. The boosters had begun to fail before the shuttle even left the pad. McDonald was assigned to the failure analysis team, but he already knew the likely cause.