Humble Pi: When Math Goes Wrong in the Real World

by Matt Parker

When the space shuttle Challenger exploded shortly after launch on January 28, 1986, killing all seven people aboard, a presidential commission was formed to investigate the disaster. The commission included Neil Armstrong, Sally Ride, and Nobel Prize–winning physicist Richard Feynman. The Challenger exploded because of a leak from one of the solid rocket boosters. For takeoff, the space shuttle had two of these boosters, each of which weighed 650 tons and, amazingly, used metal as fuel: they burned aluminum. Once the fuel was spent, the boosters were jettisoned by the shuttle at an altitude of over 25 miles and eventually deployed parachutes so they would splash down into the Atlantic Ocean. Reuse was the name of the shuttle game, so NASA would send boats out to collect the boosters and take them off to be reconditioned and refueled. As they slammed into the ocean, the boosters were basically empty tubes. They were built with a perfectly circular cross section, but the impact could distort them slightly, as could transporting them on their sides. As part of the refurbishment, they were dismantled into four sections, checked to see how distorted they were, reshaped into perfect circles, and put back together. Rubber gaskets called O-rings were placed between the sections to provide a tight seal. It was these O-rings that failed during the launch of Challenger, allowing hot gases to escape from the boosters and start the chain of events that led to its destruction. Famously...