The first loss of a Space Shuttle and its crew was a preventable disaster, but it would go onto largely change NASA for the better

Reported by Ian Evenden

J ust 73 seconds was all it took from the launch of Space Shuttle mission STS-51-L on 28 January 1986 to the Shuttle’s disintegration over the Atlantic and the loss of all seven of its crew. It was a routine mission to deploy a data relay satellite and test a probe designed to observe Halley’s Comet, but was notable for the presence of Christa McAuliffe – the first teacher in space, and a civilian, in the crew. She had been chosen for the mission out of an initial application pool of more than 11,000, and was planning to carry out experiments and beam back lessons to Earth in order to rekindle interest in the US space program, remind Americans of the role teachers play in society and demonstrate the reliability of spaceflight.

Challenger was completely destroyed in the disaster, which was traced to the failure of an O-ring seal in the Shuttle’s right-hand solid rocket booster. This allowed hot gases to flare out, burning through the strut attaching the booster to the external fuel tank and causing the two to clash together, eventually leading to structural failure of the fuel tank and allowing all parts of the launch vehicle to fly apart, disintegrating under the pressure of aerodynamic forces.

It’s not a long time, but it’s possible for a great deal to happen in such a compressed period. Those 73 seconds led to an investigation that took months to complete its analysis, and a total shutdown of the Shuttle program for 32 months. The morning of 28 January had been cold, and ice had formed on the launch pad at Kennedy Space Center, Florida. Challenger’s launch was delayed by two hours to allow the ice to melt, but this wasn’t the first delay to the mission. Originally scheduled for July 1985, STS-51-L was to be the 25th Shuttle mission, and the tenth flight of Challenger. Delays put the launch back to November. A Columbia mission scheduled to go up just before Challenger was also delayed, pushing the mission back even further to 22 January 1986, then 25 January. Bad weather set in, and the launch was rescheduled for 27 January, then finally 28 January after a problem with a hatch handle.

Engineers were worried that the amount of ice present on the pad could damage the Shuttle at liftoff, perhaps striking the Shuttle’s thermal protection tiles. The temperature on the morning of launch was as low as -2.2 degrees Celsius (28 degrees Fahrenheit) – the minimum required for a launch was -1 degrees Celsius (30.2 degrees Fahrenheit), and the previous coldest launch had been at 12 degrees Celsius (53.6 degrees Fahrenheit). But despite managers at the launch pad voicing their concerns, the mission manager in Houston, Texas, gave clearance to launch after a final inspection showed the ice to be melting.