Context is everything, and when it comes time to talk about the timeline of the Challenger shuttle disaster, it's worth talking about the fact that it was kind of inevitable. Buoyed by safety records of airlines, pretty much everyone thought that it was perfectly reasonable to think of NASA's spacecraft as similar to an airplane: infinitely reusable, reliable, comfortable, and safe.
But there was a massive problem with risk analysis. A three-volume study published over several years and starting in 1979 estimated that the chances of a shuttle breaking up on launch — exactly like Challenger did — were between 1 in 1,000 and 1 in 10,000. The weakest point? Solid-fuel rocket boosters, and keep that in mind, because that's going to become very important. Fast forward to 1983, and another study that suggested it was closer to around 1 in 100.
After the Challenger disaster, physicist Richard P. Feynman wrote a piece on his observations of the historical oversights that allowed for the lead-up to the disaster. He wrote (via IEEE Spectrum), "The higher figures [1 in 100] come from working engineers, and the very low figures [1 in 100,000] from management." The Challenger accident resulted in the establishment of a program that would collect data — including flight and test data — for risk assessment, and this was something new. In the years prior to Challenger, there was no such data collected, as NASA didn't think it was necessary. And that kind of explains how egregious oversights happened.
