The working mum who wrote the Apollo 11 guidance computer source code

A few years after graduating from Earlham College with a BA in Mathematics, Margaret Hamilton soon found herself in charge of software development and production for the Apollo missions to the Moon at the MIT Instrumentation Laboratory. 

At the MIT Instrumentation Lab in the 1960s, Margaret Hamilton was working on code for the Apollo Guidance Computer. A working mum, she sometimes did what a lot of us do: she took her daughter, Lauren, to the office. Margaret would often test programs in the simulator, and Lauren liked to play astronaut like her mom. One day, Lauren crashed the simulator after she pressed a button that set off a prelaunch program while the mission was in mid-flight. 

Margaret didn’t scold Lauren. Instead, she was struck with a thought: “What if an astronaut did the same thing during a real mission?” Margaret lobbied to add code that would prevent a system crash from actually happening if he did. 

This way of thinking came to define Margaret’s work. She’d always ask, “What if something you never thought would happen, happens?” Then, she’d develop and test a system that would be prepared for that scenario.

Her “what if” mindset was crucial throughout the Apollo missions, where the software had to work perfectly, and had to work the first time, in space. Keep in mind, this was at a time when software engineering literally wasn’t even a thing yet—Margaret herself coined the phrase “software engineering” while working on Apollo.

Margaret’s mindset most famously paid off moments before Apollo 11 was set to land. The guidance computer was overwhelmed with tasks and underwent a series of restarts, triggering alarms that could have forced an abort. But the team’s software was reliable, and the priority display (that Margaret created, and fought to include) let the astronauts and Mission Control know what they were dealing with. The Eagle was able to land safely, and Neil Armstrong was able to take that one small step.

“There was no choice but to be pioneers.” 

That’s how Margaret Hamilton describes working on the software that put us on the moon. Margaret led the team that developed the onboard flight software for all of NASA’s manned Apollo missions, including Apollo 11’s historic moon landing.

If you want to read more about Margaret and how she wrote the code, how it was ran, and what computers they used, then read this.

Many of you may have seen the photo below of Margaret but were unaware of the full story behind it.