by Jason Snell
Margaret Hamilton and the Apollo Guidance Computer
The Guardian’s Zoë Corbyn has a great interview with Margaret Hamilton, who led the software team that worked on the remarkable Apollo guidance computers.
Hamilton tells an amazing story about a bug that she noticed—or to be more accurate, her daughter noticed:
One day, she was with me when I was doing a simulation of a mission to the moon. She liked to imitate me – playing astronaut. She started hitting keys and all of a sudden, the simulation started. Then she pressed other keys and the simulation crashed. She had selected a program which was supposed to be run prior to launch – when she was already “on the way” to the moon. The computer had so little space, it had wiped the navigation data taking her to the moon. I thought: my God – this could inadvertently happen in a real mission. I suggested a program change to prevent a prelaunch program being selected during flight. But the higher-ups at MIT and Nasa said the astronauts were too well trained to make such a mistake. Midcourse on the very next mission – Apollo 8 – one of the astronauts on board accidentally did exactly what Lauren had done. The Lauren bug! It created much havoc and required the mission to be reconfigured. After that, they let me put the program change in, all right.
(If you haven’t read up on the Apollo Guidance Computer, you should—it was the world’s first fly-by-wire system and it would have been nearly impossible to navigate to and from the moon without the algorithms in the rudimentary Apollo computers, which used a novel user interface based on inputting numbers representing different “nouns” and “verbs”.)