Breaking Barriers to the Moon and Back:
How Margaret Hamilton's Software Sent
Men to the Moon
As a Problem Solver
Software Pioneer Margaret Hamilton on Apollo 11 . Christie's. July 1, 2019.
"[T]he computer was programmed to do more than recognize error conditions. A complete set of recovery programs was incorporated into the software. The software’s action, in this case, was to eliminate lower priority tasks and re-establish the more important ones…If the computer hadn’t recognized this problem and taken recovery action, I doubt if Apollo 11 would have been the successful moon landing it was.”
-Margaret Hamilton
At SAGE, Hamilton computers sounded like a seashore. One night at 4:00 AM, someone called to say the computer was silent. Hamilton rushed in and discovered she could debug her program using sound.
SAGE system sectors, direction centers, and radar sites. The Online Air Defense Radar Museum. No date.
Whirlwind magnetic-core memory banks at SAGE. MIT. No date. .
"There was no second chance. We knew that. We took our work seriously, many of us beginning this journey while still in our 20s. Coming up with solutions and new ideas was an adventure. Dedication and commitment were a given. Mutual respect was across the board."
-Margaret Hamilton
Software errors endangered the astronauts, but the error-finding machine took so long that Hamilton preferred to find errors manually. Hamilton’s team knew their code so well that they found 44% of their errors manually.
Hamilton feared being blamed for errors on Apollo 11, so she created an alarm system to sound during emergencies. Sure enough, just minutes from the Eagle’s moon landing, the 1201 and 1202 alarms sounded. Nevertheless, mission control gave permission to land. Hamilton’s team soon realized the alarms sounded because a switch, a piece of hardware, was flipped in the wrong direction. The software had worked perfectly.
Apollo 11 mission patch. NASA. 1969.
Margaret Hamilton at MIT during the Apollo 11 mission. Computer.org. No date.