The computer that took humans to the moon
Science and technology
Light Years Ahead | The 1969 Apollo Guidance Computer

Every Apollo astronaut can tell you what:
- VERB 99
- NOUN 62
It means:
Are you sure you want to land on the moon? [y/n]

If you're interested in computers and in particular operating systems, you'll be just as enthralled as i am by this amazing seminar where Robert Wills, a firmware engineer from Cisco Systems, analyzes and explains the series of 5 automatic restarts of the Apollo Guidance Computer (AGC) that took place while the Lunar Module was descending towards the Moon surface in 1969.

The computer consumed only 55 watts, was built from scratch from one type of logic gate, and controlled the entire spaceship - well, in actuality there were two spaceships (Command Module and Lunar Module), and each one had its own AGC for a total of two computers.

My favorite part is the ultra-simple GUI or control pad, called the Apollo DSKY, consisting of a display with some letters and mostly numbers, 19 buttons, and a status screen with labeled lights that turn on and off. There's a photo of it here

The Inertial Measurement Unit (IMU) is also a pretty extraordinary feat of engineering.

You will see that the design of the operating system is breathtaking in its efficiency and reliability, probably the result of being faced with enormous space and power constraints (so, NOT how we write software in 2021), constraints like a request for additional landing phase data adding 10% to the processor's load... The thing was supposed to work in outer space, after all - not exactly a place where stuff can go wrong without consequences.

And yet, this video shows that not only did things go wrong, but the true genius of the AGC was its ability to deal with things going wrong even if the problem had a one-in-a-million probability of happening and had not been foreseen by the engineers.

Nuff said - hope you enjoy this as much i did/do!
USA and the universe
Robert Wills
The National Museum of Computing
This item is shared by Philip M Shearer with the Community and the World.
Created on 2021-11-17 at 12:20 and last updated on 2021-11-19 at 13:43.