Don Eyles: Tales From The Lunar Module Guidance Computer

[Editor's Note: Originally published on THE SHORTED TURN's WordPress.com site on 2009/10/24]

Copyright © 2009 Gary R. Van Sickle

Hello once again, Gentle Reader,

If you’re like me, you can’t get enough of:

1. Spaceships
2. Computers and software that run spaceships

Perhaps somewhat surprisingly, there’s less information on the World Wide Internet concerning the latter than one might think.  Today, in an improptu Google Adventure on the topic, I ran across a a piece by Don Eyles on the Apollo LM’s control systems, entitled “Tales From The Lunar Module Guidance Computer“.  It discusses not only the well-known software restarts which happened during the Apollo 11 landing, but also a descent engine control loop stability issue (caused by a single incorrect lag value) which persisted until Apollo 14, going into considerable detail in the process.

While you won’t be able to build your own lunar lander control system after reading it, it is an interesting technical-insight piece on a number of issues and challenges encountered with that system.

Until next time, Gentle Reader, I remain,

Gary R. Van Sickle
President and CEO/Editor/Head Writer
The Shorted Turn