Archive for the ‘Apollo Guidance Computer’ Category

Journey to the Moon, Eldon C Hall

July 31, 2008

There are a large number of books about the Apollo programme. There are also many books about specific aspects of the Apollo programme – the missions, the people, the hardware, the science… Eldon C Hall’s Journey to the Moon, however, focuses on one very narrow element of NASA’s project to put a man on the Moon: the development of the Apollo Guidance Computer.

The Apollo Guidance Computer (AGC) did exactly what its name suggestions – it controlled the navigation functions of the Apollo spacecraft. There was one in the Command Module, and another in the Lunar Module. Designed and built in the early 1960s, it was one of the first production computers to use integrated circuits. It was developed by MIT Instrument Laboratory, but built by Raytheon.

By modern standards, the AGC was crude and not at all powerful. This hardly surprising – computing was still its late infancy, and integrated circuits were so new they were both unreliable and expensive. Happily, advances in IC manufacture during the AGC‘s development period improved both these factors. Reliability, of course, was paramount – astronauts could not afford for the AGC to crash or malfunction while en route to the Moon.

As someone who works in information technology, I was expecting Journey to the Moon to be a technical read, perhaps similar to books such as CJ Date’s Database in Depth or Andrew Tanenbaum’s Operating Systems: Design and Implementation. Computing, however, was a very different field during the 1960s – Journey to the Moon is more electronics engineering than it is computing.

Hall is an engineer by trade, and it shows in his prose. The writing in Journey to the Moon is at best plain, and at worst a bizarre engineering-speak which considers subjects or verbs superfluous. Despite this, the book is still readable – although I will confess that much of the maths was over my head.

Much of Journey to the Moon describes the project management aspects of the AGC‘s development. The manufacture and specification of its various modules is also described in depth. I found this less interesting than I would have done of, say, its operating system. More information on programming the AGC might well have been given in the appendices, but I’ll never know – while the text referred to appendices, the copy of the book I purchased had none.

If you’re interested specifically in the AGC, then you’ll probably find Journey to the Moon a useful addition to your library. Otherwise, it’s probably too arcane for most enthusiasts of Apollo. For those interested in further reading, here are a couple of useful links: Virtual AGC Page, MIT’s site on the AGC, AGC schematics.

Journey to the Moon, Eldon C Hall (1996, American Institute of Aeronautics and Astronautics, ISBN 1-56347-185-X, 226pp)