The Apollo Guidance Computer

by Frank O'Brien

Published 1 January 2010

The technological marvel that facilitated the Apollo missions to the Moon was the on-board computer. In the 1960s most computers filled an entire room, but the spacecraft's computer was required to be compact and low power. Although people today find it difficult to accept that it was possible to control a spacecraft using such a 'primitive' computer, it nevertheless had capabilities that are advanced even by today's standards.

This is the first book to fully describe the Apollo guidance computer's architecture, instruction format and programs used by the astronauts. As a comprehensive account, it will span the disciplines of computer science, electrical and aerospace engineering. However, it will also be accessible to the 'space enthusiast'. In short, the intention is for this to be the definitive account of the Apollo guidance computer.

Frank O'Brien's interest in the Apollo program began as a serious amateur historian. About 12 years ago, he began performing research and writing essays for the Apollo Lunar Surface Journal, and the Apollo Flight Journal. Much of this work centered on his primary interests, the Apollo Guidance Computer (AGC) and the Lunar Module. These Journals are generally considered the canonical online reference on the flights to the Moon. He was then asked to assist the curatorial staff in the creation of the Cradle of Aviation Museum, on Long Island, New York, where he helped prepare the Lunar Module simulator, a LM procedure trainer and an Apollo space suit for display. He regularly lectures on the Apollo computer and related topics to diverse groups, from NASA's computer engineering conferences, the IEEE/ACM, computer festivals and university student groups.


The Apollo Spacecraft

by Frank O'Brien

Published 9 January 2018
The Apollo Spacecraft: Evolution, Engineering, and Flight Operations' is the definitive description of the spacecraft and the technologies used for the journey to the Moon. The spacecraft that eventually landed on the Moon did not spring fully formed because of Kennedy's May 1961 challenge. 'The Apollo Spacecraft' begins by tracing its origins from 1959 when contract bids were already being prepared for a lunar spacecraft. Caught unprepared for a full lunar landing mission, von Braun and other NASA engineers recognized that the spacecraft already under development could never be reconciled with the mission architectures under consideration. Changing the mission architecture and introducing a new spacecraft, the Lunar Module, threw the development of the Apollo CSM into a lurch by requiring significant modifications to the vehicle. The resulting spacecraft, while pushing the limits of the possible, became a complex set of compromises. By tracking the spacecraft's development with its numerous fits and false starts, 'Apollo Spacecrafts' describes how the final mission design and flight operations reflected these early engineering decisions.