[ix] NASA's use of computers in spaceflight operations is a very important and large topic. Any attempt to tell the complete story of the people, calculating machines, and computer programs involved in spaceflight would fill many volumes, if, in fact, it could be told at all. The book you are about to read is a subset of all that could be said. This is the explanation of why some things appear here and others do not, and why the book is organized as it is.

 

When Monte Wright, then director of the NASA History Office, and I first discussed the outline for this project in 1981 and 1982, it seemed that he thought NASA had had a terrific impact on the development of computer technology. Many others shared his view, reasoning that since NASA used computers more extensively than almost any other organization, the Agency must have prodded the computer industry by making challenge after challenge to its computer contractors. One good reason, then, for writing a book on NASA's use of computers was to study the impact of NASA's demands. At the time, I did not know enough to hypothesize one way or another.

 

Obviously, the book required limits. Since the use of computers in administrative work paralleled that of private industry, and since the chief technological advances occurred in the flight program, we agreed to limit the project to an examination of computer systems used in actual spaceflight or in close support of it. Computers and systems used in administration and in aeronautical and other research not directly related to spaceflight were ignored.

 

Despite these restrictions, the amount of material and the number of systems involved remained enormous. Any thought of a chronological history had to be abandoned, because keeping the various threads running in order and in parallel was too difficult. Instead, I wrote a topical history, each chapter dealing with either a specific program, such as the Gemini or Apollo onboard computers, or a closely related set of systems, such as launch processing or mission control. This episodic organization made it possible to adapt the writing of the book to the present state of the subject area, and also to NASA's structure. One disadvantage to this approach is that, at first glance, the book has the appearance of a serial description of systems with no obvious relationship to one another. In fact, the decision to order the three major parts of the book as they are was strictly arbitrary. And yet, this organization actually reflects reality. Nearly all the systems described here were developed independently, by different teams, at different sites. Continuity occured only when a series of systems were built under the auspices of a single center, such as the Gemini, Apollo, and Shuttle systems through the Johnson Space [x] Flight Center. In the rare instances that some technological exchange occurred, it is highlighted. Despite the independent development of the various systems, some common problems and experiences provided threads with which to bind the chapters. These are presented in the Introduction and developed throughout the book where they apply.

 

By nature, the subject of computers is technically intensive. Many times things must be discussed that require concentration on the design and engineering attributes of a system. Often the main characters in this history are the machines themselves, and not their creators. A glossary of computer terms and frequent explanatory material in the text should be enough to help those not familiar with computers to understand the story. Additionally, technical material too important to be left out of this history but not crucial to following the flow of events is set apart in boxes. I have retained the technical material in an attempt to fulfill the second objective of the NASA internal history program:

Thoughtful study of NASA history can help agency managers accomplish the missions assigned to the agency. Understanding NASA's past aids in understanding its present situation and illuminates possible future directions.

Hopefully, my choice of the level of the material does not interfere with the first objective, which is the wide "dissemination of information concerning its activities and the results thereof." I believe that at this time a book on this subject that is more expository than interpretive in nature is of greater use to the agency and the historical community. No one before me had waded through this material, therefore, much of my job was the identification of the best sources and the recording of the most useful experiences. Now that this groundwork has been done, more selective and incisive histories can be written.

 

One final note: often in corporations and government agencies individual achievement is buried within the institution. NASA is no exception. It was exceedingly difficult to get people both in the agency and in contractor organizations to identify who did what, or even take personal credit where appropriate. Wherever I was able to assign responsibility, I did so, but, unfortunately, those instances seem less common than the times I had to credit the development to the institution. Hopefully those who are not mentioned but should have been can take pride that their collective achievements are now part of history.

James E. Tomayko
Pittsburgh, Pennsylvania
April, 1987