Apollo Guidance Computer, 1960s

There were 3 generations of AGC (Apollo Guidance Computer), or 4 if you count a minor variant, but only the final generation, called the Block II AGC, flew with astronauts in space. The name emphasized Guidance simply because "Apollo Primary Guidance Navigation & Control System Computer" would have been, well, awkward -- and an acronym of APGNCSC would have been hard to pronounce or even remember.

Having made the transition from Harvard to the MIT Instrumentation Lab, I spent the 1960s designing both hardware and software for all generations of the AGC, one of the very few with a foot in both camps. The Lab was Nirvana for engineers, a "eufunctional" family that with rare exceptions cooperated wholeheartedly to achieve the goals of Apollo GN&C without wasting any moments wondering whether it was possible.

The marvelous chips powering all our electronics today got a big boost in 1962 when AGC development gulped hard and dove into integrated circuits -- imagine, 3 whole transistors and some resistors on a single chip! And in the final generation, 6 transistors on a chip in a physically smaller package. In that year, we used at least 1/5 of all the ICs there had ever been.

Although there were crude backups in both spacecraft for the Lab's Primary GN&C System, the spec was basically, "the AGC and the rest of the PGNCS around it shall not fail in flight" and it never did. Unprecedented, almost inconceivable, in that era? Of course, but we just did it anyway. When the Space Shuttle was developed with industry computers in the next decade, NASA wasn't so confident.

Many books have been published about Apollo, several of them focusing on the AGC and the rest of the primary GN&C system. The AGC books tend to be on the dry side, oriented toward use as textbooks in engineering courses, and all get a few things wrong, as I summarize in the menu item "Other People's Apollo Books." Now I'm applying my skills as a technical writer and literate humorist to a broad-market book that will engage non-technical readers with a brisk history of computers and rockets as background for the human stories of the Lab people and how we went about our work. The "Author: Left Brains for the Right Stuff" page goes into more detail about my book.