The Apollo Guidance Computer

Jul 20th, 2009 | By | Category: Space

Let’s say you’re a NASA engineer in the 1960s, wearing your snazzy black plastic glasses, thinking of landing a man on the Moon and returning him safely to the Earth. You start thinking navigation. Getting into the right orbits is going to take a fair bit of computation–plus some fine control of rocket engines and navigation jets. Really, you’re going to need a computer.

But this is the 1960’s. Computers are HUGE. Yes, yes, transistors had been invented years before–and are now in wide use. So, at least we’re not talking vacuum tubes. Egads. Tubes! Building computers means wiring a whole bunch of these transistors together. With wire. In other words, the world’s finest computers look a bit like that box of Christmas lights you don’t want to think about in the basement: tangled, ugly, mean and prone to failure if jostled. Not exactly conducive to placement in a rocket.

No biggie, you think. You’ll just have the computer on Earth–nice solid earth–radioing back and forth to the sensors and engines in the rocket. You can even correct for the speed-of-light delays! Problem solved! Light up some Lucky Strikes and call it a day.

But then you think of the return burn. If the Apollo craft are going to get out of lunar orbit and return to Earth, they’re going to need to fire the rocket engine on the far side of the Moon–you know, where radio waves can’t reach. Crap. I guess you’ll have to figure out a way of wiring together all those (4000 or so, egads!) transistors in a way that is small, light and durable enough to survive being rocketed into space. Time to create the first integrated circuit computer–father of every damn computer most of us have used, ever.

Better call MIT.