Retrotechtacular: The Apollo Guidance Computer

There is so much amazing technology that came out of the space race. For this week’s Retrotechtacular we’re looking at the guidance computer used in the Apollo program undertaken by NASA in the 1960’s.

One of the main components of this system is the Inertial Measurement Unit or IMU. That’s a familiar term for hackers who build quadcopters or other devices for which spacial awareness is paramount. In this case the IMU provided critical information about the motion and orientation of the capsule during it’s trip from the Earth to the Moon and back. But it wasn’t just high tech electronics along for the flight. To determine actual position a sextant was used for triangulating position. Yes, this is the same type of measuring device used for centuries. The method of using the sextant is displayed above. The spacecraft was turned until the sextant pointed at a landmark on Earth. The instrument was the adjusted to line up a star as a landmark, then the computer calculated position based on time and the angles of the two points being sighted. There’s a lot more shown in this thirty-minute film including in-depth assembly and testing of the computer components.

Before we point you to a few related articles we’d like to mention that our stash of really cool Retrotechtacular tips is running low. So if you know of some old footage that’s awesome to watch please send us a tip about it.

Now if you can’t get enough about NASA electronics you should check out the LVDC board which [Fran] got her hands on. Also, it’s worth checking out the unbelievable soldering techniques specified in the NASA manual. There’s a pretty good discussion about that going on in the Reddit thread.

Retrotechtacular is a weekly column featuring hacks, technology, and kitsch from ages of yore. Help keep it fresh by sending in your ideas for future installments.

33 thoughts on “Retrotechtacular: The Apollo Guidance Computer

    1. I worked at AT&T with a guy that used to work on the Apollo program. And he was just great to be around. Taught me tons of stuff, common sense stuff.
      But one thing he mentioned to me was their soldering. He was a soldering fool at AT&T. He would work on something until it was perfect, used to drive me nuts too. I kept telling him we’re not launching this thing into space! He would say “Yeah, but it will never fail because of my solder joint either…..”
      (another gem was power supplies. He always used to biggest he could. They never even got the slightest bit warm. Because of that, there’s no stress, and they’ll probably never fail either. So now, I do the same thing, always use the biggest supplies I can. If it needs 10mA, I’ll use one that can supply a couple amps if I can)
      He also told me that with proper soldering technique at NASA, they saved something like a total of 1.7 tons of weight or something on the Saturn V. Some unGodly amount of weight. Because people used to use too much solder, nice “big blobs”. But after they looked into it, they went with the “small tee-pee” type joint. And if you think about it, all those solder joints, there’s tons and tons of them. And they used TONS and TONS of components too, not integrated circuits like today. Almost everything was discreets.
      I used to live right behind the Space and Rocket Center in Huntsville (on Redstone Arsenal) and used to go back there and “borrow” much of the “junk” sitting out back. And they had thousands and thousands of circuit boards on a single device, like a booster or something. Much of it was really spread out too, it’s not like they were trying to cram everything into small spaces. Think, a single flip-flop on a single card about the size of a small note pad.
      (they did buy up almost all the available chips, like the 7400 series, but they were limited at the time, just not that many types, and they wouldn’t use a chip, when they only needed a single, “simple” circuit, so most stuff was still done in components and not chips)
      and more recently, I had a friend that worked at some place that built one of the HellFire missiles I think it was. (General Dynamics or something). And they were real sticklers for soldering.
      He said it literally took five minutes to strip and tin a piece of wire. You had to use thermal strippers, then you had to use tweezers to pull the tiny strands of melted plastic out of the wire twist. Then it all had to be trimmed and inspected. Then you had to tin it, then clean it very carefully, then inspected again, and reworked if needed.
      He HATED that job.
      So yeah, 15 minutes to solder a single component? Yep. Plus, it’s not their money, it’s taxpayer money! But seriously, they simply can’t afford to have a failure in anything.

  1. This era of electronics design and development really fascinates me. Between Bell Labs, NASA, HP, and others, the sheer amount of brainpower was staggering. Of all the eras to wish I had been able to experience in person, this one leads the list! Thanks for a great post!

  2. So many amazing things – one type of chip, a really hardwired program memory, the interconnect mechanisms. But perhaps the most amazing thing is that the system was accurate enough given that it depended on the astronauts pushing a button to mark a time.

  3. That was very interesting. I have been wondering about how they used the sextants, and it seems so obvious by now.

    I kind of wonder why one does not see more of these kind of documentaries these days, though I would not be surprised if one of the YouTube comments was right, that we are less intelligent today (maybe we use too little time to think things through now).

    1. given some of the engineering at the edges of science i wouldnt say that we are less intelligent today.

      people working on these projects were probably above average, we shouldnt compare them to the average of today, but their relative equals.

      that said what these people could do with hard work and determination is absolutely amazing, even by todays standard.

    2. I would argue that, for the vast majority of us, we spend less time thinking than they did. Not that our best minds are any duller than theirs, but with virtually uninterruptible, instant, incessant access to (often useless) information, news and entertainment, we’ve reduced the time we have to get bored with. Where an engineer from the fifties might have spent a queue pondering a problem, one today might whip out his phone and play or check some news.

      Aside from that, the space race was a huge driving force for science – much like the Manhattan project and other wartime developments. It encouraged them to overcome obstacles at all costs. The sort of genius ideas that made the Apollo program possible might be thrown right out today. (Obviously we’re at a different level of technology – I mean new sorts of ideas that might be discarded because they’re outside the box.)

      1. I agree with you. Kids nowadays don’t memorize as much, so they depend more on their web connection or smartphone calculator. I doubt if today’s students have memorized pi or e to 8 places. They say power corrupts, and that seems to apply to computing power as well.
        A national project like the moon race got everyone in the country thinking about science, and the federal government pumped lots of money into science and math education. It was a Big Deal…as you say, on the scale of WWII. We need to do the same thing today, only we need to aim at elementary and secondary education. We should have the best students, teachers and facilities in the world, yet we are slipping behind and arguing about insane things like whether the religious fiction of creation should be taught alongside the science of evolution.

        1. I agree! The “thought-provoking” has resulted in me thinking about wonderful ways to destroy a specific network’s ability to share their crap with the rest of the world.

          A few microwave ovens fed into a feed horn with a few bit to get them all into phase, attached to a very directional antenna, pointed at a few critical bits of hardware….

    3. Same as everything else. It is the “they don’t make things like they used to” fallacy. We keep the good old stuff and throw the junk out. Throw today’s junk out and only look at the good stuff if you want a fair comparison.

    4. If you really think we are less intelligent today, just take a good look at the high tech science today. Things like the LHC, the newest generation silicon lithography systems, aircraft systems, satelites, etc. Most of them now each take more brainpower combined than was available for all those innovations back then. I’m currently right in the thick of what is probably the next big thing in lithography, EUV, and I can safely say the amount of engineering going into a machine smaller than the average shipping container is staggering.

    1. What I find more amazing is what we don’t have today. Stuff like a viable manned space program. But we have Twitter which I suppose is some small consolation. A real small one at that. Apollo was the high water mark for our species. Nothing before, or since compares.

  4. Hmm… all of the MIT guys have the same method of speech… accelerated phrases broken up by awkward pauses as they look for the proper next word. Actually I relate to this a lot, it’s the same way I tend to sound when I’ve been put on the spot to talk about something. Methinks they weren’t given much chance to rehearse.

    The Raytheon guy, on the other hand, seems to have given this speech more than once before.

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