Reproducing A DSKY

This is a project that is about a year and a half in the making, but [Fran] is finally digging into the most iconic part of the Apollo Guidance Computer and building the most accurate reproduction DSKY ever.

The Apollo Guidance Computer was a masterpiece of engineering and is frequently cited as the beginning of the computer revolution, but it didn’t really look that interesting – it looks like a vastly overbuilt server blade, really. When everyone thinks about the Apollo Guidance Computer, they think about the DSKY, the glowey keypad interface seen in the blockbuster hit Apollo 13 and the oddly accurate disappointment of Apollo 18. It’s the part of the Apollo Guidance Computer the Apollo astronauts actually interacted with, and has become the icon of the strange, early digital computers developed for NASA in the 60s.

There are a few modern DSKY replicas, but all of them are exceedingly anachronistic; all of these reproductions use seven-segment LEDs, something that didn’t exist in the 1960s. A true reproduction DSKY would use custom electroluminescent displays. These EL segments are powered by AC, and transistors back then were terrible, leading to another design choice – those EL segments were turned on and off by relays. It’s all completely crazy, and aerospace equipment to boot.

Because of the custom design and engineering choices that seem insane to the modern eye, there isn’t much in the way of documentation when it comes to making a reproduction DSKY. This is where [Fran] tapped a few of the contacts her historical deconstruction cred earned when she reverse engineered a Saturn V Launch Vehicle Digital Computer to call upon anyone who would have access to a real Apollo-era DSKY.

The first contact was the Kansas Cosmosphere who was kind enough to send extremely detailed photographs of the DSKYs in their archives. It would have been extremely nice to have old documentation made when the DSKYs were rolling off the assembly line, but that information is locked away in a file cabinet owned by Raytheon.

[Fran] got a break when she was contacted by curators at the National Air and Space Museum’s Garber facility who invited her down to DC. She was given the grand tour, including the most elusive aircraft in the museum’s collection, the Ho 229, the dual-turbojet Nazi flying wing. At the Garber facility, [Fran] received permission to take apart two DSKYs.

The main focus of [Fran]’s expedition to the Air and Space Museum was to figure out how the EL displays were constructed. The EL displays that exist today are completely transparent when turned off because of the development of transparent conductors.

The EL displays in the DSKY were based on earlier night lights manufactured by Sylvania. After looking at a few interesting items that included Gemini hardware and early DSKYs, this sort of construction was confirmed.

With a lot of pictures, a lot of measurements, a lot of CAD work, and some extremely tedious work, [Fran] was able to create the definitive reference for DSKY display elements. There are 154 separate switchable element in the display, all controlled by relays. These elements are not multiplexed; every element can be turned on and off individually.

Figuring out how the elements were put together was only one part of [Fran]’s research. Another goal was to figure out the electrical connections between the display and the rest of the DSKY. There, [Fran] found 160 gold pins in a custom socket. It’s bizarre, and more like a PGA socket than like the backplane connector [Fran] found in the Saturn V computer.

Even though [Fran]’s research was mostly on the EL panel inside the display, she did get a few more insights with her time with the DSKYs. The buttons are fantastic, and the best keys she’d ever used. This is just part one of what will be an incredibly involved project, and we’re looking forward to what [Fran] looks into next.

32 thoughts on “Reproducing A DSKY

  1. Anyone know of a breakdown of the code used in landing the LEM? It can’t be too long, there wasn’t much memory. It could be really hard to understand and clever, like HP calculators using the CORDIC algorithm for transcendental functions. In other words, what were the critical calculations and controls and inputs and outputs and how were they handled?

  2. Why are so many articles going to YouTube videos? Did people just suddenly decide to stop having blogs or websites?

    I brows HaD on my phone while I have downtime at work. I can’t really watch videos with sound, so I keep missing out on a lot of posts.

    1. Seconded. I imagine vlogging is less work. There are some topics that simply must have a video, but feels like an increasing amount of stuff not going to print. What about search engines, can they dig content out of video?

    2. I fully agree. I groan when a HAD article goes to instructables and curse when it goes to Youtube. It saves the author time but wastes mine. I can speed read through a blog page and get the info I want but I have to slog slowly through the videos. And capturing or printing something from video is a real PITA.

  3. If I recall, the Block I DSKYs had relays. The Block IIs had transitors — and also IIRC the Block IIs are the ones that went to the moon. I don’t know where I read that though, so grain of salt.

  4. During the period leading up to the last flights to the Moon, transistors grew up enough to become stable enough to work under those conditions. However…. I strongly speculate that the displays were indeed EL and were managed via relays. However the birds who brought us to Skylab did wear power transistors that were every bit as good as what’s available now. However all of the parts used were Rad hard rated. Which is interesting as the whole idea got started largely during our efforts to explore space.

    However Skylab wore Gemini period hardware, and were probably on a par with the Block I systems……

    1. Yeah, it’s truly fantastic. I moved to the town it’s located in a few years ago with my wife, and I honestly can’t remember how many times I’ve been there – it’s easy to get lost for a few hours in that museum. From the SR-71 in the lobby (It was flown in, decommissioned, and the lobby was built around it) to the Apollo 13 Command module in the museum, that place is like Disneyland for me.

  5. I’m the guy who did the electronics for the DSKY on the movie Apollo 18… we did try to be as accurate as possible, even though you scarely see any of it in the finished film. It was really fun to do though, pulling up all the reference material I could find and trying to make it look like something. I wish I’d had Fran’s terrific videos as a reference when I was doing it, this is some terrific work for sure!

    1. I have to say your work was amazing. Apollo 18 was one of the most accurate representations of living in the LM for a few days ever shown on film. It’s better than Apollo 13, better than From the Earth to the Moon.

      Then it’s rock crabs and Blair Witch in space. It remains the most disappointing movie I’ve ever seen. The LM was great though, and that’s something you should be proud of.

  6. I couldn’t help but to overlook Fran’s great achievement and instead be annoyed that the documentation for this does exist, but Raytheon refuses to release it.

    Maybe we can get a bunch of people to petition for it? At this point, it obviously doesn’t have any monetary value or trade secrets worth keeping hidden.

      1. The main one being that they probably don’t have enough interns to crawl through the warehouse(s) looking for some file folders that no one quite remembers what they did with…IF they even still have them and they weren’t waterlogged and thrown out during one of the last several hurricanes. This was forty years ago, remember.

        Never assume malice, when incompetence is an explanation.

    1. “At this point, it obviously doesn’t have any monetary value or trade secrets worth keeping hidden.”

      Industrial technology still has value since it may reveal design elements or methodology of modern systems. Ray is also protective of it’s information since the US government has something to say about technology disclosures. We really can’t say it doesn’t have value without understanding the device as an insider would see it.

      In a casual conversation with a Ray engineer about open sourcing an old protocol he said not to even try since secrecy is ingrained in the culture of the company. Too bad, but understandable when risk for the company is high and the rewards are few in their perception.

  7. How much more info. do you need on the DSKY, there are reams of the stuff on the net. It took me days to download scores of pdf. files before I started building my working replica DSKY.

  8. There is a quality replica on e-bay that uses the original NASA/MIT software and a graphic display instead of 7 segment. It has all of the features of all of the DSKY’s and AGC’s used in all of the missions. Fran does excellent work and she is working on an EL display to recreate the original, but it is not produceable in quantity at low cost and has a short life span. The LCD solution on the site enables so much more flexibility its really the best option.

    Dig a little deeper as for the 50th anniversary of the moon landing you can actually have a working DSKY with a Guidance Computer.

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