[Fran]’s New Project: The DSKY

[Fran] has already made a name for herself in some retro cool historical aviation and computer circles by tearing down a flight-ready spare of a Saturn V launch vehicle digital computer, the computer that was responsible for getting all flights to the moon into low earth orbit. Now she’s ready for another project, and again, this is something that hasn’t been done in 40 years. She’s building a DSKY, the control panel for the Apollo Guidance Computer

The Apollo Guidance Computer is a well-documented piece of computing history, with homebrew versions all over the web. The DSKY is only one small part of the AGC, but it is by far the most famous module. Being the only user interface for the AGC, it’s the only part of the AGC that gets all the screen time in Apollo 13, the travesty on BluRay that was Apollo 18, and is the only device that bears any physical resemblance to its real-life counterpart in a number of AGC simulators.

That’s not to say DSKY builds haven’t been attempted before; there are a few out there using LEDs and off-the-shelf buttons for the build, but the DSKY from the mid-60s is much, much cooler than a bunch of LEDs and light pipes. The eery green numbers are actually EL displays. Guess how those displays are controlled? Relays. It’s a masterpiece of technology, made even more impressive in that the folks at MIT who built the thing didn’t have anything better to build the display with.

Because of her deconstruction efforts with the Saturn V LVDC, [Fran] was invited down to the National Air and Space museum in the middle of Washington DC. There, she saw everyones favorite ugliest spacecraft, the Apollo LEM, along with an incredible assortment of paraphernalia from aviation history. The Wright Flyer – yes, the original one – is hanging from the ceiling next to the Spirit of St. Louis, and X-15 rocket plane, right above the command module Columbia from Apollo 11. Copies of probes currently rolling over Mars are on display, and you can walk through a training model of Skylab. If you’ve never been, spend half a day there, then take the metro out to the Udvar-Hazy center, where you’ll find all the stuff they couldn’t fit in the downtown collection like a Space Shuttle and a Concorde.

This is only the first part of [Fran]’s vlog documenting the construction of a copy of the DSKY, and we haven’t even seen the inner guts of the most famous part of the AGC yet. She’s been working on this for a while now, and there’s no doubt she’ll finish the job and come up with the best replica of a DSKY ever.

29 thoughts on “[Fran]’s New Project: The DSKY

  1. Bares should be bears in this summary.
    On topic: I like these reconstructions of old space guidance computers. I did some research a while ago because I was wondering why the Space Shuttle and other space vehicles had such limited computing power. While understandable for the Apollo era, the Space shuttle should have at least had a Pentium in it, lol. But apparently high energy radiation can change a 1 to a 0 or vice versa and really mess up some calculations and status flags. Therefore in space, you have to have “radiation hardened” memory and processor cores. Apollo used the old looped wire method, I actually saw a memory block on display at the Space Center in Huntsville, AL, and you could see the individual loops. It kinda looked like one of the LED cubes that make the rounds occasionally. I know, cool story bro, just wanted to share some of my experiences

    1. True back then but might not be true now with those private contractors building space craft… or trying to. I’ll bank some moron will push the limits of what one might consider radiation hardened and attempt to send up the latest ARM based Android as part of a flight control system.

      1. Actually, we should have pretty good data on rad-sensitivity of ARMs running Android before too long, considering how many of them are finding their way to orbit in microsats, etc.

        Also interesting in this regard… I played a very, very minor role (running an Earth station in my home) in the very late part of the AMSAT-OSCAR 40 project. The programming of the on-board computer was technically interesting (written in a multi-thread dialect of FORTH), but limited because they were constrained to use a rad-hardened 1802, of which there were only a few left. (There was a non-rad-hardened computer as well that was not flight critical which was able to do much more interesting things.)

        So what are the “contractors” doing?

        “The radiation parts tend not to have growth and upgrade paths. It’s very hard to grow, if you decide you want a little more capability, a little faster, you’re really limited – it’s that part.”


    2. NASA tries to build craft which are super reliable. The STS had triple redundant processors with one serving as main, one as double check and one arbitor. If the main and backup the arbitor had to decide which was correct and potentially block it.

      So the made the just complex enough to get the job done and no more. Complexity in space is opportunity for disaster.

    3. The Space Shuttle computers were “old” technology before it flew even the first time, the issue isn’t wholly radiation constraints or NASA going with “tried and true” systems, but more than a bit related to it being a MASSIVE multi-vendor, multi-DECADE, project with the added constraint that it’s desirable and politically correct to not KILL anyone during the projects life, aka real PEOPLE are riding this thing and one big headache IT’S A GOVERNMENT RAN MONSTER with scads of agencies involved! At some point in the design process hardware, software, methods and inter device standards MUST be locked in and considered complete or finalized, if the computer geeks keep updating the code or hardware nothing built by contractor “A” will work with Sub system X built by who knows who!! A case study of this on a substantially smaller scale would be Microsoft Vista! Where the specifications and library syntax got released to 3rd party vendor’s of hardware and software then Microsoft CHANGED the specifications so 3rd parties either redesigned and reproduced new products and on a very short time line or did not support VISTA for months after the release if they even attempted to be Vista compatible!! Was a major problem, my DSL modem from AT&T did not even try to support vista! And said so right in the product instructions! So design planning had quite a bit to do with the “old computers” on the Shuttles, That coupled with qualification test requirements for any equipment going into the shuttle project some components required thousands of hours testing and trials to get acceptance. often a part for any government technological program is out weighed many times by it’s accompanying documentation. I worked for a vendor supplying a small RC network for a DOD system, the finished part weighed under 3 oz. but each and every part had almost 500 PAGES of paperwork required to ship with the part a 500 piece order weighed almost 400 pounds!
      No exaggeration No kidding, the UPS bill for one 500 pc order was MORE than the actual manufacturing costs for ALL 10 thousand units we produced that year for them! (By the way we were required to keep a copy of the paper work physically not on computer for at least 20 years!) . Wonder how much all the Paper work on one Shuttle weighed? most likely more than an actual shuttle!!, and its probably still kept on file at vendors and in NASA’s archives still even now!!!!)

  2. Designed yes. Built no. They started building them much later. The computers used on board the first ones were based on the same standards as the S/370. Especially since IBM was the computer builder for majority of the space program. The only ones they did not build any for,as it happens was Apollo. That amazing design had other builders.

    1. I really don’t consider 1975 to be “much later”. The first shuttle flight to space was in 1981, and construction on that shuttle, Columbia, began in 1975. There was also the Enterprise, which was a flying testbed never intended for actual space flight, which was built in 1976 and was actually the first shuttle to fly, albeit in the Earth’s atmosphere.


      I’m not just pulling this stuff off of Wikipedia. These were current events during my childhood, and I remember following the shuttle program and watching the launches.

      1. Also wrong about Enterprise. She would have been first, except for the fact that the contractor and NASA upgraded their specs, several times in fact, and the end result might have been too costly to redo the mechanics behind Enterprise to give her, her first trip. So they decided to use the craft as a airborne test. Including two spectacular flights over Edwards.

        1. I’m not in a position to say whether this is revisionist history–it’s just the story I’ve always heard, and I was born after the shuttles had already started flying–but Enterprise (to my knowledge) was ALWAYS intended as a flying aerodynamics testbed, for launch off of the SCAs. The plan was to upgrade her for orbital capability later, but it was judged to be cheaper to build Endeavour instead.

  3. Some technology used in the Shuttles was pre-transistor. They had some magnetic core memory modules. Being a government program with goals and purse controlled by politicians who were (still are) mostly clueless about any technology more advanced than a light switch…

    A lot of the systems had to be fixed in design early on so that the companies building other parts to work with them would know what they needed to make.

    They were also working with the still fresh knowledge of how disastrous a change in a specification could be when combined with a failure to communicate that change to people responsible for everything else.

    There were two main causes of the Apollo 13 oxygen tank explosion.

    The first was tank had been dropped in (IIRC) 1965 (loooong lead times on the project!) and instead of being inspected for damage, repaired and re-tested, or just scrapped, nothing was done except putting it into the queue for assembly. Reviewing the report of the incident, the most likely damage was the pressure relief line got pinched shut.

    The second was doubling the voltage for much of the electronics. Making certain all contractors supplying electrical components were aware of that and all of them having to essentially start over on their designs, must have been a nightmare of a job. And someone dropped the ball when it came to the wiring inside the O2 tanks that had already been made.

    Nobody wanted a repeat of a failure like that with the Shuttle. I bet that every change, no matter how small it seemed, generated a large number of phone calls, FAXes and meetings among all the engineers, techs and project managers whose parts it could conceivably affect.

    The way most NASA sponsored space projects have been done has assured huge numbers of delays with the work spread across so many companies who all have to work together. That method has also ensured massive cost overruns.

    It’s pretty amazing that American manned space travel has only killed 20 people and nearly killed 3. 3 in Apollo 1. 7 in Challenger. 7 in Columbia. 3 ground crew killed in a nitrogen purge incident in Columbia before its first flight. And the nearly killed 3 in Apollo 13.

        1. Ah, hadn’t checked in awhile and just saw that – thanks.

          Totally understand the reasoning behind it, but I sure will miss making a drinking game out of how many times Bil mentions Commodore in one episode.

          Seriously though, it was a good series and I hope they can get together sometime to do a special or something.

  4. She doesn’t owe anyone an explanation regarding her gender or feelings. She is a human being just like the rest of us. I personally don’t know Fran, but I follow her work and she does some really great stuff to which I’ve learned from. We need to get over judging people by their gender, race, status, etc… and accept them for who they are, and to appreciate their contributions to the world. From what I see, Fran goes out of her way to make videos and share information. Sharing information about her gender is completely irrelevant and nobody’s business unless she wants to share it.

    As a space geek, and also have grown up during the Apollo and Shuttle era, I’m looking forward to seeing this project progress.

  5. I’ve looked at doing a DSKY build using an EL display, but can’t find any reasonable source for the silkscreen ink without buying industrial quantities of it. Doing it with off the shelf 7-segment displays just doesn’t look right to me.

  6. Accept them as who they are … Fine. But how do we know who they are, if they are unsure about that themselves? If people went around changing their gender at the drop of a hat, that would make things very interesting fast.

    1. To know who they are you engage in dialog, find out what they like and dislike, their interests, their hobbies. You become their friend and then you will know who they are.

      As far as what gender someone is, you ask, they tell you, you move on.

    1. Rules are meant to be broken, especially by the people who create the rules.

      Actually, that’s more of a ‘soft’ rule. It works for 90% of the posts on HaD, but I’d challenge anyone to write the lede for this post without first citing the LVDC posts. If you’re doing that, why not link to it?

  7. Folks- I am going to be blunt. Either respect our peers in Hacking or KEEP IT TO YOURSELVES!

    I openly call it “Conduct UNBECOMING HACKERS” to be disrespectful of our peers.

    Seriously enough that I consider it worth openly stating “disrespect” for Gender etc may even warrant a /banlist And anyone saying that they are justified in disrespect deserves no respect nor access to our forums. Back to Hacking, eh?

  8. People say how cool the DSKY display looks, but I am at a loss to know how they know that when none have been powered up in the last 40 yrs. I asked this question about 2 years ago when I started my DSKY project, an authoritve source informed me that even if one was powered up it would not appear as the original if it worked at all due to deterioation of the eld.

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