> 13 pins in two unequal rows were plugged into a socket on the circuit board.
I suspect this was done to ensure the device could only be plugged in one way.
This technique was forgotten by the time I worked on designing embedded systems. All kinds of devices (chips, caps, diodes, etc.) had symmetrical pinouts, so they could be plugged in the right way, or the wrong way (and would burn out as a result). At least the #1 pin on a chip had a slight depression over it. We always designed chip circuit boards so the #1 pin was always in one direction, so a visual scan of the completed board would verify the chips were all in the right way.
The board was also set up so the diodes were all pointed the same way, caps too.
Of course, the chips could still be plugged in off-by-one.
Sometimes mathematical symmetry is just a bad idea. I had an old Benz that had a mechanical fuel injection system that sat on a splined shaft. There was no key spline. If you got the spline off by one, you couldn't tell until they engine ran poorly. What a wretched design.
Boeing always used keyed splines if orientation made any difference. 4 hole bolt patterns were never symmetrical so the device could only be bolted on one, the correct, way.
It was so catastrophic to hook up hydraulics to the wrong ports that the supply and return ports used different size fittings, color codes, and even one port was left-hand and the other right-hand to prevent swapping them. The ports were placed so the tubes could not reach the wrong port.
Even then, now and then some mechanic would fashion an "adapter" in order to hook them up wrong, which is why they are also tested after assembly for correct polarity.
> We always designed chip circuit boards so the #1 pin was always in one direction, so a visual scan of the completed board would verify the chips were all in the right way. The board was also set up so the diodes were all pointed the same way, caps too.
I'm not an EE, but wouldn't this have the potential to significantly complicate the layout of traces on the board? I assume you're talking about hand-assembled boards, and hand-drawn too?
I know you reverse engineer electronic devices, but I'd love to see the low-tech side of the Apollo missions. Astronauts had substantial ability to navigate in an old-fashioned way in case of equipment failure. The landing point designator on the Lunar Module window, all these elaborate procedures baked into the sequence like the roll maneuver to visually confirm the trajectory and the landing spot etc. A lot of thought went into that. If I'm not mistaken, they also had a direct need for this during Apollo 13 pre-reentry orientation.
It's sometimes fun to imagine the alternative reality where miniaturization never happened and spaceflight is forced to use low-tech navigation aids - precise clock, periscopes, reticles, slide rules, nomograms. (and communication with the flight control center which does the bulk of the computational work)
> Onboard the Command Module, these messages were decoded by the Up-Data Link
Do you think there was any kind of primitive authentication of the received PSK signal? Even something as simple validating a preamble against a hard-code bit sequence?
There was error checking, but not security. Each bit was expanded to a 5-bit sequence, so bit errors could be detected. The message started with a 3-bit vehicle address, so separate messages could be delivered to the Command Module and the Lunar Module.
For the range safety officer's destruct control, NASA did use cryptographic security because they wanted to make sure the Russians couldn't blow up the spacecraft. This was an entirely separate system. The control unit used a secret plug that encoded the "key", that was installed just before launch so nobody could spoof the command.
Yes, the Range Safety Officer could send a coded command to "terminate the flight of an erratic vehicle" by cutting off the engine and "dispersing the propellant". Each of the three stages in the Saturn V rocket had linear shaped charges to blow up the liquid hydrogen and liquid oxygen tanks. [1] The astronauts would hopefully be pulled to safety by the launch escape system, the rocket engine on the top of the capsule.
And yes the rockets had shape charges in each stage which can be activated to destroy the rocket in a controlled fashion. If you have a rocket gone haywire, it's better to jettison the crew capsule to safety and do a controlled demolition, to prevent the rocket from flying out of control and crashing into structures or people on the ground.
This is also why rocket launch sites tend to be coastal locations with ocean to the east - there's a lot less valuable stuff under their flight path.
I'd say that RF stuff is pretty much mysterious so I generally avoid it. For instance, part of the Apollo stuff had a frequency multiplier. We opened it up and it was essentially an empty box with adjustable pegs inside. I don't want to deal with that sort of magic nonsense :-)
Another hard part is things that are encased in epoxy or welded shut. In this case I used X-rays but its generally a problem.
Overall, the main secret of reverse engineering old stuff is to spend way more time on it than an sensible person would.
> Overall, the main secret of reverse engineering old stuff is to spend way more time on it than [any] sensible person would.
quote of the week.
so many things have been laid bare to me by just putting in the time. even just staring at the thing(s) will often help me realize something important, somehow.
Your website still doesn't load from Russia. Yes, the war is indeed absolutely unacceptable, except regular people like me have exactly zero means of influencing it. Your blocking of Russian IPs thus achieves nothing but frustration. Please consider unblocking.
"A schematic diagram of the module. Component values are from curve-fitting to oscilloscope traces, so they're probably off by at least 10%."
As the modules are made of discrete components (as opposed to some thin film process) wouldn't it have been better to assume standard values, i.e.: 20k to either 18k or 22k, 4.9k to 4.7k, 155 to 150 ohms, etc. and work backwards from there?
Tooling up for such odd values would be a messy business, especially so for such a small quantity (and in that era when jigging up would have been a big effort).
Alternatively, standard components may have been used and a SOT (Select on Test) method employed to obtain those specific values (say as is done in 'film terms' matrices where exact values are of critical importance).
No doubt this could be determined by opening one of the modules and either measuring them directly or checking the color code bands on the resistors. It's very unlikely that a standard resistor made during that era would not have had the normal color coding and as far as I can recall Motorola never made resistors so it would have had to have purchased them from a manufacturer of same, Allen-Bradley (A-B), Sprague Electric, etc., so it's all the more reason the resistors would have been color-coded. (BTW, please correct me if Motorola did make resistors.)
I'm of the generation who remembers those events happening so I find it fascinating. I'd like to monitor how this project eventually unfolds.
I guess the obvious next question is whether NASA has documentation for this stuff which might be obtainable. (I don't recall whether Ken has already answered this in some other forum/thread.)
Mike Stewart has made a huge effort to dig up Apollo documentation from various archives. For the updata test box, he eventually found a high-level functional specification. It mostly confirmed what we had already figured out. We haven't found any detailed information on this box, and nothing about the internal modules. But maybe we'll be lucky and some will turn out.
In the process of archiving every document on that page, thank you! I'd love to have a full collection of Apollo documents; any other resources/websites I should know about?
The real resource is the National Archives and Records Administration (NARA). The problem is that you need to give them the number for the document you want and then pay up to $4 per page.
As far as scanned Apollo documents, archive.org has a bunch.
Fwiw I cross posted the article on the Vintage Test Equipment FB group. There are quite a few comments there but so far none answering the key questions.
I suspect this was done to ensure the device could only be plugged in one way.
This technique was forgotten by the time I worked on designing embedded systems. All kinds of devices (chips, caps, diodes, etc.) had symmetrical pinouts, so they could be plugged in the right way, or the wrong way (and would burn out as a result). At least the #1 pin on a chip had a slight depression over it. We always designed chip circuit boards so the #1 pin was always in one direction, so a visual scan of the completed board would verify the chips were all in the right way.
The board was also set up so the diodes were all pointed the same way, caps too.
Of course, the chips could still be plugged in off-by-one.
Sometimes mathematical symmetry is just a bad idea. I had an old Benz that had a mechanical fuel injection system that sat on a splined shaft. There was no key spline. If you got the spline off by one, you couldn't tell until they engine ran poorly. What a wretched design.
Boeing always used keyed splines if orientation made any difference. 4 hole bolt patterns were never symmetrical so the device could only be bolted on one, the correct, way.
It was so catastrophic to hook up hydraulics to the wrong ports that the supply and return ports used different size fittings, color codes, and even one port was left-hand and the other right-hand to prevent swapping them. The ports were placed so the tubes could not reach the wrong port.
Even then, now and then some mechanic would fashion an "adapter" in order to hook them up wrong, which is why they are also tested after assembly for correct polarity.