The electromechanical angle computer inside the B-52 bomber's star tracker (righto.com)

by NelsonMinar 113 comments 431 points
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113 comments

[−] somat 26d ago
"The second approach was to use a digital computer to determine the solution. This solution was rejected because in 1963, a digital computer was expensive, slow, and less reliable."

This inflection point between analog and digital computer is a fascinating one. At one point in time a analog computer made sense and some later point in time you would be foolish to specify anything other than a digital computer. But that time between when it could go either way is interesting. There is a good autobiography by the person responsible for introducing the first digital computer to the navy that provides an interesting view into this era. https://ethw.org/First-Hand:No_Damned_Computer_is_Going_to_T...

Now I am vaguely searching for a guide on gear train schematic diagrams, I am sure they had them, you don't reason out something this complicated without one. I know hydraulics has it's own flavor of schematic diagram, which are fascinating if all you have seen are electronic circuits. https://www.hidraoil.com/technical-resources/hydraulic-symbo...

[−] mohamedkoubaa 26d ago
They're making a comeback now, quantum computers are analog
[−] somat 25d ago
That is why I have doubts about their scalability. There are fundamental physics reasons we were able to scale digital computers and were unable to do the same to analog ones.
[−] mohamedkoubaa 25d ago
That's certainly true. But - the fastest possible machine to compute the sound of a guitar string reverberating in a concert hall is a guitar in a concert hall. The world itself does a tremendous amount of compute - the question is whether it is useful compute. I don't think this has been explored nearly enough.
[−] bzbz 25d ago
Why is it the fastest possible?

Wouldn’t you be able to run a higher clock-speed simulation, and therefore compute the sound ahead-of-time, on a digital device?

[−] mohamedkoubaa 25d ago
Nonlin ar partial differential equations through a large continuum are expensive. Even if you can scale this particular example, it doesn't refute the point, the universe does a tremendous amount of compute that we don't know how to exploit.
[−] qsera 25d ago
This assumes that the universe is computing.

But there is some hypothesis like MUH that sees reality as a sort of "recording" that we just experience.

[−] qsera 25d ago

>Why is it the fastest possible?

Why? because the "universe" takes zero time to compute it. In fact all of reality is computed in zero time. How can you beat it?

[−] qsera 25d ago
TO continue the above comment..

I think it is totally possible for the computing to take non-zero time, but we observe it in zero-time as our consciousness only steps forward only with each iteration of computing the world state. So we observe zero time reality computations.

[−] lioeters 26d ago

> No Damned Computer is Going to Tell Me What to DO

That is the best title for a story about replacing analog and mechanical instruments with digital computers. A similar process is happening now with natural intelligence, replacing or augmenting the human intellect.

An interesting resource I just found:

The analog computer museum - https://www.analogmuseum.org/english/

It has a Library section with lots of downloadable articles in German and English.

[−] qsera 25d ago

> A similar process is happening now with natural intelligence

LLMs are not AI.

[−] lioeters 25d ago
Correct. Neither are computers, analog machines, or mathematics.

I'm on your side, human comrade. No damn computer is going to tell me what to do!

[−] qsera 25d ago
I said it because, the behavior of LLMs only appear to mimic intelligence only very superficially. Even without going "behind the curtain", and by only examining the behavior of LLMs slightly deeply, the illusion of this intelligent behavior break down.

Intelligent behavior need to be consistent. You need only a single instance of non-intelligent behavior to prove that an entity is not intelligent.

[−] Animats 26d ago
This is from the era of devices where the I/O was entirely electrical but the computation was mechanical. Most of this stuff came from naval gunnery. The naval "fire control tables" started out as mechanical computers where a rather large number of people were inputting different sensor readings via cranks and dials.[1] Gradually, more of the inputs came in directly from the sensors, and more of the outputs went directly to the gun turrets. The final form of this technology was units the size of a footlocker full of gears, cams, and resolvers, with all-electric inputs and outputs. Such things used to show up in surplus stores.

I've seen the restored guidance computer for the Nike missile, at the site in Marin County.[2] That's similar, although ground-based. Analog data came in from radars, was processed with mechanical computation, and control signals went out to the missile.

[1] https://en.wikipedia.org/wiki/Admiralty_Fire_Control_Table

[2] https://www.nps.gov/goga/nike-missile-site.htm

[−] aequitas 26d ago
There are some old training videos that show how this worked: https://www.youtube.com/watch?v=gwf5mAlI7Ug

Also the Battleship New Jersey YouTube channel has some nice content on this: https://www.youtube.com/watch?v=szxNJydEqOs

[−] Animats 26d ago
See [1] for the basic mechanical components. It's a better scan of the same film the Periscope Film archive sells, which is the first one linked above. No sprocket clatter.

[1] https://www.youtube.com/watch?v=s1i-dnAH9Y4

[−] ghaff 26d ago
I forget where I saw it (probably YouTube someplace) but the fire control systems (including radar) on the Iowa-class battleships apparently way outperformed their Japanese counterparts. The Japanese has a couple (?) ships with bigger guns/longer range but they couldn't actually take advantage of that longer range to hit big US ships.
[−] pram 26d ago
Semi-related but people should look at the Sprint missile if they're interested in this, it goes so ridiculously fast the warhead begins to glow.

https://youtu.be/kvZGaMt7UgQ

[−] jvanderbot 26d ago
One of my favorite internet links is an archive of manuals from this era. Especially the Torpedo Data Computer, another fire solution calculator.

Excellent illustrations!

https://maritime.org/doc/tdc/index.php

[−] ghaff 26d ago
Haven't been there in years but the Nike facility in Marin is well worth a visit if you're there when it's open. The control stations were originally on a higher ridge but they have one of the (basically) containers next to the missile sites now. The idea at the time is that they would explode ordinance (originally conventional, later nuclear) above incoming bombers causing a pressure wave that would make them crash.

Was also a Nike base on Angel Island but there's nothing left there but some old concrete pads.

We actually had one of the Nike bases defending Philadelphia literally next to where I grew up. Don't remember personally--was very young--but there were apparently troop manoeuvres on our property from time to time.

[−] Animats 26d ago
There were fourteen Nike sites in the Bay Area.

We may see large numbers of local defense sites again, against drones and medium-range missiles. Israel and Iraq already have that.

[−] kens 26d ago
If you're looking for more, the book "Between Human and Machine: Feedback, Control, and Computing before Cybernetics" is a detailed history of the development of electromechanical fire control computers and feedback systems.
[−] bethekind 26d ago
Off topic, but this is where I see AI going. A tool that condenses work down from requiring a team and a room to a box. We're decades away from that
[−] po1nt 26d ago
Everytime I read articles like that, I envy the engineers that worked in development of such tools. First microprocessors in jet fighters, electromechanical celestial navigation...

And here I am fighting gitlab pipelines.

[−] beachy 26d ago
I think the opposite. Hardware is hard, as they say. Building such complex electromechanical designs to military specs without modern CAD tools must have been the equivalent of writing code in binary, without high level languages or even assembler.
[−] po1nt 25d ago
I'll take it any day if I wouldn't need to see docker on windows anymore.
[−] mizzao 26d ago
It seems GP was appreciating the beauty and purity of engineering required in solving such problems (as opposed to, perhaps, fighting AI slop today).
[−] echelon 26d ago
Nothing is stopping us.

One life to experience the universe. Save up for a sabbatical. Find new engineering pastures.

It's always rose colored looking back. Not everybody got to work on this. Some people were storming the beaches...

[−] colechristensen 26d ago
Eh, it's easy to get caught by the romanticism of working on things like this, but I assure you besides like 4 people in charge of the big picture, everybody else is dealing with things which are exactly as mundane as things these days. Like putting it through 1000 heat cycles of -40 to 200 degrees and then vibrating it at 2gs for 200 hours and then measuring the tolerances of each part... or being in charge of three lines in a standards document for 2 years negotiating the details with the DoD.
[−] culi 26d ago
It's a shame the only way to work on problems like these (and make a decent living) is to make tools of war.

The end game of much of silicon valley seems to be government (read: military) contracts. Probably because its the main branch of government that's thoroughly funded

[−] SlightlyLeftPad 26d ago
I’m with you. The complexity yet simplicity of these mechanical devices is fascinating.
[−] kens 26d ago

> First microprocessors in jet fighters

Don't get me started on that...

[−] pests 26d ago
Read every word. i liked this detail in the footnotes:

> The Astro Compass needed to know approximately where in the sky to find the star, in order to point its sensor in the right direction. The direction didn't need to be exact because the Astro Compass performed a spiral search pattern to find the star. This search pattern covered ±4° in bearing and ±2.5° in altitude. In comparison, the Moon is 0.5° wide, so it's a fairly large target area. ↩

[−] chiph 26d ago

> The Atro Tracker also has declination limits of +90° and -47° and a lower altitude limit of -6°. The latitude is limited to the range between -2° and +90°; the system automatically switches hemispheres so both the North and South latitudes are usable.

Why would the system need to have a much greater range of declination (celestial sphere) than latitude (Earth spheroid)? Because the Astro Tracker and Angle Computer could flip over to the Southern hemisphere (was this automatic or was there a switch?) having that much declination range seems unnecessary. Perhaps to allow for pitch of the aircraft in flight?

BTW, being able to operate in both the Northern & Southern hemispheres was an important capability for the B-52. Previous bombers (B-36 mostly) had the range but not the reliability or in-flight refueling for global reach.

Sadly, I didn't get the chance to look at the B-52 at the Museum of Flight when I was there. If you ever meet Charles Simonyi, please thank him for his support of the museum.

[−] kens 26d ago
Author here if you have questions about this analog computer...
[−] agambrahma 26d ago
This is crazy impressive ... the kind of thing that should inspire one to do more, much more, than whatever "mere plumbing" one happens to be doing at the moment
[−] black6 26d ago

> Each knob on the Master Control Panel has a different geometrical shape, allowing the user to distinguish the knobs by feel.

Auto manufacturers should take a clue here.

[−] 0xfaded 26d ago

> AI statement: I didn't use AI to write this article (details).

Meta, but thank you for including this and suggest even putting it at the top of your articles. I'm now off to bother to read something that someone bothered to write :)

[−] t0mas88 26d ago

> The Angle Computer is one piece of the Astro Compass, a system that locked onto a star and produced a highly accurate heading (i.e., compass direction), accurate to a tenth of a degree.

I think it provides ground track information not just heading? Which is far more valuable for aircraft navigation, because the main issue is unpredictable wind drift.

[−] ForHackernews 26d ago
Similar but arguably even more insane is the Minuteman ICBM's inertial guidance computer https://www.righto.com/2024/08/minuteman-guidance-computer.h...

> The diagram below shows the guidance system of the Minuteman III missile (1970). This guidance system contains over 17,000 electronic and mechanical parts, costing $510,000 (about $4.5 million in current dollars). The heart of the guidance system is the gyro stabilized platform, which uses gyroscopes and accelerometers to measure the missile's orientation and acceleration.

[−] TMWNN 26d ago
It's amazing, the things that can be done without what we would consider modern technology.

The 8-bit Guy recently released a video asking "What if everything still ran out vacuum tubes?" <https://www.youtube.com/watch?v=mEpnRM97ACQ>. Conclusion: A surprising amount of things we take for granted today would still be possible.

[−] ChrisMarshallNY 26d ago
Reminds me a bit of this[0]. I have an iOS app[1] that models its operation. Sextants[2] are damn clever devices, and have been around for about three hundred years. Theodolites[3] are even older, but are used for terrestrial measurements.

[0] https://en.wikipedia.org/wiki/Antikythera_mechanism

[1] https://apps.apple.com/app/id989574753

[2] https://en.wikipedia.org/wiki/Sextant

[3] https://en.wikipedia.org/wiki/Theodolite

[−] enjeyw 26d ago
The story of the navigator in the photo is also worth a read [1]. Very reminiscent of Joseph Heller’s work.

1. https://www.rbogash.com/B-52/Carls_Letter.html

[−] sltr 26d ago
Mentioned in the footnotes, CuriousMarc has 3 videos on this device. https://youtu.be/aPIZwqq_W_k?si=wAkRagRx-B06TXwY
[−] thecodemonkey 26d ago
Fun! I was just reading about the star tracker in "Skunk Works: A Personal Memoir of My Years at Lockheed". Really fascinating when you're thinking about how this all happened in the 50's and 60's.
[−] runjake 26d ago
Before GPS (and after), B-52s navigated using redundant Inertial Navigation Systems (INS).

The angle computers were removed from the H models in the early to mid 1990s and I doubt they added them back.

[−] lb1lf 26d ago
In a very similar vein, Ars Technica did a very interesting story on the electromechanical targeting computers on WW2 battle ships a few years ago; the instructional videos embedded in the story are gold.

https://arstechnica.com/information-technology/2020/05/gears...

[−] 93po 26d ago
Someone recreating this and allowing access to it sort of in the style of an escape room business would be pretty cool - motion flight sim where you can learn to fly the plane or learn to operate the other parts of engineer/bombing/navigation etc. And maybe not simulating the problematic "let's bomb human targets" but rather just bullseyes in fields.
[−] matheusmoreira 26d ago
The Air Almanac... Reminds me of the celestial navigation military training videos:

https://youtu.be/UV1V9-nnaAs

[−] staplung 25d ago
Honest question: how do you track stars during daylight? Is it the case that at the operational altitude of the B-52, bright stars are always visible?
[−] tmoertel 26d ago
Check out those wire harnesses! Serious workmanship there.
[−] esaym 25d ago
What is wrong with just using a compass??
[−] kylehotchkiss 26d ago
in a way we're still trying to build stuff like this (world models??)
[−] brcmthrowaway 26d ago
Could Claude make this?
[−] SecurityPill 26d ago
I wonder if we would ever be able to vibe code the design and 3d print it someday
[−] kuzivaai 26d ago
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