Basic Mechanisms In Fire Control Computers

August 24, 2024 5:55 PM

1953 U.S. Navy training films"Basic Mechanisms In Fire Control Computers" on how a analog computer uses many inputs to determine how to aim big guns at a target. How? With shafts, gears, racks, differentials, cams, integrators, multipliers, etc.
posted by ShooBoo (20 comments total)

Fun fact: When the Iowas were reactivated in the 80s they still used the mechanical fire control, because the electronics of the time couldn't match their robustness.
posted by ChurchHatesTucker at 6:56 PM on August 24 [4 favorites]

Just wild to think about a mind that understands both the math of the ballistics and the mechanical engineering required to design a physical calculator to do that math....

When I was young I thought I was smart, but I can barely make out the outlines of this problem. DAMN.
posted by wenestvedt at 7:00 PM on August 24 [2 favorites]

YesYesYes, thank you!
posted by mollweide at 7:23 PM on August 24

I am bad at math, and ignorant of most things mechanical. This was fascinating for its relative simple explanation of the mechanical components and how they work together. Thank you! I'm a smidgen smarter than I was an hour ago.
posted by lhauser at 7:46 PM on August 24

I still say the Jeune École was right . . . I'd rather have 8,000 radio-controlled jet skis vs 1 700' armored warship . . .
posted by torokunai at 7:49 PM on August 24 [1 favorite]

I remember 1953. But the train never made it out there. My dad got a new Lincoln. But that's about all I remember besides the work in progress O gauge train set complete with a tunneled plaster hill in the garage. That train never left the living room carpet before we moved. Back in the days of shaft and gear macrochunk technology. When cars and refrigerators were all R. Crumb curvy.
posted by y2karl at 9:54 PM on August 24 [1 favorite]

Also, the computer in the film brought William Gibson and Bruce Sterling's The Difference Engine to mind.
posted by y2karl at 10:04 PM on August 24 [2 favorites]

My Mum, born 1920, failed algebra at school. She joined the ATS in 1940 and had a rather adventurous war being useful in a variety of fields. She became a dab hand at operating a kine-theodolite which tracked incommming with a pair of cameras to triangulate the target in real time on film. She taught trig to recruits not as useless book-learning but as a challenge with real-world implications. She celebrated VE day in Breda having spent the previous several months trying to get a fix on flying bomb launch sites so they could be bombed. That never worked a) because precision bombing was The Future b) the rockets were being launched from Meillerwagen trailers.
posted by BobTheScientist at 10:53 PM on August 24 [17 favorites]

Wow, what a terrific video! Just yesterday, I fell down a rabbit hole learning about the naval battles of the Pacific theater in WW2. The superiority of American fire control computers was a major advantage. Notably in the Battle off Samar (Wikipedia), when a few American destroyers spent hours plinking away with their 5" guns at a massive fleet of Japanese battleships and cruisers. It took an embarrassingly long time for the Japanese ships to hit the much smaller destroyers, and the long distraction saved four out of six of the American escort carriers the destroyers were protecting.

Weird fact: The Japanese shells included dye packs, so they could tell where their shots were landing in the water and adjust accordingly. Different ships had different colors.

Just wild to think about a mind that understands both the math of the ballistics and the mechanical engineering required to design a physical calculator to do that math....

You don't really need one mind that understands both (although I expect the engineers of this did)... a ballistics expert writes down the equations, and an engineer translates them into a physical machine. The components described in the video can be treated as black boxes: they take inputs and produce outputs; they're functions. You figure out which black boxes you need and how they should be connected (this part is basically the same as what computer programmers do today), and then you need to solve the 3D puzzle of how you fit the pieces together (that sounds really intimidating to me, as a programmer, but I expect one would get good at it with time and experience)
posted by qxntpqbbbqxl at 12:28 AM on August 25 [5 favorites]

(and now that I'm thinking about this, I kind of want to write a compiler that compiles mathematical equations into 3D-printable machines)
posted by qxntpqbbbqxl at 12:34 AM on August 25 [15 favorites]

In James Gleick's biography Genius - The Life and Science of Richard Feynman, he describes Feynman's work on a war project before he had been enlisted at Los Alamos:

Feynman spent his summer at the Frankford Arsenal working on a primitive sort of analog computer, a combination of gears and cams designed to aim artillery pieces. It all seemed mechanical and archaic [..] Still, even in his college workshops, he had never confronted such an urgent blending of mathematics and metal. To aim a gun turret meant converting sines and tangents into steel gears. Suddenly trigonometry had engineering consequences: long before the tangent of a near-vertical turret diverged to infinity, the torque applied to the teeth of the gears would snap them off. Feynman found himself drawn to a mathematical approach he had never considered, the manipulation of functional roots. He divided a sine into five equal subfunctions, so that the function of the function of the function of the function of the function equaled the sine. And the gears could handle the load.

posted by rochrobbb at 3:46 AM on August 25 [11 favorites]

On a tour of the battleship Massachusetts, I learned that there was one man whose job it was to continually adjust a guage to tell the analog computer what was horizontal as the ship pitched in the seas.
posted by SemiSalt at 5:17 AM on August 25 [6 favorites]

When the Iowas were reactivated in the 80s they still used the mechanical fire control

One of the requirements of a Fire Control Computer is that it will fail safe should say a bullet go right through the main CPU, you wouldn't want such an event releasing a bunch of bombs. So even modern computer controlled FCCs use (multiple) mechanical relays with springs that by default hold them in a safe position.
posted by Lanark at 5:53 AM on August 25 [3 favorites]

That's a WOPR of a story, Lanark.
posted by Ickster at 7:19 AM on August 25 [5 favorites]

If you're curious how they hit targets in-flight without computers, but only trigonometry, see this Army Air Force training film from ten years previous, Position Firing. Trigger Joe voiced by Mel Blanc.
posted by Rash at 9:01 AM on August 25 [1 favorite]

Great post, thank you! Just a reminder of how much I still want a Curta.
posted by The Bellman at 7:04 AM on August 26 [3 favorites]

In college (early 1980s) the physics department had an old electronic analog computer. It was a console with a patchboard with which one could build circuits, or systems of circuits, out of resisters, capacitors, inductors, and such. Its purpose was the electrically solve systems of differential equations. The output could be wired to an oscilliscope. I used it briefly and thought it was pretty clever. The machine was probably manufactured in the 1960s. The ability to solve math problems digitally was just becoming available.

In my freshman year numerical calculus course we ran our programs remotely at the big state university's supercomputer. That computer (CDC 6600?) filled a room. Our modem was the size of a washing machine. Our lil college paid the big university by the microsecond of CPU time, so we worked hard to make our code tight and prevent infinite loops. By the time I finished college we were doing calculus in Fortran on our TRS-80s.
posted by neuron at 9:23 AM on August 26 [2 favorites]

At any moment the
sum of range change and
initial range
is present range.

If own ship is moving
towards the target,
present range is obtained
by subtracting range change
from initial range.
posted by paper chromatographologist at 11:14 AM on August 26 [1 favorite]

This brought to mind a course I took in college (1972). I still have the textbook, though with a different cover.
My favorite mech was the Geneva, and then a year later I was trained on the 2540 card punch, which uses a Geneva. (That's how it could punch so fast)
I also was fascinated with 4-bar linkages. Pretty sure I did some of my homework in Fortran for this course, for fun.
posted by MtDewd at 3:06 PM on August 27 [1 favorite]

Previously.
posted by mabelstreet at 2:33 PM on August 28