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posted by LaminatorX on Tuesday March 18 2014, @01:27PM   Printer-friendly
from the Surigao-Strait dept.

ed.goforth writes:

"Gears of war: When mechanical analog computers ruled the waves over at Ars is a quick recap of the history of naval targeting & fire control systems and the transition from analog to digital. In short, you'll never believe just how good those old designs were, and how much work it's taken to make GPS-based guidance be as accurate."

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  • (Score: 5, Interesting) by Geezer on Tuesday March 18 2014, @01:34PM

    by Geezer (511) on Tuesday March 18 2014, @01:34PM (#18073)

    It confirms my general impression when I visited a WWII heavy cruiser about to be scrapped (USS Toledo in San Diego, many years ago). The visible mechanisms of the fire control solution table in Main Battery Plot were like some clockwork-builder's wet dream, and yet allowed for extremely accurate prediction of a projectile's over-the-horizon flight based on numerous analog inputs.

    • (Score: 5, Interesting) by frojack on Tuesday March 18 2014, @08:26PM

      by frojack (1554) on Tuesday March 18 2014, @08:26PM (#18222) Journal

      It is also interesting to note that these mechanical marvels also calculated the firing solution based on a specific ship position. Once that solution was locked into the gun, the turret officer would pull the electric trigger, but nothing would happen until the ship rolled or pitched into the calculated position.

      There could be a disconcertingly long delay between the firing bell and the actual shot, especially if the trigger was pulled as the ship nosed down into a wave, as the computer would delay the firing until the bow rose again.

      This was a totally separate computer, (rather simple compared to the fire control computer). Some turrets were mounted on gimbals, but that wasn't practical on the largest naval guns.

      --
      No, you are mistaken. I've always had this sig.
  • (Score: 5, Informative) by randmcnatt on Tuesday March 18 2014, @01:52PM

    by randmcnatt (671) on Tuesday March 18 2014, @01:52PM (#18081)
    When I first got interested in computers my dad handed me his copy of the US Navy's Basic Fire Control Mechanisms (I'm not at all sure he was supposed to). Amazingly, the manual is online [hnsa.org] [PDF]. It makes for an amazing read.
    --
    The Wright brothers were not the first to fly: they were the first to land.
  • (Score: 5, Informative) by Doogman on Tuesday March 18 2014, @02:11PM

    by Doogman (1299) on Tuesday March 18 2014, @02:11PM (#18091)

    There's quite a bit of old armed services training videos on Youtube. Despite their age, they are usually well done and still interesting.

    Here's a batch about the mechanical computers mentioned in the article:

    https://www.youtube.com/user/navyreviewer/search?q uery=mechanical+computer [youtube.com]

  • (Score: 5, Insightful) by sce7mjm on Tuesday March 18 2014, @02:17PM

    by sce7mjm (809) on Tuesday March 18 2014, @02:17PM (#18095)

    My Grandfather designed a gun and targeting system used in Africa in ww2. My dad still has his notebooks which have control system diagrams which I recognised from my degree studies.
    It was all handwritten in fountain pen with drawings in pencil and barely a mistake in them. Best documentation I have ever seen.

    I often wondered if universities should show this sort of stuff as a guide for professionals.

  • (Score: 5, Interesting) by Sir Garlon on Tuesday March 18 2014, @02:37PM

    by Sir Garlon (1264) on Tuesday March 18 2014, @02:37PM (#18103)

    One of the earliest applications of electronic computers was the computation of artillery tables in World War II. There's a fascinating documentary called ''Top Secret Rosies [topsecretrosies.com]'' (you can get the disk from Netflix, but I don't know about streaming) about the young women who were first hired to compute those tables by hand, then later to program the electronic computer.

    I knew about the women mathematicians in the war effort from the biographical information about famous mathematicians in my undergrad textbooks, but my wife was amazed at this "untold" history. It's odd that we found this historical perspective in the abstract algebra textbook but not the women's studies books.

    --
    [Sir Garlon] is the marvellest knight that is now living, for he destroyeth many good knights, for he goeth invisible.
    • (Score: 4, Informative) by carguy on Tuesday March 18 2014, @03:03PM

      by carguy (568) Subscriber Badge on Tuesday March 18 2014, @03:03PM (#18118)

      > about the young women who were first hired to compute those tables by hand

      They also used mechanical calculators (generically, "adding machines"). These people (mostly women) were called "computers" since their job was to "compute" things. A family friend is in her 90s now, she worked as a computer for several years around 1950. She is probably the most meticulous person I know, perfect for the job.

  • (Score: 5, Insightful) by egcagrac0 on Tuesday March 18 2014, @03:21PM

    by egcagrac0 (2705) on Tuesday March 18 2014, @03:21PM (#18126)

    It's accurate in exactly the same way a slide rule or a vernier caliper is accurate.

    It's a bit more impressive, since it has more inputs and outputs.

    Digital computers are great, if you're dealing with data and operations that nicely break down into 0 and 1. Analog computers don't suffer from rounding errors in the same way, but can be a touch more difficult to get precise readouts from.

    • (Score: -1, Flamebait) by Anonymous Coward on Tuesday March 18 2014, @06:20PM

      by Anonymous Coward on Tuesday March 18 2014, @06:20PM (#18197)

      from TFA

      "Because they use physical rather than digital inputs and outputs, they can represent curves and other geometric elements of calculations with an infinite level of resolution "

      No, they can't, for the same reason that a photograph doesn't have an infinite level of detail just because it's "analog"

      • (Score: 4, Informative) by egcagrac0 on Tuesday March 18 2014, @10:55PM

        by egcagrac0 (2705) on Tuesday March 18 2014, @10:55PM (#18283)

        The limit of a photograph's resolution is the grain size of the silver halide (or dye cloud, if color). Back when I was doing film photography, we were typically unable to do better than about 35 megapixels from a 35mm double frame (the "common" 35mm still format, 24x36mm) - with a few exceptions for things like TechPan.

        Accuracy and precision are different. With an analog scale readout, I may know very well that it's about halfway between 24 and 25, but because the scratches on the bar are fairly close together, it can be difficult to determine if that's 24.47, 24.48, or 24.49.

        Fortunately, if the explosion is big enough, "close enough" on the order of "about 24.5" works just fine. (As in horseshoes, with a 2700lb high-explosive shell, close counts.)

        As for the accuracy of a mechanical analog computer, that limit is tied to the mating surfaces of the cogs, pinions, cams and followers - if they're machined accurately, if they're not particularly worn, if the backlash is controlled, that accuracy is very high indeed. Further, there's no interstage rounding error - the rounding errors really only show up at the output stage.

  • (Score: 4, Funny) by Anonymous Coward on Tuesday March 18 2014, @04:27PM

    by Anonymous Coward on Tuesday March 18 2014, @04:27PM (#18149)

    Really nice, long, detailed article with lots of links. Other authors could learn quite a bit from it. I especially like the point that analog can be as good or better than digital, something many folks refuse to accept. But I really got a kick out of this statement:

    take away the fancy GPS shells, and the AGS and its digital fire control system are no more accurate than mechanical analog technology that is nearly a century old.

    So take away the technology that makes the AGS what it is and suddenly it becomes only as accurate as the technology it's replacing? Whodathunkit!

    • (Score: 2, Informative) by MozeeToby on Tuesday March 18 2014, @06:40PM

      by MozeeToby (1118) on Tuesday March 18 2014, @06:40PM (#18200)

      The way it's written doesn't make it entirely clear, the GPS they are talking about lives inside the shells they are firing. You could drop the GPS guided shells into the old system and achieve similar accuracy to the new system; albeit with 100 times the weight, 1000 times the power requirements, and 10 times more crew to run it.

      • (Score: 5, Informative) by frojack on Tuesday March 18 2014, @08:07PM

        by frojack (1554) on Tuesday March 18 2014, @08:07PM (#18217) Journal

        Projectiles in that day did not have Guidance fins of any kind steering. Adding GPS would not be enough, you also have to add control mechanisms to the projectile.

        Some of the 5inch guns still found on ships, were designed around the time of WWII, and do indeed have the capability to use highly sophisticated munitions. But don't discount the accuracy of dumb chunk of metal projectiles.

        Most large bore naval guns (which these days are pretty much limited to 5 inch guns) can use a variety of projectiles, some of which are simply old schools spinning projectiles which are radar monitored for corrections on subsequent shots, others are highly sophisticated saboted munitions [photoshelter.com], some with rocket assist.

        This page [defense-update.com] describes an army 155mm shell with both inertial and satellite based GPS guidance to execute course corrections through the flight.

        --
        No, you are mistaken. I've always had this sig.
  • (Score: 1) by CluelessMoron on Wednesday March 19 2014, @01:19AM

    by CluelessMoron (1374) on Wednesday March 19 2014, @01:19AM (#18339)

    I have some faint memories from the past of reading that the fuel mixer control on some Soviet jet engines being some amazingly clever analog blob of titanium with pushrods all over. Does that ring a bell with anyone?

    And then, there's the Norden Bombsight [wikipedia.org]. This and putting people on the moon and going back makes me feel pretty small.