[pmcf]

In 1989 I was a data systems tech on a Destroyer going through some overhaul at the shipyard in Pascagoula Mississippi. Moored right next to us was the battleship Wisconsin. Huge relic from WW2 but still going through modernization. A bunch of us that worked on combat systems got invited for a tour of their fire control systems.

Wow. Just wow. All mechanical computers calculating fire control solutions for the big 16 inch guns. The guys giving the tour were well beyond the age for regular military retirement. Come to find out, they were all reactivated because practical knowledge of the mechanical computers had since left the navy. That was a very cool day.

[retrac]

By the end of WW II American torpedoes were automatically programmed (direction, speed, fusing) before firing. The heavy calculations would be done by the shipboard firing computer while the parameters set would be used by the simple computer on the torpedo (which had inertial guidance). I struggle to imagine how people managed to design such things with just pencils and slide rules.

[nine_k]

BTW these computers were mostly very functional, in the modern sense. They took inputs from instruments and controls, and computed functions, all usually continuous, smooth, real- or complex-valued. These functions' values, computed as voltages, frequencies, angles, etc were directly controlling some actuators, rudders, throttles, etc.

It's also highly compositional, as in applying relatively simple functions to results of other such functions, etc., which you can reason about analytically, and can plot on paper or an oscilloscope as a part of development and testing loop.

Disclaimer: all my hands-on experience with analog computers is from a one-semester course decades ago, using analog electronic, not mechanical devices.

[nradov]

WW II American torpedoes didn't have inertial guidance. They used gyros for directional control and just ran in a straight line after making a single turn onto the set course. Occasionally the torpedo would get stuck in that turn and run in a circle. Towards the end of the war the Navy also started introducing homing torpedoes, but those didn't use inertial guidance either.

[ploxiln]

> Occasionally the torpedo would get stuck in that turn and run in a circle.

Well that's not a great failure mode, if it can come right back at vessel which launched it ... imagine trying to implement a self-destruct failsafe with that tech back then ...

[nradov]

At least two US Navy submarines were sunk by their own torpedoes making circular runs. The main failsafe mechanism disabled the detonators until the weapon had run out a certain minimum distance but obviously that wasn't effective in circular runs.

https://www.usni.org/magazines/naval-history-magazine/2011/j...

[speakspokespok]

Clear the Bridge [0] was an autobiographical account of WW2 from the captain of the Tang. O'Kane covers the experience of this incident in the book.

While two US Navy subs were known to be sunk in this manner, there remain several subs not claimed by either Germany or Japan that just never returned.

0 - https://www.amazon.com/Clear-Bridge-Patrols-U-S-S-Tang/dp/08...

[fipar]

This may have been common enough that I distinctly remember it as something that could happen when playing Sub Battle Simulator in ‘91 (or around that year): https://en.wikipedia.org/wiki/Sub_Battle_Simulator

[pocketstar]

A gyro by definition IS inertial guidance.

[nradov]

Not really. By definition an inertial guidance or navigation system has to do some sort of integration of inputs over time. Gyroscopes are typically used as part of inertial guidance systems, but connecting a gyro output directly to a rudder input wouldn't by itself be considered as inertial guidance. The device wasn't doing anything to calculate absolute position based on inertia.

[flohofwoe]

Not exclusive to the US though, check out the "Torpedovorhalterechner" ;)

http://www.tvre.org/en/torpedo-fire-control-system-on-german...

Scrolling down there's a nice photo with removed cover.

[InDubioProRubio]

There were also a large number of captains, who refused to trust anything coming out of the navys design bureau and testing facilities and personally made sure, that computers were never used or even ripped out, to only use a "working" impact fuse. Those distrusting captains continued there "protecting the crew from dysfunctional crap" missions well up into the vietnam war. Engineering failures have serious consequences and ripple effects.

[grumpyprole]

Yes, in fact even a Harrier Jump Jet was designed with pencils and a slide rule!

[nine_k]

I.suspect they used tabulators and other such mechanical calculation devices, with a higher precision and faster speed than a slide rule.

[UncleOxidant]

In 1981 I was just out of high school and had a summer job at NUWES - Navel Undersea Warfare and Engineering Station in Keyport, WA. I was in a group that was refurb'ing fire control computers from submarines. They kind of looked like those stand up video game consoles that became popular in arcades soon after - except these cabinets were made of solid aluminum. They were full of gears and resolvers - analog computers. The "display" was all analog. And they were all being replaced with new gears and resolvers. I recall that there was another group nearby that was experimenting with microcomputers - they had some S-100 boxes like IMSAI 8080s.

[flavius29663]

I remember seeing one of those computers on Wisconsin, but I only saw it after decommission, as a museum piece. Those computers are truly mind boggling, if you're reading this and you're close to Norfolk you should visit battleship Wisconsin.

[ricktdotorg]

same goes for being in SoCal and going to visit the USS Iowa in San Pedro. it also has similar mechanical computers, it's a fantastic day spent clambering around the ship. sometimes they do "stay overnight in the bunks" nights, I can highly recommend it!

[teqsun]

For anyone along the Northeastern corridor, the USS New Jersey in Camden is another well-preserved Iowa class museum ship.

[mrguyorama]

The Battleship New Jersey has a good youtube channel where the head curator walks you through some things.

https://www.youtube.com/@BattleshipNewJersey

They also sell broken parts of the ship that they fix up as souvenirs, like the entire deck's worth of wooden planking, and for $1000 you can take a tour where the mildly charismatic head curator takes you into the smallest and hardest to reach parts of the ship!

Or fire a 5 inch gun, you know, if that's more your speed.

[jabl]

> Or fire a 5 inch gun, you know, if that's more your speed.

Depends on what the target is.

[teqsun]

For $1k it's just a blank round.

But if you donate $1M, you're allowed to shoot the USS New Jersey's curator Jordan with an HE shell from the 16" guns.

[cwillu]

Apropos: https://www.navalgazing.net/Fire-Control-Part-1

[zerohm]

I had a co-worker at the Navy Yard that said he was an Anti-Aircraft tech during the Korean War. When he said they used 'mechanical computers' I had to stair up into space for a minute to figure out what that meant.

[Loughla]

My uncle was on the Wisconsin and operated the big guns during the first Gulf war.

I never really had context as a kid for how large that ship is, and was just astounded by the distances they would shell.

[pmcf]

This was right before the gulf war so I may have met him! Assuming he was a gunners mate, that crew had a lot of moments of touching history. Besides mechanical computers, it’s a really dangerous place since they had to handle massive bags of flash powder.

My ship was near the USS Iowa when turret two went up. A sobering experience when you think how much risk the turret crews are in just by doing their jobs.

[teachrdan]

For those like me who didn't get this reference:

"On 19 April 1989, an explosion occurred within the Number Two 16-inch gun turret of the United States Navy battleship USS Iowa (BB-61) during a fleet exercise in the Caribbean Sea near Puerto Rico.[1] The explosion in the center gun room killed 47 of the turret's crewmen and severely damaged the gun turret itself."

https://en.wikipedia.org/wiki/USS_Iowa_turret_explosion

[lazyant]

thanks, I ended up reading the whole thing. If you watched a movie about this you'd think the writers went too far.