From Now On, No More Defeats: The Siege, 3: Metacentric Heights

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This is not a real submarine.

 Neither are these, (1, 2, 3, , 4, 5, 6), but they're a good place to start the discussion. Since time immemorial, man has longed to travel underwater. I don't know for sure about women, but I'm thinking of asking my niece. She's 7, so she should have some insight. It started being vaguely safe with the introduction of electric motors with the Gymnote of 1888, although as usual it is obligatory to pretend that a Nineteenth Century American inventor produced the first submarine, because patent trolls.**

That is a pretty short interval between the introduction of a technology and its first use in action, and the Royal Navy's attempts to use the things show a certain, uhm, experimental flair. Besides the gigantic steam-powered "K" class and the 12" gun-equipped "M" class monitors already noted, check out this incredibly precocious hunter-killer type.

The problem here is pretty clear. The Gustave Zede was developed as a submersible torpedo boat. The point of torpedo boats in French naval strategic thinking is that they sneak up on blockading battleships and poke holes in their hulls with torpedoes, weapons with an unparalleled potential for mission-killing a battleship in an asymmetric encounter. You just have to get close, hence the "sneaking" part. Torpedo boats were good at sneaking, because they were small and close to the water. At night, their silhouettes would be small, and they would be hard to spot.

This is all well and good, but the design effort breaks down quickly. You want a torpedo boat with a big enough torpedo to have an effect, and a big engine to push it through the water quickly, while the whole "too small to see" thing pushes it down in size. Small boats are also hard to fight in a seaway.

The result of the dialectic, well known in military technology in general, is to push the size of "small" units up to the point of diminishing returns, and, let the hands on the reins relax, well beyond. Then someone comes along and takes the left-hand path, does the outside-the-box thinking, and comes up with a new paradigm. Boats that go underwater are really good at sneaking up on battleships!

Well, okay, electric motors are pretty dinky, so it's hard to catch up with a battleship that's actuallly moving. But they're really good at sneaking up on battleships that are swinging at anchor off Le Havre. In somewhat baddish weather. When they're not likely to be swinging at anchor. But, hey, work the wrinkles out and maybe you've got something there, you think.

Just what, exactly, would be what the Ks and the Ms were about. Electric motors are just a way of transforming potential into kinetic energy, and electric batteries are far less efficient than oxidising engines, and always will be, because half of the fuel mass of an oxidising engine is pulled in from the air, which submarines can never, never do.  So the Ks had a steam power plant, that made them quite fast on the surface. That allowed them to tag along with the battleships until they got to the battle, and then sneak up on the enemy battleline while it was busy fighting. Only the "Ks" kept getting run over by friendly ships, and the whole steam plant thing proved a little dicey when they were submerging, a lengthy and laborious process.

Next after the "Ks" came the "Ms." Once it was admitted that submarines weren't going to be chasing battleships down, the obvious solution became a weapon that covered more space. (Ammunition storage was also an issue. No matter how big the shell and propellant, they were still smaller than a torpedo.) A 12" gun was big enough, it was thought, or anyway a submarine big enough to fire something larger than a 12" round was thought too ambitious, or somewhere in there the naval architects wrestled the parameters into this particular design.

If only they had been so successful in defeating reality! The "Ms" had tragic careers, and certainly never shot a German battleship with a 12" round.

The next major experiment in very large submarines came from the French. The Surcouf is a legend that sprang from straightforward, if cracked reasoning.

i) It may be assumed that ships that are large enough not to go plunging and rolling about will be armed with guns if they are threatened by commerce raiders, or (obviously) intended to fight commerce raiders.
ii) It may be assumed that the easiest way of doing this is with a gun that doesn't require any special loading arrangements.
iii) Therefore, it will carry a 100lb round, as that is the biggest round that a seaman can stagger about with, at least on a ship that isn't rolling, plunging and etc. This is a 6" gun.
iv) Then we build a long range submarine with 8" guns!
v) . . .  .
vi) Profit!

Is that facetious? It's facetious. The suppressed (because incoherent or simply nonexistent) step is not obviously problematic in my story to this point. Obviously the idea behind the Surcouf is that it runs around the world bombarding armed freighters from a safe range and thereby obviating the huge effort that the Admiralty has undertaken to arm freighters with guns that are bigger than submarine deck guns and thus drive off the submarine freighter-sinkers that somehow bubbled up from the froth of the World War to become the actual submarine killer app. Forcing submarines to rely on their torpedoes greatly reduces their effectiveness, for reasons to be discussed above and beyond the question of ammunition supply, so a guns-versus-guns race has some merit for a navy that wants to put pepper on the Admiralty's tail. Supposedly, the Surcouf was so awesome that Admiral King hated it and stuff, and eventually he personally bombed it and it sank and stuff.

Why am I being so facetious? Do I hate conspiracy theorists? No, I hate ...well, let's get on with this.

From Surcouf my list of submarine follies moves on to the famed I-400s, the largest pre-nuclear submarines ever built.

Traditionally, this has been written off to the fact that they are hard to see, but that's only part of the story.

The rest of it, regrettably, involves math.

*Publicity still from Lorelei (2005). Directed by Shinji Higuchi and Cellin Gluck
**Note that Holland doesn't invent the submarine in this patent. He invents an "armoured caisson at the centre of the ship" that carries an air shaft, conning position and valves, i.e., a conning tower. As far as I can tell, the Gymnote's successor, the Gustave Zede, had not at this point been equipped with a conning tower, but I'll happily eat a hat if no-one was talking about them in 1892. Notice that the principals of the Electric Boat Company were wealthy lawyers.