Owning a fleet of nuclear submarines puts you in an exclusive club, owning a fleet of nuclear submarines full of unstoppable apocalypse rockets is yet more exclusive. There are several reasons why this is the case, firstly the existing members agree that no one else should build unfindable extinction ships and you have to listen to them because of the same ships. The second reason is the staggering cost.
To build a nuclear submarine, you need a nuclear industry. These are large organizations concerned mostly with certification, regulation, audits and assorted paperwork that occasionally build cooling systems around some physics. To have a nuclear industry, you need a network of other industries that deliver materials, services and personnel that do what they're supposed to.
Once you have the prerequisites, you can set about building a steel tube with a miniaturized nuclear power station and many explosives. This is tricky. To make it more difficult, the submarine should be fast, have lots of endurance, quiet and not blow up if accidentally driven into a sandbank. More difficult still, it needs to be reliable. It needs to keep working in harsh conditions since the shipyards that repair nuclear submarines are right at the top of the target lists for nuclear submarines.
Much of the complexity and cost derives from the nuclear fission reactors used as a power source. Typically, a 50-500 MW reactor is used to make steam to drive a turbine for propulsion and electrical power to run everything else. Should the reactor go wrong, you can end up with a meltdown that sends you right to the bottom of the Specific ocean.
So lets simplfy the whole arrangment. Do we need the steam turbine and associated piping? From detailed research* some of the pipes serve only to make loud and tactically inconvenient whooshing noises as they leak steam at inopportune moments. At least until Kowalski closes some valve or other. We can eliminate steam by going with Sterling engines and/or thermoelectric generators. We can also eliminate the troublesome reactor by making the submarine a large Radioisotope Thermal Generator <link>.
There's two good candidates, Strontium 90 and plutonium 238. At ~0.5W/g you'd need 1.0x10^9 grams, or 1000 metric tons. That's chump change in a marine environment. Ballistic missile subs are 15-50,000 tons. Even the volume is very manageable, 1000 tons of plutonium is 55m^3 It's a small roomful.
Admittedly, the arrangement of plutonium is somewhat... critical. It might be wise to use a mix of Pu/Sr and lay the material out along the full length of the keel. Heat transmission to the Stirling engines and thermoelectric generators could be achieved with heat pipes and heat storage in phase change materials could allow for varied power delivery and perhaps a smaller mass of material.
While steam turbines are ~35% efficient, compared to the ~10% of thermoelectric generators, they're solid state and therefore silent. They don't need generators with associated losses and noise. Sterling engines can be 50% efficient and have been demonstrated in submarines. So a mix of the two could easily equal traditional drive efficiency with fewer moving parts. If things get desperate, then you could easily hot-rod your submarine with Polonium 210, 280 fold more power per unit volume, although you'll need to refuel every few months.
Supplementary benefits include being able to say "we've moved away from lagacy fission reactors in our strategic submarine fleet" which will keep the CND lot happy. Meanwhile, the subs can be tooling around under the icecap, clearly demonstrating nuclear-powered performance. A wink and a nod from the right ambassador and before you know it the Chinese think you've cracked fusion.
*I watched several movies-- bs0u0155, May 06 2019 Radioisotope Thermoelectric Generators https://en.wikipedi...oelectric_generator [bs0u0155, May 06 2019] Sterling Engine submarine propulsion https://en.wikipedi...and-class_submarine [bs0u0155, May 06 2019] Submarine Cost https://www.ft.com/...9-9d01-cd4d49afbbe3 [bs0u0155, May 06 2019] The World's Worst Warships https://www.goodrea...ld_s_Worst_WarshipsDisquieting. [8th of 7, May 07 2019] We regret to inform you that while this is a good idea, you are a little behind the curve; however, that's entirely excusable as while USVs powered by RTGs are Baked, they are definitely not WKTE.
We could tell you more, but then we'd have to kill you.Well, we wouldn't exactly have to, but we would do it anyway just for the look of the thing.
[suggested-for-deletion], not an innovation.-- 8th of 7, May 06 2019 Surely these days you can run a submarine off a USB port?-- MaxwellBuchanan, May 06 2019 Quite a few submarines run out of USA ports, but that's not quite the same.-- 8th of 7, May 06 2019 Guessed it would be an RTG as soon as I read the subtitle.
Wikipedia says Gotland-class submarines can generate power while submerged, without consuming air, by using their Stirling engines. But it doesn't say what the heat source is. I don't see how it could be combustion of diesel.-- notexactly, May 07 2019 They use HTP. They bought the design of the RN's "Fancy" torpedo (c.f. HMS Sidon) and evolved it into AIP, far better than the WW2-era Kreislauf sysrem developed by the Kriegsmarine (and subsequently by the Ivans).
<<link>-- 8th of 7, May 07 2019 I never heard of power over HTTP - I presume it's the modern day equivalent of powering an old telephone handset over the telephone cables?-- pocmloc, May 07 2019 Hang on. Stirling, thermoelectric... all too complicated.
Nuclear stuff needs cooling, right? So, why faff around extracting heat only to turn it into electricity to turn a propeller to push the sub along? Just let water in the front end, squirt superheated steam out the back end, and you're good to go.
Better yet still - you could squirt 90% of the steam out the back, and the other 10% out of an annulus near the nose, to give a cavitating submarine capable of a few hundred knots.-- MaxwellBuchanan, May 07 2019 // you're good to go.//
... and easy meat for the first acoustic torpedo that happens along.
That sort of propulsion isn't exactly stealthy. Stealth is an important thing for subs ...-- 8th of 7, May 07 2019 Only because they don't have speed. When you're supercavitating at 300mph I think you'll be happy to let everyone know.-- MaxwellBuchanan, May 07 2019 //When you're supercavitating at 300mph I think you'll be happy to let everyone know.//
I wonder what the energy requirements for that would be? Also I think the supercavitating would generate a couple of minor issues, the sonar operator might mention some issues with a high noise floor. Any failure in the supercavitation machinery would result in the sort of deceleration experienced by pilots flying into cumulo granite formations.-- bs0u0155, May 09 2019 //deceleration// So, crumple zones, then. Maybe one of those collapsible steering wheels.-- MaxwellBuchanan, May 09 2019 It might work well for surface vessels, but nuclear-powered surface vessels tend to be aircraft carriers, and those can't move very fast without failing at their stated purpose.-- notexactly, May 15 2019 I'd've thought a fast-moving aircraft carrier would make it easier to take off and land. If you can get up to 150 knots you could operate A380s, which would be pretty intimidating.-- MaxwellBuchanan, May 15 2019 //you could operate A380s, which would be pretty intimidating//
Oooooh, gin soaked business class passengers. Scary. I'll take a B52 with a mix of AMRAAMs, anti-ship, anti-submarine and anti-satellite missiles.-- bs0u0155, May 15 2019 This is why the 2nd Amendment was intended to recognize every red-blooded American's God-given right to build defensive lighthouses on their property. A lighthouse with space-age technology (e.g. lasers illuminating the land for miles around) and maaaaaaybe some defensive plutonium tucked away somewhere sounds like a croissant tier idea. Build a moat around it and call it a submarine.-- sninctown, May 18 2019 //and maaaaaaybe some defensive plutonium//
Ah, the ol' Recreational McNuke™, every true Libertarian's dream.-- discontinuuity, May 23 2019 random, halfbakery