Simplified Nuclear Submarine

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