Realised that most modern submarines (and some aircraft carriers) use nuclear power, but destroyers and frigates don’t. I don’t imagine it’s a size thing, so I’m not sure what else it could be.
In: Engineering
Really short ELI5 version: It’s in a submarine because it lets a submarine pursue and destroy targets while remaining submerged, in a way no other plant can. It’s in almost nothing else because it’s expensive – but it used to be in other things!
Longer version:
Nuclear reactors in a naval vessel offer three big advantages: air independence, unlimited range, and horsepower.
For a submarine to stay submerged, it needs to be air independent for at least a period. For long patrols, it needs to carry enough fuel. Other systems have this as well, so what make the difference compared to other air independent propulsion is the amount of power available. Moving underwater requires much more energy than moving a ship on the surface, so **without a nuclear reactor a submarine, when submerged, becomes a smart naval mine**. It can maneuver around some, even into the teens of knots, but warships on the surface move at more than twice the speed when in a combat area, with the fleet speed of Halsey’s fleet during WWII over 25 knots. With the available horsepower, a submarine is now capable of pursuing and destroying targets, instead of waiting and being lucky. It becomes an, “Attack,” submarine. To put it in perspective how much is available, the battleship USS New Jersey (BB-62) displaced 45,000 tons and had 212,000 horsepower, and hit almost 34 knots in 1968; the submarine USS New Jersey (SSN-796) displaces 17% of that, and has 260,000 horsepower. And for how important speed is, during WWII most US submarines attacked on the surface rather than submerge, so they could keep their speed up.
For an aircraft carrier, it needs to get wind over the flight deck in order to conduct flight operations, so it has to be fast, which means more horsepower, big engines, and a lot of fuel. And just the air wing itself has a voracious fuel appetite, so by using a compact nuclear reactor, you’re able to achieve the same or higher speeds while giving more room to armor and consumables.
For other ships, there were nuclear powered cruisers and destroyers that were decommissioned at the end of the Cold War. They were sent around the world with the first nuclear powered aircraft carrier in Operation Sea Orbit in 1964, but were not significantly developed further because despite the advantages, they were very expensive to run, and nuclear reactors can only be so small due to the shielding, so they were replaced by gas turbines in modern destroyers and cruisers as they take up less room in the ship, even with fuel, and were cheaper and easier to run.
If you want to learn more about why nuclear propulsion matters for submarines, anything by Bill Toti discussing submarines (he’s been on several podcasts) is a goldmine. Also what it’s like to not have a nuclear plant, Thunder Below by Eugene Fluckey.
Latest Answers