Before the advent of nuclear energy, submarines had to surface approximately 3000 times as frequently as they do now – all thanks to the development of a nascent energy source – nuclear energy. A nuclear submarine can remain underwater for up to 30 years at a time whilst even the most advanced conventional submarine can only stomach a few days submerged. How is it that the only discernible difference – nuclear power – can account for such a huge gulf in underwater endurance?
How do conventional submarines work?
Conventional submarines rely on a system of propulsion known as diesel-electric transmission, which, for the uninitiated, consists of a diesel generator and an electric motor. Going into greater detail, the electric motor is directly attached to the propellers which, as you can guess, actually propel the boat forward. For this reason, the movement of the boat is solely dependent on the electric motor. The diesel generator is used to either charge the battery or drive the electric motor itself. This, of course, means that the submarine has to resurface frequently in order to refuel the diesel generator.
How do nuclear submarines work?
Nuclear submarines, on the other hand, are more complex. But it is this very complexity that makes them superior. The energy produced by a relatively small nuclear reactor is used to heat water, producing steam that, in turn, powers turbines, and the boat itself. Whilst it isn’t quite rocket science, it is pretty close. By the process of nuclear fission, uranium atoms are split apart, which releases heat and radiation. More specifically, the nucleus of an unstable, radioactive uranium atom loses energy and becomes stable and non-radioactive, and, in the process, loses energy as heat and radiation.
Combatting the complications of nuclear power
Radioactive decay
Because of the radioactive material involved, great care must be taken to ensure the submarine, and the nuclear reactor it houses, are properly protected. Fuel rods are encased in an alloy that corrodes extremely slowly whilst the entire reactor itself, is surrounded by a hardy steel structure. Both measures are enough to guard against the prospect of radioactive material being released into the world’s oceans for thousands of years, by which time most, if not all, of the radioactive substances will have decayed.
Stealth
In the case of the nuclear-powered attack submarines of the HMS Astute class, their success is dependent on their ability to be stealthy, and this adds a whole new layer of complications. The 40,000 acoustic tiles that cover the exterior of the sub is only the start. A coolant pump constantly provides a source of seawater to mitigate the heat of the reactor system, and the pumps themselves are mounted on rafts and damped, all for the sake of minimising noise.
Cost
Needless to say, nuclear submarines are far from cheap – the cost of constructing the UK’s Astute class totals £10 billion. But without major investment, new technology is unlikely to develop and reach the stage where it can be implemented for real world use, and the superior nature of nuclear submarines compared to the conventional submarines of yesteryear, goes a long way in justifying its admittedly hefty price tag.
