How Submarines Work

Learn how a submarine is powered using steam turbines, nuclear reactors and diesel engines etc.

Submarines are divided into two types, diesel submarines and nuclear submarines. The nuclear ones use steam turbines and reduction gearing to drive the propeller shaft, which provides the forward and reverse thrusts in the ocean. An electric motor drives the shaft when docking or during an emergency.

Submarines need electric power to operate the onboard equipment. To get this power, submarines come with diesel engines that burn fuel or/and nuclear reactors that operate on nuclear fission technology. Submarines have batteries to supply electric power. Often the onboard equipment is run off the batteries and the batteries are in turn charged by the diesel engine or nuclear reactor. During emergency periods, batteries may be the only source of electric power to keep the submarine running.

Most diesel submarines have two or more diesel engines. The engines can run propellers or they can run generators that recharge batteries. They can also work in combination, one driving a propeller and the other driving a generator.



The submarine must surface or cruise just below the ocean to run the diesel engines. When the batteries are charged, the submarine can head for deep waters. Batteries power electric motors, which drive the propellers. Battery operation is the only way a diesel submarine can submerge. The amount of time a diesel submarine can stay underwater is severely limited by the state of battery technology.

Nuclear powered submarines are much more efficient. As nuclear generators do not need any oxygen, a nuclear submarine can stay underwater for weeks at a time. Nuclear fuel also lasts longer than diesel fuel, enabling a nuclear submarine to refuel less often and stay in the ocean longer.

The nuclear reactors used in nuclear submarines are similar to the reactors in commercial nuclear plants. The reactors produce heat to generate steam so as to drive a steam turbine. The turbines drives the propellers, and also the electrical generators.

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