The propulsion system of submarine

The propulsion system of a conventional submarine is designed to meet two different operating condition. The first one is when the submarine is moving on the surface of the water and the second one when it is moving under water.

If it is on the surface the resistances it has to overcome are the same as those of conventional surface ships. There will be water (frictional and wave making resistances) and some air resistance. If the submarine is operating under deep water it will not face wave making resistance. Due to greater wetted surface, the submarine will have greater frictional resistance.

Every submarine has been designed and constructed to operate in three dimensions. It can move forward, diving, and manouvering to the right and left sides both on the surface or under water. To have such abilities, a submarine will need not only rudders for moving on horizontal planes but hydroplanes for controlling depth.

When moving on submerged condition, a submarine needs to be fitted with Air Independent Propulsion (AIP). The diesel-electric scheme is the most common form of the submarine propulsion system. Diesel engine will be used to propel the ship if it is on the surface but electrical drive supplied by batteries will be needed to propel the submarine when it moves underwater.

Often submarines need to operate in longer period of time underwater especially when encountering enemies. This operating condition needs highly efficient batteries that can provide greater and longer endurance. In the past, naval architect decided to equip such submarines with nuclear power plant.

Now other alternatives such as closed cycle diesel engines, fuel cells and Stirling engines are being developed. Actually, diesel engine is not an ideal choice for a submarine due to its toxic fumes which can harm the ship crews. Therefore, efforts to improve the efficiency and size of the batteries are now being carried out to increase the overall performance of the propelling system of the submarine. by Charles Roring in Manokwari of West Papua