Types of Sailing Ships - Submarine: Understanding the underwater watercraft

Types of Sailing Ships - Submarine: Understanding the underwater watercraft
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The word submarine resounds the pictures of wars and underwater invasions. No doubt the submarines were introduced with the warfare purpose, there is definitely more to this technological masterpiece. Everyone knows that a submarine is nothing but a ship floating underwater. It not only allows the privilege of sailing in a concealing manner but also creates an environment to stay below the water for months together.

In this article we won’t be focusing on the utility aspect but on the technical ones. How a submarine dives and surfaces in the water? How it maintains a healthy environment and from where does it gets its power. A submarine does not fall strictly in the category of types of ships but is certainly an underwater ship. Learn about these interesting and technically complex machines in the article below.

Submarine Application in Brief

Submarines were introduced with the sole purpose of fighting wars. They were extensively used in world war- I & II . Submarines were used for protecting aircraft carriers, for blockade running, for patrolling a country’s boundaries etc.

Nowadays the use of submarines have proliferated across many fields. Today they are used for marine sciences research, underwater oil and minerals exploration, salvaging and surveying purposes, underwater cable repairs and also for tourism purpose.

sub reaserch


A submarine also works on the same principle as that used by other ships, i.e Archimedes Principle of buoyancy. A normal surface ship sails on water by creating a positive buoyant force, by displacing more water than its weight. But in order to submerge a ship hydrostatically, a negative buoyant force needs to be generated. This can be done by increasing the weight of the ship or by reducing the amount of water displaced. For this purpose, ballast tanks are used.

Submarines can easily control their buoyancy. When the submarine is at the surface, its ballast tanks are filled with air, thus increasing making its density less than that of the surrounding water. In order to submerge, the ballast tanks are filled with water, making the overall density of the ship higher than the surrounding water. When the submarine submerges in the water, a continuous supply of compressed air is supplied in order to support life inside it. Also the air from the ballast tanks is pushed out with the help of pumps. Hydroplanes, small movable wings at the stern helps to adjust the angle of dive. The wings are so arranged that the water moves over the stern area, pushing it upwards and thus alligning the submarine in a downward angle.

sub submerge


Once underwater, the desired crusing depth is maintained by neutralizing the bouyance force. This means that a balance of air and water is maintained inside the tanks in order to equalize the buoyant force of the submarine and the water surrounding it. This is known as neutral buoyancy. On reaching the crusing depth, the hydroplanes are leveled and thus the submarine can travel parallel to the water level. The port and starboard movement is controlled by tail rudder.


Contruction and Design

Almost all the submarines are cigar-shaped. This is done in order to reduce the hydrodynamic drag when the submarine is in water. The pressure hulls are made spherical instead of cylindrical for even distribution of stress at great depths. The raised tower on submarine is where the navigation system is fixed. It accommodates a periscope, radio, electronic radars and other navigation systems.

The hull and outer body are made extremely thick and of a material that can resist excessive stress when the submarine is at greater depths.

sub mast


The main propulsion systems that a submarine uses are steam turbines, nuclear reactors or diesel engines. The electric power on the ship is mainly supplied by the diesel engines. An emergency backup system is provided by using batteries, which can be charged using propulsion systems. There are more than 2 diesel engines on each submarines.

Nuclear reactor submarines are the most commonly used ones as they don’t require a continuous fuel supply and produces zero pollution.


Parker. J. (2007) The World Encyclopedia of Submarines: An Illustrated Reference To Underwater Vessels Of The World Through History, From The Nautilus And Hunley To Modern Nuclear-Powered Submarines. London: Lorenz Books

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