Submarine Principles and Design

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has only limited underwater capability.

The term submarine most commonly refers to large crewed autonomous vessels; however, historically or more casually, submarine can also refer to medium sized or smaller vessels (midget submarines, wet subs), Remotely Operated Vehicles or robots.

The word submarine was originally an adjective meaning "under the sea” and so consequently other uses such as "submarine engineering" or "submarine cable" may not actually refer to submarines at all. Submarine was shortened from the term "submarine boat", and is often further shortened to "sub".

Submarines are referred to as "boats" for historical reasons because vessels deployed from a ship are referred to as boats. The first submarines were launched in such a manner. The English term U-boat for a German submarine comes from the German word for submarine, U-Boot, itself an abbreviation for Unterseeboot ("undersea boat"). [wikipedia].

The submarine operates using the Archimedes' principle by manipulating the buoyancy.

The buoyancy is controlled by the ballast tank system. A submarine resting on the surface has positive buoyancy, which means it is less dense than the water around it and will float. At this time, the ballast tanks are mainly full of air. To submerge, the submarine must have negative buoyancy. Vents of the ballast tanks are opened.

Seawater coming in through the flood ports forces air out the vents, and the submarine begins to sink. The submarine ballast tanks now filled with seawater is denser than the surrounding water. The exact depth can be controlled by adjusting the water to air ratio in the ballast tanks. Submerged,

the submarine can obtain neutral buoyancy. That means the weight of the submarine equals the amount of water it displaces. The submarine will neither rise nor sink in this state. To make the submarine rise again, compressed air is simply blown into the tanks forcing the seawater out. The submarine gains positive buoyancy becomes less dense than the water and rises.

In current design concept of the submarines modularity at design level, construction and manufacturing contributes the main factor for efficiency in building a submarine.
For example Malaysian Scorpene Submarines constructions are being held at France and Spain shipyards. Beside the modularity the main factor for safety design is to improve acoustic detection by improving the sonar performances, data computations performances, reduce the hydrodynamics and self noise.
In most submarines design all the equipments shall not linked directly to the pressure hull and elastic mounting system to reduce the vibration level on ship. Some design used the suspended platforms and cradles to fit these requirements.

Sonar stands for (Sound Navigation & Ranging) are the main navigation subsystem for submarine. It becomes an eye for the submarine during underwater operation since there is no direct manual visibility.
For underwater applications the acoustic signals are being manipulated for ensuring safety for the submarine to avoid any obstacles and threats.
The main functions for sonar subsystem are for detection in active or passive mode, tracking, localization, acoustic classification and obstacle avoidance.

Cylindrical Array: Main sonar for medium range detection. Frank Array: Second main sonar for long range detection. Distributed Array: Sonar for short and medium range detection. Intercept Array: Sensor for pulse detection. Active Array: Sonar for active ranging. Mine Avoidance Array: Sonar for short range and objects detection.