What s working principle of a submarine?
A submarine is submerged by allowing water into the main ballast tanks so that its total weight is equal to the weight of the water displaced, hence it attains neutral buoyancy. To bring back the submarine to the surface, the water in the main ballast tanks is blown out by air and the submarine gains positive buoyancy. The main ballast tanks however are either full (when submerged) or empty (when the vessel is on the water surface). Variations in the loading of the submarine are compensated by means of smaller tanks called the trim tanks. There are normally three of these; one at the forward part of the sub, one at the midships, and one aft. These tanks are designed to compensate the changes in the loading of the vessel and the longitudinal moment of the variation in loading. The contents of these tanks are preset before the submarine goes on a dive so that when the main ballast tanks are filled, the submarine will submerge and still remain on even trim. Other smaller tanks in the subm
