INS Kalvari India’s first locally built Scorpene Class Submarine would soon be handed over to Indian Navy and sent to Indian Ocean on operational deployment. It is a class of diesel-electric attack submarine, the first of the six such submarines being built at Indian shipyard Mazagon Dock Shipbuilders Limited (MDL) at Mumbai port with the technical support of French naval shipbuilding firm Naval Group, earlier known as DCNS. It features diesel propulsion and additional air-independent propulsion (AIP). However, it would be some time before the vessel is fitted with torpedoes – its primary weapon. The second locally built Scorpene Class Submarine named INS Khanderi is undergoing sea trials and would only be available to the Indian Navy next year. The remaining four boats will all be delivered by 2020 at an interval of nine months.
Indian defense ministry in 2012 had approved procurement of 198 ships and submarines by 2027, out of which 40 ships and submarines are being constructed at different Indian shipyards. The present fleet available with the Navy includes 121 ships, 14 submarines, and 232 aircraft.
Submarine is a sea-going vessel designed to navigate underwater in dived condition as well as on sea surface. Efforts to design and develop this class of seafaring vessels date back to early 1776. The earliest submarine, Turtle was designed by David Bushnell in 1776 at Yale University, USA. Later, Nautilus, another new design submarine was built by Robert Fulton in the US. The next discovery was the submarine Hunley, which really operated underwater and sank the Union ship Houstanic by ramming the surface ship with a charge of gun powder in 1864. The submarine Holland was built for the US Navy by John P. Holland in 1900. The next design, an unproven submarine model by name Skipjack, came into existence in 1911 with a diesel engine. Subsequently, based on designs made in the US and Germany, a series of submarines and U-boats were produced, which were employed in World Wars I and II respectively.
The submarine is a shell enclosing a volume that weighs less than an equal volume of water and hence it floats over water. When it is required to dive underwater, its weight is increased by intake of sufficient seawater into the ballast tanks built in around the hull until its weight is greater than the weight of water it displaces. When it is desired to bring the submarine to surface, the water from the ballast tanks is expelled out by compressed air. The depth for navigation is adjusted using control surfaces referred to as forward/aft planes. The submarine body is shaped in a pointed manner to provide streamlining to minimise hydrodynamic resistance. The forward motion of the vessel through water is achieved by means of a propeller and the steering to right or left by a rudder. When the vessel is fully submerged, two sets of hydroplanes press against the resisting water and make the submarine go up or down. They also control the angle at which the vessel has to operate. The superstructure of a submarine has a snorkel which allows the submarine to operate submerged (at periscope depth) while taking in air from the atmosphere through the snorkel tube for running its diesel engines. There are no decks on the submarine superstructure. All machinery, weaponry and utilities are enclosed in the interior of the capsule. In actual operation, diesel-electric power is used for propulsion of submarine on surface and electric power (from storage batteries) for underwater propulsion, the reason being that lot of air is required for burning diesel oil when the ship is underwater; so much of air otherwise is not available at that time when the whole submarine is sealed from the outside environment. After the introduction of snorkel by the Germans during World War II, the normal underwater depth range with diesel power has been extended up to the periscope height level. With the advent of atomic power for nuclear submarines, the scarcity of power is no more there and travel underwater with the same prevailing air has become possible for extended periods, even up to six months. The nuclear fission occurring in an atomic reactor fitted on board a submarine gives enormous power supply to drive generators and produce electricity sufficient for continuously running the vessel for years together.
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