Dept. of Mechanical Engineering


A submarine is a watercraft capable of independent operation below the surface of the water. The word submarine originally is 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" rather than as "ships", regardless of their size. Submarines have one of the largest ranges of capabilities in any vessel, ranging from small autonomous examples to one or two-person vessels operating for a few hours, to vessels which can remain submerged for 6 months such as the Russian Typhoon class - the biggest submarines ever built and in use. Submarines can work at greater depths that are not survivable or impractical for human divers.

The submarines have both military uses and civilian uses. The submarines are used for homeland defence and under-sea patrolling. The submarines are run with the help of parts such as sail, sail planes, rudder and propeller. The design of the submarine depends on the application it is used to. The propulsion of the submarine is done with the help of steam engines, diesel/gasoline – electric transmissions, air-independent propulsion or nuclear energy. The parts and propulsion of the submarines will be dealt in detail in subsequent chapters.

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all of which would culminate in them making a large impact on the coming World War I. but this first known attack by submarine failed. Diesel electric propulsion would become the dominant power system and equipment such as the periscope would become standardized. Though the first submersible vehicles were tools for exploring under water. The first submarine not relying on human power for propulsion was the French Plongeur (Diver). and using compressed air at 180 psi (1241kPa). of Mechanical Engineering Submarines 2. it was added to the Navy fleet in 1900. All the submarines till now were run by either treadmills or screws which had to be propagated by humans. Flach and Alligator were a failures to name a few. The low efficiency led to further research. After these there were many submarine designs that were aimed at being used for military purposes to gain upper hand over hand over the enemies. The turn of the 20th century marked a pivotal time in the development of submarines. a Dutchman. it did not take long for inventors to recognize their military potential. with a number of important technologies making their debut. The submarines were run by steam engines or electrically powered. It was created to the standards of the design outlined by English mathematician William Bourne. As the time progressed the evolution of scientific knowledge led to better designs and as a result the attack of Hunley on Housatonic became the first successful submarine attack on a warship. It could travel 6 knots (7 miles. became a deadly menace to surface ships as World War I (1914-1918) unfolded. The Turtle attempted to sink a British warship in New York Harbor in 1776. Large numbers of experiments were done by countries on effective tactics and weapons for submarines. Germany led the way in submarine development. It was the first verified submarine capable of independent underwater operation and movement. as well as the widespread adoption and fielding of submarines by a number of nations. electrical engines. It was propelled by means of oars. EARLY HISTORY The first submersible with reliable information on its construction was built in 1620 by Cornelius Jacobszoon Drebbel. but all these like Brandtaucher. Germany’s Unterseeboote. a one-man submersible. or U-boats. Many more designs were built at this time by various inventors to run on steam engines. The first somewhat reliable American submarine was the invention of John Holland. launched in 1863.RVCE Dept. Named the USS Holland. In the next few years. After Page 2 . but submarines were not put into service by navies until 1900. American David Bushnell designed the Turtle. 11 kilometers) per hour under water.

American designers made improvements in their submarines by studying the much more reliable German subs. Submarines also carried World War II raiders (similar to the Special Forces of today) to enemy shores. Navy developed the first ballistic missile submarines. of Mechanical Engineering Submarines America’s entry into the war in 1917. the United States had launched the first of the big (560-foot. The Nautilus. U.S. launched in 1954. as now—volunteers. and rescued downed flyers and shipwreck survivors. laid mines. all of them—then. was revolutionary. American subs sank over 30 percent of the Japanese Navy and over half of its merchant ships.6 million metric tons) of shipping. Trident-carrying Ohio-class submarines. 171-meter). By 1981. Page 3 .RVCE Dept. and it was a major success. a total of 1.506 submariners. it broke all existing speed and endurance records for submarines. submarines were used largely to patrol American coasts. Fifty-two American subs were lost along with 3.S. After the war. American attack submarines fired cruise missiles at targets in Iraq and in Serbia during conflicts in the 1990s.314 military and merchant ships 1 including 8 Japanese aircraft carriers and almost 5 million tons (4. America’s undersea war was fought largely against the Japanese. In the late 1950s the U. As the first nuclear-powered submarine.

Modern American submarines can actually travel faster under water. That shape slices more easily through an undersea. of Mechanical Engineering Submarines 3. About 20 feet (6 meters) tall. the nuclear-powered attack submarine USS Albany slips through Chesapeake Bay after a six-month mission. than on the surface. the Nautilus. A submarine’s streamlined hull is made of titanium. The smooth flow of the hull is interrupted by the submarine’s sail. all-water environment than through a water-and-air environment. Even the first American nuclear sub. Almost like a steel cigar. the tall. their primary environment. which a sub encounters on the ocean surface. Page 4 . slender structure that rises from the submarine hull. If necessary.RVCE Dept. it can spend up to six months submerged. The submarine captain uses the top of the sail as a command bridge when the ship is on the ocean surface The nuclear energy that powers a submarine allows a sub to stay on patrol almost indefinitely. returning to base only for food and supplies. a very strong but lightweight metal. or conning tower. CHARACTERISTICS OF A SUBMARINE A submarine is long and rounded. the sail houses periscopes and radar and radio equipment. was designed with a narrow bow for more surface speed. The nuclear material of a submarine needs to be replaced only once or twice in the ship’s lifetime. like a cigar with a teardrop head.

lighter and is not ferromagnetic. High-strength alloy steel remains the primary material for submarines today. the high cost of titanium construction led to the abandonment of titanium submarine construction as the Cold War ended. Despite its benefits. important for stealth. houses its periscope and much of its electronic systems. of Mechanical Engineering Submarines A submarine’s sail. or conning tower. Titanium alloys allow a major increase in depth.RVCE Dept. Page 5 . Titanium can be stronger than steel.

The earliest rudders were oars. submerged at a shallow depth. SUBMARINES NOMENCLATURE Periscope: . of Mechanical Engineering Submarines 4. and by tipping them up. The hemispheres are contained in a flotation jacket which carries them above the surface of a liquid on which the jacket floats.The radio antenna includes a solid hemisphere of conductive material concentric with a hollow hemisphere of a dielectric material. the periscope is retracted to into the hull. the periscope. It remains level while slowly hanging depth. Radio antenna: . held vertically.Propeller design is so important to both speed and noise levels. The rudder works by acting against the water flow as the ship moves through the water. to search for targets and threats in the surrounding area.A rudder is one of the oldest innovations in the ship design. Sail: . the sown force they impart ‘pushes the boat down’. When not in use. The dielectric material permits an antenna of small physical dimensions. Sail planes: . since it creates an observable wake and may detected to radar. Concentric spheres may used if desired.RVCE Dept. Propeller: . The force generated by the planes when they are used will act in a way that causes the boat to sink a bit more or rise a bit more. While designing the submarine propeller the focus is on achieving the greatest speed possible so the submarine can Page 6 . The sail planes take advantage of the boat’s neutral buoyancy. radar and the antenna. This is how a submarine is able to receive and send out radio communications while submerged. Rudder: . A sub commander in tactical conditions must exercise discretion when using his periscope. giving away the sub’s position.Periscope allows a submarine.Sail of a submarine is the tower-like structure found on the top surface of the submarines. Swinging the rear end of the rudder to the right makes the stern to move to the left. A submarine sail usually houses the conning tower (command and communications data center). and moved from side to side to steer the ship.The sail planes are approximately amidships.

Tipped oppositely.RVCE Dept. This is the portion of the hull that we see from the inside.Boats have stern planes back at the aft. When the boat needs to surface or dive steeply. Stern planes: . The outer hull is spaced apart from the inner hull on a submarine and in between is the ballast tank. Inner hull: . The angle that the vessel is moving through the water. When there is no water in the ballast tanks the submarine is lighter or more buoyant and will float.The outer hull is the outer wall of the submarine which is what we see on the outside of submarine. of Mechanical Engineering Submarines speed through the water while having the least amount of noise and turbulence which could revel the boat’s position. the boat can be pointed to the surface. By tipping the bow planes up and the stern planes down.the ballast tanks are in an essence the spacing between the inner and outer hulls. So when there is no water in the ballast tank the submarine will be surfaced. Page 7 . the bow and stern planes are used to ‘point’ the boat in the desired direction. Outer Hull: . the ‘bubble’ of the boat is changed.The inner hull is the inner wall of the submarine that separates the crew from the ballast tanks and the outer hull which are used to submerge and surface a submarine. Ballast tanks: . It has vents and openings to take on water which will allow the ship to surface or submerge. As it takes on water it will submerge as the submarine is taking on weight. the boat heads down.

it either sinks or floats according to its density. and allows the sub to maneuver underwater. the sub rises to the surface. pushing water backward so that the submarine moves forward. The new combination of metal. water. resulting in a mixture of air. A propeller moves the sub through the water. and water that is now less dense than the water surrounding the sub. with just a little bit of air in the centre for the crew to breathe. The crucial problem for a submarine is that it must either sink or float on command.RVCE Dept. while objects less dense than water (like air-filled balloons) float. Under these conditions. While the submarine is sinking. but can't do both. is more dense than the surrounding ocean water. Submarines are a mixture of metal (the hull). metal. Unlike water or metal. Once the submarine is underwater. WORKING OF A SUBMARINE  Submarines are designed for use at great depths. air is pumped into the ballast tanks. and water (the "ballast"). Water fills the compartments called the ballast tanks. This is called "neutral buoyancy". The secret of a submarine's ability to either sink or float lies in a special property of air. neither sinking nor rising. air can be squashed into a tiny space. double-walled hulls allow the crew to live and work normally underwater for as long as air and power supplies last. so the submarine hovers. its air is compressed. This pushes water out. air. of Mechanical Engineering Submarines 5.     Page 8 . Objects denser than water (like metal) sink. When it's time to rise. Most things either sink or float. and so the submarine sinks. Submarines are steered by turning a rudder left and right. The combination of water and metal. When an object is placed into water. Their rigid. and air is just as dense as the surrounding water. even more air is pushed into the ballast tanks.

either by increasing its own weight or decreasing its displacement of water. or MBTs. For general submersion or surfacing. or separated along the submarine body to prevent affecting trim. which are filled with water to submerge or with air to surface. When submerged. To submerge hydrostatically. submarines have ballast tanks. Water density also increases with depth.500 psi) for titanium submarines like Komsomolets. This difference results in hull compression. To control their weight. or DCTs . Trimming Trimming is a method of operating seagoing vessels in a way that ensures minimum water resistance in all circumstances. as well as surfaced submarines. while interior pressure remains relatively unchanged. called Main Ballast Tanks. as the salinity and pressure are higher. submarines use smaller Depth Control Tanks. For more precise and quick control of depth. Depth control tanks may be located either near the submarine's center of gravity. Keeping a constant depth requires continual operation of either the depth control tanks or control surfaces. weighing less than the volume of water they would displace if fully submerged. A submerged submarine is in an unstable equilibrium. which decreases displacement. due to their ability to withstand higher pressure.also called hard tanks. which can hold varying amounts of water and air. Page 9 . SUBMARINE TECHNOLOGIES Submarines Submersion All surface ships. having a tendency to either fall or float to the surface. but this incompletely compensates for hull compression. are in a positively buoyant condition. the water pressure on submarine's hull can reach 4 MPa (580 psi) for steel submarines and up to 10 MPa (1. The amount of water in depth control tanks can be controlled to change depth or to maintain a constant depth as outside conditions (chiefly water density) change.RVCE Dept. so buoyancy decreases as depth increases. of Mechanical Engineering 6. a ship must have negative buoyancy. submarines use the forward and aft tanks.

If the shape is not perfect. and external for optimal shape.RVCE Dept. to reduce detection. which withstands sea pressure and has normal atmospheric pressure inside. Building a pressure hull is difficult. located near the propeller and normally horizontal. controlling the trim. Hydrodynamic maneuvering is done by several surfaces. and causes only hull compression. The occupied pressure hulls of deep diving submarines are spherical instead of cylindrical. The outer hull is covered with a layer of sound-absorbing rubber. Pumps can move water between these. the pressure is evenly distributed. which actually forms the shape of submarine. Page 10 . creating a moment pointing the sub up or down. All hull parts must be welded without defects. Inevitable minor deviations are resisted by stiffener rings. and all joints are checked multiple times with different methods. internal for holding pressure. The hydrostatic effect of variable ballast tanks is not the only way to control the submarine underwater. or anechoic plating. This external hull. submarines use forward and aft trim tanks. which can be moved to create hydrodynamic forces when a submarine moves at sufficient speed. A similar system is sometimes used to maintain stability. The hull must therefore be constructed with high precision. This allows a more even distribution of stress at the great depth. contributing to the high cost of modern submarines. as it must withstand pressures at its required diving depth. serve the same purpose as the trim tanks. as it does not have to withstand a pressure difference. changing weight distribution. or by using two hulls. it was realized that the optimal shape for withstanding pressure conflicted with the optimal shape for safekeeping and minimal drag. Initially. is called the outer hull (casing) or light hull. and construction difficulties further complicated the problem. Large submarines generally have an additional hull or hull sections outside. To maintain desired trim. Inside the outer hull there is a strong hull or pressure hull. Submarine hull We have already learnt that most modern submarines are cigar shaped structures. the hull is bent. of Mechanical Engineering Submarines Submarines in a neutral buoyancy condition are not intrinsically trim-stable. This was solved either by a compromise shape. with several points heavily strained. The stern planes. It reduces the hydrodynamic drag when submerged. When the hull is perfectly round in cross-section. but even a one inch (25 mm) deviation from roundness results in over 30 percent decrease of maximal hydrostatic load and consequently dive depth.

The nuclear reactor also supplies power to the submarine's other subsystems. The stealth weakness of nuclear submarines is the need to cool the reactor even when the submarine is not moving. AIP is usually implemented as an auxiliary source. but due to the high cost and large size of nuclear reactors. Early submarines used gasoline. etc. of Mechanical Engineering Submarines Propulsion Originally. this would result in reduced oxygen being available for the crew. and describes augmentation or replacing the electric propulsion system of nonnuclear vessels. which used compressed air for propulsion. so that the motor could drive the propeller.RVCE Dept. The diesel or gasoline engine and the electric motor. The first mechanically driven submarine was the 1863 French Plongeur. By eliminating the need for atmospheric oxygen. This allowed the engine to drive the electric motor as a generator to recharge the batteries and also propel the submarine. Diesel-electric submarines have a stealth advantage over their nuclear counterparts. as breathing air was recycled and fresh water distilled from seawater. This problem was overcome by powering the steam engines with the help of nuclear energy. were initially on the same shaft driving the propeller. then diesel. such as for maintenance of air quality. because of reduced flammability. submarines were human propelled. Air independent propulsion system for submarines. All naval nuclear reactors currently in use are operated with diesel generators as a backup power system. The term usually excludes the use of nuclear power. Most such systems generate electricity which in turn drives an electric motor for propulsion or recharging the submarine batteries. fresh water production by distilling salt water from the ocean. separated by clutches. Air independent propulsion (AIP) system is a term that encompasses technologies. The nuclear-powered steam turbine will be driving the generator. This would reduce the amount of time that the submarine could be submerged. smaller submarines still use diesel-electric propulsion. Nuclear power is now used in all large submarines. temperature regulation. This leaves a Page 11 . which allow a submarine to operate without the need to surface or use a snorkel to access atmospheric oxygen. Nuclear-powered submarines have a relatively small battery and diesel engine/generator power plant for emergency use if the reactors must be shut down. but this quickly gave way to kerosene (paraffin). Diesel-electric became the standard means of propulsion. As we know that the diesel or gasoline engine will require oxygen for the combustion purposes. Later many other chemical processes were experimented to provide both the heat to run the steam engine and oxygen to the crew (including hydrogen-peroxide based method). about 70% of the reactor output heat is coupled into the sea water. the length of time that a modern submarine could remain submerged was limited only by its food stores. The clutch between the motor and the engine would be disengaged when the submarine dived.

are designed to be deployed by a submarine's torpedo tubes. The towed array is the mainstay of submarine detection systems. a plume of warm water of lower density which ascends to the sea surface and creates a "thermal scar" observable by thermal imaging systems Nuclear submarines generate noise from coolant pumps and turbo-machinery needed to operate the reactor. Active systems are rarely used. Modern submarine-laid mines. With at most 20 to 25 torpedoes stored onboard. Sensors A submarine will have a variety of sensors determined by its missions. His invention is essentially the same now as it was 140 years ago. Active sonar relies on an audible "ping" to generate echoes to reveal objects around the submarine. the number of attacks was limited. such as the British Mark 6 Sea Urchin. generally several hundred feet long. Modern military submarines rely almost entirely on a suite of passive and active sonar to find their prey. Armament The success of the submarine is inextricably linked to the development of the torpedo. Passive sonar is a set of sensitive hydrophones set into the hull or trailed in a towed array. Diesel-electric engines are used to cool off the reactor. multiple "straight-running" torpedoes were required to attack a target. Page 12 . Mine laying submarines of World War I and World War II were specially built for that purpose. even at low power levels. Such missiles required the submarine to surface to fire its missiles. Until the perfection of the guided torpedo. Hull mounted sonar is employed to back up the towed array. both the US and the USSR experimented with submarine launched cruise missiles. The ability of submarines to approach enemy harbors covertly led to their use as minelayers. invented by Robert Whitehead in 1866. as it reduces the flow noise heard by operators. which can be fired from the torpedo tubes of submerged submarines. and in confined waters where a towed array could be fouled by obstacles. as doing so reveals the sub's presence. After World War II.RVCE Dept. They were the forerunners of modern submarine launched cruise missiles. of Mechanical Engineering Submarines "thermal wake". when the nuclear reactors are shut down.

Sub captains are more likely to use radar detection gear rather than active radar to detect targets. Antenna masts and antennaequipped periscopes can be raised to obtain navigational signals but in areas of heavy surveillance. dead reckoning course information. making them hard for other ships to see and identify. as radar can be detected far beyond its own return range. only for a few seconds or minutes. revealing the submarine. Operating in stealth mode. of Mechanical Engineering Submarines Submarines also carry radar equipment for detection of surface ships and aircraft. they cannot use their active sonar systems to ping ahead for underwater hazards such as undersea mountains. Surfaced submarines entering and leaving port navigate similarly to traditional ships but with a few extra considerations because most of the ship rides below the waterline. Navigation Submarine navigation underwater requires special skills and technologies not needed by surface ships. Deep water navigation is provided by.RVCE Dept. except for position fixes and to verify a contact's identity. radial navigation and celestial navigation. this could also be considered an estimated position as long as the ocean current is computed in. measured speed and estimates of local ocean currents. travelling greater distances and at higher speed. obtained from the ship's gyrocompass. Surfacing to obtain navigational fixes is precluded by pervasive anti-submarine warfare detection systems such as radar and satellite surveillance. The challenges of underwater navigation have become more important as submarines spend more time underwater. drilling rigs or other submarines. active sonars. Military submarines travel underwater in an environment of total darkness with neither windows nor lights. Periscopes are rarely used. Page 13 . Surface and near-surface navigation is provided by GPS. current radar technology can detect even a slender periscope while submarine shadows may be plainly visible from the air.

Active sonar uses the reflection of sound emitted from the search equipment to detect submarines. Tourism Academic research Under water cable repairs. where the airmen would be told of safe places to crash-land so the submarines could rescue them. Undersea archeology Page 14 . Mine laying submarines are useful in sinking the enemy ships.   2. Civilian applications         Tourism Exploration Oil and gas platform inspections and pipeline surveys Polar expeditions. Submarines are also used to rescue aircrew during air attacks on islands. using torpedoes or (on the surface) deck guns. Submarines could carry cargo through hostile waters or act as supply vessels for other submarines. Military applications    Submarines would attack either on the surface or submerged. of Mechanical Engineering Submarines 7.RVCE Dept. APPLICATIONS OF SUBMARINE 1. Submarine-launched ballistic missile and submarine-launched cruise missiles give submarines a substantial and long-ranged ability to attack both land and sea targets with a variety of weapons ranging from cluster bombs to nuclear weapons.

Tourism for reefs at greater depths of the oceans. ADVANTAGES AND DISADVANTAGES OF SUBMARINES Advantages     Stealth operations. Page 15 . Defence operations for the country.RVCE Dept. Complex running operations. Limitations     High cost of production. Rescue operations for under water scenarios. No emergency backup available from the surface in case of accidents. of Mechanical Engineering Submarines 8. High maintenance cost.

S-4 6SSN Propulsion Diesel electric Shishumar class Akula class (SSN) Arihant class Arihant Class (SSBN) Scorpène class Diesel electric Nuclear nuclear Nuclear Diesel Electric INS Sindhughosh Shishumar class Page 16 . Classes of Indian submarines Class Sindhughosh Submarines Sindhughosh (S55) Sindhudhvaj (S56) Sindhuraj (S57) Sindhuvir (S58) Sindhuratna (S59) Sindhukesari (S60) Shishumar (S44) Shankush (S45) INS Chakra INS Arihant S-2. and the submarine was manned by an Indian crew. India has started construction of six Scorpène class submarines with MESMA. Upon expiration of the lease term in 1991. S-3. the submarine was returned to Russia and joined the Pacific Fleet of the Russian Navy. India acquired an ex-Soviet Charlie class nuclear powered guided missile submarine with eight Ametist (SS-N-7 Starbright) anti-shipping missile launchers on a 3-year lease. These submarines will join the Indian Navy starting from the second half of 2015. The Indian Navy operates a sizeable fleet of Sindhughosh and Shishumar class submarines. of Mechanical Engineering Submarines 9. In the Indian Navy.RVCE Dept. India issued a request for information for another six submarines in 2011. INDIAN SUBMARINES In 1988. the vessel was commissioned as the INS Chakra.

RVCE Dept. of Mechanical Engineering Submarines INS Chakra 3 SSBN (Arihant class) S-71 (INS chakra. Charlie Class submarine) Scorpène class submarine Page 17 .

of Mechanical Engineering Submarines 11. Modularization coupled with the development and use of off-board systems will allow a wide range of payloads to be employed by submarines. Page 18 . FUTURE OF SUBMARINES Submarine technology changes quickly. and new forms of submarine based systems for Anti-Submarine. undersea acoustic and non-acoustic sensors and weapons. and Anti-Air Warfare. These capabilities combined with the submarine’s advantage of being able to remain on-station and undetected for extended periods will multiply the effectiveness of these systems by adding the element of surprise and survivability. advanced cruise missiles. These remote sensors and weapons will include Unmanned Aerial Vehicles (UAVs). These deployed systems will act to increase the area over which the submarine performs its missions and improve its effectiveness in performing these missions.RVCE Dept. The evolution of future submarines for military use will be driven by the trend to use smaller. while reducing the threat to the submarine and its crew. and unmanned vehicles to perform missions both under and above the sea. Submarines of the future will be used for their inherent stealth to link and provide support to a deployed network of sensors and weapons. Unmanned Undersea Vehicles (UUVs). Anti-Surface. autonomous. Ships already under construction cannot always accommodate the new technology. But the plans are on to build its newest class submarines with a modular design that will permit easier replacement of outdated equipment and systems.

Elementary Classical Physics. Roger (2007). REFERENCES Submarines  http://www.htm Page 19 .naval-technology.usna. US Naval Institute Press.edu/naoe/courses/en200/ch10.php  http://www. of Mechanical Engineering 12.iaea.com/training/nctp/submariner.  http://inventors.com/od/sstartinventions/a/Submarines.fr/transport.about.pdf  http://www.com/projects/scorpene/scorpene1.html  Thompson.ISBN 9781591148654.webcadets. Retrieved 2006-10-07  http://www. 34.htm  "Physics Of Liquids & Gases".org/Publications/Magazines/Bulletin/Bull413/article1.michellehenry. p. Lessons Not Learned.pdf  http://www.RVCE Dept.