Submarine refers to a special class of warships with the ability to swim under water, maneuvering at the rate and depth. As a physical object, it is subject to the law of Archimedes on the body immersed in a fluid, acts upward force equal to the weight of the displaced and their liquid. This "lift" can manage by changing the weight of the boat. To dive the submarine seawater taken in its ballast tanks. To the boat surfaced - they are dried by blowing compressed air. Therefore, the submarine are two displacement - above water (normal) and scuba. Boat at a considerable depth under enormous pressure. Its housing including manned space and underlying mechanisms has a cylindrical shape and is made of a thick stainless steel or titanium alloy with stiffeners. It is called rugged. To improve the seaworthiness of the boat on top of the robust "wearing" lightweight body. Between them are usually ballast tanks and fuel tank. This boat is called doublecase. If the light body is not completely surrounded by rugged - it relates to polutorakorpusnym ships. There are also single-hull boats. To improve the survivability of its submarine pressure hull is divided by transverse watertight bulkheads into several independent compartments (three to ten). The boat is under water in a suspended state. It moves up and down is controlled by horizontal fore and aft rudders. When the leading edge of the rudder over the back, the incoming flow of water creates a lifting force. If on the contrary, counter-flow pressure on the working plane of the pen from top to bottom. Fixed boat uncontrollable and must either float or gaining additional ballast, to lie on the ground. Submarine movement forward or backward, like any vehicle, depends on which direction the screw rotates. Rotate left - right by changing the position of the vertical rudder in the stern. Submarines are divided into diesel-electric and nuclear power. The lack of first - limited residence time in the water. Their main engine - diesel, working on the solarium, needs a constant supply of oxygen. Therefore, it is usually used only for surface travel. Under the water the boat is moving on electric motors fed by batteries. Battery capacity is low, and the boat has to float periodically to recharge them with a diesel generator. From the time there is a device for the diesel engine of the Second World War under the water shallow - snorkel. Simply put, this is a pipe, put forward to the surface for air intake. The valve prevents ingress of water into the system. Unclosed snorkel was the cause of death is not a submarine. Nuclear reactor without replenishment uranium can years continuously produce energy. Water, turning it into steam heat, drives the steam turbine. That, in turn, moves the boat and through the turbine generator generates an electric current. Using the huge energy resources of nuclear power, from the seawater easy to get air, always so scarce at submarines. Management submarine is concentrated in the central office, located in the middle part of the body under the conning tower. Through it or close by sliding the device. Foremost among these is the periscope, allowing out of the water to observe the situation on the sea. When it is raised, the head protrudes above the lens with water. Through a system of lenses and prisms image is transferred into the boat. Periscope depth does not exceed a few meters. The ship, being deeper, can only be guided with the help of sonar. Hull form boat until the second half of the twentieth century, more suited for swimming on the surface as they dive relatively short time. Modern submarines, on the contrary, are adapted primarily for underwater hydrodynamics. Their native element - the world of silence.