To understand the workings of a submarine, we first need tounderstand the principle based on which it functions.
Buoyancy, which is also referred to as buoyant force, is theforce that acts upon any object that is submerged/immersed in water. Buoyancyis a vector, which means that it is expressed by magnitude, unit and direction.The SI unit of buoyancy is Newton Symbol: N.
This force is a result of the difference in pressure ofdifferent sides of the object. The pressure exerted at the bottom of the objectis greater than the top, because pressure exerted is directly proportional todepth(pressure increases, depth increases.) The bottom force(stronger) pushes the object up, while thetop force(weaker) pushed the object down. Since the force is stronger at thebottom, the net force is in the upward direction. Thus, buoyancy is referred toas an ‘upthrust force’. Archimedes’ principle: The Archimedes’ principle states that the buoyant forceexerted on an object is the same as the weight of the fluid that it displaces.
Therefore, a paper boat floats, because the mass is the sameas(equal to) the water it displaces and an iron nail sinks because the waterdisplaced is not the same as the mass of the iron nail. A submarine functions basedon this principle. A submarine is able to floaton water because the weight of water that it displaces, is the same as thevolume of the submarine. This process creates the buoyant force that wediscussed about earlier. This force acts in the opposite direction to gravity.
Unlike most watercraft machines, a submarine can control the buoyant force actingon it, with the help of its parts. To help control the buoyancy,which will help it float or sink deeper at its will, the submarine has partscalled ‘ballast tanks’ and ‘trim tanks’. The ballast tanks are filled with airwhen afloat, to make the density of it less that the surrounding water. As weall know, less dense objects float on top of more dense objects. When the submarinegoes deeper, the air is removed, and these tanks are filled with water. This makesthe density of the submarine greater than water, enabling it to sink and godeeper in water.
This is called negative buoyancy. In all submarines, there iscompressed air, usually in air flasks for the ballast tanks. Additionally, hydroplanes area crucial part of the submarine. They are like short wings, which help to anglethe direction that the submarine is moving in. They are usually angled upward,so the submarine is angled downward. The angle of the hydroplane is inverselyrelated to the angle of the submarine.(Hydroplane angled up, submarine angleddown.
) In emergency situations, these tanks can also be filled quickly to takethe submarine to the surface very fast. Now we are going to discussthe role of the trim tanks. In order for the submarine to remain at a certainlevel/depth under water, it uses these tanks. The submarine balances the airand water in the trim tanks, until the density of the submarine is the sameas(equal to the density of the water in its vicinity).
This is called neutralbuoyancy. The hydroplanes are also levelled, so that the submarine doesn’t continueto move at a downward angle and is stable. Finally, when the submarineneed to resurface, the compressed air carried in the air tanks is released intothe ballast tanks and water is forced out, to decrease the density of submarinein comparison to the water.
This is called positivebuoyancy. The hydroplanes are angled downwards, so the submarine starts to movein the upward direction. The three major issues toovercome when you’re in a submarine are the· Air quality· Fresh watersupply· The idealtemperature· Lightand navigation Here isa little bit information, on how these problems are solved. (air)As weall know, oxygen is vital for our survival underwater. It need to be refilledat the same rate at which it is consumed. If not, then people will suffocate.Hence, oxygen is supplied by pressurized tanks and an oxygen generator.
Another issuewith the air, is that carbon-dioxide(a gas we exhale) has to be removed fromthe air. If not, there will be an extremely high percentage of it in the air,which is toxic and harmful for us. Therefore, submarines have ‘scrubbers’, adevice which removes CO2 using soda lime. Themoisture that we exhale must also be taken out.
It is removed in submarinesusing a machine called a ‘dehumidifier’. This machine prevents it fromcondensing inside the submarine. (water)We allneed fresh water for survival(drinking water). In submarines, there is adistillation apparatus that takes sea water, and produces fresh water out ofit. This is done through the process of distillation that im sure most of usare familiar with. (heating and condensing water to separate the salt and otherimpurities from it.) (temperature)On anaverage, the temperature around submarines is 4 degrees Celsius which is thesame as 39 degrees Fahrenheit. Thesubmarine walls are made of metals, which conduct heat.
They pass on the heatto the surrounding waters dropping the temperature inside the submarine aswell. We need a warmer temperature to comfortably survive. Thus, submarines areelectrically heated(by nuclear reactors, batteries, etc) to obtain a comfortabletemperature. Light doesnot reach very far under the ocean, so submarines must navigate without it.They are equipped with GPS (global positioning system) which helps themnavigate, only on the surface, by providing them with the latitude and longitudeof positions.
But this system does not work under water. Thesubmarine uses an inertial guidance system to navigate. It helps record andobserve the motion of the submarine from the reference point/fixed point. These systemsare accurate and work until 150 hours only. Using this system, the submarinecan navigate within 100 feet from the surface. To find a target the submarine uses SONAR, which stands for sound navigationand ranging.
There are two types of sonar, active and passive. Activesonar emits sound waves that travel through water and reflect off the thetarget and echo back to the submarine. Computers can calculate the distancebetween the target and the submarine, just by know the speed of sound in waterand the time it took for the sound to echo.(speed=distance/time). This processis very similar to ‘echoloacation’ which is used by numerous aquatic creatureslike whales, dolphins, etc.
Thesecond type, passive sonar, is just listening to the sounds emitted by thetarget. Allthese parts, and many more put together, enables the submarine to function.