To understand the workings of a submarine, we first need to
understand the principle based on which it functions.
Buoyancy, which is also referred to as buoyant force, is the
force that acts upon any object that is submerged/immersed in water. Buoyancy
is 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 of
different sides of the object. The pressure exerted at the bottom of the object
is greater than the top, because pressure exerted is directly proportional to
depth(pressure increases, depth increases.)
The bottom force(stronger) pushes the object up, while the
top force(weaker) pushed the object down. Since the force is stronger at the
bottom, the net force is in the upward direction. Thus, buoyancy is referred to
as an ‘upthrust force’.
The Archimedes’ principle states that the buoyant force
exerted 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 same
as(equal to) the water it displaces and an iron nail sinks because the water
displaced is not the same as the mass of the iron nail.
A submarine functions based
on this principle.
A submarine is able to float
on water because the weight of water that it displaces, is the same as the
volume of the submarine. This process creates the buoyant force that we
discussed about earlier. This force acts in the opposite direction to gravity.
Unlike most watercraft machines, a submarine can control the buoyant force acting
on 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 parts
called ‘ballast tanks’ and ‘trim tanks’. The ballast tanks are filled with air
when afloat, to make the density of it less that the surrounding water. As we
all know, less dense objects float on top of more dense objects. When the submarine
goes deeper, the air is removed, and these tanks are filled with water. This makes
the density of the submarine greater than water, enabling it to sink and go
deeper in water. This is called negative buoyancy.
In all submarines, there is
compressed air, usually in air flasks for the ballast tanks.
Additionally, hydroplanes are
a crucial part of the submarine. They are like short wings, which help to angle
the direction that the submarine is moving in. They are usually angled upward,
so the submarine is angled downward. The angle of the hydroplane is inversely
related to the angle of the submarine.(Hydroplane angled up, submarine angled
down.) In emergency situations, these tanks can also be filled quickly to take
the submarine to the surface very fast.
Now we are going to discuss
the role of the trim tanks. In order for the submarine to remain at a certain
level/depth under water, it uses these tanks. The submarine balances the air
and water in the trim tanks, until the density of the submarine is the same
as(equal to the density of the water in its vicinity). This is called neutral
buoyancy. The hydroplanes are also levelled, so that the submarine doesn’t continue
to move at a downward angle and is stable.
Finally, when the submarine
need to resurface, the compressed air carried in the air tanks is released into
the ballast tanks and water is forced out, to decrease the density of submarine
in comparison to the water.
This is called positive
buoyancy. The hydroplanes are angled downwards, so the submarine starts to move
in the upward direction.
The three major issues to
overcome when you’re in a submarine are the
a little bit information, on how these problems are solved.
all know, oxygen is vital for our survival underwater. It need to be refilled
at 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.
with the air, is that carbon-dioxide(a gas we exhale) has to be removed from
the 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’, a
device which removes CO2 using soda lime.
moisture that we exhale must also be taken out. It is removed in submarines
using a machine called a ‘dehumidifier’. This machine prevents it from
condensing inside the submarine.
need fresh water for survival(drinking water). In submarines, there is a
distillation apparatus that takes sea water, and produces fresh water out of
it. This is done through the process of distillation that im sure most of us
are familiar with. (heating and condensing water to separate the salt and other
impurities from it.)
average, the temperature around submarines is 4 degrees Celsius which is the
same as 39 degrees Fahrenheit.
submarine walls are made of metals, which conduct heat. They pass on the heat
to the surrounding waters dropping the temperature inside the submarine as
well. We need a warmer temperature to comfortably survive. Thus, submarines are
electrically heated(by nuclear reactors, batteries, etc) to obtain a comfortable
not reach very far under the ocean, so submarines must navigate without it.
They are equipped with GPS (global positioning system) which helps them
navigate, only on the surface, by providing them with the latitude and longitude
of positions. But this system does not work under water.
submarine uses an inertial guidance system to navigate. It helps record and
observe the motion of the submarine from the reference point/fixed point.
are accurate and work until 150 hours only. Using this system, the submarine
can navigate within 100 feet from the surface.
To find a target the submarine uses SONAR, which stands for sound navigation
and ranging. There are two types of sonar, active and passive.
sonar emits sound waves that travel through water and reflect off the the
target and echo back to the submarine. Computers can calculate the distance
between the target and the submarine, just by know the speed of sound in water
and the time it took for the sound to echo.(speed=distance/time). This process
is very similar to ‘echoloacation’ which is used by numerous aquatic creatures
like whales, dolphins, etc.
second type, passive sonar, is just listening to the sounds emitted by the
these parts, and many more put together, enables the submarine to function.