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BRIEF HISTORY OF SUBMARINES

1580

The first published prescription for a submarine came from the pen

of WILLIAM BOURNE.

First submersibles

The first submersible boat was built in 1620 by Cornelius Drebbel

First military models

The first military submarine was the Turtle (1775), a hand-powered acorn-shaped device

designed by the American David Bushnell to accommodate a single person.

In 1800, France built a human-powered submarine designed by American Robert Fulton, the

Nautilus.

In the American Civil War

The Alligator was the first U.S. Navy submarine ,designed by Brutus de Villeroi, first launched

on May 1, 1862,

Turtle The 1862 Alligator,

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SUBMARINE TECHNOLOGYWhether a submarine is floating or submerging depends on the ship's buoyancy. Buoyancy is controlled by

the ballast tanks, which are found between the submarine's inner and outer hulls.

positive buoyancy.

-- A submarine resting on the surface

--means it is less dense than the water around it and will float

--the ballast tanks are mainly full of air.

negative buoyancy.

-when the submarine submerge

--Vents on top of the ballast tanks are opened. Seawater coming in through the flood ports forces air out thevents, and the submarine begins to sink.

The submarine ballast tanks now filled with seawater is denser than the surrounding water. The exact depthcan be controlled by adjusting the water to air ratio in the ballast tanks.

neutral buoyancy.

-That means the weight of the submarine equals the amount of water it displaces. The submarine will neitherrise nor sink in this state.

To make the submarine rise again, compressed air is simply blown into the tanks forcing the seawater out.The submarine gains positive buoyancy, becomes less dense than the water and rises.

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MAIN PARTS AND FUNCTIONS

Ballast Tanks

Pressure hull

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PRESSURE HULL

The pressure hull of submarines resists water pressure to make underwater

transport possible. Pressure hulls make it possible to breathe in theextreme water pressure levels that are present in submarines. As a

result, officers and crew on submarines can travel with comfort and

ease. Pressure hulls are usually made of titanium or steel.

The pressure hull is the inner hull of a submarine; this holds the difference

between outside and inside pressure.Modern submarines are usually cigar-shaped. This design, already visible

on very early submarines is called a "teardrop hull", and was patterned

after the bodies of whales. It significantly reduces the hydrodynamic

drag on the sub when submerged, but decreases the sea-keeping

capabilities and increases the drag while surfaced.

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BOUYANCY OF THE SUBMARINE

Buoyancy = weight of displaced fluid

The buoyant force tends is a force that acts in the upward direction when an object ispartially or fully submerged in water.

The equation for the force is:=

Fbis the buoyant force, pointing upwards, in Newtons (N).

Vs

is the volume submerged in metres cubed (m3).

Lis the density of the liquid (or gas) that the object is being submerged in kilograms

per metre cubed (kg/ m3).

gis the force of gravity in Newtons per kilogram (N/ kg).

The Buoyant force depends on the equation Fb=mfg =

-- where Fbis the buoyant force, mfis the mass of the fluid (water) that is displaced

by the body and g is the Earth's gravitational constant 6.673x10-11Newton Meters

squared per kilograms squared (Nm2/kg2)

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Submarines use buoyant forces and gravity to move up and down with

in the water. When the Buoyant force is less than the Earth's

gravitational pull on the submarine, it sinks, when the buoyant force isgreater than the Earth's gravitational pull on the submarine, it rises.

Once the submarine is already submerged, the buoyant force is

constant.

Submarines adjust the Earth's gravitational pull on it by filling the space

in between the inner walls and outer walls with water and/or gasses.

With out buoyant forces, the submarine would never return to the

surface of the water.

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