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Most people have some sort of familiarity with submarine crafts; most of which are most likely related

to the navy. This is a very accurate depiction of submarines, as they are primarily used for this,

however, they are used in areas of scientific research as well.

A Submarine can float on water because the weight of the water displaced is equal to the weight of

the craft. The upward force that the water has on the vessel is known as they buoyant force. The key

to controlling a submarine’s diving and resurfacing, is to control the buoyancy.

Submarines are equipped with ballast tanks and trip tanks that can be filled with either water or air. To

have the submarine sitting on the surface, the ballast tanks must be empty; to descend, the air in the

tanks is replaced with water. The density of a submarine then becomes greater than the water and it

will submerge. There is a supply of compressed air on board that is used for both life support and to

fill the ballast tanks.

The speed of descent is additionally helped with a set of diving planes or “wings” on the top of the

submarine. The angle of the wings is controlled, thus influencing the angle of descent.

To keep the submarine level at any depth, the submarine maintains a balance of air and water in the

trip tanks, so that the overall density is equal to the surrounding water. The diving planes also help

keep the depth of the submarine constant. The rudder on the back of the craft helps steer it.

Power Supply

Nuclear submarines use nuclear reactors, steam turbines, and reduction gearing to drive the main

propeller shaft. Electric power is also used to operate equipment, this is made from diesel engines

and nuclear reactors. Batteries may also be used for electric power, and they may be charged using

either a diesel engine or a nuclear reactor.

Nuclear submarines have an advantage to diesel submarines because they can stay submerged for

weeks at a time. Diesel engines can only be used while the submarine is surfaced, or at least using a

snorkel, to recharge the batteries. Once the batteries are charged, the submarine can descend using

electric power. Because nuclear fuel lasts much longer than diesel fuel, nuclear submarines can stay

under water or at sea for long periods of time, without having to port to refuel.

Navigation

Submarines navigate using global positioning system while on the surface, however, this will not work

while the vessel is submerged. Underwater, the crafts use inertial guidance systems that keep track of

the ship’s motion from a fixed starting point using gyroscopes. These systems are very complex and

difficult to use, and very accurate at the same time. They are accurate up to 150 hours at a time.

To locate targets, submarines use passive sonar. This works by emitting sound waves through water

and allowing the sound waves to reflect off the target and return; by knowing the speed of sound inwater and the time it took for the sound wave to travel back, submarines can calculate the distance to

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the target. This is the same technique that bats, dolphins, and whales use. These systems can also

help recalibrate the inertial guidance systems.

Air Supply

Oxygen is supplied from either compressed tanks, or an oxygen generator, which works by

electrolysis. Oxygen can either be released in periods throughout the day, or whenever a computer

senses the oxygen level is low. Carbon Dioxide must be removed from the air as well. This can be

done chemically using soda lime in “scrubbers”. The carbon dioxide is trapped and removed from the

air in chemical reactions. Moisture is removed by a dehumidifier, this prevents condensation buildup

within the ship.

Water Supply

Most submarines can take in seawater and turn it into fresh water through a distillation process. The

distillation plant on submarines can produce 10,000 to 40,000 gallons of water per day. The water is

mainly used for cooling equipment and for the crews’ personal use.