A submarine is an interesting type of vessel which is useful to navigate under the water and surface because it has a special system of variable buoyancy. These vessels were used on the First World War. Actually, submarines are part of all major navies. Submarine is a term that comprehends different vessels from small to nuclear ones. The smalls can stay submerged few hours while the nuclear could stay around one year and half. The smalls are used for examining the seabed while the nuclear are able to destroy cities with their missiles. You could find specialist submarines like the submarine rescue.
In the decade of the 1950, the diesel-electric propulsion was biased replaced by nuclear power. The same system was used for extract the oxygen from seawater. Also this vessel was used for being submerged for during weeks or even months. So, this type of vessels allowed trips that were impossible before. For instance, in 1958 the USS Nautilus crossed the North Pole under the Arctic ice cover.
In the United States and the Soviet Union, the majority of military submarines constructed were propelled by nuclear reactors. There are some factors that restricted the underwater permanence. The crew could feel claustrophobia because of the limited space. Also, in this type of vessels there are limitations of food supplies.
Submarines are good for long distance missions or for protecting aircraft carrier force. The diesel-electric submarines have been produced by countries with or without nuclear capability because they are not easy to perceive.
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