Submarinos

SUBMARINES

A submarine is a ship that can travel under water. Military submarines are used in wars to attack enemy vessels. They are very large, up to 60 metres long.Scientists use submarines to explore the oceans and get information about plant and sea life deep under the surface.

Parts of a submarine

Submarines are often shaped like a cigar, so that they can travel quickly under the ocean surface. A submarine’s outer part is the hull. It is made out of strong steel; otherwise it would be crushed by the pressure of the water. Tanks are in the hull. When a submarine dives these tanks are filled with water and the sub becomes heavier. If a sub wants to come up to the surface the water is pumped out of the tanks and replaced by air, which makes the submarine lighter.

The sail is the tall thin tower at the top of a submarine. It is the command bridge of a sub with all the instruments, antennae andperiscopes which allow the captain or other crew members to see what happens on the surface.

How a submarine works

Modern submarines spend most of their sailing time under water. They can dive to a depth of about 400 metres. Today’s submarines have a nuclear reactor on board. It produces the heat that is needed to make steam. Steam turns theturbines and propellers that make the ship move forward.

Earlier submarines were propelled by diesel engines. They ran when the submarine was on the surface .Under water they used batteries to operate. Such subs were not able to stay under water for a very long time and had to come up forair supplies every few hours. Nuclear submarines do not need air. Special machines turn salt water into drinking water and extract oxygen to make air. They can stay under water for months without surfacing.

Life on a submarine

Submarines usually travel for about two or three months before they come back to their home port.

Sailors on board modern submarines can enjoy many luxuries in their free time. There are cinemas, libraries game rooms, satellite TV and other facilities to help them spend their time when they are off duty.

When a submarine reaches its home port it is checked and repairs are made if necessary. The crew leaves the sub and a new crewreplaces it.

History

The first submarine was built in 1620 by a Dutch scientist. He covered a row boat with hides and could travel in water that was 4 metres deep.

In the 1800s many types of submarines were built. They were powered by gas, steam and batteries. By 1900 most submarines had diesel engines and electric motors that worked with battery power.

In World War I Germany started using submarines effectively as warships. In May 1915 a German sub sank the British passenger ship Lusitania, killing over 1,200 passengers.

In World War II German U-boats sank thousands of Allied ships. They travelled in groups called wolf packs. American submarinesoperated mainly in the Pacific Ocean where they attacked and destroyed Japanese vessels.

Diesel engines in a submarine

In 1954 the first nuclear-powered submarine, the Nautilus, was built by the Americans. It was the fastest sub in the world and could stay under water for a long time. In 1958 the Nautilus was the first submarine to sail under the ice of the North Pole.

In the decades that followed nuclear submarines carried missiles an d nuclearweapons that could hit targets thousands of kilometres away. This made submarines a very dangerous weapon of war.

Today the USA, Russia and China have the biggest submarine fleets.

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