WHAT ARE SUBMARINES.
Submarines are ships that travels underwater. Most Submarines are designated for use in war to attack enemy ships or to fire missiles at enemy countries. These ships range in length from about 200 feet to more than 500 feet. There rounded hulls are about 30 feet in diameter. More than 100 crew members live and work aboard such warships.
Some submarines are used for scientific research. These underwater crafts explore the ocean depths and gather scientific information. They are smaller than military submarines and carry only a few crew members.
In war, a submarine usually attacks from beneath the surface of the water. A submarine must remain underwater to be effective. Early submarines could not stay submerged for long periods. They had to surface every few hours for air for their engines and crews. Enemy planes and ships could then attack them. Today, nuclear submarines can stay underwater for months at a time. Nuclear engines do not need oxygen to operate, and modern submarines can produce all the air their crews need.
A submarine’s long, cigar-shaped body enables it to move swiftly underwater. Two hulls protect the submarine from water pressure. An inner hull, called the pressure hull, shields the ship from the crushing force of water at great depths. The pressure hull is built of strong, thick steel. The outer hull fits around it. Openings in the hull let in water to give the submarine ballast (weight) for diving.
A tall, thin structure called the sail rises from the middle of the submarine’s deck. The sail stands about 20 feet high. It holds the periscopes and the radar and radio antennas. The top of the sail also serves as the bridge, from where the captain (or officer of the deck) directs the submarine on the surface. Steel fins called diving planes stick out from both sides of the sail and from the stern. These diving planes guide the ship to different depths. A propeller in the stern drives the submarine. Two rudders mounted above and below the propeller steer the craft.