A torpedo is a guided, self-propelled weapon which is designed to be deployed in the water, detonating on contact with the hull of an enemy ship or submarine. Any fan of war movies with scenes on the open water is probably familiar with the basic concept of the torpedo, and it may be a surprise to learn that torpedoes are fairly old; the first weapon we would recognize as a torpedo was built in 1866, by an enterprising British inventor. Today, most militaries have a wide array of torpedoes to choose from for an assortment of situations.
Several things distinguish torpedoes from other types of weapons. For one thing, they are designed to function in the water, with-self enclosed housings to protect the detonator and explosives from the corrosive effects of sea water. Torpedoes also have their own power source, which is used to propel the projectile until it reaches its source, and they are capable of being guided in some way. Guidance systems are increasingly common on military projectiles, and torpedoes have very sophisticated guidance systems.
There are several ways to launch a torpedo, and several different designs intended for different applications. Aircraft can drop torpedoes, which activate when they hit the water, and torpedoes may also be launched by ships and submarines. Once launched, the torpedo typically turns into its own entity, beyond the control of the people who launched it. Modern torpedoes use a homing mechanism to find their targets, scanning for the characteristic signs of a ship or submarine in the water.
The earliest torpedoes were actually sea mines, stationary explosives planted around harbors and heavily traveled areas with the goal of sinking the enemy. However, in the mid-1800s, people began to realize that a torpedo which could be launched and guided could be a very useful thing, and early torpedoes began to be developed. A variety of different styles and designs were played with, ranging from torpedoes guided by wires to projectiles which were simply aimed at a target and sent on their way.
The explosives in a torpedo are capable of penetrating the heavy hulls of ships and submarines, and most are calibrated to create a maximum amount of damage. In addition, when a torpedo is aimed at a vulnerable location like ammunition magazines, it can trigger secondary explosions, ensuring that the target will sink as desired.