I.

Introduction

Bomb, explosive free-falling weapon that primarily uses gravity to travel from its launcher to its target. Bombs carry and disperse either a lethal or a nonlethal substance called the payload. Bombs are similar to explosive artillery shells, but bombs are dropped from the air rather than being propelled from the ground. A typical bomb has a long, streamlined form and is comprised of a steel casing containing the payload and a detonating mechanism that causes the bomb to explode. Most bombs also have small stabilizing fins at the rear. A bomb usually hangs from shackles, either in a bomb bay inside an airplane or mounted under its wing, until the pilot or bombardier triggers its release. After the bomb has fallen a preselected distance, a spinning wheel arms the bomb, readying it for detonation. A fuse detonates the bomb and can be triggered in several ways, such as by barometric pressure, a radio altimeter, a timer, or by contact with the target.

Bombs have played an important part in warfare of the last 150 years. The first bombs were dropped from airships (lighter-than-air vessels such as balloons, dirigibles and other airships) in the mid-1800s, but bombing from the air began in earnest during World War I (1914-1918). Countries began using airplanes as bombers because they were faster and less vulnerable than airships, and could bomb with greater precision. World War II (1939-1945) saw even greater use of bombing as a weapon of war. Airplanes could travel great distances and drop bombs well behind battle lines, deep into enemy territory. Bombs were first used against troops and other military targets, but as technology and the range of airplanes improved, the role of bombing expanded. During World War II, factories, cities, railroads, and bridges were bombed in an effort to weaken a country’s ability to make war. This strategy continues today.

Both smart and dumb bombs are in use today. Most bombs are “dumb,” meaning they fall where gravity takes them. Bombsights are used by high-altitude bomber aircraft to drop the bomb as close as possible to the target area. These types of bombs cost less per pound of payload than weapons such as guided missiles or artillery projectiles, but they are also much less accurate. Weapons designers have improved the accuracy of some bombs by adding pop-out wings, moveable fins, and laser seekers; these are called smart bombs. Another version of a smart bomb is a Joint Direct Attack Munition (JDAM). The JDAM is a guidance system attached to a dumb bomb. It is also known as a satellite-guided precision bomb because it is guided by an array of satellites that form part of the global positioning system. Users of smart bombs hope to knock out their targets with fewer bombs, while reducing damage to structures or injury to people near the target. Modern bombs are broadly classified as conventional (nonnuclear) bombs or nuclear (atomic or hydrogen) bombs. See also Smart Bomb.