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.
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.
CONVENTIONAL BOMBS
Conventional bombs can carry a variety of payloads. Bombs that carry an explosive are called general-purpose bombs. Firebombs are designed to spread fires, rather than explode their targets. Chemical bombs are filled with chemical or biological warfare agents, such as nerve gas. Cluster bombs break apart into smaller bombs when dropped. Leaflet bombs are used to drop messages over enemy territory, often to demoralize an enemy or to provide surrender instructions.
General-Purpose Bombs
Most bombs carry high-explosive fillers and are known as general-purpose (GP) bombs. Fillers make up as much as 50 percent of a bomb’s weight. The filler’s blast contributes most of the destructive effect, including burning and shattering buildings, people, and other targets. British GP bombs of World War II, which they called “cookies,” were large and bulky, and had relatively thin walls to carry as much explosive as possible. Smaller jet aircraft (from the 1950s onward) began carrying bombs externally under their wings, rather than within the plane in large bomb bays. As a result, later GP bombs took on a much more streamlined shape to improve accuracy and reduce drag when carried externally.
Some types of bombs first penetrate deep into the target, then explode. These are used against armored targets such as tanks or fortified buildings such as command posts. Two of the biggest conventional bombs ever used were deep penetrators developed by Britain during World War II. The “Tallboy” weighed 5,400 kg (11,900 lb) and the “Grand Slam” weighed 10,000 kg (22,000 lb). The Grand Slam’s powerful underground explosion was so massive that it became known as the earthquake bomb. Other bombs have casings designed to fragment readily, shredding into thousands of pieces that spray out in a deadly cloud. Fuel-air explosives are bombs that carry flammable liquid that is vaporized in mid-air over a target. As the flammable fuel vapor drifts down, a detonator explodes, creating a tremendous blast effect.
Some types of bombs first penetrate deep into the target, then explode. These are used against armored targets such as tanks or fortified buildings such as command posts. Two of the biggest conventional bombs ever used were deep penetrators developed by Britain during World War II. The “Tallboy” weighed 5,400 kg (11,900 lb) and the “Grand Slam” weighed 10,000 kg (22,000 lb). The Grand Slam’s powerful underground explosion was so massive that it became known as the earthquake bomb. Other bombs have casings designed to fragment readily, shredding into thousands of pieces that spray out in a deadly cloud. Fuel-air explosives are bombs that carry flammable liquid that is vaporized in mid-air over a target. As the flammable fuel vapor drifts down, a detonator explodes, creating a tremendous blast effect.
One of the earliest bomb fillers was trinitrotoluene (TNT), first used in 1904. Amatol is a filler that combines TNT with ammonium nitrate for a more intense explosion. Other fillers include RDX (trimethylene trinitramine or cyclonite), which has a greater shattering effect, and Torpex (TNT, cyclonite, and aluminum powder).
Smart bombs are modified general-purpose bombs that can be guided to their target. These are also sometimes known as glide bombs. Some smart bombs are fitted with a laser seeker that homes in on a laser beam focused on the target. The beam can be aimed by the plane dropping the bomb, another plane, or an operator on the ground. Other smart bombs use a TV camera mounted in the nose of the bomb to guide it to its target. The camera can locate the target as the pilot guides the bomb, or the pilot can lock on the image, and the bomb will adjust itself to keep that image in view. When the bomb drifts off target, fins steer it back on course. Recent smart bombs use the global positioning system (GPS) for guidance. GPS satellites in orbit transmit location information to the bomb, so the bomb can guide itself to a preset destination.
Smart bombs are modified general-purpose bombs that can be guided to their target. These are also sometimes known as glide bombs. Some smart bombs are fitted with a laser seeker that homes in on a laser beam focused on the target. The beam can be aimed by the plane dropping the bomb, another plane, or an operator on the ground. Other smart bombs use a TV camera mounted in the nose of the bomb to guide it to its target. The camera can locate the target as the pilot guides the bomb, or the pilot can lock on the image, and the bomb will adjust itself to keep that image in view. When the bomb drifts off target, fins steer it back on course. Recent smart bombs use the global positioning system (GPS) for guidance. GPS satellites in orbit transmit location information to the bomb, so the bomb can guide itself to a preset destination.
Firebombs
Firebombs (sometimes called incendiary bombs) usually consist of a carrier holding many small sticks that explode into flame. Firebombs are used to start fires over large areas, usually industrial sites. The sticks scatter loosely as the bomb falls, sprinkling a target with hundreds of fire-starters. The first incendiaries were made by Germany during World War I, but were developed too late to be used in the war. These Elektron bombs weighed only 1.0 kg (2.2 lb) and consisted of 10 percent aluminum and 90 percent magnesium with an igniter. The Thermite bombs (aluminum and iron oxide) of World War II burned at 2200° C (4000° F). Under the right conditions, incendiary bombs can start a firestorm, a self-sustaining fire that can engulf an entire city. The rising heat from the fire creates an upward draft that draws air towards the center of the fire, fueling it even more. Napalm is an antipersonnel incendiary delivered in tumbling canisters from low altitude. Consisting of jellied gasoline and additives to enhance stickiness and burning time, napalm burns at 1090° C (1990° F) for several minutes.
Other Non-Nuclear Bombs
Chemical bombs carry chemical agents such as nerve gas, or biological weapons such as the contagious disease anthrax. Bombs carrying nerve gas or anthrax were built but are rare, and have never been used by the United States or any other major military power. Usually, the bomb’s bursting charge turns the agent into a spray. Nerve gas bombs can be built as binary weapons, in which two ingredients that are relatively nontoxic ride in separate compartments until a charge blends the two chemicals to make nerve gas. Like all chemical weapons, these bombs are imprecise and have unpredictable results (see Chemical and Biological Warfare).
Cluster bombs (sometimes called scatter bombs) house submunitions, smaller explosives contained in individual cases. These bombs are used against large areas containing many targets, such as columns of vehicles or large troop concentrations. They are also often used to bomb enemy airplane runways, causing enough damage so that planes cannot take off or land. Some cluster bombs carry several hundred very small explosives, while others carry larger submunitions that can find specific targets such as tanks. Some types of submunitions don’t blow up immediately, but remain behind and act as landmines (see Mine, Warfare).
Leaflet bombs carry propaganda leaflets. When a leaflet bomb is dropped, it breaks open at a preset altitude and allows the flyers to flutter down. A random tactic, leaflet bombing can deliver information or even a surrender ticket to dispirited enemy forces.
Cluster bombs (sometimes called scatter bombs) house submunitions, smaller explosives contained in individual cases. These bombs are used against large areas containing many targets, such as columns of vehicles or large troop concentrations. They are also often used to bomb enemy airplane runways, causing enough damage so that planes cannot take off or land. Some cluster bombs carry several hundred very small explosives, while others carry larger submunitions that can find specific targets such as tanks. Some types of submunitions don’t blow up immediately, but remain behind and act as landmines (see Mine, Warfare).
Leaflet bombs carry propaganda leaflets. When a leaflet bomb is dropped, it breaks open at a preset altitude and allows the flyers to flutter down. A random tactic, leaflet bombing can deliver information or even a surrender ticket to dispirited enemy forces.
NUCLEAR BOMBS
Nuclear bombs represent a giant increase in explosive power over conventional bombs. Nuclear bombs have only been used against another country twice, when American B-29 bombers dropped them on the Japanese cities of Hiroshima and Nagasaki in August 1945 during World War II. In addition to blast and heat, nuclear bombs also release radioactive substances, often in the form of radioactive fallout. Radioactivity can cause radiation sickness that can lead to death months or years later and pollute the target for centuries.
There are two types of nuclear weapons: atomic and hydrogen (often referred to as A-bombs and H-bombs). Atomic bombs release huge amounts of energy by splitting the nuclei of atoms in a process called fission. High-energy neutrons bang into atoms of uranium or plutonium and cause the atoms to split, releasing more neutrons. In the Hiroshima bomb nicknamed “Little Boy,” a device similar to a gun fired two masses of enriched uranium at each other. When they merged, the two pieces made up a supercritical mass, in which enough neutrons were present to cause a chain reaction that had the force of 12.5 kilotons tons of TNT (12,500 tons). The Nagasaki bomb (nicknamed “Fat Man”) contained two hemispheres of radioactive plutonium wrapped in a sphere of explosive. The explosive squeezed the plutonium spheres together, creating a supercritical mass and an explosion equal to 22 kilotons (22,000 tons) of TNT.
In the 1950s scientists developed hydrogen bombs that used a fission trigger to generate enough heat to fuse atomic nuclei in a process called fusion. Fusion generates much more heat and blast than fission, and increased the power of nuclear weapons considerably. Some of the H-bombs carried in U.S. Air Force B-36 bombers in the 1950s could yield 24 megatons (24,000,000 tons of TNT), which equaled more than 1,000 Nagasaki atomic bombs. The Union of Soviet Socialist Republics (USSR) tested a device that yielded 57 megatons. Eventual miniaturization of warheads meant that even small aircraft could carry nuclear bombs or depth charges.
Other types of nuclear bombs concentrated their effects not on heat or blast, but on the deadly radiation produced. The neutron bomb was designed to maximize short-term radiation, deadly to humans, but leave buildings and other structures standing. Several were built in the 1980s, but they have since been dismantled. See also Nuclear Weapons.
In the 1950s scientists developed hydrogen bombs that used a fission trigger to generate enough heat to fuse atomic nuclei in a process called fusion. Fusion generates much more heat and blast than fission, and increased the power of nuclear weapons considerably. Some of the H-bombs carried in U.S. Air Force B-36 bombers in the 1950s could yield 24 megatons (24,000,000 tons of TNT), which equaled more than 1,000 Nagasaki atomic bombs. The Union of Soviet Socialist Republics (USSR) tested a device that yielded 57 megatons. Eventual miniaturization of warheads meant that even small aircraft could carry nuclear bombs or depth charges.
Other types of nuclear bombs concentrated their effects not on heat or blast, but on the deadly radiation produced. The neutron bomb was designed to maximize short-term radiation, deadly to humans, but leave buildings and other structures standing. Several were built in the 1980s, but they have since been dismantled. See also Nuclear Weapons.
HISTORY
Bombs have been used in warfare for over 150 years. The first recorded aerial assault with explosives occurred in 1849, when an Austrian officer launched paper balloons carrying 13.5 kg (30.0 lb) bombs over Venice, Italy; no injuries were reported. In 1910 American aviator Glenn Curtis demonstrated the practicality of dropping bombs from airplanes as he successfully dropped bombs on an outline of a battleship on Keuka Lake in New York. The first aerial bombing by aircraft in combat came a year later in 1911, when an Italian Blériot XI airplane dropped four 2.0 kg (4.4 lb) grenades on Ottoman forces in Libya.
Aerial bombing became more widespread in World War I, ranging from attacks against troops to extended campaigns against large cities. Both sides disregarded the then-recently signed Hague Conventions, which prohibited bombing, and attacked military installations such as airship hangars and troop concentrations as soon as the war began in August 1914. In addition to small explosives, aircraft dropped solid-steel arrows called flechettes on enemy troops.
German airships were used as the first strategic bombers during World War I, but suffered heavy losses. They moved slowly and could be easily shot down from the ground. Later bombing campaigns over London featured multiengine airplanes. British and French bombers carried out similar missions over western Germany. The first bombs used in these attacks were converted from grenades and artillery shells, with fins attached for stability. Ultimately, bombs specifically designed for aerial bombardment came into use in all countries. Targeting equipment remained primitive and bombing was haphazard and relatively ineffective.
From 1919 to the beginning of World War II, bomb development led to more streamlined casings, better fusing, and more powerful explosives. The Unites States and especially Germany practiced dive-bombing, where a plane dives on its target and releases the bomb at low altitude. Bombing remained inaccurate, however, despite improvements in bombsights, and often the bombs would fail to explode on impact. In raids against large cities, hundreds of bombers dropped thousands of bombs per raid to blast structures or start fires. Naval dive-bombers saw greater success in their attacks against ships, while some fighter-bombers enjoyed success hitting single targets such as tanks. A few radio-controlled glide bombs, which were controlled by the bombardier, were dropped successfully by Germany starting in 1943; two sank the Italian battleship Roma as it sailed to surrender to the British. At the end of World War II, however, the basic bomb remained an unguided, gravity-driven weapon.
Smart-bomb technology first made a measurable impact during the late stages of the Vietnam War (1959-1975), where a few U.S. laser-guided bombs knocked down bridges that several hundred dumb bombs had missed. Bomb delivery became more deliberate because each bomb’s target could be chosen individually.
In the Persian Gulf War (1991) between Iraq and an international coalition of forces led by the United States, smart bombs made up only 10 percent of the tonnage dropped but were credited with most of the damage. Special deep penetration laser-guided smart bombs were developed for the war to attack reinforced or underground targets. These bombs could find a target and penetrate deep into it before exploding. Dumb bombs were also used in the conflict and continue to be used by military planners in conjunction with smart bombs. B-52 bombers dropped thousands of tons of dumb bombs on Iraqi troop and equipment positions. Cluster bombs shredded defenses and littered the desert with unexploded submunitions, making Iraqi military movement (and postwar cleanup) difficult.
Aerial bombing became more widespread in World War I, ranging from attacks against troops to extended campaigns against large cities. Both sides disregarded the then-recently signed Hague Conventions, which prohibited bombing, and attacked military installations such as airship hangars and troop concentrations as soon as the war began in August 1914. In addition to small explosives, aircraft dropped solid-steel arrows called flechettes on enemy troops.
German airships were used as the first strategic bombers during World War I, but suffered heavy losses. They moved slowly and could be easily shot down from the ground. Later bombing campaigns over London featured multiengine airplanes. British and French bombers carried out similar missions over western Germany. The first bombs used in these attacks were converted from grenades and artillery shells, with fins attached for stability. Ultimately, bombs specifically designed for aerial bombardment came into use in all countries. Targeting equipment remained primitive and bombing was haphazard and relatively ineffective.
From 1919 to the beginning of World War II, bomb development led to more streamlined casings, better fusing, and more powerful explosives. The Unites States and especially Germany practiced dive-bombing, where a plane dives on its target and releases the bomb at low altitude. Bombing remained inaccurate, however, despite improvements in bombsights, and often the bombs would fail to explode on impact. In raids against large cities, hundreds of bombers dropped thousands of bombs per raid to blast structures or start fires. Naval dive-bombers saw greater success in their attacks against ships, while some fighter-bombers enjoyed success hitting single targets such as tanks. A few radio-controlled glide bombs, which were controlled by the bombardier, were dropped successfully by Germany starting in 1943; two sank the Italian battleship Roma as it sailed to surrender to the British. At the end of World War II, however, the basic bomb remained an unguided, gravity-driven weapon.
Smart-bomb technology first made a measurable impact during the late stages of the Vietnam War (1959-1975), where a few U.S. laser-guided bombs knocked down bridges that several hundred dumb bombs had missed. Bomb delivery became more deliberate because each bomb’s target could be chosen individually.
In the Persian Gulf War (1991) between Iraq and an international coalition of forces led by the United States, smart bombs made up only 10 percent of the tonnage dropped but were credited with most of the damage. Special deep penetration laser-guided smart bombs were developed for the war to attack reinforced or underground targets. These bombs could find a target and penetrate deep into it before exploding. Dumb bombs were also used in the conflict and continue to be used by military planners in conjunction with smart bombs. B-52 bombers dropped thousands of tons of dumb bombs on Iraqi troop and equipment positions. Cluster bombs shredded defenses and littered the desert with unexploded submunitions, making Iraqi military movement (and postwar cleanup) difficult.
During the U.S. and British invasion of Iraq in 2003, a majority of the bombs used were smart bombs, particularly JDAM-equipped general-purpose bombs. Cluster bombs were also used, as were bunker-busting bombs, devices designed to penetrate underground bunkers housing Iraqi command and control facilities.
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