II.

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.

A.

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.

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.

B.

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.

C.

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.