A Bomb is an explosive weapon. Bombs are usually used in warfare, although terrorists groups also use them. Bombs kill or injure people and destroy buildings, aeroplanes, ships, and other targets. Most bombs consist of a metal case filled with explosives or chemicals and a means of exploding or scattering the contents. Most bombs are large and dropped from aeroplanes, but some bombs are small enough to be carried by hand. Such bombs are often used by terrorists. In warfare, small bombs may be thrown as grenades or fired from artillery.

Bombs are set off by a small device called a fuse. A contact fuse sets off the explosion when the bomb strikes a target. A bomb with a proximity fuse goes off a short distance above the ground. One type of proximity fuse uses a radar to measure the distance to the ground. Yet another type of proximity fuse reacts to the level of air pressure.

Bombs are either conventional or nuclear. Conventional bombs vary in size and design. They are usually classed as; general-purpose, guided, armour-piercing, fragmentation, and incendiary bombs.

General-purpose bombs use explosives like RDX or TNT. The bomb destroys by the combination of the blast, the vacuum pressure, the fragmentation, and the shock wave. The blast is the enormous wave of air pressure produced by the explosion, a wave that destroys everything in it’s path. The vacuum pressure is the suction effect caused when air rushes back into the partial vacuum caused by the blast. Fragmentation is when the bomb breaks into little pieces which fly everywhere and cause damage and injury. The shock wave is the blow transmitted through the ground, water or physical structures in which the bomb explodes. It can weaken and destroy underground foundations and structures. General-purpose bombs usually weigh between 100kg (215lbs) and 900kg (1938lbs). Their length ranges from around 180cm (6ft) to 3.8m (2ft 8in).

Guided bombs, A.K.A. “Smart bombs”, are directed towards targets by electronic equipment like a TV monitor or a laser beam. Armour-piercing bombs have a heavy steel nose designed to penetrate a battleships armour. The bomb then explodes inside the ship.

Fragmentation bombs have many metal fragments or bars that that break into jagged pieces upon detonation. These fragments scatter fly out with tremendous speed to kill and injure. A certain fragmentation bomb, know as a cluster bomb, has hundreds of small bombs (bomblets) packed into a light container. They either explode on impact to the target or lay dormant until they are bumped by a car or person.

Incendiary bombs contain substances like petrol compounds or thermite (a mix of aluminium and iron oxide). When detonated, they spread a sticky mixture that ignites and causes a fire that is very hard to put out.

Other conventional bombs include chemical bombs, depth bombs, leaflet bombs and photoflash bombs. Chemical bombs spread smoke or poison gas. Depth bombs work underwater against submarines. Leaflet bombs spread propaganda to the enemy. Photoflash bombs provide the light needed for aerial photography at night.

Gunpowder burns rapidly to produce a high-pressure gas. The expansion of this gas inside a gun barrel caused the bullet to accelerate faster, so gunpowder is used as an propellant in a variety of ammunition. It’s also used in explosives for blasting operations, fireworks, and fuses.

There are various kinds of gunpowder. One kind is black powder, which was used a lot in muskets, canons, and old pistols. Black powder is usually made up of 75% saltpetre (potassium nitrate), 15% charcoal, and 10% sulphur. These substances are firstly ground into fine powder separately, and are then mixed together. The mix is then dampened with water and pressed together into a “cake” with a hydraulic press. The cake is then broken up, sifted into grains of various sizes (from fine grains to pellets), and dried. Sometimes graphite is added.

Sulphurless black powder is 70% saltpetre and 30% charcoal. Although it’s not as powerful as regular black powder, it is less corrosive to the gun barrel. The black powder used for commercial purposes (fireworks and blasting) sometimes has sodium nitrate instead of the more expensive saltpetre.

Black powder can cause corrosion, dirt, and large amounts of smoke, so smokeless powder was developed. Smokeless powder is made up mostly of nitrocellulose, but some contain nitrate salt and other additives. When the nitrocellulose is dissolved in nitroglycerin the powder is called a colloided powder.

Dynamite is an important industrial explosive used in blasting out dam sites, canal beds, mines, quarries, and the foundations of large buildings. It’s also used for demolition in warfare.

The main explosive ingredient in dynamite is an oily liquid called nitroglycerin. It is mixed with other materials, some of which are explosive, and packed into cylinders of plastic or waxed paper. The cylinders are called cartridges and can range from 22 to 200 mm in diameter and from 10cm (4in) to 76cm (2.5 ft) in length.

Dynamite was invented by Alfred Nobel (the founder of the Nobel prize) in 1867. Nobel developed Straight dynamite and blasting gelatin. Ammonia nitrate and ammonia gelatin were developed in the early 1900’s. During the mid 1900’s, ANFO, a mix of ammonium nitrate and fuel oil, was preferred by blasting operators instead of dynamite. Blasting operators also used slurry explosives, slushy mixtures of nitrocarbonitrates. ANFO and slurry explosives are cheaper to use than dynamite but still need to be detonated by dynamite or something similar.

Dynamite is set off by inserting a detonating cap or blasting cap into the end of the cartridge and setting off the cap with a fuse or electric current.

There are 4 main varieties of dynamite; straight dynamite, ammonia dynamite, straight gelatin, and ammonia gelatin.

Straight dynamite is made up of nitroglycerin and a substance that is both chemically reactive and absorbent, such as wood pulp and sodium nitrate. This is the oldest kind of dynamite and it isn’t used much anymore.

Ammonia dynamite contains ammonium nitrate and is stronger, and cheaper than straight dynamite. It’s also safer than straight dynamite, producing less toxic fumes and cooler gases. Ammonia dynamite is called a permissible explosive, which means that it is safe to use in mines where tremendous heat could ignite gas or dust in the air. It is the most commonly used form of dynamite.

Straight gelatin is made from a stiff gel called blasting gelatin. Blasting gelatin is a mix of nitroglycerin and a small amount of guncotton. Straight gelatin is made when blasting gelatin is mixed with sodium nitrate and other ingredients.

Ammonia gelatin is made when blasting gelatin has ammonium nitrate and other ingredients added. Ammonia gelatin is waterproof and used for underwater and hard-rock blasting.

Nitroglycerin, A.K.A. nitroglycerol, is a powerful explosive by itself, as well a being an ingredient in explosives like dynamite. Pure nitroglycerol is a heavy, oily, clear liquid. Commercial nitroglycerin is usually straw coloured. When nitroglycerin is detonated the liquid changes into gases which can take up more than 3000 times the space of the original liquid. The detonation is 3 times as powerful as gunpowder and 25 times faster.

Nitroglycerin is made by slowly adding glycerine (A.K.A. glycerol) to concentrated nitric and sulphuric acids. The nitroglycerin forms a layer on top of the 2 acids. The layer is drawn off and washed with water and then a solution of sodium carbonate.

Nitroglycerin was discovered in 1846 but was not used regularly because it was unreliable. In 1864 the invention of a detonating cap made of mercury fulminate made nitroglycerin easier to use. In 1867 dynamite, which contained nitroglycerin, was invented, and the substance became widely used.

Nitroglycerin is used as an ingredient in many smokeless powders like cordite and ballistite. It is also used to treat certain health conditions like heart disease.

Saltpetre, A.K.A. nitre, is known chemically as potassium nitrate. It occurs naturally in limestone caves and is used in making matches, gunpowder, explosives, and fertilizers. It is used in chemistry as a reagent. Saltpetre is also the oxidizer in liquid rocket fuel propellants.

Saltpetre is either a crystalline powder or white/colourless crystals. It dissolves in water and melts at around 337 degrees Celsius. Saltpetre is created by the reaction between potassium chloride and either sodium nitrate or nitric acid.

Chile saltpetre, (sodium nitrate), is used to make fertilizer, nitric acid, and potassium nitrate. Lime saltpetre, (calcium nitrate), A.K.A. Norwegian saltpetre, is made from limestone and is used to make fertilizer, matches, explosives, and other chemicals. Barya saltpetre, (barium nitrate), is used to make barium oxide and green fireworks.

Guncotton is obtained when cotton or purified wool cellulose is soaked in a mix of sulphuric acids and nitric acids. The soaked cotton is drained from the acid mixture and then boiled in water to remove the impurities. It’s then ground to a pulp and drained, and pressed into small slabs while damp. The guncotton is then air dried to make blocks. It can be used in the making of plastics and lacquers, or as an explosive.

When ignited, dry guncotton is very unstable. It burns very rapidly and can be set of by a blow from a metal tool. Guncotton is safer when wet as it will not burn. Wet guncotton can be kept in storage indefinitely and will not explode by itself.

Ordinary guncotton burns to rapidly to be used in firearms. However, the burning rate can be controlled when the guncotton is colloided (gelatinised) in nitroglycerin and other solvents. Colloided guncotton is one of the main ingredients in smokeless powder.

TNT is a powerful solid explosive. TNT stands for trinitrotoluene. Trinitrotoluene is made up of nitrogen, hydrogen, carbon, and oxygen.

TNT is made by nitrating the chemical compound toluene. TNT looks like pale yellow crystals that can darken to brown. TNT can be handled safely and can even be melted at low heat without it going off. TNT is mainly used as the explosive charge for shell and bombs, but can be used in conjunction with PETN, RDX, and ammonium nitrate.

PETN stands for pentaerythritol and is more powerful than TNT. It is capable of exploding small devices and so is used as the core of detonating caps and fuses. TNT and PETN mixed together is known as pentolite.

Picric acid, known chemically as trinitrophenol, is an industrial chemical best known for its use as an explosive. Picric acid is no longer used in shells because it corrodes the metal casings. When combined with metals it forms salts known as picrates. Picrates are unstable and are used to set off more stable explosives.

Picric acid appears as a yellow crystalline solid that is slightly soluble in water.

Plastic explosives are putty-like substances that can be moulded into any shape. They are made up of either RDX or a mix of RDX and PETN combined with a “plasticizer” to make the substance flexible. Only a powerful detonator can set it off.

Their flexibility makes them easy to hide, which makes plastic explosives a favourite for terrorists and secret agents.

M118 Composition C4 Block Demolition Charge The M118 block demolition charge, or sheet explosive, is a block of four .50-pound sheets of flexible explosive packed in a plastic envelope. Twenty M118 charges and a package of 80 M8 blasting cap holders are packed in a wooden box. Each sheet of the explosive has a pressure-sensitive adhesive tape attached to one surface. Relative effectiveness factor is 1.14.

The Composition C4 is a cutting charge especially to be used against steel targets. The sheets of explosive can easily be cut to any shape or volume and their flexibility ensures they can be quickly applied to irregular and rounded surfaces. It can be used for small breaching charges but should not be used as a bulk explosive charge as it can be quite expensive.

The flexibility and adhesive backing of the sheets allow them to be applied to a large selection of targets. The .50-pound sheets can be cut to the desired dimensions and applied in layers to achieve the desired thickness. They are waterproof and may be used underwater.

Adhesive tape will not adhere to wet, dirty, rusty, or frozen surfaces. These sheet explosives are sensitive to sparks and should be cut with a sharp steel knife (not shears) on a non-sparking surface. Composition C4 explosives are poisonous and dangerous if chewed or ingested(?) as their detonation produces toxic fumes.