The first explosives were crude clay containers containing black powder, with some form of rudimentary ignition mechanism, like that of a burning match. Black powder is a chemical mixture made up of potassium nitrate a.k.a saltpeter, sulfur, and charcoal. Potassium nitrate is the main component of the powder and can take up as much as 75% of its mass, with charcoal and sulfur being in lesser quantities respectively.
In 1847, nitroglycerin was developed by Ascanio Sobrero, which was viewed as a more effective explosive compared to black powder. Then, the world-renowned Swedish chemist Alfred Nobel invented dynamite two decades later in 1867. Dynamite is a high explosive that uses nitroglycerin soaked sawdust, diatomaceous earth, a blasting cap and an electric cable called a fuse. It is roughly 60% more powerful than trinitroluene, a.k.a TNT. Contrary to popular belief, dynamite is different from TNT. TNT is a yellowish chemical compound that is a stable explosive, it is relatively insensitive to friction and shock compared to other high explosives like nitroglycerin. TNT was also discovered around that time by a German chemist called Julius Wilbrand. TNT did not receive the attention like other contemporary explosives as it was difficult to detonate and was less powerful.
In 1846, chemist Christain Friedrich Schonbein accidentally spilled a bottle of concentrated nitric acid on his kitchen table, and he wiped it up with a cotton apron. As he hung it on his stove door to dry, the apron soaked with nitric acid ignited with a flash. Schonbein discovered that the mixture for his “gun-cotton” was cotton infused with an equal blend of nitric and sulfuric acid in the ratio of 1 to 15. He had created the highly-flammable combustible known as nitrocellulose. Nitrocellulose was three times more effective than black powder, and it also produced less smoke than other explosive compounds of the time. This was a vital component of smokeless powder, the gunpowder used in most modern firearms. This modern gunpowder burns much more steadily than traditional black powder, and also has a detonation velocity of 7300m/s. This has led to improvements in firearms design and explosives engineering: such as metallic cartridges and sea mines respectively.
In 1875, Nobel again invented a revolutionary explosive: Gelignite. Gelignite is the world’s first plastic explosive, or PE in short. Plastic explosives are more stable than standard HE, and can be moulded into a variety of shapes without detonating. Combat engineers often use plastic explosives to destroy enemy obstacles and structures like doors and bridges respectively. The earliest use of PE in military context was Nobel’s Explosive 808, manufactured by Nobel Chemicals Ltd. prior to World War 2. It was used extensively throughout the Second World War by British Special Forces for sabotage missions in Nazi-occupied France.
In 1898, Georg Friedrich Henning discovered RDX, or cyclotrimethylene-trinitramine. During World War 2, RDX was mixed with TNT to form the charges used in the bouncing bombs dropped on German hydroelectric dams in Operation Chastise. After the war, RDX was used as the basis for military scientists to develop the Composition C family of plastic explosives. They primarily comprised of RDX, a plasticizer, a binder and SAE 10 non-detergent motor oil. The C-4 PE is so effective that it remains in use today.
In 1883, Max von Foerster discovered the first shaped charge. Shape charges work via the Munroe effect: focusing all the blast energy in a single direction by the use of a conical liner. In conventional explosives, the explosive force radiates outwards from the point of detonation and distributes its energy evenly around the blast radius. In a shaped charge, the front of the explosive is lined with an inward-facing copper cone that turns into a high-velocity jet stream upon detonation. This superheated stream of molten copper possesses enough kinetic energy to pierce conventional tank armour as thick as 203mm.
Most contemporary warheads contain shaped charges for eliminating tanks, ships and other hard targets. The warhead has to be detonated at a precise distance away from the target, to allow the high-velocity molten copper to form and enable it to reach optimum pressure. The stream’s kinetic energy quickly dissipates when it travels past 2 meters, losing its ability to penetrate all the way through the armor. This is how bar or cage armour protects vehicles from HEAT warheads; either by prematurely detonating the explosive to render it ineffective, or by damaging the fuze and preventing ignition altogether. An iconic weapon that uses shape charges is the RPG-7, in which the actual grenade is larger than the rocket itself. It is notoriously simple to operate and easy to use against multiple types of light-armoured targets, including APCs, Humvees and helicopters like in the Black Hawk Down incident in 1993. However, there is another type of explosive capable of defeating heavily armoured vehicles such as modern tanks.
Used by British soldiers in World War 2, the High-Explosive Squash Head, or HESH shell, used the target’s thick armour against itself. It does so via the precise transmission of shockwaves through the armour using a plastic explosive, notably the Nobel 808. A HESH warhead is made up of RDX topped with plastic explosive filling at the nose, an impact-delay fuze affixed to the base of the PE filling, all contained in a thin shell body. The HESH warhead was first used by the British in 1940 to destroy or even level heavily reinforced German bunkers.
The plastic explosive in the shell’s nose would make contact with the bunker’s hardened exterior, the fuze would then be triggered by the RDX exploding behind it, initiating the detonation of the Nobel 808 that was spread out on the exterior. The resulting shockwave propagated through the concrete, creating a deadly spray of shrapnel, known as spall, to fly towards the intended target. This is especially effective in steel armour, where steel shards are propelled at high velocity at personnel and hardware, causing massive damage and destruction.