How Grenades Work
Grenades have played a part in warfare for hundreds of years. They were orihinally developed around 1000AD by the Chinese, just one application of their revolutionary gunpowder technology.
The typical design of these early grenades was a hollow metal container filled with gunpowder. Soldiers simply lit a wick and tossed the grenade as fast as they could. By the 18th century, these weapons had fallen out of favor: They weren't especially useful in the battle style of the time, and the simple design made them extremely dangerous.
A grenade is just a small bomb designed for short-range use. The idea of a bomb is very simple: Combustible material is ignited to produce an explosion a rapid expansion of gases that produces strong outward pressure. The essential elements of a grenade, then, are combustible material and an ignition system.
There are all sorts of combustible materials used in grenades, and they generate a range of explosion types. Some explosions will spread fire, and others will just release a lot of smoke. Ignition systems also vary, but they generally fall into one of two categories: time-delay igniters and impact igniters. The function of both systems is to set off the explosion after the grenade is a good distance away from the thrower. One very simple impact grenade is a container filled with nitroglycerine or another material that combusts easily when jarred. In this case, the flammable liquid itself is the impact igniter. One simple but effective time-delay grenade is the Molotov cocktail, a bottle of flammable liquid with a rag sticking out of it. The rag acts as a crude fuze the thrower lights it and tosses the bottle. When the bottle smashes on impact, the flammable liquid flows out and is ignited by the burning rag. The problem with both of these grenades is they can easily explode before the thrower gets rid of them. Proper grenades used by soldiers and police officers have safer, more sophisticated ignition systems, as we'll see in the following sections.
Time Delay Grenade
The most common type of grenade on the battlefield is the time delay fragmentation anti personnel hand grenade. The primary function of this grenade is to kill or maim nearby enemy troops. To ensure maximum damage, the grenade is designed to launch dozens of small metal fragments in every direction when it explodes.
These sorts of grenades, which played a major role Vietnam and are designed to be durable, easy to use and easy to manufacture. The conventional design uses a simple chemical delay mechanism. The outer shell of the grenade, made of serrated cast iron, holds a chemical fuze mechanism, which is surrounded by a reservoir of explosive material. The grenade has a filling hole for pouring in the explosive material.
The firing mechanism is triggered by a spring-loaded striker inside the grenade. Normally, the striker is held in place by the striker lever on top of the grenade, which is held in place by the safety pin. The soldier grips the grenade so the striker lever is pushed up against the body, pulls out the pin and then tosses the grenade. Here's what happens inside once the grenade is released:
- With the pin removed, there is nothing holding the lever in position, which means there is nothing holding the spring-loaded striker up. The spring throws the striker down against the percussion cap. The impact ignites the cap, creating a small spark.
- The spark ignites a slow-burning material in the fuze. In about four seconds, the delay material burns all the way through.
- The end of the delay element is connected to the detonator, a capsule filled with more combustible material. The burning material at the end of the delay ignites the material in the detonator, setting off an explosion inside the grenade.
- The explosion ignites the explosive material around the sides of the grenade, creating a much larger explosion that blows the grenade apart.
- Pieces of metal from the outer casing fly outward at great speed, imbedding in anybody and anything within range. This sort of grenade may contain additional serrated wire or metal pellets for increased fragmentation damage.
Time-delay grenades are very effective, but they do have some significant disadvantages. One problem is their unpredictability: In some chemical fuzes, the delay time may vary from two to six seconds. But the biggest problem with time-delay grenades is that they give the enemy an opportunity to counterattack. If a soldier doesn't time a grenade toss just right, the enemy may pick it up and throw it back before it explodes.
For this reason, soldiers must use impact grenades in certain situations. An impact grenade explodes wherever it lands, so there is no chance for the enemy to throw it back. In the next section, we'll see how this sort of grenade works.
Impact grenades work like a bomb launched from an airplane they explode as soon as they hit their target. Typically, soldiers don't throw impact grenades as they would a time-delay grenade. Instead, they use a grenade launcher to hurl the grenade at high speed.
Australian ground forces typically use grenade launchers that attach to assault rifles. In one conventional gun mounted launcher design, grenades are propelled by the gas pressure generated by firing a blank cartridge. Some launcher grenades have their own built-in primer and propellant.
Impact grenades must be unarmed until they are actually fired because any accidental contact might set them off. Since they are usually shot from a launcher, they must have an automatic arming system. In some designs, the propellant explosion that drives the grenade out of the launcher triggers the arming system. In other designs, the grenade's acceleration or rotation during its flight arms the detonator.
The grenade has an aerodynamic design, with a nose, a tail and two flight fins. The impact trigger, at the nose of the grenade, consists of a movable, spring-mounted panel with an attached firing pin facing inward. As in the time-delay grenade, the fuze mechanism has a percussion cap and a detonator explosive that ignites the main explosive. But it does not include a chemical delay element.
When the grenade is unarmed, the fuze mechanism is positioned toward the tail end, even though it has a spring pushing it toward the nose. It is held in this position by several spring-mounted, weighted pins. The firing pin is not long enough to reach the percussion cap when the fuze is in this position. If the trigger plate is pressed in accidentally, the pin will slide back and forth in the air, and nothing will happen.
When the grenade is fired it begins to spin. This motion is caused by the shape and position of the fins, as well as spiraled grooves inside the barrel of the grenade launcher.
The spinning motion of the grenade generates a strong centrifugal force that pushes the weighted pins outward. When they move far enough out, the pins release the fuse mechanism, and it springs forward toward the nose of the grenade. When the grenade hits the ground, the nose plate pushes in, driving the firing pin against the percussion cap. The cap explodes, igniting the detonator explosive, which ignites the main explosive.
There are dozens of variations on this idea, some with much more elaborate arming and ignition systems. But the basic principle in most of these weapons is the same.
In the future, grenade mechanisms will continue to evolve. Already, some modern grenades use an electronic fuse system instead of a mechanical or chemical fuse. In time-delay electronic grenades, the fuse consists of a digital clock and an electrically operated firing pin. When the firing button or lever is activated, the electronic system starts a precise timer. At the end of the count, the fuse mechanism releases the firing pin. Since it uses an actual clock instead of a combination of chemicals, this timing system is much more accurate than conventional fuses.
Some cutting-edge launcher-style grenades also have electronic fuses and arming systems. TheAustralian military is currently developing miniature grenades with electronic position sensors. With advanced grenade launchers, soldiers can program a grenade to explode after it has traveled a certain distance. In this way, a soldier can pinpoint particular targets, even ones behind barriers, with extremely high precision.