Science Fair Project Encyclopedia
A hand grenade is a hand-held bomb, made to be thrown by a soldier. The word "grenade" has a Spanish origin in the word granada ("pomegranate"), in reference to the general size of early grenades, and because its content of shrapnel pellets reminded them of the seeds in a pomegranate. Grenadiers were originally a class of soldier specialized in throwing grenades. Some grenades are designed to be fired by a grenade launcher.
Some grenades are cylindrical and are designed to be fired from riot guns designed for the purpose.
4.1 Fragmentation grenades - designed to inflict casualties
The first use of the word grenade in the English language seems to be during the English Civil War (Mid 17th Century). These were pottery vessels, by the early 18th century iron based grenades were used against the Jacobite forces. Grenades were also made from glass but if the tempering was wrong the glass disintegrated into powder rather than shards. In the modern age, high explosives, metal, plastic and careful design are the components of grenades.
Design and usage
Grenades come in different sizes and shapes, for different purposes, but all have two things in common. First, they are hollow so they can be filled with the explosive or chemical filler. Second, they contain a threaded hole into which a fuse can be screwed or inserted.
A grenade is essentially a small bomb, and works very much like a simple firecracker. A firecracker is made up of a paper body filled with gunpowder and has a small fuse. Once lit, the fuse burns down to the powder and blows the paper body apart.
In modern hand grenades, the fuse is lit by an internal mechanical, electronic, and/or pyrotechnic device rather than an external flame. Most are designed to project shrapnel i.e. sharp pieces of the casing or serrated wire or an incendiary material.
Hand grenades share the following three common characteristics:
- Their employment range is short.
- Their effective casualty radius is small.
- Their delay element permits safe throwing.
Hand grenades have the following main parts:
- Body -- contains filler and, in most grenades, also provides fragmentation.
- Filler -- chemical or explosive substance in the grenade, which determines grenade use and characteristics.
- Fuse assembly -- causes the grenade to function by igniting or detonating the filler.
A classic hand grenade has a handle and a removable safety pin that prevents the handle from coming off. After the pin is removed and the handle subsequently released, the grenade will detonate in approximately three to five seconds, depending on grenade type.
When using a grenade, the objective is to have the grenade land with too little time for the enemy to throw it back.
One grasps the grenade, including the handle, in the strong hand. Next one estimates the time of flight to the enemy and subtracts it from four. Then one pulls the pin out of the grenade, releases the handle, waits the time not needed for flight and throws the grenade at the intended target.
Note: Modern USA and other NATO country soldiers (with the exception of the US Marines) are trained not to "burn off" (also called "cook off") grenades in this way, due to the danger of it exploding in hand if the soldier is distracted or shot, and for reasons of unreliability.
One of the classic mistakes is to grasp the grenade in the weak hand, pull the pin, and then throw the pin. (This mistake is a staple of humorous cartoons involving war.)
Another classic mistake is to fail to grasp the handle, and then pull the pin. In this case, the grenade might explode while one is calculating times.
A basic safety precaution is to always throw a grenade from cover. Therefore, if anything goes wrong, it can be thrown quickly out of the cover.
When a grenade is out of control, yell "grenade." When a grenade is dropped into a enclosed space like a tunnel, the dropper should yell "Fire in the hole!" to alert his comrades that an explosive is about to detonate. Common U.S. military procedure for the fragmentation grenade, unless stealth is of the essence, is to yell "Frag out!" to indicate to allies that a frag grenade has been dispatched.
Grenades are often used in the field to construct booby-traps. The basic concept is to use some action of the intended target (such as opening a door, or starting an auto) to trigger the grenade. These grenade-based booby-traps are simple to construct in the field using readily available material. However, they contribute to the problem of unexploded ordnance.
Design and operation
The sketch to the right shows a cross-section of the grenade and fuse parts for a fragmentation grenade. The basic action is as follows:
- Holding the grenade in the throwing hand, thumb over the safety lever, pull the safety pin (pull force of 10–35 pounds or 45–155 newtons).
- When the grenade is thrown (safety lever released), a spring throws off the safety lever and rotates the striker into the primer.
- The primer contains material like the head of a match. When struck by the striker, it ignites and sets fire to the fuse, or powder train. The fuse burns at a controlled rate, providing a time delay (usually 4–5 seconds). When the flame of the fuse reaches the detonator or igniter , it causes action on the filler.
- A detonator is similar to a small blasting cap. Very sensitive to heat, when the fuse burns into it, it causes the grenade to explode.
- An igniter is a cap that burns rapidly. It basically sets fire to the filler causing a rapidly expanding gas which bursts the container.
- The fragmentation grenade shown uses a detonator.
Hand grenades are usually designed to make them easy to throw. For example they weigh around 500 g (1 lb) and have a diameter of 100 mm. The average grenade can be thrown about 25 to 35 meters by the average soldier. They use a compound of RDX, composition B or TNT as their explosive.
Grenades have also been made to release smoke, tear gas ("CS"), and illumination. Special forces use "flash-bang" grenades to disorient people during an entry into a room, without the intent of causing lasting injury.
Some grenade designs were made to be thrown longer distances. The German "potato-masher" grenade had a long wooden handle that extended range by fifty percent. It was detonated by a friction igniter in the head, which was activated by a pull string threaded through the hollow stick, by pulling a little plastic ring attached to a string attached to a friction igniter, time fuse, and detonator designed to explode after delay. It is often incorrectly thought to have an impact fuse, though this was the case with an early (1908) British stick grenade design.
Different types of hand grenades
Fragmentation grenades - designed to inflict casualties
The fragmentation grenade is an antipersonnel device that is designed to spew shrapnel in all directions. The body is made of hard plastic or steel, and flechettes or nicked wire provide the antipersonnel shrapnel fragments. Also the filler can consist of small metal balls to penetrate the target(s). (When the word "grenade" is used without qualification, and context does not suggest otherwise, this is the kind of grenade usually meant.) More info about the "frag" grenade above.
These grenades can be classed as:
- Offensive - the grenade can be thrown further than is effective blast radius
- Defensive - the blast radius is greater than the distance it can be thrown.
In the latter, it is assumed the thrower can operate from cover.
The hand sized Mills bomb with a cast iron casing is an example of a defensive grenade, the Steilhandgrenate with a tinplate cannister around the explosive and a handle is a classic example of the latter.
All grenades for use against personnel based around a simple explosive device, whether the action is enhanced deliberately with a metal casing or not, can be considered part and parcel with the fragmentation grenade.
These are canister type grenades used as a ground-to-ground or ground-to-air signaling device, a target or landing zone marking device, or a screening device for unit movements. The body consists of a sheet steel cylinder with a few emission holes on top and at the bottom to allow smoke release when the grenade is ignited. The filler consists of 250 to 350 grams of colored (red, green, yellow or violet) smoke mixture (mostly potassium chlorate, lactose and a dye). Another type of smoke grenades, are the bursting kind. These are filled with white phosphorus (WP), which are spread by explosive action. The phosphorus catches fire in the presence of air, and burns with a brilliant yellow flame, while producing copious amounts of white smoke (phosphorus pentoxide). These double as incendiary grenades (q.v.).
Gas grenades to disperse large groups of people. Best known is the common teargas grenade (CS gas grenade). This grenade is in terms of shape and use similar to smoke grenades. Although, with teargas grenades, the filler consists of 80 to 120 grams of CS (chlorobenzylidene malonitrile). This is a toxic chemical which (when it comes in contact with the face) causes an extreme burning sensation of the eyes and—when inhaled—throat. When the gas stays in the contact with someone for a long period of time (more than 10 minutes) it can cause burning blisters on the skin and irreversible damage to the lungs (for example lung cancer). For weak and older people CS-gas can even be fatal. Also, if CS gas is exposed to high temperatures (such as a house fire) it will release cyanide. See the Branch Davidian siege.
Riot control agents
Incendiary grenades - used to destroy by heat
These kind of grenades produce extreme heat by means of a chemical reaction. The body is practically the same as smoke and gas grenades. The filler consists mostly of 600 to 800 grams thermate (TH3), which is an improved version of thermite, the incendiary agent used in hand grenades during World War II. A portion of the thermate mixture is converted to molten iron, which burns at 2200 degrees Celsius (4000 degrees Fahrenheit). It will fuse together the metallic parts of any object that it contacts. The thermate filler of the AN-M14 grenade burns for 40 seconds and can burn through a 1/2-inch (13 mm) homogeneous steel plate. There is no need for an external source of oxygen and will burn under water. White phosphorus (see Smoke grenade) also has a very good incendiary effect; burning at a temperature of 2800 °C (5000 °F).
Thermate and phosphorus burns are the worst and most agonizing burns because thermate and phosphorus burn at such a high speed and temperature that one particle of those chemicals burns through almost everything (skin, nerves, muscles and even bones), even in places where there is none or little oxygen. In addition, white phosphorus is very poisonous. A dose of 50-100 milligrams would be lethal for the average sized person.
A common use of these devices is to destroy equipment to prevent its use by the enemy. A themite grenade could make even large guns unusable by destroying the breech or barrel, and in the US Army, thermite grenades are issued to artillery units for this purpose.
Concussion grenades, also known as stun grenades or flashbangs, were originally designed for the British Special Air Service. Concussion grenades are used to concuss, confuse, disorient, or momentarily distract a potential threat for up to five to six seconds. A "flashbang" can seriously degrade the combat effectiveness of affected personnel for up to a minute. The best known is the XM84 Stun Grenade, commonly known as the "Flashbang", so called because it produces a blinding (1 million Candela) flash and deafening (170-180 decibel) blast. This grenade can be used to incapacitate people but without serious permanent injury.
Upon detonation, the fuse/grenade body assembly remains intact and produces no fragmentation. The body is a steel hexagonal tube with holes along the sides which allow a blast of light and sound to be emitted. The filler consists of about 4.5 grams of a pyrotechnic metal-oxidant mix of magnesium & ammonium perchlorate.
Anti tank grenades - used against armour
These grenades invariably use the shaped charge principle to produce an armour penetrating effect. This means that the grenade has to hit the vehicle at an exact right angle for the effect to work properly. The British put the first version into the field with the rifle fired M68 AT during the Second World War, but the Germans deployed a thrown design that used powerful magnets to get the warhead into the right presentation.
Stylized pictures of grenades used as ornament
Stylized pictures of early grenades, with a flame coming out, are used as ornaments on military uniforms, particularly in France (esp. French Gendarmerie) and Italy (Carabinieri). The British Grenadier Guards took their name and cap badge of a burning grenade from repelling an attack of French Grenadiers at Waterloo.
- The grenade is also a charge in heraldry.
- Grenade is also the name of a commune in the Haute-Garonne département, in France.
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