How Explosives work-Chapter-3 Landmines

How Explosives work-

Chapter-3

Landmines

By:- Anindo Chatterjee

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Contents:

1.  Introduction

2.  Landmine Basics

3.  Anti-personnel mines

4.  M-14 and m-16

5.  Anti-tank mines

6.  Locating mines

7.  Mine clearing machines

Introduction

 This PMA-2 landmine was found hidden under snow and foliage in Rajlovac, Bosnia.

Photo courtesy U.S. Department of Defense

­One of the most deadly legacies of the 20th century is the use of landmines in warfare. Anti-personnel landmines continue to have tragic, unintended consequences years after a battle and even the entire war has ended. As time passes, the location of landmines is often forgotten, even by those who planted them. These mines continue to be functional for many decades, causing further damage, injury and death.
Landmines are basically explosive devices that are designed to blow when triggered by pressure or a tripwire. These devices are typically found on or just below the surface of the ground. The purpose of mines when used by armed forces is to disable any person or vehicle that comes into contact with it by an explosion or fragments released at high speeds.
Currently, there are more than 100 million landmines located in 70 countries around the world, according to OneWorld International. Since 1975, landmines have killed or maimed more than 1 million people, which has led to a worldwide effort to ban further landmine use and clear away existing landmines. In this article, we will look at the different types of landmines, their basic operation and the techniques used to clear minefields.
Landmine basics

Landmines create the dotted lines through this desert scene.

Photo courtesy United Nations

­Landmines are easy to make, cheap and effective weapons that can be deployed easily over large areas to prevent enemy movements. Mines are typically placed in the ground by hand, but there are also mechanical minelayers that can plow the earth and drop and bury mines at specific intervals.
­Mines are often laid in groups, called minefields, and are designed to prevent the enemy fro­m passing through a certain area, or sometimes to force an enemy through a particular area. An army also will use landmines to slow an enemy until reinforcements can arrive. While more than 350 var­ieties of mines exist, they can be broken into two categories:

1. Anti-personnel (AP) mines
2. Anti-tank (AT) mines

The basic function of both of these types of landmines is the same, but there are a couple of key differences between them. Anti-tank mines are typically larger and contain several times more explosive material than anti-personnel mines. There is enough explosive in an anti-tank mine to destroy a tank or truck, as well as kill people in or around the vehicle. Additionally, more pressure is usually required for an anti-tank mine to detonate. Most of these mines are found on roads, bridges and large clearances where tanks may travel.
In the next two sections, you will get a closer look at a few landmines and the parts that make them work.

Landmine Terms

• Belleville spring - A piece of curved steel shaped like a doughnut, used to cushion heavy loads
• Black powder - A gunpowder used as an explosive, typically made of potassium nitrate or sodium nitrate, charcoal and sulfur
• Delay element - A chemical compound that burns for a set time before igniting a fuse or explosive
• Detonator - A small amount of explosive used to ignite larger amounts of explosive
• Firing pin - The metal pin that is forced down into the detonator when the mine is activated
• Fuse - A combustible material used to ignite an explosive charge
• Igniter - A metal rod (in bounding mines) that protrudes from the ground, triggering the mine when it's stepped on; also called the striker
• Magnetic mine - A mine equipped with magnets, triggered by large metal objects entering its immediate area
• Main charge - The large of amount of explosive in the mine that causes it to explode
• Percussion cap - A chemical compound detonated by striking or applying pressure to it
• Pressure plate - The metal disc on top of the mine that depresses and triggers the mine when stepped on
• Projectiles - Metal balls or glass fragments placed in the mine to cause greater injuries to victims (The mine's metal casing can also become projectiles after the mine explodes.)
• Propelling charge - A small amount of explosive placed at the bottom of a bounding mine to propel it into the air
Safety pin/clip - A pin placed in the mine to prevent it from being activated while not in use

Anti-personnel mines

Close-up of a bounding anti-personnel mine exposed by the shifting sands of an unspecified desert

Photo courtesy United Nations

Anti-personnel landmines are designed specifically to reroute or push back foot soldiers from a given geographic area. These mines can kill or disable their victims, and are activated by pressure, tripwire or remote detonation. There are also smart mines, which automatically deactivate themselves after a certain amount of time. These are the most common types of mines currently used by the U.S. military.

Anti-personnel mines fit into three basic categories:

1. Blast - The most common type of mine, blast mines are buried no deeper than a few centimeters and are generally triggered by someone stepping on the pressure plate, applying about 11 to 35.3 pounds (5 to 16 kilograms) of pressure. These mines are designed to destroy an object in close proximity, such as a person's foot or leg. A blast mine is designed to break the targeted object into fragments, which can cause secondary damage, such as infection and amputation.
2. Bounding - Usually buried with only a small part of the igniter. When activated, the igniter sets off a propelling charge, lifting the mine about a meter into the air. The mine then ignites a main charge, causing injury to a person's head and chest. protruding from the ground, these mines are pressure or tripwire activated. You may also hear this type of mine referred to as a "Bouncing Betty."
3. Fragmentation - These mines release fragments in all directions, or can be arranged to send fragments in one direction (directional fragmentation mines). These mines can cause injury up to 200 meters away and kill at closer distances. The fragments used in the mines are either metal or glass. Fragmentation mines can be bounding or ground-based.

There are several-hundred different kinds of anti-personnel mines in use by many countries. For the purposes of this article, we have chosen two landmines developed by the United States military that demonstrate the varying characteristics of landmines. The first landmine, the M14, is a pressure-operated blast mine. We also examine the M16 bounding/fragmentation landmine.

The M-14 and M-16

Source: U.S. Department of Defense

M14 Blast Mine

The M14 is a small, cylindrical, plastic-bodied blast mine. It is just 1.57 inches (40 mm) tall and 2.2 inches (56 mm) in diameter. It was originally developed and used by the United States in the 1950s, but it has been used and copied by many nations around the world. This particular anti-personnel mine contains only a small amount of explosive, about 31 grams of Tetryl. It is designed to cause damage to people and objects in close proximity to it.

The M14 is initially equipped with a U-shaped safety clip, which is fitted around the pressure plate. In order to activate the M14, the safety clip is removed and the pressure plate is rotated from its safety position to its armed position. The letters A (armed) and S (safety) are embossed on the pressure plate. Soldiers simply align an arrow with the A to arm the mine.

Once it is armed, any pressure of at least 19.8 pounds (9 kg) can cause the mine to detonate. When the proper amount of pressure is applied it pushes down on the Belleville spring underneath the pressure plate. This spring pushes the firing pin down on to the detonator, which ignites the main charge of Tetryl explosive.

M16 Bounding/Fragmentation Mine

Bounding mines fire up out of the ground and then explode. The M16 is made of three main parts: a mine fuse, a propelling charge to lift the mine and a projectile contained in a cast-iron housing. It is 7.83 inches (199 mm) tall and 5.24 inches (133 mm) in diameter. The M16 mine contains about 1.15 pounds (521 grams) of trinitrotoluene (TNT) explosive.

Source: U.S. Department of Defense

The fuse extends through the center of the mine to the bottom, where the propelling charge is located. To arm the mine, a safety pin is removed from the striker on top of the fuse. There are three prongs located on top of the fuse, connected to a spring-loaded wedge. The fuse encloses a percussion cap, a delay element and a black-powder charge.

The M16 can be detonated in two ways: by applying pressure or by pulling the spring-loaded release pin. Either method causes the pin to pull out of the fuse, releasing the striker and igniting the percussion cap. The percussion cap fires a delay element in the fuse, which fires a detonator after a short delay. The detonator ignites the black powder in the fuse, firing the propelling charge in the bottom of the mine. The mine flies upward to about 1.2 meters; the main charge then detonates and releases a shower of metal fragments.

Anti-Tank mines

 A close-up look at an M15 anti-tank mine

Photo courtesy U.S. Department of Defense

When it comes to developing new military weaponry, countries try to keep up with the developments of other countries. The development of tanks during World War I led to anti-tank mines, and anti-personnel mines were developed to prevent enemy armies from moving anti-tank mines.

Anti-tank mines are very similar to their anti-personnel cousins, but are much larger. These mines are pressure activated, but are typically designed so that the footstep of a person won't detonate them. Most anti-tank mines require an applied pressure of 348.33 pounds (158 kg) to 745.16 pounds (338 kg) in order to detonate. Most tanks and other military vehicles apply that kind of pressure. Let's take a closer look at one of these anti-tank mines.

M15 Pressure-operated Blast Mine

All anti-tank mines are blast mines, because the goal of the anti-tank mine is to destroy the tank's tracks and as much of its body as possible. There's no need for a bounding or fragmentation anti-tank mine. The M15 is a circular, steel anti-tank mine that contains a main charge of TNT. It has a diameter of 13.27 inches (337 mm) and a height of 4.92 inches (125 mm). The main component of the M15 is the 22.82 pounds (10.35 kg) of Composition B explosive. Composition B is a mix of TNT and cyclotrimethylene trinitramine (RDX).

Source: U.S. Department of Defense

The M15 is armed by rotating the arming switch so that it is set atop the head of the fuse. The cylindrical fuse is made of iron and is attached to the pressure plate by a copper cover. As a tank rolls over the mine, it pushes down on the pressure plate. Underneath the pressure plate is a Belleville spring with a firing pin affixed to its underside. The firing pin is driven down into the detonator, which detonates and fires the M120 booster charge beneath the fuse, which then sets off the main charge.

Locating Mines

A de-mining team in Lipovac, Croatia, locates an undestroyed mine.

Photo courtesy United Nations/J. Isaac

Landmines can remain active more than 50 years after they are planted in the ground. For this reason, there is a growing worldwide effort to rid the world of landmines. To do this, we must first locate the millions of landmines that are still buried in dozens of countries around the world. Finding these landmines is extremely difficult, as most minefields are unmarked. And those that are marked can take years to de-mine.

Landmine detection is a slow, methodical process due to the danger involved in locating landmines. While location technology is improving, the following conventional techniques are still relied on heavily:

• Probing the ground - For many years, the most sophisticated technology used for locating landmines was probing the ground with a stick or bayonet. Soldiers are trained to poke the ground lightly with a bayonet, knowing that just one mistake may cost them their lives.
• Trained dogs - Dogs can be trained to sniff out vapors coming from the explosive ingredients inside the landmine.
• Metal detectors - Metal detectors are limited in their ability to find mines, because many mines are made of plastic with only a tiny bit of metal.

Scientists at Ohio State University are developing a new ground-penetrating radar (GPR) device that may be more effective in locating and disarming landmines. This new device would be helpful in locating mines that have little or no metal content. All landmines, including plastic ones, are filled with explosive agents that have electrical properties that make them detectable to the right technology, such as GPR.

A GPR device focuses radar energy just below the ground and just a few feet in front of the user, according to researchers. The device ignores signals that bounce back from the surface and uses specially designed software to make buried objects shine brighter in the radar image. The GPR has been successful in detecting two common landmine casings filled with a waxy substance that is similar to TNT.

Once a landmine is detected, the GPR device shoots two chemical agents into the ground to deactivate it. One agent solidifies the triggering mechanism along with surrounding soil, allowing soldiers to cross the ground. The second chemical agent then solidifies the mine and soil permanently. The mine can then be shoveled out and destroyed.

Mine Clearing machines

A remotely controlled Panther armored mine-clearing vehicle leads a column of armored vehicles down a road near McGovern Base, in Bosnia-Herzegovina on May 16, 1996.

Photo courtesy U.S. Department of Defense

When there is not a lot of time for an army to clear a minefield, it will often employ the use of certain machines to roll through and clear a safe path. Military forces employ several kinds of mine-clearing machines to clear out or detonate mines. Some machines are specifically designed for the task of mine clearance, while tanks can also be fitted with certain mine-clearing devices.

There are several types of mine-clearing machines. New machines are remote controlled, which minimizes the risk to personnel. Mine-clearing machines use one of three techniques, including flailing chains to beat the ground, rollers to roll over and detonate mines, and rakes or blades to plow through the minefields, pushing the mines to the side. Let's look at a few of these machines:

• Tanks - Tanks, like the U.S. Army M-1A1 Abrams main battle tank, are often equipped with a mine plow designed to push mines out of the tank's path. The plow consists of several blades that extract the mines, a moldboard to push the mines to the side and a leveling skid to control the depth of the blade. Click here to see an M-1A1 Abrams tank equipped with a mine-clearing plow.
• Panther - The Panther is a 60-ton remote-controlled vehicle that is based on a modified M-60 tank hull. Using a joy stick, an operator navigates the Panther through a minefield. The vehicle, as you can see in the picture above, uses metal rollers to set off blast or magnetic mines.
• Aardvark - The Aardvark Mk III vehicle is designed with a flail mechanism that beats chains against the ground in a rotating motion to detonate and destroy mines. This machine is often used in humanitarian de-mining operations, according to the Norwegian Peoples Aid.
• Berm Processing Assembly - As a plowing machine rolls through a minefield, it leaves large mounds of soil that contain landmines. The Berm Processing Assembly gets its name from the word berm, which means a mound of earth. The machine scoops up dirt, shakes out mines from the dirt and leaves the mines exposed on the ground for de-mining units to safely destroy them. Click here to see an image of the Berm Processing Assembly.

New mines are laid at a rate 25 times faster than they are being cleared. New technologies will make it easier to find and locate mines, but can't prevent their placement. As long as nations continue to use landmines, these devices will be a danger for civilians as well as soldiers.

*Landmines by the Numbers*

Source: OneWorld International, International Campaign to Ban Landmines

• 33 billion - Cost in U.S. dollars to remove every mine in the world, if no others are planted
• 250 million - Stockpiled landmines worldwide
• 110 million - Landmines in the ground worldwide
• 2.5 million - New landmines laid each year
• 1 million - People killed or maimed by anti-personnel mines since 1975
• 100,000 - Americans killed or injured by landmines in the 1900s
• 26,000 - People killed or maimed annually by landmines
• 1,000 - Cost in U.S. dollars to remove one landmine
• 350 - Minimum number of different types of landmines
• 70 - Number of people killed or injured daily by landmines
• 33 - Percent of U.S. casualties caused by landmines during the Vietnam War
3 - Cost in U.S. dollars of a cheap landmine

……………………………………..The End………………………………………………

…………………….How Explosives work-Landmines…………………………………

End Credits:

1. Howstuffworks.com.

2. Wikipedia.

3. Kevin Bonsor.

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How Explosives Work-Chapter-2 Grenades

How Explosives work-

Chapter-2

Grenades

By:- Anindo Chatterjee

Click To Download this Article in .docx format Below

Password: Geniusindeed

 

Download now

Contents:

1.  Introduction

2.  Grenade Basics

3.  Time-Delay Grenades

4.  Impact Grenades

5.  Links

Introduction

Grenade is a small hand explosive, capable of destroying its target on impact. Grenades have played a part in warfare for hundreds of years. They were originally developed around 1000 AD by the Chinese, just on­e application of their r­evolutionary gunpowder technology. Europeans came up with their own versions in the 15th and 16th centuries, with mixed results.
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.
­The weapon saw a resurgence in the 20th century with the development of new modes of combat. In the trench warfare of World War I, soldiers could use grenades to take out machine gunners without ever revealing themselves to the enemy. Thanks to mechanical ignition systems that made the weapons relatively practical and safe, grenades took their place as an indispensable element in modern warfare.

In this article, we'll look inside some typical grenades to find out what sets them off and see what happens when they explode. We'll also look at those invaluable elements that keep everything from exploding too early.

What's in a Name?

The term grenade comes from the French term for pomegranate. In the 16th century, French soldiers (as well as other European armies) used round, pomegranate-sized bombs containing large grains of gunpowder, which resembled a pomegranate's seeds. The French army established the Grenadiers, troops trained to lob these grenades toward the enemy line.
The name "grenade" was picked up again when the weapon was reintroduced in the early 20th century. Soldiers in World Wars I and II had several other names for the weapons, however, such as pineapples, in reference to their shape and bumpy shells.
Grenade Basics­
­Broadly speaking, 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. Some produce little more than a loud noise and a flash of light. Some release toxic gases.
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. As you might expect, the igniter in an impact grenade is activated by the force of the grenade landing on the ground. With a time-delay grenade, the thrower sets off a fuze, a mechanism that ignites the grenade after a certain amount of time has passed (generally a few seconds).
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 Grenades

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 in World War I, World War II, Vietnam and many other 20th century conflicts, are designed to be durable, easy to use and easy to manufacture. The conventional design uses a simple chemical delay mechanism. The diagram below shows a typical configuration of this system, dating back to the first World War.
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 proper way to throw a hand grenade: Depress the striker lever, pull the pin, hurl the grenade.

Photo courtesy Department of Defense

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

 

A soldier prepares to fire an M-203 grenade launcher mounted to an M-16 assault rifle. U.S. forces typically use rifle-attached grenade launchers like this one.

Photo courtesy U.S. Department of Defense

Impact Grenades

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.
U.S. 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.
Afghan fighters and many other forces around the world use rocket-propelled grenade launchers, once mass produced by the Soviet Union. Like missiles, these grenades have a built-in rocket propulsion system.
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 arming system is triggered by the propellant explosion that drives the grenade out of the launcher. In other designs, the grenade's acceleration or rotation during its flight arms the detonator.
The diagram below shows the elements in a simple impact grenade with a rotation arming mechanism.

And below is a flash of the Impact-Grenade:

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.

 




 

















A Kurdish refugee with a Soviet RPG-7 grenade launcher, a common weapon in smaller armies and resistance forces

Photo courtesy Department of Defense

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 (like a well-thrown football). This motion is caused by the shape and position of the fins, as well as spiraled grooves inside the barrel of the grenade laun

cher.
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 fuze 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 fuze system instead of a mechanical or chemical fuze. In time-delay electronic grenades, the fuze 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 fuze 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 fuzes.

This Mark 19 Mod 3 machine gun fires grenade rounds rather than ordinary bullets.

Photo courtesy U.S. Department of Defense

Some cutting-edge launcher-style grenades also have electronic fuzes and arming systems. The U.S. military is currently developing miniature grenades with electronic position sensors. With advanced grenade launchers, soldiers can program a grenade to explode after it has travelled a certain distance. In this way, a soldier can pinpoint particular targets, even ones behind barriers, with extremely high precision.
To learn more about grenades, including their role in military history, check out the links below:-

• Hand Grenade Information and History
• Grenade History

…………………………………………..The End………………………………………………
……………………………….How Explosives work-Grenades…………………………………

End Credits:
1.Howstuffworks.com
2.Wikipedia
3.Tom Harris
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