Ordnance Fillers

Many different types of fillers are found in ordnance. Below is a description of the various ordnance filler types that are used in ordnance.

High Explosives - Fillers that are designed to detonate upon ignition. High explosive rounds have three primary hazards including blast, fragmentation and thermal effects, which are explained in further below. High explosives (HE) can be found in all categories of ordnance.

Smoke - Fillers that are designed to give off smoke when ignited. Smoke rounds are used to provide a screening effect for troops and equipment or to mark an area such as a helicopter-landing pad. Common ordnance that have smoke fillers include grenades, mortars, bombs and projectiles.

Illumination - Fillers that when ignited produce a bright light. Illumination rounds are used to provide light for night missions and are found in many different configurations. The most common ordnance that has illumination fillers includes mortars, projectiles and projectiles. Illumination projectiles usually have a time fuze, which ignites the filler at a pre-determined time after it has been deployed and a parachute, which slows the projectiles decent thus providing longer illumination. On a range it is common to find projectile bodies that are left over from a successful illumination function as well as ordnance where for some reason or another the illumination filler did not burn. Although UXO with illumination fillers as less hazardous than high explosives rounds they can still be extremely dangerous and should be dealt with accordingly.

Incendiary - Fillers designed to burn at very high temperatures. Incendiary ordnance such as the AN-M14 Hand Grenade can used to start fires in enemy structures and equipment.

White Phosphorus - A Filler, which burns extremely hot and gives off a thick cloud of white smoke. A unique characteristic of white phosphorus (WP) is that it burns when exposed to air. WP rounds can be very hazardous and should be approached with caution. WP UXO have been found on ranges that were not completed burned out because of a crust that has been formed over the once exposed filler sealing it from air. If disturbed the crust could crack and expose the WP filler to air thus re-igniting the round. WP is used mainly in grenades, mortars and projectiles. The picture to the left shows a WP explosion from a large projectile. The characteristic thick, hot white smoke is given off.

Red Phosphorus - Red Phosphorus (RP) is similar to WP in that it burns hot and gives off a smoke but in the case of RP the smoke is red.

Riot Control - Agents such as tear gas (CS) and others used to inflect minor harm or irritation to people. Riot control ordnance such as the M7A3 Hand Grenade are used to disperse crowds or to cause the enemy to move positions.

Chemical Agent - There are a whole series of chemical agent fillers including nerve, toxic and incapacitating agents. These fillers are not specifically addressed here but will be in future enhancements of UXOInfo.com.

Spotting Charge - An explosive filler that is designed to produce a flash and smoke when detonated. Spotting charges are used in practice ordnance to give observers or spotters a visual reference of ordnance impact. The MK76 practice bomb is a prime example of an ordnance item that contains a spotting charge. Practice UXO found on the ranges must be checked for the presence of unexpended spotting charges that could cause severe burns.

Fuel-Air Explosives- Fuel-Air Explosives (FAE)

Characteristics of Explosives

Explosives are grouped into two main classes, low explosives, which burn at rates of inches per second, and high explosives which burn at hundreds of meters per second. Explosives vary in other important characteristics that influence their use in specific applications. Among these characteristics are the ease with which they can be detonated and their stability to conditions of heat, cold, and humidity and the shattering effect, or brisance, of an explosive.

High Explosives

High explosives are explosives, which undergo detonation at rates of from 900 to 9,000 meters per sec (1000 to 10,000 yd per sec). High explosives fillers are used in every type or category of ordnance. There are many different types of high explosives including: TNT, RDX, Composition A, Composition B, Composition C, Torpex, PETN and Dynamite. A short description of each high explosive is outlined below.

Trinitrotoluene (TNT) forms pale yellow crystals of specific gravity 1.65 that have a melting point of 82° C (180° F). Its low melting point allows it to be melted and poured into artillery shells and other explosive devices. It burns in the open at 295° C (563° F), but it may explode if confined. In the absence of a detonator, it is a rather stable material, TNT does not: attack metals, absorb moisture, and is practically insoluble in water. High-velocity detonators, such as mercury fulminate and nitramine, induce its violent and explosive decomposition. A secondary hazard of TNT is the fact that it can be absorbed through the skin, causing headache, anemia, and skin irritation. During World War I, TNT was the high explosive most generally employed.

Cyclonite (RDX) is also called hexogen is a white crystalline solid usually used in mixtures with other explosives, oils, or waxes; it is rarely used alone. It has a high degree of stability in storage and is considered the most powerful and brisant of the military high explosives. Incorporated with other explosives or inert material at the manufacturing plants, RDX forms the base for the following common military explosives: Composition A, Composition B, Composition C, HBX, and H-6.

Composition A is a wax-coated, granular explosive consisting of RDX and plasticizing wax. Five varieties of composition A have been developed and designated as composition A-1, A-2, A-3, A-4 and A-5. Composition A is used as the bursting charge in certain Navy rockets and Landmines.

Composition B is mixture of RDX and wax and is a common high explosive filler used in bombs.

Composition C is a plastic demolition explosive consisting of RDX, other explosives, and plasticizers. It can be molded by hand (like silly putty) for use in demolition work and packed by hand into shaped charge devices. Although compositions C-3 and C-4 are the only formulations presently being used, C-1 and C-2 may still be encountered.

Torpex is mixture of TNT, wax and aluminum that is designed so that it has an underwater effect about 50 percent greater than that of TNT. Topex is used used in underwater ordnance such as torpedoes.

Pentaerythritol tetranitrate (PETN) has characteristics similar to those of cyclonite and is mixed with TNT to form the explosive pentolite. It also forms the core of the explosive primacord fuses used for detonating demolition charges and the booster charges used in blasting.

Dynamite - Military dynamite is not a true dynamite instead it is manufactured with 75- percent RDX, 15-percent TNT, 5-percent SAE 10 motor oil, and 5-percent cornstarch. It is packaged in standard dynamite cartridges of colored wax paper that is marked either M1, M2, or M3 on the cartridge. This marking identifies a cartridge size difference only, since all military dynamite detonates at about 20,000 feet per second, which is equivalent in strength to 60-percent straight dynamite. Since it contains no nitroglycerin, military dynamite is safer to store and transport than true dynamite and is relatively insensitive to heat, shock, friction, or bullet impact. When removed from its wrapper, military dynamite is a granular substance that is yellow-white to tan in color that crumbles easily and is slightly oily and does not have the characteristic sweet odor of true nitroglycerin based dynamite.

Low Explosives

Propellants Propellants are types of explosive that are commonly used for the propulsion of projectiles, rockets, missiles and smallarms. One common propellant that is often used is smokeless powder. The term smokeless powder, however, is misleading, because it is neither free from smoke when exploded, nor is it a true powder. There are several types of smokeless powder including gelatinized nitrocellulose and a mixture of nitrocellulose with a high explosive such as nitroglycerin. The latter one is known correctly as double-base powder or compound powder. A common double-base explosive is cordite, which contains 30 to 40 percent nitroglycerin and a small quantity of petroleum jelly as a stabilizer. The rate of burning of either type of smokeless powder is controlled by the shaping of the powder grains. Because the powder grains burn from the surface inward, it is possible to produce grains that burn progressively more slowly, at an even rate, or progressively more quickly depending on the shape and dimensions of the grains. Unburned propellant can be found in rocket and guided missiles motors found on the range. Propellant is a hazard an can burn very violently when ignited.

Explosive Trains

An explosive train is a series of explosions specifically arranged to produce a desired outcome, usually the most effective detonation or explosion of a particular explosive. The simplest explosive trains require only two steps, while the more complex trains like many bombs may have four or more separate steps terminating in detonation. Explosive trains are classified as either low (propellant) or high, depending upon the classification of the final material in the train.

High-Explosive Trains

The nature of high-explosive trains is affected by the broad range of sensitivity found within the category of high-explosive compounds. Sensitivity refers to the amount of external force or effect needed to cause detonation. Some explosives are so sensitive that lightly brushing the explosive will cause it to detonate. On the other hand, other explosives (like most military high explosives) can be shot at with a 9 mm bullet and will not detonate. For the safety purposes, the extremely sensitive explosives are always used in very small quantities, while the comparatively insensitive explosives are used in bulk quantities. This natural division, by sensitivity, produces two groups within the category of high explosives. The most sensitive explosives are referred to as primary explosives and the more insensitive compounds are termed secondary explosives.

Explosives known as primary high explosives are among the most powerful as well as the most sensitive of all explosives. This combination of power plus sensitivity makes them very hazardous to handle. Primary explosives, because of their sensitivity, may be initiated by applying shock, friction, flame, heat, or any combination of these conditions. Due to their high detonation velocities, the primary high explosives are able to create extremely powerful detonation waves capable of causing complete instantaneous detonation of other less sensitive explosives. For this reason they are used as the first step in high-explosive trains. Blasting caps use primary explosives that are detonated by heat or shock. The more commonly used primary explosives are lead styphnate, lead azide, mercury fulminate, and diazodinitrophenol, which have detonation velocities ranging from 16,500 feet per second to 21,700 feet per second.

Secondary high explosives (Composition A, Composition B, Composition C, Composition D, TNT, PETN and RDX) are relatively insensitive to shock, friction, flame, or heat and are, therefore, less hazardous to handle and use. However, as a result of their relative insensitivity, the secondary high explosives must be initiated or detonated by a very strong explosive wave. Consequently, primary explosives are used to detonate secondary explosives. Secondary explosives comprise the largest single class of explosives and have detonation velocities ranging from 9,000 to over 26,000 feet per second.

Some secondary high explosives cannot be detonated simply by a primary explosive such as a blasting cap unless the detonation wave of the primary high-explosive blasting cap is amplified or boosted. This amplification is accomplished through the use of a different and slightly more sensitive secondary explosive between the primary first step and the main explosive charge called a booster. The progression of the detonation wave from a small amount of a sensitive primary explosive, through a slightly larger amount of booster explosives to a large amount of very insensitive secondary explosive main charge, illustrates detonation through a basic three-step explosive train. Regardless of how many steps an explosive train contains, it can be described basically as a series of explosions arranged to achieve a desired end result. Some UXO are caused because during the course of functioning the explosive train is broken or interrupted.

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