What type of explosive is widely used by the military

An ingenious solution is to have the KKV "bloom" just prior to impact, spreading its destruction over a wider area of the target. Like the SBI, its payload must meet stringent weight and cost requirements. Because mid-course is the longest flight phase, ERIS has the most time to accomplish its mission.

To accomplish this, HEDI uses a high-explosive fragmentation warhead detonated very close to the target, resulting in aerothermal structural kill. But high-current armature arcing, mechanical erosion of the bore, and near-melting point temperatures with rapid fire operations make employment of this launcher very doubt-ful in the near term.

Lasers kill by burning through the target's skin or impart-ing such a high impulse on the skin that it spalls, destroy-ing vital interior systems or resulting in aerothermal structural kill.

Neutral particle beams penetrate the skin ionizing as it transits. Inside the target, its damage is done by ionization of materials in its path.

Besides poss-ibly ionizing electronics resulting in a soft kill , the energy deposited in the high explosives surrounding the nuclear warheads may be sufficient to ignite them, giving a non-nuclear hard kill.

DEW programs have evolved in three areas: the space based chemical laser, the free electron laser, and neutral particle beam. A hydrogen-flouride HF chemical laser is designed to destroy targets in the boost and post-boost phases.

Although the technology for this system is mature begun in the '70's , the large number of space platforms and the limited fuel supply carried on each mitigate against its deployment unless transportation can be made less expensive. Several ground based stations would provide the lasers. The free electron laser is among the newest SDI technologies with inherent problems.

Besides the power inefficiency associated with all lasers, the laser's transmission through the atmosphere will present heretofore insoluble problems. Despite 50 years of accelerator experien-ce, present technology cannot meet the requirements for low mass, and continuous, high power levels. From this broad definition, explosions may be divided into three types: mechanical, chemical, and nuclear. Mechanical explosions, such as the disruption of a steam boiler, are of little con-cern in weapons applications and are not discussed here.

For our purposes, an explosion must be suitable for military use. In this context, chemical and nuclear explosions apply. An explosive may be defined as a material chemical or nuclear that can be initiated and undergo very rapid, self-propagating decomposition, resulting in: 1 the formation of more stable material; 2 the liberation of heat; 3 the development of a sudden pressure effect through the action of heat on produced or adjacent gases.

One of the basic properties by which a weapon's effectiveness is measured is the quantity of energy, and thus damage potential, it delivers to the target. Modern weapons use both kinetic and potential energy systems to achieve maximum lethality.

A typical modern projectile might have a mass of 25 kg and contain 20 kg of explosive in a 5 kg case. If the chemical explosive were detonated on impact, an additional 60 X joules of energy would be released, or 2. Many substances not ordinarily classed as explosives may do one, or even two, of these things. For example, a mixture of nitrogen and oxygen can be made to react with great rapidity and yield the gaseous product nitric oxide; yet the mixture is not an explosive since it does not evolve heat, but rather absorbs heat.

Gases may be evolved from substances in a variety of ways. When wood or coal is burned in the atmosphere, the carbon and hydrogen in the fuel combine with the oxygen in the atmosphere to form carbon dioxide and steam, together with flame and smoke. When the wood or coal is pulverized, so that the total surface in contact with the oxygen is in- creased, and burned in a furnace or forge where more air can be supplied, the burning can be made more rapid and the com-bustion more complete.

When the wood or coal is immersed in liquid oxygen or suspended in air in the form of dust, the burning takes place with explosive violence. In each case, the same action occurs: a burning combustible forms a gas. The generation of heat in large quantities accompanies every explosive chemical reaction. It is this rapid liberation of heat that causes the gaseous products of reaction to expand and generate high pressures.

This rapid generation of high pressures of the released gas constitutes the explosion. It should be noted that the liberation of heat with insuffic-ient rapidity will not cause an explosion.

For example, al-though a pound of coal yields five times as much heat as a pound of nitroglycerin, the coal cannot be used as an explo-sive because the rate at which it yields this heat is quite slow. Rapidity of reaction distinguishes the explosive reaction from an ordinary combustion reaction by the great speed with which it takes place.

Unless the reaction occurs rapidly, the thermally expanded gases will be dissipated in the med-ium, and there will be no explosion. Again, consider a wood or coal fire. As the fire burns, there is the evolution of heat and the formation of gases, but neither is liberated rapidly enough to cause an explosion.

A reaction must be capable of being initiated by the applic-ation of shock or heat to a small portion of the mass of the explosive material. A material in which the first three factors exist cannot be accepted as an explosive unless the reaction can be made to occur when desired.

Low explosives burn rapidly or deflagrate. High explosives ordinarily deton-ate. There is no sharp line of demarcation between low and high explosives. The chemical decomposition of an explosive may take years, days, hours, or a fraction of a second. The slower forms of decomposition take place in storage and are of interest only from a stability standpoint.

Of more in-terest are the two rapid forms of decomposition, burning and detonation. The term "detonation" is used to describe an explosive phenomenon of almost instantaneous decomposition. The properties of the explosive indicate the class into which it falls. In some cases explosives may be made to fall into either class by the conditions under which they are initiated.

For convenience, low and high explosives may be differentiated in the following manner. These are normally employed as propellants. They undergo autocombustion at rates that vary from a few centimeters per second to approximately meters per second.

Included in this group are smokeless powders, which will be discussed in a later chapter, and pyrotechnics such as flares and illumination devices. These are normally employed in warheads. They undergo detonation at rates of 1, to 8, meters per second. High explosives are conventionally subdivided into two classes and differentiated by sensitivity: These are extremely sensitive to shock, friction, and heat. They will burn rapidly or detonate if ignited.

These are relatively insensitive to shock, friction, and heat. They may burn when ignited in small, unconfined quantities; detonation occurs otherwise. The usefulness of a military explosive can only be appreciated when these properties and the factors affecting them are fully understood.

Many explosives have been stud-ied in past years to determine their suitability for mili-tary use and most have been found wanting. Several of those found acceptable have displayed certain characteristics that are considered undesirable and, therefore, limit their use-fulness in military applications. The requirements of a military explosive are stringent, and very few explosives display all of the characteristics necessary to make them acceptable for military standardization.

Some of the more important characteristics are discussed below: In view of the enormous quantity demands of modern warfare, explosives must be produced from cheap raw materials that are nonstrategic and available in great quantity. In addi-tion, manufacturing operations must be reasonably simple, cheap, and safe. Regarding an explosive, this refers to the ease with which it can be ignited or detonated--i.

When the term sensitivity is used, care must be ta-ken to clarify what kind of sensitivity is under discussion. The relative sensitivity of a given explosive to impact may vary greatly from is sensitivity to friction or heat.

Some of the test methods used to determine sensitivity are as follows: 1 Impact--Sensitivity is expressed in terms of the distance through which a standard weight must be dropped to cause the material to explode. Sensitivity is an important consideration in selecting an explosive for a particular purpose.

The explosive in an armor-piercing projectile must be relatively insensitive, or the shock of impact would cause it to detonate before it penetrated to the point desired. Stability is the ability of an explosive to be stored without deterioration. The following factors affect the stability of an explosive: 1 Chemical constitution--The very fact that some common chemical compounds can undergo explosion when heated indicates that there is something unstable in their struc-tures. While no precise explanation has been developed for this, it is generally recognized that certain groups, nitro dioxide NO2 , nitrate NO3 , and azide N3 , are intrin-sically in a condition of internal strain.

Increased strain through heating can cause a sudden disruption of the mole-cule and consequent explosion. In some cases, this condi-tion of molecular instability is so great that decomposition takes place at ordinary temperatures.

As a rule of thumb, most explosives becomes danger-ously unstable at temperatures exceeding 70oC. The term power or more properly, performance as it is applied to an explosive refers to its ability to do work. In practice it is defined as its ability to accomplish what is intended in the way of energy delivery i. Explosive power or performance is evaluated by a tailored series of tests to assess the material for its intended use.

Of the test listed below, cylinder expansion and air-blast tests are common to most testing programs, and the others support specific uses. Data is collected concerning the rate of radial expansion of the cylinder and maximum cylinder wall velocity.

This also establishes the Gurney constant or 2E. The fragments are collected and the size distribution analyzed. The procedure involves the detonation of a series of charges of different diameters until difficulty in detonation wave propagation is observed.

The hydrodynamic theory of detona-tion used in predicting explosive phenomena does not include diameter of the charge, and therefore a detonation velocity, for an imaginary charge of infinite diameter. This proced-ure requires a series of charges of the same density and physical structure, but different diameters, to be fired and the resulting detonation velocities interpolated to predict the detonation velocity of a charge of infinite diameter.

The values obtained are compared with that for TNT. The results are tabulated and expressed in TNT equivalent. In addition to strength, explosives display a second charac-teristic, which is their shattering effect or brisance from the French meaning to "break" , which is distinguished form their total work capacity. This characteristic is of prac-tical importance in determining the effectiveness of an ex-plosion in fragmenting shells, bomb casings, grenades, and the like.

The rapidity with which an explosive reaches its peak pressure is a measure of its brisance. Brisance values are primarily employed in France and the Soviet Union. Density of loading refers to the unit weight of an explosive per unit volume. Several methods of loading are available, and the one used is determined by the characteristics of the explosive. The methods available include pellet loading, cast loading, or press loading.

High load density can reduce sensi-tivity by making the mass more resistant to internal fric-tion. If density is increased to the extent that individual crystals are crushed, the explosive will become more sensi-tive. Increased load density also permits the use of more explosive, thereby increasing the strength of the warhead. Suggested fates of energetic compounds in the environment [ 33 , 36 , ]. Figure 4. Biological transformation pathway of TNT [ ]. Reproduced with kind permission from The American Society for Microbiology.

Figure 5. Biological transformation pathway of RDX [ 37 ]. Figure 6. Biological transformation pathway of HMX [ 33 ]. Figure 7. Biological transformation pathway for NG [ ].

Reproduced with kind permission from Elsevier. Figure 8. Biological transformation pathway for perchlorate Adapted from [ 64 , ].

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