EXPLOSIVES

The main purpose of any warhead is to inflict damage on the target. The way the damage is caused may vary with different types of warheads, but in the most general sense, damage is caused by the transfer of energy from the warhead to the target.

There are many chemical reactions that will release energy. These are known as exothermic reactions. If the reaction proceeds slowly, the released energy will be dissipated and there will be few noticeable effects other than an increase in temperature. On the other hand, if the reaction proceeds very rapidly, then the energy will not be dissipated. Thus, a great quantity of energy can be deposited into a relatively small volume, then manifest itself by a rapid expansion of hot gases, which in turn can create a shock wave or propel fragments outwards at high speed.
Chemical explosions may be distinguished from other exothermic reactions by the extreme rapidity of their reactions. In addition to the violent release of energy, chemical explosions must provide a means to transfer the energy into mechanical work. This is accomplished by expanding product gases from the reaction. If no gases are produced, then the energy will remain in the products as heat.

Not only must explosive materials be highly energetic, as characterized by the relative strength, but they must also react violently. The speed of the reaction is vital to the build up of a large amount of energy into a small volume.

Reactions that proceed slowly allow the energy that is released to be dissipated (this is a consideration involving the interaction of the shock wave with targets).

This rapidity of reaction is called the brisance, or shattering potential of the explosion. It is a property of the material and the degree of confinement. If an explosion is restrained initially, it can build up a large pressure and achieve the same effect. The rapidity of the reaction is used as a method of classification of explosive materials.

Explosive materials which react very violently (are brisant) are known as high explosives. They are used solely for their destructive power. In contrast, there are some materials that react more slowly. These are known as low explosives. They release a large amount of energy, but due to the relatively slow rate of reaction the energy is more useful as a propellant where the expansion of the gases is used to move projectiles.

THE PURPOSE AND USE OF EXPLOSIVE

ACTIVATORS
- Very sensitive explosive used as the first element in the chain of explosion to activate other elements. its destructive power is limited, or very weak. e.g. mercury feliminate, lead or silver azed.
BOOSTERS
- Less sensitive than activators but has more destructive power, used as 2 nd element in the chain of explosion chain, to cause less active or weak material to detonate and some types can be used as main charge e.g. RDX, titrayl, nitro-glycerine.
MAIN CHARGE
- explosive material used to do the destruction needed, main charge is the last in the chain of explosion (e.g. TNT, DYNAMITE) and it makes up the bulk of the explosive materials.
NON SENSITIVE
- These are mostly salts or fertilisers e.g. urea and many nitrates such as ammonium nitrate.
PROPELLANT
- Liquid or solid - used in bullets or rockets e.g. gun powder or nitro cellulose. than propels the bullets of the rocket.
HEAT
- Aluminium powder is used in hollow charges to create great amounts of heat.
ILLUMINATION
- e.g. phosphor and magnesium.