AUSTRALIAN BOMB DATA CENTRE PHILIPPINE BOMB DATA CENTER

AUSTRALIAN BOMB DATA CENTRE PHILIPPINE BOMB DATA CENTER Introduction to Explosive Theory

What is an Explosive? An explosive is a chemical composition, either solid, liquid or gas that is in a state of unstable equilibrium. When suitably initiated by shock, friction or heat, they under go a rapid chemical change from their original compound into one or more stable compounds, usually gasses. In the process of changing from an unstable to more stable compounds they give out energy in the form of heat, light and sound, which as a final result is a violent expansion of gasses (pressure).

Safety Considerations Explosives can be sensitive to: Heat Shock Friction Treat all explosives with respect and care.

Explosion The process of internal burning. Instead of the oxygen being supplied from the surrounding air, it is supplied in the form of oxidisers or oxidants and is actually a solid material that is in intimate contact with the fuel. The energy produced normally appears in the form of heat and light. If a substance is capable of burning and giving off gaseous products and burns in a confined space, an increase in pressure results. This pressure increase causes the rate of burning to increase to a maximum, (burning rates are from a fraction of a metre per second up to 300 metres per second) and eventually the container will burst. This process is known as an explosion of low explosives.

Detonation is the transmission through an explosive substance (at speeds in the order of 3000 - 9000 metres per second), of a shock wave which brings about complete molecular disintegration. The extreme violence of this type of reaction is associated with the fact that the chemical change is taking place between atoms of the same molecule, instead of between separate particles as in the explosion process. The speed at which a detonation takes place is known as the Velocity of Detonation (VOD). The disintegration reduces the original composition to its basic, more stable elements, some or all of which are gaseous.

Characteristics of an explosion 10, 000 to 15, 000 times the original volume of gas produced. Velocity of gas about 6, 000 m/second. Temperature of 3, 000 to 4, 000 degrees Celsius. Within about 10 milliseconds.

Resulting Effects Shock (induced by the rapid increase in pressure) Incendiary (fire/heat) Fragmentation Primary – parts of the device Secondary – anything, those things that are part of the surrounding area and not part of the actual device

Resulting Effects Incendiary

Resulting Effects Fragmentation Primary • device components Secondary • as a result of the explosion

Resulting Effects Shock

CHARACTERISTICS OF AN EXPLOSION BLAST PRESSURE EFFECT Gases are produced within 0. 0001 seconds These gases reach velocities of up to 11, 000 kilometers per hour Exert pressures of up to 110 tons per square cm The gases move away from the blast seat and Are referred to as a “Blast Pressure Wave”

CHARACTERISTICS OF AN EXPLOSION POSITIVE PRESSURE PHASE NEGATIVE PRESSURE PHASE

CHARACTERISTICS OF AN EXPLOSION

CHARACTERISTICS OF AN EXPLOSION

CHARACTERISTICS OF AN EXPLOSION

CHARACTERISTICS OF AN EXPLOSION BLAST PRESSURE EFFECT Secondary Blast Pressure Effects Reflection Focusing Shielding

Shrapnel is something added to the device for an Anti Personnel effect For example: nails, nuts, bolts, glass etc

Woomera - September 1999

Safety considerations – Protection from explosive effects Shielding Fragmentation Incendiary Distance Fragmentation Incendiary Overpressure/Shock

CHARACTERISTICS OF AN EXPLOSION Velocity of detonation can be defined as; “The speed at which the detonation wave travels through an explosive substance. ”

1 2 3 4

Time in microseconds after the connection of current to the detonator

TYPES OF EXPLOSIVES Low Explosive High Explosive

Explosives LOW EXPLOSIVES

TYPES OF EXPLOSIVES Low Explosive: This type of explosive has ‘Velocity of Detonation’, below 2, 000 meters per sec (6000 feet per/ sec. ) Produces greater propellant effects and few blasting effects. The Low explosives are generally sensitive to fire, impact and friction and are easily initiated. Examples: Black Powder, Chemical Powder, and Pyrotechnics.

EXPLOSIVES M HIGH EXPLOSIVES

TYPES OF EXPLOSIVES High Explosive: This type of explosive has a ‘Velocity of Detonation’, above 2, 000 meter per sec (6000 feet per/ sec) and produces fewer propellant effects and greater blasting effects. High Explosives can be sub-classified into: • Primary High Explosive • Secondary High explosive

Primary high explosives Extremely sensitive to initiation by heat, shock, friction static electricity and flame or combination of these. They are ignited easily and reach their detonation velocities upon ignition. Valued for their extreme sensitivity than for their damage capability

Primary High Explosives They are used in the beginning of a firing train to detonate secondary high explosives. Primary high explosives are used in the manufacture of commercial and military detonators (easily initiated by flame or bridge wire in electric blasting caps)

Secondary High Explosives. Used as a main charge and sometimes as a booster for much less sensitive explosives such as anfo. Relatively insensitive to heat, shock, friction and static electricity. Usually require the help of high explosives in order to detonate. Some of the least sensitive items cannot be detonated unless the detonation wave of the primary explosive is amplified by a booster

EXPLOSION (Low Explosive) 1. Rapid burning in a confined space. DETONATION (High Explosive) Molecular disintegration by a shock wave, always accompanied by the release of heat. 2. Can be initiated by heat, spark or flame. Normally initiated by some form of shock. Secondary High Explosives. 3. Surface burning, therefore is controllable. An uncontrolled process once initiated. 4. Rate of burning never exceeds 2000 metres per second. Velocity of detonation is usually between 3000 - 9000 metres per second. 5. Impurities can impede the burning process. Impurities do not impede a shock wave. 6. Air gaps do not impede burning. Air gaps will impede a shock wave.

EXPLOSIVE INITIATION A three stage explosive train Typically uses small amounts of highly sensitive explosive to initiate larger amounts of less sensitive explosives

INITIATOR BOOSTER MAIN CHARGE PRIMERY EXPLOSIVE (VERY SENSITIVE) INTERMEDIARY EXPLOSIVE (SOME WHAT SENSITIVE) SECONDARY EXPLOSIVE (INSENSITIVE)

INITAITOR Primary explosive (very sensitive) BOOSTER Secondary explosive (some what sensitive) MAINCHARGE Secondary explosive (insensitive) typically uses small amounts of sensitive high explosive to initiate larger amounts of less sensitive explosives.

POWER CARRIER INITIATOR WAVE CARRIER BOOSTER MAIN CHARGE

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