Blast Explosives Flashcards
What is an explosion?
A rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases.
How are explosives catergorised?
- low and high explosives
- high explosives: primary and secondary
What are mechanical explosions?
High pressure gas produces a physical reaction, vessel failure or rupture of the container. Flammable material may be ignited by heat and oxygen, results in fire
What is a chemical explosion?
Exothermic reaction resulting from the initiation of chemical explosives or fuel gases, resulting in the generation of high pressure gas
What is a nuclear explosion?
High quantities of heat and gas are produced by fusion or fission processes
What is an electrical explosion?
High energy electrical arcs may generate sufficient heat to cause an explosion, resulting in a mechanical explosion. This reaction may or may not result in subsequent fire
What are the 4 types of explosions?
Chemical
Mechanical
Physical
Nuclear
What are the types of blast injuries?
Primary, secondary, tertiary, quaternary
What are primary blast injures?
Results from the high-pressure shock front and associated blast wave. Organs are susceptible to spilling, implosion, inertial mismatches and pressure differentials
What are secondary blast injuries?
Results from missiles propagated by the explosion
What are tertiary blast injuries?
Stems form the victims body being thrown as a projectile by the blast (fractures, head trauma, other blunt injury)
What are quaternary blast injuries?
Represents miscellaneous blast-related injuries:
- injury from structural collapse
- additional burns as well as smoke and dust inhalation from secondary fires
- exposure to irradiation as well as toxic gas and other chemical and biological pathogens
Low explosive
- slow and deflagrating (under 21000ms)
- includes black powder, smokeless powder, flash powder
High explosive
- rapid and detonating (<1000ms)
- two types: primary and secondary
Primary explosive
- initiating explosive
- extremely sensitive to mechanical shock, friction and heat
- generally used in detonators
- e.g. Mercury fulminate, lead azide, lead styphnate, tetrazene and DDNP
Secondary explosive
- non-initiating explosive
- relatively insensitive to heat and shock
- requires detonation by primary explosive
- e.g. TNT, RDX (cyconite), high melting explosives (HMX), tetryl
What is a bomb?
A container filled with explosive or incendiary material, designed to explode on impact or when detonated by a timing, proximity or remote controlled device
What is an improvised explosive device? (IED)
A bomb constructed and deployed in ways other than conventional military action
What is explosive ordnance?
A military term used for all munitions containing explosives, nuclear fission or fusion materials, and biological and chemical agents
What is unexplored ordnance? (UXO)
Ammunition which has been fired, but has not gone off, is particularly dangerous as all the normal safety arrangements have been overcome. In this case very little hand,ing may be needed to make the ammunition go off
What is a detonator?
A device used to trigger an explosive. Detonators can be chemically, mechanically or electrically initiated
What are some common types of bombs?
- pipe bombs
- vehicle bombs
- letter and parcel bombs
- suicide bombers
What are pipe bombs?
A short length of pipe (both ends capped), detonators indented through one end, either high or low explosives are used, parts of the bomb survives blast
What is a vehicle bomb?
Bomb placed inside vehicle, use large quantities of low explosive with high explosive booster
What are letter and parcel bombs?
Contain a small amount of high explosive packages inside a letter of package
What are suicide bombers?
An individual wearing a waistcoat of explosives or carrying a device places themselves in a position to cause maximum destruction
What are the different mechanisms of explosions?
- Dispersed (diffuse) explosion
2. Concentrated explosion
Dispersed (diffuse) explosion
- absence of blast seat (no crater/epicentre)
- extensive fire damage
- minimal fragmentation
- no bomb components
- widespread low-blast pressure effects (ceilings lifted, window frames pushed out, walls pushed over)
- usually accidental
- caused by gas, vapour, dust, air
Concentrated explosion
- crater/epicentre
- shattering damage (holes blown in brick walls)
- penetration of relatively substantial material by high velocity fragment
- explosives present
- usually incendiary and deliberate
- TNT, dynamite, tetryl, plastic explosives, Mercury fulminate etc
What occurs in an explosion?
- blast wave
- fragmentation
- thermal effects
Fragmentation
- projectiles: shrapnel from the bomb contents and casing
- objects (especially glass broken by the blast wave are propelled forwards
Thermal effects
A hot but brief fireball is produced at the bomb seat upon detonation, may result in secondary fires
Post-blast examination
At the scene the post-blast examiner will look for:
- undetonated explosive residue
- exploded residue
- remnants of the device
Explosive residue
The aim of analysis of post-blast explosion products is to determine the type of explosive material and its manufacturer
- visual and microscopic analysis
- instrumental analysis
Mechanical explosions cause…..
A physical reaction
What are the steps involved in an explosion?
- The blast wave from the explosion creates highly compressed air particles
- Shockwaves carry energy through the medium
- Fragmentation throws shrapnel outward
- The explosion creates heat and fire
- The intense heat can cause secondary fires or explosions
- The blast wind creates a vacuum that refines itself with air and pulls shrapnel back in
What is a blast wave?
The rapid outward expansion of gas that exceeds the speed of sound
What is the blast wind?
The mass outward movement of ambient air following a blast wave
