Conventional Explosives Flashcards
What is an explosion
The sudden and rapid escape of gases from a confined space, accompanied by high temperatures, violent shock and loud noise
Types of explosions
Mechanical
Nuclear
Chemical
What is a mechanical explosion
A mechanical explosion occurs when pressure inside a container overcomes the strength of the container, causing it to rupture
A container IS required for a mechanical explosion to occur
What is a nuclear explosion
A nuclear explosion may be induced either by fission (the splitting of the nuclei of atoms) or fusion (the joining together under great force of the nuclei of atoms)
What is a chemical explosion
A chemical explosion is defined as the extremely rapid conversion of a solid or liquid explosive compound into gases having a much greater volume than the substance from which they are generated
A container is NOT REQUIRED for a chemical explosion to occur
Nature of chemical explosions
Most commonly encountered by public safety personnel
In all chemical explosion’s, the changes that occur are the results of combustion or burning. Combustion of any type produces several well-known effects such as heat light and release of gases
- Ordinary combustion
- Rapid combustion (explosion)
- instantaneous combustion (detonation)
What is ordinary combustion
A combustible material (something that can be burned) and a supporter of combustion (something that will stimulate burning) must be brought together and the temperature raised to the point of ignition. The most effective supporter of combustion is oxygen
Air contains 21 parts of oxygen and serves as the most common Source of support for combustion
What is rapid combustion (explosion)
An example of rapid combustion is the automobile engine. Inside the cylinder of the engine, combustible fuel (gasoline) is mixed with a combustion supporter (air) and the mixture is raised close to ignition temperature by compression. When I spark plug ignites the mixture, rapid combustion (explosion) occurs
An explosion is merely a rapid form of combustion
What is instantaneous combustion (detonation)
Detonation is the most rapid form of combustion
The example given shows that a garden hose filled with RDX (a high explosive with a detonation velocity of 27,400 FPS) filled at a length of 27,400 feet, it would take 1 second for the detonation at one end to reach the other end
What are the effects of an explosion
The block or stick of chemical explosive material is instantaneously converted from a solid into a rapidly expanding mass of gases.
The definition of a chemical explosive will produce three primary effects that include:
1- Fragmentation
2- Incendiary
3- Blast pressure
What is radiation effect
The radiation affect is only found if nuclear material is present in the bomb.
What is the fragmentation effect
A simple fragmentation bomb can be composed of an explosive placed inside a length of pipe that has end caps screwed into place. When the explosive is detonated not only will the blast pressure effect produce damage, but shattered fragments of the pipe will be hurled outward
What is the difference between primary fragmentation and secondary fragmentation
Primary fragmentation is from the actual explosive or device
Secondary fragmentation is fragmentation made up of adjacent objects that are energized from the blast and set in motion
How fast does the average bomb fragmentation travel
The average bomb fragment will reach 2700 FPS a few feet from the point of detonation. The speed is similar to a bullet from a military rifle and will follow a trajectory path similar to the bullet eventually falling to the earth or striking an object
Describe the fragments resulting from a high explosive versus a low explosive
High explosive fragments will be stretched, torn, and thinned due to the tremendous heat and pressure produced by the explosion
Low explosive fragments will not have this effect and typically have a uniform size shape and weight
What is serration or pre-engraving
This is the technique of grooving that is applied to hand grenades
What is shrapnel
Pre-cut or preformed objects (ball bearings, nails, fence staples) that are placed inside or attached outside of the bomb
What is the difference between the Incendiary thermal effect for a low explosive versus a high explosive
Lower explosives will produce a longer incendiary thermal affect and a high explosive or produce a much higher temperature
Incendiary thermal effects are generally the least damaging of the three primary detonation effects
What is radiant heat
The incendiary thermal effect that is usually seen as a bright flash (fireball) And last for a fraction of a second at the instant of detonation
What is direct flame
Direct flame is a contact burn that is longer in duration and can last up to several minutes
What is the blast pressure effect
With a high explosive is that needed the solid charge is rapidly converted to a gaseous product. This occurs in 0.0001 seconds exerting pressure of 700 tons per square inch forcing atmosphere surroundings to rush away at 13,000 mph
The wave of pressure is called the blast pressure wave
What is the positive pressure phase
The positive pressure phase follows the blast pressure and creates a cyclone-like sudden and violent push causing debris to be moved away from the detonation point.
What is the negative pressure phase
After the positive pressure face pushes the surrounding air away and create a vacuum
The vacuum causes the compressed and displaced atmosphere to rush back to fill the void. This can cause a strong Gale displacing objects in the direction of the detonation
What is a secondary Blast pressure effect
Blast effects are enhance by confinement due to the reflection of blast waves by the confining surfaces. If a bomb detonates within a building there is considerable reflection of the blast waves from all the walls
Describe the focusing, reflecting, and shielding of the pressure wave
The pressure wave reflects off of objects and can either scatter or focus is energy in a different direction. Shielding occurs when the pressure wave goes around an object and then reforms
Describe Blast effects underground
Explosive charges whether on top or under the ground will create scoring or creators based upon the depth and type of explosive.
Personnel entering enclosed underground spaces near a recent explosion may counter atmospheric conditions with insufficient oxygen and toxic gases
Describe the last affects underwater
Blast affects underwater result in shock waves of extremely high pressure. Because water is non-compressible the shock wave travels faster in further creating more damage
What are energetic materials
Energetic materials are chemical compounds or mixtures of chemical compounds that are divided into three classes according to use
- Explosives
- Propellants
- Pyrotechnics
What is the difference between explosives, propellants, and pyrotechnics
Explosives produce high pressure and are very fast
Propellants produce lower pressure in our slower
Pyrotechnics produce large amount of heat but less gas then propellants or explosives
What is the primary requisite of a chemical explosive
The primary requisite is oxygen. Since an adequate supply cannot be drawn from the air, a source of oxygen must be incorporated into the elements called an oxidizer
What is an explosive mixture
It is when fuel and an oxidizer are blended mechanically
I.E. pistol or rifle powder
What is an explosive compound
And explosive compound is formed when fuel and the oxidizer are molecularly bonded
What are the minimum components required to form an explosive
Fuel and an oxidizer
What two oxidizers agents are currently used in manufacturing explosives
Nitric acid and sulfuric acid
What is nitrating
Nitrating is the process of combining fuel with nitric acid
What oxidizing agent is the essential ingredient in mini commercial explosives
Ammonium nitrate
What percentage will an explosive grade of ammonium nitrate be
33% to 35%
What are the most frequently used fuels
Powdered aluminum and magnesium
What are low explosives
Lower explosives are said to deflagrate (burn) rather than detonate (explode).
They are used primarily as propellants
They do not require the shock of a blast in cap
What are high explosives
High explosives must be initiated by shock
The arbitrary figure that separates high explosives and low explosives is 3,300 FPS
What is high order detonation
Hi order detonation indicates that the explosive completely detonated as it was designed to do
What is low order detonation
Low order definition is the term typically use to indicate that the detonation was incomplete or less than expected
Some factors could be
- inadequate blasting caps
- Poor continuity
- deteriorated explosives
- a booster wasn’t used when required
What is an explosive train
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
Think of a booster
What is a low explosive train
A low explosive train is a two-step process.
The firing pin in a weapon converts the mechanical energy into a flame when striking the primer. The gas is produced and is used to drive the bullet through the bore of the weapon
What is a high explosive train
A high explosive train use a two or three step train and typically uses a blasting cap
A two-step train would be a blasting cap inside of a stick of dynamite
A three-step train would be a safety fuse to a blasting cap inside of a stick of dynamite
What are the characteristics of chemical explosives
Sensitivity Energy Strength/power Sensitiveness/sympathetic Fumes Flammability Water resistance Hygroscopicity Detonating velocity
What is energy
Energy is the potential for an explosive to do work
What is strength/power
Strength/power Is an explosive’s ability to do useful work
- Brisance-the shattering capability of an explosive
- Cratering effect- Ability of an explosive to push, shove or heave a solid
- Blast effect- The ability of an explosive to compress its surroundings by means of a shock wave of compressed air
What are fumes
Fumes are toxic gases resulting from the detonation or burning of an explosive
What is flammability
Flammability is the ease with which in explosive can be ignited by flame and heat
What is water resistance
Water resistance is the number of hours in explosive can be loaded in water and still function
What is hygroscopicity
Hygroscopicity Is the ability of an explosive to absorb moisture from its surroundings
What is detonating velocity
Detonating velocity is the speed at which a detonation wave travels through a column of an explosive
High explosives range from 3,300 FPS to over 33,000 FPS
Low explosives range under 3,300 FPS
What is the Munroe (shaped charge) effect
This is where the explosive is cut or shaped to provide opposing surfaces so the explosive force can be focused directionally
What determines the speed and density of the jet in shaped charges
The angles of the walls
What is standoff distance
The standoff distance is the distance the explosive is placed from the material to be cut
Optimum stand off is a function of what
Detonating velocity, explosive density, the liner, and the cone angle
What affects the efficiency and function of a shape charge
The type of explosive and the initiation point
What are the two basic types of shape charges
Conical shape charge and the linear shape charge
There is also a flexible linear shaped charge (V shaped) that is a high explosive that provides a sharply defined cutting action
What is the concentrated blast effect
This is the explosive for us that’s concentrated over a wide focal point giving tremendous thrust against an object. Deep penetration will not occur
What is the Misnay-Schardin effect (plate effect)
This where a steel plate is loosely attached to the explosive designed to penetrate the object
What is the spalling effect
This is where a large mass of explosive is detonated directly against the surface of a target. Shockwaves move to the opposite surface and overcome the strength of the metal causing it to fail
What is the Fougasse effect (improvised shotgun)
This effect is an improvised directional munition constructed with pipe or tubing and is made very much like a shotgun shell
What is shock tube
Shock tube is a small diameter, laminated plastic tube with an inside coating of aluminized HMX. When detonated, the detonation wave travels 6,500 FPS
What is a Primadet
Primadet is shock tube with a blasting cap pre crimped on one end.
What is black powder
Black powder is a little explosive they can also be used as a propellant.
Black powder is a physical mixture of potassium nitrate (75%), charcoal (15%) and sulfur (10%)
Black powder is referred to as being the most hazardous and dangerous of all explosives
Black powder is a mixture not a compound
Black powder is used in safety and time fuses and some ignitors
What are the four classes of propellants
- Single base
- Double base
- Triple base
- Composite
What consists of a non electric system
The basic priming materials consist of a non-electric blasting cab the safety fuse and the igniter
Detonation cord must be used if more than one charge is needed
What is a safety and time fuse
It is used in general not electric demolition operations. It consists of a black powder core tightly wrapped with several layers of fiber and waterproofing material. The most common colors are orange and green but it can be any color The burning rate average is 30 to 45 seconds per foot
