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