Conventional Explosives Flashcards
What are the types of explosions?
Mechanical
Nuclear
Chemical
What is a Mechanical Explosion?
An explosion where the pressure inside a container overcomes the strength of the container, causing a rupture. A container is required for a mechanical explosion to occur.
What is a Nuclear Explosion?
A nuclear explosion is caused by either fission (the splitting of the nuclei of atoms) or fusion (the joining together under force of the nuclei of atoms) causing the release of energy, heat, gas and shock.
What is a Chemical Explosion?
The extreme rapid conversion of a solid or a liquid explosive compound into gases having a much greater volume then the substances from which they are generated. A container is not required for a chemical explosion to occur.
What are the three effects of a chemical explosion?
1) Fragmentation
2) Incendiary
3) Blast pressure
What are the three classes of energetic material?
1) Explosives
2) Propellants
3) Pyrotechnics
What are the three types of combustion?
1) Ordinary Combustion
2) Rapid Combustion (explosion)
3) Instantaneous combustion (detonation)
Air contains what supporter of combustion and in what ratio?
oxygen at 21 parts
Detonation can be defined as?
Instantaneous combustion (However even in detonation there must be some interval)
What is the average velocity of a bomb fragment (measured a few feet from detonation)?
2,700 fps (the approximate speed of a bullet fired from a military rifle)
What is the difference between primary and secondary fragmentation?
Primary fragmentation is from the bomb casing, secondary fragmentation is made up of adjacent objects energized by the blast.
Describe the appearance of fragments from a bomb with high explosive filler?
a stretched, torn and thinned configuration due to tremendous heat and pressure produced by the explosion.
Describe the appearance of fragments from a bomb with low explosive filler?
larger fragments lacking a stretched or thinned configuration.
What will grooving (serration or pre-engraving) a bomb achieve?
fragments produced will have a uniform size, shape and weight.
What is shrapnel?
Pre-cut or pre-formed objects (i.e., nails, ball bearings, or fence staples) that are placed either inside the bomb or attached on the outside.
What is the advantage of shrapnel?
Part of the energy released during the explosion is used to propel the shrapnel rather than being expended in fracturing the case body.
What is the incendiary thermal effect known as radiant heat?
The bright flash (fireball) lasting a fraction of a second at the instant of detonation.
What is the incendiary thermal effect known as Direct Flame?
A contact burn that is longer in duration and can last up to several minutes.
What is generally the least damaging of the three primary detonation effects?
Incendiary Thermal Effect
In a high explosive detonation how fast does the conversion from solid charge to gaseous product take?
0.0001 seconds
In a high explosive detonation how fast do the gases rush away from the point of detonation?
13,000 miles per hour
In a high explosive detonation how much pressure is exerted on the surrounding atmosphere?
700 tons per square inch
How much available energy is used to expand the bomb casing?
half with the remainder used to compress the surrounding environment.
What is the shock front?
The compressed layer of air formed at the instant of detonation that is the leading edge of the positive pressure wave (visible in some cases as a white rapidly expanding circle).
Describe the shock front and positive pressure wave effect on objects?
The shock front delivers a massive blow followed by the strong winds of the positive pressure wave.
Describe the negative pressure phase?
The positive pressure wave pushes outward from the point of detonation leaving a partial vacuum in the area surrounding the detonation. This partial vacuum causes the compressed and displaced atmosphere to reverse movement and rush in to fill the void.
The negative pressure phase lasts how long compared to the positive pressure phase?
Three times as long (though less powerful).
What is the most powerful of the explosive detonation effects?
The Blast Pressure Effect.
What are the secondary Blast Pressure Effects?
Focusing, Reflecting, and Shielding of the pressure wave.
If an explosive charge is detonated underground the pressure exerted causes?
A radius or rupture
How is a crater caused?
When the explosive charge burial depth is less than the radius or rupture.
Why is the crater from an explosive charge on the surface of the ground shallower than one placed underground?
Due to the scouring action of gases projected downward from the explosive charge.
What is a Camouflet?
An underground cavity caused by an explosive buried at a depth exceeding the radius or rupture.
What should personnel entering an underground space after a recent explosion be concerned with?
Atmospheric conditions with insufficient oxygen and toxic gases.
Why do explosive charges detonated underwater produce damage at greater distances?
Water is not compressible, so it absorbs energy and transmits it in a shock wave much faster and farther.
Why are structural fires considered a secondary effect of a detonation?
Most structural fires originate from broken electrical circuits and/or ruptured natural gas and oil lines after the detonation.
What are the three types of energetic materials?
1) Explosives
2) Propellants
3) Pyrotechnics
What is an Energetic Material?
Chemical compounds, or mixtures of Chemical compounds, that are divided into three classes according to use.
What is the difference between explosives and propellants?
Both produce large volumes of hot gases in a short time, the rate at which the reaction proceeds is the difference.
Describe pyrotechnics as an energetic material?
Pyrotechnics produce a large amount of heat but much less gas than propellants or explosives.
Describe propellants as an energetic material?
Propellants have a slower reaction process and produce lower pressure over a longer period of time capable of propelling objects.
Describe explosives as an energetic material?
Explosives have a fast reaction that produces a very high pressure shock capable of shattering objects.
What is an Oxidizer?
A source of oxygen incorporated into the combustible elements of an explosive.
What do all explosive compositions contain?
Oxidizers and Fuels.
When a fuel and oxidizer are blended mechanically what is formed?
An explosive mixture.
What is formed when a fuel and oxidizer are molecularly bonded?
An explosive compound.
What are two oxidizers currently used in manufacturing explosives?
1) Nitric Acid
2) Sulfuric Acid
What is Nitrating?
The process of combining fuel with nitric acid.
What oxidizing agent is used in common fertilizer?
Ammonium Nitrate (8-13%)
What is the typical concentration of Ammonium Nitrate in commercial explosives?
33-35%
What is the most frequently used fuels in explosives?
Powered Aluminum and Magnesium.
How are explosives commonly classified?
By velocity of detonation or deflagration is used to distinguish between high and low explosives.
What is Deflagrate?
Burn
What is detonate?
explode
Do low explosives Deflagrate or Detonate?
Deflagrate
What are low explosives primarily used for?
Propellants.
Describe the forces exerted by a low explosive?
Rapid pushing effect.
How can the combustion process of low explosives be started?
Application of a simple flame, acid/flame reaction, shock or friction, but do not require the shock of a blasting cap.
What are high explosives designed to do?
Shatter and Destroy.
What are the range of detonation velocities for high explosives?
3,300 fps to 29,900 fps. (or 33,000 fps per page 21)
What is the arbitrary detonation velocity that separates low explosives from high explosives?
3,300 fps.
What is the general difference between detonating high and low explosives?
high explosives must be initiated by shock.
What is the most common means to initiate the detonation of high explosives?
A blasting cap.
What is the detonation wave?
The internal shock wave that radiates outward form the point of initiation in the explosive material.
What is detonation velocity?
Maximum sustained velocity of the detonation wave as it moves through the explosive material, measured in fps or mps.
What is High Order Detonation?
The complete detonation of the explosive at it’s designed velocity.
What is Low Order Detonation?
An incomplete detonation or one with a rate lower than it’s expected rate.
What are four factors that can cause a Low Order detonation?
1) Inadequate Blasting Caps
2) Poor Continuity
3) Deteriorated explosives
4) Booster not used when required
What is an explosive train?
A series of explosions specifically arranged to produce a desired outcome.
What are the elements of an explosive train?
1) Initiator - small highly sensitive material
2) Booster - larger quantity of less sensitive, more powerful material
3) Main or Bursting Charge - least sensitive and bulk of the charge
What are the three major ways secondary explosives differ from primary explosives?
1) Small, unconfined charges (1-2 grams) of secondary explosives, even ignited, do not transfer easily from deflagration to detonation.
2) Except for dust clouds, ignition by electrostatic spark is difficult.
3) The shock required for detonation is much greater for secondary explosives than for primary explosives.
What is an example of a low explosive train?
A round of small arms ammunition.
How are explosive trains classified?
As high or low depending on the final material in the train.
What does sensitivity refer to in an explosive?
The amount of external force or effect needed to cause detonation.
What is the normal explosive train used with high explosives?
two or three step train.
Describe a three step explosive train?
A low explosive (black powder), primary explosive (blasting cap), Secondary explosive (booster) and then a larger quantity of an insensitive Secondary explosive (varies).
What is an explosive firing train?
A series of explosions arranged to achieve a desired end result. If the explosive train is broken or interrupted the main charge will not detonate.
What are the nine characteristics of chemical explosives?
1) Sensitivity
2) Energy
3) Strength/Power
4) Sensitiveness/Sympathetic
5) Fumes
6) Flammability
7) Water Resistance
8) Hygroscopicity
9) Detonating Velocity
Describe sensitivity as a characteristic of chemical explosives?
The minimum amount of energy, pressure or power required to initiate an explosive.
What is the difference in sensitivity between military and commercial explosives?
Military explosives are less sensitive to initiation than commercial explosives.
Describe energy as a characteristic of chemical explosives?
Energy is the potential for an explosive to do work.
Describe strength/power as a characteristic of chemical explosives?
An explosive’s ability to do useful work. Brisance, Cratering Effect and Blast Effect.
Describe sensitiveness/sympathetic as a characteristic of chemical explosives?
A measure of an explosive to propagate from a donor, and initiate an acceptor (receptor).
What is Brisance?
The shattering capability of an explosive.
What is Cratering Effect?
The ability of an explosive to push, shove, or heave a solid.
What is Blast Effect?
The ability of an explosive to compress it’s surroundings by means of a shock wave or compressed air.