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Pyrotechnic Glossary.

Pyrotechnic Glossary | Energetic Materials Terms | Common Acronyms

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Pyrotechnic Glossary

Making sense of commonplace terms and acronyms can sometimes be a challenge, especially when an industry speaks a language of its own. Pyrotechnic and energetic materials can certainly seem that way. While not comprehensive, this list of common terms and acronyms should help you understand what you read and hear on our website and elsewhere.

A

Acceptable Quality Level (AQL)
A nominal value expressed as a percentage defective per hundred units, used to identify a group of sampling plans.

Actuator
A mechanical device that transforms chemical energy into mechanical motion to perform work against an external load. Types of actuators include bellows, dimple, piston and retractable.

All-fire
Minimum stimulus which must be applied to a device for it to reliably function.

Ambient
Surrounding meteorological conditions such as temperature, humidity and pressure.

Apparent density
The ratio of mass to volume of a finely powdered material, under stated conditions, which is always less than true density. Sometimes called loading density.

Arm
To prepare an explosive item for imminent use by removing safing mechanisms.

Average burning rate
The arithmetic mean (statistical average) of the rate at which a pyrotechnic or propellant will burn at specific pressures and temperatures.

B

Ballistic pendulum
An instrument used for measuring the velocity of a projectile or the output of a cartridge or explosive charge.

Binder
Compositions that hold together a charge of finely divided particles and increase the mechanical strength of plugs or pellets of these particles when consolidated under pressure. Binders usually are resins, plastics, asphaltics, or hard waxes used dry or in solution.

Black powder
A low explosive consisting of an intimate mixture of potassium or sodium nitrate, charcoal, and sulfur. It is easily ignited and burns consistently at low pressures.

Blasting caps
Detonators specifically designed and produced in high volume far commercial blast- ing operations. They come in various sizes (strengths) and can incorporate a delay. Initiation can be electric or non-electric.

Booster
(1) A high-explosive device used to transfer the detonation from the detonator to the main explosive charge. (2) An auxiliary propulsion system to aid the early launching phase of a missile.

Bridgewire
A relatively fine resistance wire incorporated into an ignition element attached to the electrical leads of an electra-explosive device (EED).

Brisance
The shattering ability of explosives.

Bruceton Analysis
A statistical analysis approach to the problem of determining, as economically as possible, the behavior characteristics of explosive components by using a limited number of samples to determine a reliability factor. In this test, the level of variable applied depends on the results of the previous test.

Bulk density
The mass per unit volume of a bulk material such as grain, cement, coal. Used in connection with packaging, storage or transportation.

Bureau of Mines Test
A test for determining the impact sensitivity of an explosive. A small sample of the explosive is placed between two hardened steel plates, and a weight is dropped on the upper plate. The figure representing the lowest height in centimeters at which at least one of ten trials results in explosion is the sensitivity index. The highest drop provided is 100 cm, so sensitivity may be given as 100±, meaning that at 100 cm no explosion resulted.

Burning
A rapid evolution of energy through chemical reaction between a fuel and an oxidizing agent.

Butter charge
An increment of explosive material that is applied in a paste form and dried in place.

C

Cable cutter
An explosively powered device that cuts a cable upon the receipt of a firing stimulus.

Carbon bridge
A resistive element consisting of two electrical conductors bridged with a thin spot of colloidal graphite. Used in initiation systems.

Cartridge-actuated device (CAD)
A mechanical device actuated by a contained or inserted propellant charge.

Casting
See melt loading.

Closed bomb
A fixed-volume chamber used far testing the pressure-time characteristics of gas generators, cartridges or combustible materials.

Column length
The length of a propellant or pyrotechnic composition.

Combustion
A continuous, rapid chemical reaction accompanied by the evolution of energy, commonly caused by the union of a fuel and an oxidizing agent. (See burning.)

Compatibility
Ability of materials to be stored intimately without chemical reaction occurring. In- compatibility may result in a loss of effectiveness, or may be hazardous.

Composition, pyrotechnic
A physical mixture of finely powdered fuel and oxidant, with or without additives, to produce a desired effect.

Confidence level
A statistical evaluation of the percentage of statements or tests expected to be correct using a given analytical system.

Controlled-burning squib
A hot gas/ flame producing device in which the output charge is de- signed to burn within the device.

D

Decomposition
The process of breaking down a material into more simple products. Disintegration, dissociation.

Deflagration
The relatively slow burning or chemical decomposition of a propellant or pyrotechnic mix such that the reaction front advances into the unreacted material at less than sonic velocity.

Delay
A pyrotechnic or explosive train component that introduces a controlled time delay in the functioning of a device or fuze mechanism.

Delay element
An explosive train component normally consisting of a primer, a delay column, and a relay detonator or transfer charge assembled in that order in a single housing to provide a controlled time interval.

Density of charge
The weight of pyrotechnic or propellant charge per unit volume of the chamber, usually expressed in grams per cubic centimeter.

Detonate
To be changed by exothermic chemical reaction, usually from a solid or liquid to a gas, so quickly that the advancing reaction zone is preceded by a shock wave.

Detonation
The extremely rapid chemical decomposition of a material such that the reaction front advances into the reacted material at greater than sonic velocity.

Detonation velocity
See velocity of detonation.

Detonator
An explosive train component which, when initiated, detonates a less sensitive, but larger high explosive. Types of detonators include percussion, stab, electric and flash.

Drogue gun
An explosive device designed to elect a weight which is attached to a drag parachute or similar device.

Dry blend
A combination of powders that are mixed in a dry state.

Dud
An explosive device that has failed to initiate as intended.

Dwell time
In press-loading powders into cavities, the interval of time that the powder is held at the full loading pressure.

E

EED (electro-explosive device)
Any cartridge, squib, igniter, etc., which is initiated electrically.

Explode
To be changed in chemical or physical state, usually from a solid or liquid to a gas )as by chemical decomposition or sudded vaporization), so as to suddenly transform considerable energy into the kinetic form. See explosion.

Exploding bridgewire (EBW) detonator
A device that achieves detonation by exploding a bridge element in proximity to, but not in contact with, a secondary high explosive. Special high-power output-firing sources must be used to function these devices.

Explosion
A chemical reaction or change of state that is effected in an exceedingly short period of time with the generation of a high temperature and generally a large quantity of gas.

Explosive
A substance or mixture of substances that may be made to undergo a rapid chemical change, without an outside supply of oxygen, with the liberation of large quantities of energy generally accompanied by the evolution of hat gases.

Explosive bolt
A bolt that is intended to be fractured by a contained or inserted explosive charge.

Explosive nut
A nut that is intended to be fractured by a contained or inserted explosive charge For the purpose of releasing a load.

Explosive train
A train of combustible and explosive elements arranged in order of decreasing sensitivity. The explosive train accomplishes the controlled augmentation of a small impulse into one of a suitable energy to actuate a main charge.

F

Flame
A chemical reaction or reaction product, partly or entirely gaseaus, that yields heat and light.

Flash
1) A burst of heat or flame of short duration. 2) A method of initiating an explosive device using elements that are sensitive to flame and/or mild shock.

Frangible link
A mechanical link that is capable of supporting a tensile load and releasing the load upon the receipt of a firing stimulus.

Fuel
Any substance used to produce heat by burning.

Functioning time
Lapsed time between application of the firing stimulus to start of pressure rise.

Fuse
(Not to be confused with fuze.) An igniting or explosive device in the form of a cord, consisting of a flexible fabric tube and a core of low explosive. Used in blasting and demolition work, and in certain munitions.

Fuze
A device with explosive or pyrotechnic components designed to initiate a projectile, bomb, mine, etc.

Fuze, delay
Any fuze incorporating a means of delaying its action. Delay fuzes are classified according to the length of time of the delay.

G

Gas generator
A device in which a propellant is burned to produce a sustained flow of pressurized gas.

Grain
A single mass of solid propellant in the final geometric configuration for use in a gas generator or rocket motor.

H

Hermetic seal
A seal made impervious to air and fluids. Hermetically sealed devices are generally welded or solder sealed as opposed to being sealed with epoxy resin, etc.

High explosive
One that detonates.

Hygroscopicity
The tendency of a substance to absorb moisture from its surroundings; specifically, the absorption of water vapor from the atmosphere.

I

Igniter
A pyrotechnic device used to initiate burning of a fuel mixture or a propellant.

Ignition dropping
A method of loading explosives in which the explosive is mixed with a liquid vehicle and applied to the bridgewire. Also called primer spotting.

Incendiary
A highly exothermic composition or material that is primarily used to start fires.

Increment
The amount of pyrotechnic composition added to the charge, at one time, during the process of loading.

Inert
Descriptive of the condition of a device that contains no explosive, pyrotechnic or chemical agent.

Inhibited propellant
A propellant grain in which a portion of the surface area has been treated to control or prevent burning.

Initiation
The beginning of the deflagration or detonation of the explosive in an explosive item.

Initiator
A device used as the primary stimulus component in all explosive or pyrotechnic devices such as a detonator, primer or squib, which, upon receipt of the proper mechanical or electrical stimulus, produces a burning or detonating action.

Input test
A test applied to an explosive device to determine if it functions upon receiving proper stimulus.

L

Lead (pronounced ”leed”)
A column of high explosive used as one component of an explosive train.

Linear burning rate
The distance normal to any burning surface of the pyrotechnic or propellant burned through in unit time.

Loading density
The quantity of pyrotechnic or propellant composition per unit volume, usually expressed as grams per cubic centimeter.

Loose charging
Loading an explosive by pouring it into a container without any pressing. lot acceptance test (LAT) – See production lot sampling test.

Low explosive
One that burns or deflagrates rapidly, but does not detonate.

M

Melt loading
Process of loading an explosive device by melting the explosive and allowing it to solidify in the device. Also called casting.

N

No-fire current
Maximum current which can be applied to a bridgewire circuit without igniting the prime material.

O

One-amp/one-watt device
An EED which will not fire or degrade when one ampere and/or one watt is passed through the bridgewire circuit (usually for a five-minute period).

Output test
A test applied to an explosive device to determine if it does what it is required to do.

Oxidizer
A chemical compound which provides the oxygen for combustion. pellet – A free-standing, consolidated increment.

P

Percussion
A method of initiating an explosive device by a sudden sharp blow.

Piston actuator
A relatively small actuator which can receive a stimulus and provide a linear me- chanical output to move, puncture, etc.

Power
The rate of doing work.

Pressure cartridge
A pyrotechnic device in which a propellant is used to produce pressurized gas for a short duration.

Primary high explosive
One that detonates if merely ignited.

Primer
A primary initiating device to produce a hot flame. A primary stimulus component generally used to generate a brisant output for initiating detonating compositions.

Primer mixture
An explosive mixture containing a sensitive explosive and other ingredients, used in a primer.

Primer spotting
See ignition dropping.

Priming composition
A physical mixture of materials that is very sensitive to impact or percussion and, when so exploded, undergoes very rapid autocombustion.

Production lot sampling test (lot acceptance test)

Test conducted on a sample of a production lot to determine that the lot meets the specified dimensional and functional characteristics.

Progressive burning
The burning of a propellant grain in which the reacting surface area increases during the combustion.

Propellant
An explosive material whose rate of combustion is low. May be either solid or liq- uid.

Propellant-actuated device (PAD)
A mechanical device actuated by a contained or inserted propel- lant charge.

Pyrotechnic composition
A mixture of materials consisting essentially of an oxidizing agent (oxi- dant) and a fuel. It is capable of producing a self-sustaining reaction when heated to its ignition temperature.

Q

Qualification test
A series of tests conducted on an item or system to determine if it meets the requirements established for the specified use.

R

Recommended firing current
The current which must be applied to a bridgewire circuit to cause operation of the device within a specified time.

Recommended test current
The maximum current that can be applied to a bridgewire circuit for an extended period of time without degrading the prime material.

Relay
A explosive train component that, when initiated, provides the explosive energy needed to reliably initiate the next element in the train.

Reliability
A statistical evaluation of the probability of a device performing its designed function.

S

Safe
1) A mechanism that mechanically isolates the primary explosive from the subsequent elements of an explosive train. This keeps the item safe for handling until it is ready for use. 2) To activate a safing mechanism.

Safe-arm
A mechanical and/or electrical system used to arm and safe explosive devices.

Secondary high explosive
One that generally must be detonated by a detonating device.

Sensitivity
Susceptibility of an explosive pyrotechnic component to react to externally applied en- ergy or changes in environment.

Spark gap
A method of initiating an explosive device using high voltage that arcs across an air gap.

Squib
Used in a general sense to mean any of various small size pyrotechnic or explosive devices. Specifically, a small explosive device similiar in appearance to a detonator, but loaded with low explosive, so that its output is primarily heat (flash). Usually electrically initiated and provided to initiate action of pyrotechnic devices and rocket igniters.

Stability test
Accelerated test to determine the probable suitability of a pyrotechnic or explosive charge for a long-term storage under a variety of environmental conditions.

Stab
A method of initiating an explosive device that uses a small firing pin and friction-sensitive priming mix.

Stability
Ability of explosive or pyrotechnic materials to withstand long storage under service conditions.

Standard Deviation (sigma)
The square root of the sum of the squared deviations from the mean. For a given sample this must be divided by the sample size in order to correct for bias and be a proper estimate of the true population. A measure of the variability or dispersion of a number of observations.

Stoichiomefric
Relating to components involved in a burning process which are present in exactly the quantities needed for reaction, without an excess of any compound.

T

Thermate
An incendiary mixture of various combinations of thermite and barium nitrate, sulfur and flake aluminum.

Thermite
An incendiary or welding composition consisting of 2.75 parts black iron oxide (ferroso- ferric oxide) and 1.0 part aluminum powder.

V

Velocity of detonation
The rote at which a detonation front proceeds through a high-explosive charge, generally measured in thousands of feet or meters per second.

W

Wet blend
A combination of powders mixed with the aid of a liquid agent which is subsequently evaporated.

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