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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.
Acceptor
An explosive element that receives a detonating impulse from a previously exploded element, called a donor, and serves to propagate the detonation. An acceptor is also known as a receptor.

Acceptor Assembly Product Page

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.
Pyrotechnic Actuator Product Page
All-Fire Rating
Minimum stimulus which must be applied to a device for it to reliably function. The lowest level of energy which results in initiation of a first element within a specific reliability and confidence level as determined by test and analysis
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.
Application
Refers to the end item use of an explosive system, e.g., the space vehicle separation system, deployable mechanism, etc.
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.
Booster Charge
An explosive charge downstream of the first element of an explosive train that is used to cause ignition or detonation of a main explosive charge or to increase the energy output to the end item.
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 (Bruceton Test)
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. This approach includes estimates of mean ignitiona stimulus levels, standard deviations, all-fire and no-fire ratings. 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
Another term that may be used to describe an EED
Cartridge-actuated device (CAD)
A mechanical device actuated by a contained or inserted propellant charge.

Cartridge Actuated Device Product Page

Casting
See melt loading.
Charge
A quantity of explosive loaded in an explosive device
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.
Confined Detonating Cord (CDC)
A linear explosive transfer assembly where the explosive material is confined in a metallic sheath and various types of over wrap materials intended to limit radial expulsion of detonation products but promote linear propatation of detonation waves. Fittings at both ends of the assembly may be threaded, or otherwise configured for ease of installation in the application, and are configured to accept a detonation input and deliver a detonation output. Linear detonation wave velocities in typical CDC configurations are greater than 20K feet per second.
Controlled-burning squib
A hot gas/ flame producing device in which the output charge is de- signed to burn within the device.
Cook-off Temperature
The lowest temperature at which an exothermic reation of an explosive material occurs, i.e., detonation or deflagration.
Crossover
An explosive connection or link between redundant explosive trains.

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.
Deflagration to Detonation Transition (DDT)
A physical process that occurs with some secondary explosives in specific confinement, porosity and particle size conditions where the initial ignition event generates a deflagration wave front in the material that rapidly transitions to detonation.
Delay
A pyrotechnic or explosive train component that introduces a controlled time delay in the functioning of a device or fuze mechanism.

Delays Product Page

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.
Destruct Charge
An explosive assembly used to sever or penetrate through elements of a space vehicle to cause structual break-up or to disable propulsive systems.
Destruct Charge Product Page
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, High Order
A chemical reaction propagating with such rapidity that the rate of advance into the reaction zone of the un-reacted material exceeds the velocity of sound in the un-reacted material. This explosion generates extremely high temperatures and pressures that form shock waves that violently act on the surrounding environment. Detonation is not a surface phenomenon. The rate of advance of the reaction zone is termed detonation rate or detonation velocity. When this rate of advance attains such a value that it will continue without diminution through the un-reacted material, it is termed the stable detonation velocity.
Detonation, Low Order
A chemical reaction where the reaction rate is lower than the stable detonation velocity and higher than the reaction rate of a deflagration. An explosive charge that detonates low order is usually incapable of initiating a high order detonation in a succeeding secondary explosive charge.
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.
Detonators Product Page
Donor
An explosive charge that transmits a detonation output into succeeding explosive elements, the acceptor or receptor, of an explosive train.
Donor Assembly Product Page
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 charge or component that fails to fire or function upon receipt of the prescribed initiating stimulus. 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

Electro-explosive device (EED)
Any cartridge, squib, igniter, etc., which is initiated electrically. The first element of an explosive train. It is activated by electrical energy, joule heating, applied to an internal bridgewire that transfers energy to a primary explosive charge pressed over it. An EED may include other explosive charges downstream of the primary charge. Detonators, squibs, hot bridgewire devices, and cartridges when electrically actuated are EEDs.

Explode
To be changed in chemical or physical state, usually from a solid or liquid to a gas (as by chemical decomposition or sudden 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.

Explosing Foil Initiator (EFI)
An EED that requires high voltage inputs for actuation. These do not use primary explosive materials. Ignition occurs by application of high voltage to an internal membrane element that is then energized and rapidly propelled into a secondary explosive causing DDT.

Exploding Foil Initiator (EFI) Product Page

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 Nut Product Page
Explosive Ordnance
A term used in DOD-E-83578 and Mil-Std-1576 defined as any component or assembly containing, or operated by an explosive material.
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.
Explosive Transfer Assembly (ETA)
An explosive transfer assembly is an explosive train consisting of an assembly of linear charges used to transfer a detonation from an initiator to an end function. The purpose of the ETA is to allow the initiator to be located away from the end function for accessibility. An example is a solid motor igniter, located inside a spacecraft, connected to the initiator, located on the exterior of the spacecraft, by an ETA.
Esplosive Transfer System (ETS)
An assemblage of ETA components, inert connecting elements and other components, i.e., time delays, that transfers explosive energy to another ET element or to an explosive actuated device.
Explosively Formed Projectile (EFP)
An explosive device that when activated causes detonation products to act on an integral concave metallic liner that is projected at high velocity toward a predetermined target. The concave liner is reshaped during this process into a slug of metal simulating a finned projectile that can be used to penetrate space vehicle structures.

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.
Flexible Confined Detonating Cord (FCDC)
CDC whose over wrap material allows for flexure of the core for ease in handling and installation. Radial expulsion of detonation products may not be totally contained in this type of design.

Flexible Confined Detonating Cord Product Page

Flexible Linear Shaped Charge (FLSC)
A linear column of explosive material in a soft metal sheath, over wrapped with material that allows flexibility that when placed on a substrate and ignited causes severance or penetration. MDF can be configured to be a FLSC.
Flexible Linear Shaped Charge Product Page
Flight Termination System (FTS)
An explosive system that when actuated causes losses of integrity of space vehicle structural elements or propulsion systems. An FTS is used in applications requiring compliance with Eastern and Western Range Safety Regulations 127-1.
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.

Fuse Product Page

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 (HE)
One that detonates. Secondary explosives are also known as high explosives.
High Voltage Initiator (HVI)
Another name for an EBW device.
HMX
A secondary explosive chemically known as cyclo tetra methylene tetra nitramine, and is also known as either Her or His Majesties Explosive. HMX is by-product from the manufacture of RDX and can exhibit DDT characteristics.
HNS
A secondary explosive which is chemically known as hexa nitro stilbene.

HNS Initiator Product Page

Hot Bridge Wire Device (HBW)
Another name for a electro explosive device.
Hot Bridgewire Product Page

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.

Igniters Product Page

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.
Ignition System
The initial element of an explosive system that provides power, command and control of electrical, optical or mechanical input stimuli to the first element of an explosive train.

Impulse

In rocketry, product of the average thrust and the burning time.

Impulse Cartridges Product Page

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.

Inter-connect assembly

The Donor and Acceptor units make up the Inter-connect Assembly. The donor is a single or dual input port unit that has an extending piston. The Acceptor Assembly is a receiving unit designed to function when struck by the piston of the donor.

Inter-Connect Assembly Product Page

L

Laser Initiated Device (LID)
A first element containing secondary explosives that are ignited by energy produced from collimating coherent light excited in the infrared region of the electromagnetic spectrum. This energy density is optically transmitted by way of silicone fibers from crystalline rod or semiconductor diode lasers onto secondary explosives altered to enhance thermal absorption properties. The incident energy density is absorbed into the explosive allowing it to undergo DDT. The output energy of a LID can be configured to be equivalent to an EED.
Laser Initiated Ordnance System (LIOS)
An explosive system whose ignition system and explosive train are configured to use lased light energy sources to actuate a LID.

LIOS Product Page

Lead (pronounced ”leed”)
A column of high explosive used as one component of an explosive train.A lead is an explosive charge contained in a can or in pellet form used within a device to transfer a detonation from one point to another downstream of the first element.

Linear Explosive Assembly
Another name for an ETA.
Linear burning rate
The distance normal to any burning surface of the pyrotechnic or propellant burned through in unit time.
Linear Shaped Charge
A linear explosive charge in a metal sheath whose cross section is formed into a chevron shape. The chevron shape results in concentrated directionality of a jet of molten sheath material expelled perpendicular to the linear propagation of detonation waves. Properly positioned the LSC can be used to sever or penetrate a substrate. Optimum jet performance is obtained using dense yet ductile sheath materials like lead or nearly pure copper or aluminum.

Linear Shaped Charge Product Page

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.
Mild Detonating Cord (MDC) | Mild Detonating Fuse (MDF)
A linear explosive transfer assembly where the explosive material in confined in a metallic sheath and various types of over wrap materials intended to limit radial expulsion of detonation products but promote linear propagation of detonation waves. Linear detonation wave velocities in typical MDF configurations are greater than 20K feet per second. An MDC/MDF can be configured to sever or penetrate a substrate when placed in contact with it.

Mild Detonating Cord Product Page

N

No-fire current
Maximum current which can be applied to a bridgewire circuit without igniting the prime material.
NASA Standard Initiator (NSI)
An unique EED designed and used by the NASA for various applications. See Space Standard Initiator

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).

Ordnance Transfer Assembly (OTA)
Another name for an ETA.
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, such an in intential sudden pinching or crushing of the explosive material, as between a blunt firing pin and an anvil.
Percussion Fired Initiator Product Page
Percussion Fired Detonator Product Page
PETN
A secondary explosive chemically known as penta erythritol tetra nitrate. PETN can exhibit DDT characteristics.

Pin Puller

A mechanical device in which a pressure cartridge causes a pin or piston to retract, usually against a side load.

Pin Puller Product Page

Pin Pusher

A mechanical device in which a pressure cartridge drives a pin or piston along its central axis.

Pin Pusher Product Page

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.
Pressure Cartridge Product Page
Primary high explosive
One that detonates if merely ignited.A primary explosive is an explosive material that is extremely sensitive to heat or shock as the initiating mechanism, such as azides and styphnates. Primary explosives are normally used in first elements.
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.

Percussion Primer Product Page

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
A group of components or assemblies of a single type and size, fabricated at one place in a continuous manufacturing process using the same tooling and material batches.
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.
Pyrotechnics
Pyrotechnics are mixtures of fuels and oxidizers that may include organic binders and color intensifiers. Pyrotechnic compositions produce considerable amounts of heat and gases.

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

RDX
A high or secondary explosive chemically known as cyclo tri methylene tri nitramine, AKA Research and Development Explosive
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 Device
A mechanical and/or electrical system used to arm and safe explosive devices.A mechanical or electromechanical device that provides a means to remotely safe or arm an explosive train by means of a structural barrier in the train downstream of the first element.

Secondary high explosive
One that generally must be detonated by a detonating device. An explosive material that is relatively insensitive to heat or impact and must be initiated by a suitable primary explosive or another secondary explosive.

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

Shaped Charges
A severing or penetrating explosive actuated device whose physical shape is used to focus explosive energy in a desired direction. Shape charges include EFP and LSC designs.
Shielded Mild Detonating Cord (SMDC)
Same basic design as CDC except over wrap materials are designed to resist detonation by lateral high velocity impacts.

Shielded Mild Detonating Cord Product Page

Shock to Detonation Transition (SDT)
A process occurring when a shock wave impacting a secondary explosive is not strong enough to initiate detonation directly but does cause a chemical decomposition that accelerates until it becomes a self supporting detonation wave within the material.
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.

Squib Product Page

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.

Thru Bulkhead Initiator (TBI)
A thru bulkhead initiator is a high order detonation transfer element which propagates the detonation through an integral metal bulkhead by transmitting shock waves from the donor side to the acceptor side. The thru bulkhead initiator is generally used where complete sealing is needed between explosive elements after firing.
Thru Bulkhead Initiator Product Page

Thruster

An explosively activated, mechanical device designed to exert a thrust through a short stroke

Thrusters Product Page

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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