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A

Absolute Deviation
The shortest distance between the center of the target and the point where a projectile hits or bursts.
Absolute Error
Shortest distance between the center of impact or the center of burst of a group of shots and the point of impact or burst of a single shot within the group.
AC
Alternating current.
Acceptance Quality Level (AQL)
A nominal value expressed in terms of percentage defective per hundred units, by which a group of sampling plans is identified. The sampling plans so identified have a high probability of accepting lots containing material with a process average not greater than the designed value of the AQL.
Accuracy
Closeness to true value; not to be used indiscriminately as a synonym for precision which latter means reproducibility of measurement.
Accuracy Life

The estimated average number of rounds that a particular weapon can fire before its tube becomes so worn that its accuracy tolerance is exceeded.

Accuracy Of Fire
         The measurement of the precision of fire expressed as the distance of the center of impact from the            center of the target.

Acetone
Acetone or dimethyl ketone or 2-propanone (CH3COCH3), colorless, flammable liquid. Acetone is widely used in industry as a solvent for many organic substances and is a component of most paint and varnish removers. It is used in making synthetic Resins and fillers, smokeless powders, and many other organic compounds.
Acetylene
Acetylene or ethyne (HC CH), a colorless gas and the simplest alkyne ( Hydrocarbon). Explosive on contact with air, it is stored dissolved under pressure in Acetone. It is used to make neoprene rubber, plastics, and resins. The oxyacetylene torch mixes and burns oxygen and acetylene to produce a very hot flame—as high as 6300°F (3480°C)—that can cut steel and weld iron and other metals.
Acids & Bases
Acids and bases are two related classes of chemicals; the members of each class have a number of common properties when dissolved in a solvent, usually water. Acids in water solutions exhibit the following common properties: they taste sour; turn litmus paper red; and react with certain metals, such as zinc, to yield hydrogen gas. Bases in water solutions exhibit these common properties: they taste bitter; turn litmus paper blue; and feel slippery. When a water solution of acid is mixed with a water solution of base, a salt and water are formed; this process, called neutralization, is complete only if the resulting solution has neither acidic nor basic properties. When an acid or base dissolves in water, a certain percentage of the acid or base particles will break up, or dissociate, into oppositely charged ions. The Arrhenius theory of acids and bases defines an acid as a compound that can dissociate in water to yield hydrogen ions (H+) and a base as a compound that can dissociate in water to yield hydroxyl ions (OH-). The Brönsted-Lowry theory defines an acid as a proton donor and a base as a proton acceptor. The Lewis theory defines an acid as a compound that can accept a pair of electrons and a base as a compound that can donate a pair of electrons. Each of the three theories has its own advantages and disadvantages; each is useful under certain conditions. Strong acids, such as hydrochloric acid, and strong bases, such as potassium hydroxide, have a great tendency to dissociate in water and are completely ionized in solution. Weak acids, such as acetic acid, and weak bases, such as ammonia, are reluctant to dissociate in water and are only partially ionized in solution. Strong acids and strong bases make very good Electrolytes (see Electrolysis), i.e., their solutions readily conduct electricity. Weak acids and weak bases make poor electrolytes. Also Amphoterism; Buffer; Catalyst; Indicators Acids-Base Titration.
Actuator
A mechanical device, such as a pin puller, operated by a Pressure Cartridge.
Acoustic Impedance
A material’s acoustic impedance is the product of the material’s sound speed multiplied by the material’s density.
Acoustics
The science of Sound, including its production, propagation, and effects. An important practical application of acoustics is in the designing of auditoriums, which requires a knowledge of the characteristics of sound Waves. Reflection of sound can cause an Echo, and repeated reflections in an enclosed space can cause reverberation, the persistence of sound. Some reverberation in auditoriums is desirable to avoid deadening the sound of music. Reflection can be reduced through the proper configuration and texture of walls, and by the use of sound-absorbent materials. Another acoustical problem is Interference, which can create “dead spots” in auditoriums for certain frequencies.
Actinide Series
The radioactive metals, with atomic numbers 89 through 103, in group IIIb of the periodic table. They are Actinium, Thorium, Protactinium, Uranium, Neptunium, Plutonium, Americium, Curium, Berkelium, Californium, Einsteinium, Fermium, Mendelevium, Nobelium, and Lawrencium. All members of the series have chemical properties similar to actinium. Those elements with atomic numbers greater than 92 are called Transuranium Elements.
Additive
Something added to a basic composition to accomplish some special purpose - mostly in small proportions.
Adhesion
Adhesion and cohesion, attractive forces between material bodies. Adhesive forces act between different substances, whereas cohesive forces act within a single substance, holding its atoms, ions, or molecules together. Without these forces, solids and liquids would act as gases. Surface Tension in liquids results from cohesion, and Capillarity results from a combination of adhesion and cohesion. Friction between two solid bodies depends in part on adhesion.
 
Adiabatic
Occurring without gain or loss of heat; a change of the properties, such as volume and pressure of the contents of an enclosure, without exchange of heat between the enclosures and its surroundings.
Adiabatic Flame Temperature
As applied to interior ballistics calculation, the temperature which the gaseous products of combustion of the propellant would attain if maintained at constant volume and without loss of energy to the surrounding medium.
Adiabatic Temperature
The temperature attained by a system undergoing a volume or pressure change in which no heat enters or leaves the system.
Aerosol
A mixture of extremely fine liquid or solid particles and a gas or air such as smoke or fog.
Aerodynamics
Aerodynamics is the study of gases in motion. Because the principal application of aerodynamics is the design of airplanes, air is the principal gas with which this science is concerned. Bernoulli's principle, which states that the pressure of a moving gas decreases as its velocity increases, has been used to explain the lift produced by a wing having a curved upper surface and a flat lower surface ( Airfoil). Because the flow is faster across the curved surface than across the plane one, a greater pressure is exerted in the upward direction. Aerodynamics is also concerned with the drag caused by air friction, which is reduced by making the surface area of the craft as small as possible. At speeds close to the speed of sound, or Mach 1 ( mach number), there is also a large, sudden increase of drag, which has been called the sonic, or sound, barrier. Aerodynamics is also used in designing automobile bodies and trains for minimum drag and in computing wind stresses on bridges, buildings, and the like. The wind tunnel is one of the basic experimental tools of the aerodynamicist. Shock wave; Sonic boom.
Afterburner
An auxiliary combustion chamber in certain jet engines.
Agglomeration
The property of particles to cohere, thereby increasing apparent particle size.
Air Blast
The airborne shock wave or acoustic transient generated by an explosion.
Air Burst
A burst of a projectile or bomb above the ground.
Airfoil
A surface designed to develop a desired force by reaction with a fluid, especially air, that is flowing across the surface. Examples of airfoils are the fixed wings of airplanes, which produce lift ( aerodynamics), and control surfaces, such as ailerons, elevators, rudders, and flaps, that are manipulated to produce variable forces. Other airfoils include spoilers, propeller blades, and the blades utilized in turbojet engines.
Alcohol
Alcohol is any of a class of organic compounds with the general formula R-OH, where R is an alkyl group made up of carbon and hydrogen and -OH is one or more hydroxyl groups, each made up of one atom of oxygen and one of hydrogen. Although the term alcohol ordinarily refers to Ethanol, the alcohol in alcoholic beverages, the class of alcohol also includes Methanol and the amyl, butyl, and propyl alcohols, all with one hydroxyl group; the glycols, with two hydroxyl groups; and glycerol, with three. Many of the characteristic properties and reactions of alcohols are due to the polarity, or unequal distribution, of electric charges in the C-O-H portion of the molecule.
Alkali
Alkali, Hydroxide of an Alkali Metal. Alkalies are soluble in water and form strongly basic solutions. They neutralize acids, forming salts and water. Strong alkalies (e.g., those of sodium or potassium) are called caustic alkalies. The term alkali is sometimes applied to sodium or potassium carbonate or to the hydroxide of an Alkaline-Earth Metal.
Alkali Metals
Alkali metals are elements in group Ia of the Periodic Table. In order of increasing atomic number, they are Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium. They are softer than other metals, and have lower melting points and densities. All react violently with water, releasing hydrogen and forming hydroxides. They tarnish rapidly, even in dry air. They never occur uncombined in nature.
Alkaline-Earth Metals
Alkaline-earth metals are elements in group IIa of the Periodic Table. In order of increasing atomic number, they are Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium. They are softer than most other metals and react readily with water. Their properties are exceeded by the corresponding Alkali Metal.
All-Fire Current
The minimum amperage (or wattage) level which must be applied to a bridgewire circuit to reliably ignite the surrounding explosive material without regard to the time of operation. Operation at all-fire level should be avoided.
Allotropy
The occurrence of certain chemical elements in two or more forms; the forms are called allotropes. Allotropes generally differ in physical properties, such as color and hardness; they may also differ in molecular structure or in chemical activity but are usually alike in most chemical properties. Diamondand Graphite are two allotropes of the element Carbon.
Alpha Particle
A particle emitted in one of the three forms of natural Radioactivity.
Aluminized Explosive
A high explosive to which aluminum powder or flake has been added. Metallized.
Amatol
High explosive made of a mixture of ammonium nitrate and trinitrotoluene; sometimes used as a bursting charge in high-explosive projectiles.
Ambient
Surrounding meteorological conditions such as ambient temperature, humidity and pressure.
Amine
A type of organic compound containing the NH2 group. (Example: ethylendiamine.)
Amino acid
An amino acid is any of a class of organic compounds having a carboxyl group (COOH) and an amino group (NH2). Some 22 amino acids are commonly found in animals and more than 100 less common forms are found in nature, chiefly in plants. When the carboxyl carbon atom of one amino acid binds to the nitrogen of another with the release of a water molecule, a linkage called a peptide bond is formed. Chains of amino acids, joined head-to-tail in this manner, are synthesized by living systems and are called polypeptides (up to about 50 amino acids) and Proteins (over 50 amino acids). The process of digestion releases individual amino acids from food protein by cleaving to the peptide bonds.
Ammine
An inorganic compound containing NH3 molecules as part of a complex salt or coordination compound. (Example: hexammine cobalt (III) nitrate; also spelled hexaammine.)
Ammonia
Ammonia is a chemical compound (NH3), colorless gas with a characteristic pungent, penetrating odor. It is extremely soluble in water. Ammonia solutions are used to clean, bleach, and deodorize; to etch aluminum; to saponify oils and fats; and in chemical manufacture. Ammonia and ammonia vapors are irritating—prolonged exposure and inhalation cause serious injury and may be fatal. Water-free ammonia is used in refrigeration. The major use of ammonia and its compounds is as Fertilizers. Ammonia is usually produced by direct combination of nitrogen with hydrogen at high temperature and pressure in the presence of a catalyst.
Ammonium Nitrate
The ammonium salt of nitric acid represented by the formula NH4NO3 .
Ammonium Nitrate Satchel Charge
A mixture of ammonium nitrate fertilizer and melted wax. The mixing ratio is 4 pounds of fertilizer to 1 pound of wax.
Ammonium Perchlorate
Material to be added.
Ammonol
High-explosive substance made of a mixture of ammonium nitrate, trinitrotoluene, and flaked or powdered aluminum. Ammonal is sometimes used as a bursting charge in high-explosive projectiles, and produces bright flashes on detonation.
Ammunition
Generic term for all kinds of missiles, explosive and pyrotechnic devices. Ordnance means, in addition, also non-offensive military items. Munition(s) equals ordnance.
Ammunition Data Card
Identification card prepared for each individual lot of ammunition manufactured, giving the type and composition of the ammunition, and identifying its components by lot number and manufacturer. When necessary, it may also include instructions for handling the ammunition.
Ampere
A unit of electrical current produced by 1 volt acting through a resistance of 1 ohm. Also referred to as an “amp” or “amps”.
Amphibious Warfare
Amphibious Warfare describes the use of combined land and sea forces to take a military objective, typically through an air-supported assault on an enemy coastline. Although the strategy is ancient, e.g., the Athenian attack on Sicily in 415 BC, the term came into widespread use during WW II. Early in the war, coordinated land, sea, and air attacks by the Japanese in the SW Pacific met little opposition. By contrast, Allied attacks on Europe and the Pacific islands were mounted against heavily defended coasts, requiring construction of special vessels (called landing craft) that were seaworthy and yet capable of allowing Tanks and fully equipped Infantry to disembark in shallow water. Such landings were preceded and accompanied by continuous air and naval bombardment of coastal defenses. By this method the Allies were able to invade such Pacific strongholds as Saipan (1944), Iwo Jima (1945), and Okinawa (1945), and to launch the most spectacular amphibious invasion in history, on the coast of Normandy, France, on June 6, 1944. Amphibious landings later occurred in the Korean War and Vietnam War and in the British attack (1982) on the Falkland Islands.
Amphoterism
Amphoterism, in chemistry, the property of certain compounds of acting either as acids or as bases ( Acids & Bases), depending on the reaction in which they are involved. Many hydroxide compounds and organic molecules that contain both acidic (e.g., carboxyl) and basic (e.g., amino) Functional Groups are usually amphoteric.
Amplifier
Amplifier, a device in which a varying input signal controls a flow of energy to produce an output signal that varies in the same way but has a larger amplitude; the input signal may be a current, a voltage, a mechanical motion, or any other signal, and the output signal is usually of the same nature. The ratio of the output voltage to the input voltage is called the voltage gain. The most common types of amplifiers are electronic and have Transistors as their principal components. In most cases today, transistors are incorporated into Integrated Circuits chips. Most amplifiers include more than one transistor. Transistor amplifiers are used in Radio and Television transmitters and receivers, stereophonic record players, and intercoms.
AN
Ammonium nitrate.
AN/FO
A commercial blasting agent consisting of AN and fuel oil.
AN slurry
Ammonium Nitrate Slurry.
Analysis
A branch of mathematics that uses the concepts and methods of the Calculus. It includes basic calculus; advanced calculus, in which such underlying concepts as that of a Limit are subjected to rigorous examination; differential and integral equations, in which the unknowns are functions rather than numbers; Vector and tensor analysis; differential geometry; and many other fields.
Angle Attack
A method of attack used in bridge demolition.
Angle Of Departure
Angle between the line of sight and the axis of the bore of a gun at the instant the projectile leaves the muzzle. Angle of departure is the sum of the angles of site, elevation and vertical jump.
Angle Of Fall
Angle between the horizontal and the tangent to the trajectory at the point at which a projectile falls.
Angle Of Impact
Acute angle between the tangent to the trajectory at the point of impact of a projectile and the plane tangent to the surface of the ground at the point of impact; angle at which a projectile strikes the ground or target.
Anode
The positive pole of a direct current device. Opposite Cathode (adj.: anodic).
Antenna
Antenna or aerial, a system of wires or other conductors used to transmit or receive radio or other electromagnetic waves ( Radio; Television). In a transmitting antenna, the signal from an Electrical Circuit causes electrons in the antenna to oscillate; these moving electric charges generate Electromagnetic Radiation, which is then transmitted through space. The distribution pattern of the transmitted wave depends on the design of the antenna; radio broadcast-station antennas are frequently designed to emit waves in all directions, whereas those used for Radar and for certain communication systems focus the waves in a single direction. In a receiving antenna, electromagnetic waves cause the electrons in the antenna to oscillate, inducing a signal that can be detected by an electric circuit. In general, a longer antenna is used to transmit or receive signals of longer wavelengths. Theoretically, the same antenna can be used both for sending and for receiving signals, but in practice, transmitting antennas are constructed to handle higher power loads than receiving antennas.
Antifreeze
Antifreeze is a substance added to a solvent to lower its freezing point. Antifreeze is typically added to water in the cooling system of internal combustion engines so that it may be cooled below the freezing point of pure water (32° F or 0° C) without freezing. Automotive antifreezes include ethylene glycol (the most widely used), methanol, ethanol, isopropyl alcohol, and propylene glycol. WARNING: Straight antifreeze can be deflagrated and / or be very flammable if directly exposed to a high explosive detonation.
Antimatter
Material composed of antiparticles, which correspond to ordinary protons, electrons, and neutrons but have the opposite electrical charge and magnetic moment. When matter and antimatter collide, both may be annihilated, and other Elementary Particles, such as photons and pions, are produced. In 1932 Carl D. Anderson, while studying cosmic rays, discovered the positron, or antielectron, the first known antiparticle. Any antimatter in our part of the universe is necessarily very short-lived because of the overwhelming preponderance of ordinary matter, by which the antimatter is quickly annihilated.
Antipersonnel (AP)
Designed to kill, wound or obstruct single persons.
Anti-Removal Device
A mechanical device which prevents de-fuzing of a land mine, etc., setting it off in the attempt.
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. Because apparent density depends on the method used to obtain it, the method should always be specified. Bulk Density.
 
 
Approx.
Approximately.
Archimedes' Principle
The Archimedes' principle states that a body immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid. The principle applies to both floating and submerged bodies, and to all fluids. It explains not only the buoyancy of ships but also the rise of a helium-filled balloon and the apparent loss of weight of objects underwater.
Area Target
Target or gunfire or bombing covering a considerable space, such as ammunitions factory, airport or freight yard. An area target differs from a point target, which is a particular object or structure.
Argon
(Ar), gaseous element, discovered in 1894 by Sir William Ramsay and Lord Rayleigh. An odorless, tasteless, and colorless inert gas, it makes up 0.93% of the atmosphere by volume. Argon is used in light bulbs and neon signs, in refining reactive elements, and for protection in arc welding.
Arm-To-Arm
As applied to fuses, the changing from an armed condition to a state of readiness for initiation.
Arming
As applied to fuzes, the changes from a safe condition to a state of readiness for initiation. Generally a fuze is caused to arm by acceleration, rotation, clock mechanism or air travel, or by combinations of these. Armor Protective covering, especially metal plates used on ships, tanks, motor vehicles, etc.
Armor Piercing
A term applied to bullets and projectiles designed to pierce armor plate.
Army
An army is a land based armed force under regular military organization, as distinguished from the horde, or armed mass of all able-bodied men in a tribe. The earliest known professional army was that of Egypt, followed by those of Assyria and Persia. Military service became obligatory for citizens of Greece. The Roman army evolved from a citizen soldiery into a professional standing army increasingly composed of barbarian mercenaries. In the Middle Ages, the armed knight and yeoman owed a set number of days of military service each year to a great lord; but with the decline of feudalism and the advent of firearms, this system also gave way to the service of mercenaries. In the 1t7 h century. Louis XIV of France organized a national standing army that set the pattern for all of Europe: a highly disciplined, professional body set apart from civilian life. The concept reached a harsh perfection under Frederick II of Prussia. It was the introduction of conscription during the French Revolutionary Wars that set in motion the development of modern mass armies built around a professional nucleus and organized into specialized units for combat and support. Although conscription was used in the U.S. Civil War and WW I, the U.S., until 1940, traditionally relied in emergencies on its citizen militia, the National Guard, and on voluntary enlistment in the armed forces; the peacetime draft was again lifted in 1973. The term army generally applies to all armed land forces of a nation (e.g., the French army); it can also designate a self-contained fighting force in a given area (e.g., the Army of the Potomac in the U.S. Civil War) or a unit of 100,000 men composed of two or more corps. A corps in turn is composed of two or more divisions (usually about 15,000 men). Traditionally, an army was made up of major Infantry, Cavalry, and Artillery commands, but these gave way to more complex forms of organization. Today, each division typically includes infantry, airborne, mechanized, and other specialized battalions or brigades.
ARNG
US term for Army National Guard.
Aromatic Compound
An aromatic compound is any of a large class of organic compounds including Benzene and compounds that resemble benzene in chemical properties. Aromatic compounds contain unusually stable ring structures, often made up of six carbon atoms arranged hexagonally. Some of the compounds, however, have rings with more or fewer atoms, not necessarily all carbon. Furan, for example, has a ring with four atoms of carbon and one of oxygen. Also, two or more rings can be fused, as in naphthalene. The characteristic properties of the class, notably the stability of the compounds, derive from the fact that aromatic rings permit the sharing of some electrons by all the atoms of the ring, which increases the strength of the bonds.
Artillery
Artillery is a term now applied to heavy firearms, as distinguished from Small Arms. It came into use in the mid-14th century with the introduction in Europe of Gunpowder, which had been discovered many centuries earlier in China. First employed mainly against fortifications, artillery was increasingly used in the field from the early 17th century. It was characteristically smooth-bore and muzzle-loaded, firing solid, round shot, until the late 19th century, when breech-loaded, rifled, and shell-firing artillery became standard. Modern artillery includes a variety of long-range guns that fire their shells with rapid muzzle-velocity in a low arc; howitzers, which fire on a high trajectory at relatively nearby targets; antiaircraft guns, which fire rapidly and at high angles; armor-piercing antitank guns; and many field-artillery pieces used in support of infantry and other ground operations. Mobility has become a key factor in the usefulness of heavy firearms, most of which now either are self-propelled or can be towed. Ash Combustion products, usually in the form of slag or crust, accumulating at the surface, along the cavity wall and immediately beyond the flame area, which tend to interfere with combustion and visibility of the flame or colored smoke or pyrotechnic ammunition.
ASP
Ammunition Supply Point.
Astronomical Unit
Astronomical unit (AU), means distance between the earth and the sun. One AU is c.92,960,000 mi (149,604,970 km).
AT
Antitank.
Atmosphere
The envelope of air surrounding the earth; also, the body of gases surrounding or comprising any planet or other celestial body. Atmospheric pressure may be measured as weight per area. On earth, normal air pressure at sea level is 14.7 pounds of weight per square inch, or 1033 grams of weight per square centimeter. Expressed in more formal units of force per area, one atmosphere is equal to 1,013,300 dynes/cm2. One million dynes per square centimeter has been set equal to one bar, therefore one atmosphere is equal to 1.0133 bars.
Atom
The atom is the smallest unit of a chemical Element having the properties of that element. An atom contains several kinds of particles. Its central core, the nucleus, consists of positively charged particles, called Protons, and uncharged particles, called Neutrons. Surrounding the nucleus and orbiting it are negatively charged particles, called Electrons. Each atom has an equal number of protons and electrons. The nucleus occupies only a tiny fraction of an atom's volume but contains almost all of its mass. Electrons in the outermost orbits determine the atom's chemical and electrical properties. The number of protons in an atom's nucleus is called the Atomic Number. All atoms of an element have the same atomic number and differ in atomic number from atoms of other elements. The total number of protons and neutrons combined is the atom's Mass Number. Atoms containing the same number of protons but different numbers of neutrons are different forms, or Isotopes, of the same element. Atomic Weight.
Atomic Bomb
A weapon deriving its great explosive force from the sudden release of Nuclear Energy through the fission, or splitting, of heavy atomic nuclei. The first atomic bomb was successfully tested by the U.S. near Alamogordo, N.Mex., on July 16, 1945 ( Manhattan Project). In the final stages of World War II the U.S. dropped atomic bombs on Hiroshima on Aug. 6, 1945, and on Nagasaki three days later to force Japan to surrender. Atomic bombs were subsequently developed by the USSR (1949), Great Britain (1952), France (1960), China (1964), and India (1974), and a number of other nations, particularly Pakistan, South Africa, and Israel, are believed to have atomic bombs or the capability to produce them readily. Practical fissionable nuclei for atomic bombs are the isotopes Uranium-235 andPlutonium-239, which are capable of undergoing chain reaction. If the mass of the fissionable material exceeds the critical mass, the chain reaction multiplies rapidly into an uncontrollable release of energy. An atomic bomb is detonated by bringing together very rapidly (e.g., by means of a chemical explosion) two subcritical masses of fissionable material. The ensuing explosion produces great amounts of heat, a shock wave, and intense neutron and gamma radiation. The region of the explosion becomes radioactively contaminated, and wind-borne radioactive products may be deposited elsewhere as fallout. Nuclear, Hydrogen Bomb.
Atomic Number
Often represented by the symbol Z, the number of Protons in the nucleus of an Atom. Atoms with the same atomic number make up a chemical Element. The elements are arranged in the Periodic Table in the order of their atomic numbers. Atomic Weight
Mean (weighted average) of the masses of all the naturally occurring Isotopes of a chemical Element; the atomic mass is the mass of any individual isotope. Atomic weight is usually expressed in atomic mass units (amu); the atomic mass unit is defined as exactly 1/12 the mass of a carbon-12 atom. Each proton or neutron weighs about 1 amu, and thus the atomic mass is always very close to the Mass Number (total number of protons and neutrons in the nucleus). Because most naturally occurring elements have one principal isotope and only insignificant amounts of other isotopes, most atomic weights are also very nearly whole numbers. For the atomic weight of individual elements, see Element.
Atomized
In pyrotechnics, an atomized metal powder consists of regular spherical particles which may be as small as 5 microns in diameter.
Attitude
The position or orientation of an aircraft, spacecraft, munition, device, etc., either in motion or at rest, as determined by the relationship between its axes and some reference line or plane such as the horizon.
Attn.
Attention.
Aurora
The sporadic visible emission from the upper atmosphere over middle and high latitudes. Also called "northern lights" in the northern hemisphere.
Autogenous Pressurization System
Pressurizing tanks with available propulsion system propellant gases, on-board devices.
Autoignition
A temperature is reached at which the rate of reaction is so rapid that deflagration occurs.
Automatic (self-acting)
Moving or acting by itself. After the first round is fired, an automatic weapon fires, extracts, ejects and reloads without application of power from an outside source, repeating the cycle as long as the firing mechanism is held in the proper position. Automatic action involves repeating the cycle of operation, as distinguished from semi-automatic, which is restricted to one complete cycle at a time.
Automatic Feed Mechanism
Mechanism in an automatic gun that puts fresh shells into the chamber in position for firing.
Auxplosive Group
Atom groupings commonly present in a high explosive, but which by their presence do not produce an explosive. They can, however, have an effect upon the power of an explosive, usually not in a helpful direction.
Average Burning Rate
The arithmetic mean (statistical average) burning rate of pyrotechnic or propellants at specific pressures and temperatures. Dimension - length/time or mass/time.
AVLB
Armored vehicle launch bridge.
Axis
A straight line about which a body rotates, or around which a plane figure may rotate to produce a solid; a line symmetry. One of a set of reference lines for certain systems of coordinates. (Plural: axes).

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