Propellant
Encyclopedia
A propellant is a material that produces pressurized gas that:
Common chemical propellants are energetic materials and consist of a fuel
; like gasoline
, jet fuel
, rocket fuel, and an oxidizer. Chemical propellants are burned or otherwise decomposed to produce the propellant gas. Other propellants are simply liquids that can readily be vaporized into the desired pressurized gas. Such propellants include the nitrous oxide
that is dissolved in the butterfat
canned whipped cream
, and the dimethyl ether
or low-boiling alkane
used in hairspray
.
Propellants are used in pressurised dispensing systems, such as aerosol sprays, to force a material through a nozzle.
In rockets, the propellant produces an exhaust and the exhausted material is usually expelled under pressure through a nozzle
. The pressure may be from a compressed gas, or a gas produced by a chemical reaction. The exhaust material may be a gas
, liquid
, plasma
, or, before the chemical reaction, a solid, liquid or gelled.
In aircraft, the propellant is usually a fuel and is combusted to generate energy to power the aircraft's flight.
cans, the propellant is simply a pressurized gas in equilibrium with its liquid (at its saturated vapour pressure). As some gas escapes to expel the payload, more liquid evaporates, maintaining an even pressure. (See aerosol spray propellant for more information.)
Amongst the English-speaking laymen, used to having fuels propel vehicles on Earth, the word fuel is inappropriately used. In Germany, the word Treibstoff—literally "drive-stuff"—is used; in France, the word ergols is used; it has the same Greek roots as hypergolic, a term used in English for propellants which combine spontaneously and do not have to be set ablaze by auxiliary ignition system.
In rocket
s, the most common combinations are bipropellants, which use two chemicals, a fuel and an oxidiser. There is the possibility of a tripropellant combination, which takes advantage of the ability of substances with smaller atoms to attain a greater exhaust velocity, and hence propulsive efficiency, at a given temperature.
Although not used in practice, the most developed tripropellant systems involves adding a third propellant tank containing liquid hydrogen to do this.
and pyrotechnics
, a propellant is a generic name for chemicals used for propelling projectiles from guns and other firearms.
Propellants are usually made from low explosive materials, but may include high explosive chemical ingredients that are diluted and burned in a controlled way (deflagration
) rather than detonation
. The controlled burning of the propellant composition usually produces thrust
by gas
pressure
and can accelerate a projectile
, rocket
, or other vehicle. In this sense, common or well known propellants include, for firearm
s, artillery
and solid propellant rocket
s:
Propellants that explode in operation are of little practical use currently, although there have been experiments with Pulse Detonation Engine
s.
There are three types of burns that can be achieved with different grains.
Progressive Burn: Usually a grain with multiple perforations or a star cut in the center providing a lot of surface area.
Digressive Burn: Usually a solid grain in the shape of a cylinder or sphere.
Neutral Burn: Usually a single perforation; as outside surface decreases the inside surface increases at the same rate.
Triple Based Propellant: Triple based propellants consist of nitrocellulose, nitroquanidine, nitroglycerin or other liquid organic nitrate explosives. Triple based propellants are used in cannons.
Composite: Composites contain no nitrocellulose, nitroglycerin, nitroquanidine or any other organic nitrate. Composites usually consist of a fuel such as metallic aluminum, a binder such as synthetic rubber, and an oxidizer such as ammonium perchlorate. Composite propellants are used in large rocket motors.
Common monopropellant used for liquid rocket engines include:
- can be directed through a nozzle, thereby producing thrust (rocket propellant used in a rocket motor);
- fills the interior of an ammunition cartridge or the chamber of a gun or cannon, leading to the expulsion of a bullet or shell (gunpowderGunpowderGunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...
, smokeless powderSmokeless powderSmokeless powder is the name given to a number of propellants used in firearms and artillery which produce negligible smoke when fired, unlike the older gunpowder which they replaced...
, and large gun propellants); - can fill an expansible bag or membrane, such as an automotive airbag (gas generator propellants).
Common chemical propellants are energetic materials and consist of a fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...
; like gasoline
Gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
, jet fuel
Jet fuel
Jet fuel is a type of aviation fuel designed for use in aircraft powered by gas-turbine engines. It is clear to straw-colored in appearance. The most commonly used fuels for commercial aviation are Jet A and Jet A-1 which are produced to a standardized international specification...
, rocket fuel, and an oxidizer. Chemical propellants are burned or otherwise decomposed to produce the propellant gas. Other propellants are simply liquids that can readily be vaporized into the desired pressurized gas. Such propellants include the nitrous oxide
Nitrous oxide
Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...
that is dissolved in the butterfat
Butterfat
Butterfat or milkfat is the fatty portion of milk. Milk and cream are often sold according to the amount of butterfat they contain.- Composition :The fatty acids of butterfat are typically composed as follows :...
canned whipped cream
Whipped cream
Whipped cream is cream that has been beaten by a mixer, whisk, or fork until it is light and fluffy. Whipped cream is often sweetened and sometimes flavored with vanilla, in which case it may be called Chantilly cream or crème Chantilly ....
, and the dimethyl ether
Dimethyl ether
Dimethyl ether , also known as methoxymethane, is the organic compound with the formula . The simplest ether, it is a colourless gas that is a useful precursor to other organic compounds and an aerosol propellant. When combusted, DME produces minimal soot and CO, though HC and NOx formation is...
or low-boiling alkane
Alkane
Alkanes are chemical compounds that consist only of hydrogen and carbon atoms and are bonded exclusively by single bonds without any cycles...
used in hairspray
Hairspray
Hairspray may refer to:* Hair spray, a personal grooming product* Hairspray , a film by John Waters** Hairspray , the film's soundtrack album* Hairspray , a stage musical based on the original film...
.
Propellants are used in pressurised dispensing systems, such as aerosol sprays, to force a material through a nozzle.
In rockets, the propellant produces an exhaust and the exhausted material is usually expelled under pressure through a nozzle
Nozzle
A nozzle is a device designed to control the direction or characteristics of a fluid flow as it exits an enclosed chamber or pipe via an orifice....
. The pressure may be from a compressed gas, or a gas produced by a chemical reaction. The exhaust material may be a gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
, liquid
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...
, plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
, or, before the chemical reaction, a solid, liquid or gelled.
In aircraft, the propellant is usually a fuel and is combusted to generate energy to power the aircraft's flight.
Aerosol sprays
In aerosol sprayAerosol spray
Aerosol spray is a type of dispensing system which creates an aerosol mist of liquid particles. This is used with a can or bottle that contains a liquid under pressure. When the container's valve is opened, the liquid is forced out of a small hole and emerges as an aerosol or mist...
cans, the propellant is simply a pressurized gas in equilibrium with its liquid (at its saturated vapour pressure). As some gas escapes to expel the payload, more liquid evaporates, maintaining an even pressure. (See aerosol spray propellant for more information.)
Propellant used for propulsion
Technically, the word propellant is the general name for chemicals used to create thrust. For vehicles, the term propellant refers only to chemicals that are stored within the vehicle prior to use, and excludes atmospheric gas or other material that may be collected in operation.Amongst the English-speaking laymen, used to having fuels propel vehicles on Earth, the word fuel is inappropriately used. In Germany, the word Treibstoff—literally "drive-stuff"—is used; in France, the word ergols is used; it has the same Greek roots as hypergolic, a term used in English for propellants which combine spontaneously and do not have to be set ablaze by auxiliary ignition system.
In rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
s, the most common combinations are bipropellants, which use two chemicals, a fuel and an oxidiser. There is the possibility of a tripropellant combination, which takes advantage of the ability of substances with smaller atoms to attain a greater exhaust velocity, and hence propulsive efficiency, at a given temperature.
Although not used in practice, the most developed tripropellant systems involves adding a third propellant tank containing liquid hydrogen to do this.
Solid propellant
In ballisticsBallistics
Ballistics is the science of mechanics that deals with the flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.A ballistic body is a body which is...
and pyrotechnics
Pyrotechnics
Pyrotechnics is the science of using materials capable of undergoing self-contained and self-sustained exothermic chemical reactions for the production of heat, light, gas, smoke and/or sound...
, a propellant is a generic name for chemicals used for propelling projectiles from guns and other firearms.
Propellants are usually made from low explosive materials, but may include high explosive chemical ingredients that are diluted and burned in a controlled way (deflagration
Deflagration
Deflagration is a term describing subsonic combustion that usually propagates through thermal conductivity; hot burning material heats the next layer of cold material and ignites it. Most "fire" found in daily life, from flames to explosions, is deflagration...
) rather than detonation
Detonation
Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives, as well as in reactive gases...
. The controlled burning of the propellant composition usually produces thrust
Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
by gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
and can accelerate a projectile
Projectile
A projectile is any object projected into space by the exertion of a force. Although a thrown baseball is technically a projectile too, the term more commonly refers to a weapon....
, rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
, or other vehicle. In this sense, common or well known propellants include, for firearm
Firearm
A firearm is a weapon that launches one, or many, projectile at high velocity through confined burning of a propellant. This subsonic burning process is technically known as deflagration, as opposed to supersonic combustion known as a detonation. In older firearms, the propellant was typically...
s, artillery
Artillery
Originally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...
and solid propellant rocket
Solid rocket
A solid rocket or a solid-fuel rocket is a rocket engine that uses solid propellants . The earliest rockets were solid-fuel rockets powered by gunpowder; they were used by the Chinese in warfare as early as the 13th century and later by the Mongols, Arabs, and Indians.All rockets used some form of...
s:
- Gun propellants, such as:
- GunpowderGunpowderGunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...
(black powder) - NitrocelluloseNitrocelluloseNitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton...
-based powders - CorditeCorditeCordite is a family of smokeless propellants developed and produced in the United Kingdom from 1889 to replace gunpowder as a military propellant. Like gunpowder, cordite is classified as a low explosive because of its slow burning rates and consequently low brisance...
- BallistiteBallistiteBallistite is a smokeless propellant made from two high explosives, nitrocellulose and nitroglycerine. It was developed and patented by Alfred Nobel in the late 19th century.-The development of smokeless powders:...
- Smokeless powderSmokeless powderSmokeless powder is the name given to a number of propellants used in firearms and artillery which produce negligible smoke when fired, unlike the older gunpowder which they replaced...
s
- Gunpowder
- Composite propellants made from a solid oxidizer such as ammonium perchlorateAmmonium perchlorateAmmonium perchlorate is an inorganic compound with the formula NH4ClO4. It is the salt of perchloric acid and ammonia. It is a powerful oxidizer, which is why its main use is in solid propellants...
or ammonium nitrate, a rubber such as HTPB, or PBANPBANPolybutadiene acrylonitrile copolymer, also noted as polybutadiene — acrylic acid — acrylonitrile terpolymer.This was the binder formulation widely used on the 1960-70's big boosters...
(may be replaced by energetic polymers such as polyglycidyl nitrate or polyvinyl nitratePolyvinyl nitratePolyvinyl nitrate is a polymeric explosive material, an ester of nitric acid and polyvinyl alcohol. It is prepared by nitration of polyvinyl alcohol or transesterification of polyvinyl acetate...
for extra energy) , optional high explosive fuels (again, for extra energy) such as RDXRDXRDX, an initialism for Research Department Explosive, is an explosive nitroamine widely used in military and industrial applications. It was developed as an explosive which was more powerful than TNT, and it saw wide use in WWII. RDX is also known as cyclonite, hexogen , and T4...
or nitroglycerin, and usually a powdered metalMetalA metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
fuelFuelFuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...
such as aluminum. - Some amateurAmateur rocketryAmateur rocketry, sometimes known as amateur experimental rocketry or experimental rocketry is a hobby in which participants experiment with fuels and make their own rocket motors, launching a wide variety of types and sizes of rockets...
propellants use potassium nitratePotassium nitratePotassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...
, combined with sugarSugarSugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
, epoxyEpoxyEpoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....
, or other fuels / binder compounds. - Potassium perchloratePotassium perchloratePotassium perchlorate is the inorganic salt with the chemical formula KClO4. Like other perchlorates, this salt is a strong oxidizer and potentially reacts with many organic substances...
has been used as an oxidizer, paired with asphaltAsphaltAsphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...
, epoxyEpoxyEpoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....
, and other binders.
Propellants that explode in operation are of little practical use currently, although there have been experiments with Pulse Detonation Engine
Pulse detonation engine
A pulse detonation engine, or "PDE", is a type of propulsion system that uses detonation waves to combust the fuel and oxidizer mixture. The engine is pulsed because the mixture must be renewed in the combustion chamber between each detonation wave initiated by an ignition source. Theoretically, a...
s.
Grain
Propellants are used in forms called grains. A grain is any individual particle of propellant regardless of the size or shape. The shape and size of a propellant grain determines the burn time, amount of gas and rate produced from the burning propellant and consequently thrust vs time profile.There are three types of burns that can be achieved with different grains.
Progressive Burn: Usually a grain with multiple perforations or a star cut in the center providing a lot of surface area.
Digressive Burn: Usually a solid grain in the shape of a cylinder or sphere.
Neutral Burn: Usually a single perforation; as outside surface decreases the inside surface increases at the same rate.
Composition
There are four different types of solid propellant compositions:- Single Based Propellant: A single based propellant has nitrocellulose as its chief explosives ingredient. Stabilizers and other additives are used to control the chemical stability and enhance the propellant’s properties.
- Double Based Propellant: Double based propellants consist of nitrocellulose with nitroglycerin or other liquid organic nitrate explosives added. Stabilizers and other additives are used also. Nitroglycerin reduces smoke and increases the energy output. Double based propellants are used in small arms, cannons, mortars and rockets.
Triple Based Propellant: Triple based propellants consist of nitrocellulose, nitroquanidine, nitroglycerin or other liquid organic nitrate explosives. Triple based propellants are used in cannons.
Composite: Composites contain no nitrocellulose, nitroglycerin, nitroquanidine or any other organic nitrate. Composites usually consist of a fuel such as metallic aluminum, a binder such as synthetic rubber, and an oxidizer such as ammonium perchlorate. Composite propellants are used in large rocket motors.
Liquid propellant
Common propellant combinations used for liquid propellant rockets include:- Red fuming nitric acid (RFNA) and keroseneKeroseneKerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
or RP-1RP-1RP-1 is a highly refined form of kerosene outwardly similar to jet fuel, used as a rocket fuel. Although having a lower specific impulse than liquid hydrogen , RP-1 is cheaper, can be stored at room temperature, is far less of an explosive hazard and is far denser... - RFNA and Unsymmetrical dimethyl hydrazine (UDMH)
- Dinitrogen tetroxideDinitrogen tetroxideDinitrogen tetroxide is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium mixture with nitrogen dioxide; some call this mixture dinitrogen tetroxide, while some call it nitrogen dioxide.Dinitrogen tetroxide is a powerful oxidizer, making it highly...
and UDMHUDMHUnsymmetrical dimethylhydrazine is a toxic volatile hygroscopic clear liquid, with a sharp, fishy, ammoniacal smell typical for organic amines. It turns yellowish on exposure to air and absorbs oxygen and carbon dioxide. It mixes completely with water, ethanol, and kerosene. In concentration...
, MMHMonomethylhydrazineMonomethylhydrazine is a volatile hydrazine chemical with the chemical formula CH3 NH2. It is used as a rocket propellant in bipropellant rocket engines because it is hypergolic with various oxidizers such as nitrogen tetroxide and nitric acid...
and/or hydrazineHydrazineHydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually... - Liquid oxygenLiquid oxygenLiquid oxygen — abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries — is one of the physical forms of elemental oxygen.-Physical properties:...
and keroseneKeroseneKerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
or RP-1RP-1RP-1 is a highly refined form of kerosene outwardly similar to jet fuel, used as a rocket fuel. Although having a lower specific impulse than liquid hydrogen , RP-1 is cheaper, can be stored at room temperature, is far less of an explosive hazard and is far denser... - Liquid oxygenLiquid oxygenLiquid oxygen — abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries — is one of the physical forms of elemental oxygen.-Physical properties:...
and liquid hydrogenLiquid hydrogenLiquid hydrogen is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.To exist as a liquid, H2 must be pressurized above and cooled below hydrogen's Critical point. However, for hydrogen to be in a full liquid state without boiling off, it needs to be... - Liquid oxygenLiquid oxygenLiquid oxygen — abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries — is one of the physical forms of elemental oxygen.-Physical properties:...
and ethanolEthanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a... - Hydrogen peroxideHydrogen peroxideHydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
and alcoholAlcoholIn chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
or RP-1RP-1RP-1 is a highly refined form of kerosene outwardly similar to jet fuel, used as a rocket fuel. Although having a lower specific impulse than liquid hydrogen , RP-1 is cheaper, can be stored at room temperature, is far less of an explosive hazard and is far denser... - Chlorine pentafluorideChlorine pentafluorideChlorine pentafluoride is an interhalogen compound with formula ClF5. It was first synthesized in 1963.Its square pyramidal structure with C4v symmetry was confirmed by its high resolution19F NMR spectrum.-Preparation:...
and hydrazineHydrazineHydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...
Common monopropellant used for liquid rocket engines include:
- Hydrogen peroxide
- Hydrazine
- Red fuming nitric acid (RFNA)