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A solid-propellant rocket or solid rocket is a
rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entir ...
with a
rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accorda ...
that uses
solid propellants Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemical ...
(
fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy b ...
/
oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...
). The earliest rockets were solid-fuel rockets powered by
gunpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). T ...
; they were used in
warfare War is an intense armed conflict between states, governments, societies, or paramilitary groups such as mercenaries, insurgents, and militias. It is generally characterized by extreme violence, destruction, and mortality, using regu ...
by the
Arabs The Arabs (singular: Arab; singular ar, عَرَبِيٌّ, DIN 31635: , , plural ar, عَرَب, DIN 31635: , Arabic pronunciation: ), also known as the Arab people, are an ethnic group mainly inhabiting the Arab world in Western Asia, ...
, Chinese,
Persians The Persians are an Iranian ethnic group who comprise over half of the population of Iran. They share a common cultural system and are native speakers of the Persian language as well as of the languages that are closely related to Persian. ...
,
Mongols The Mongols ( mn, Монголчууд, , , ; ; russian: Монголы) are an East Asian ethnic group native to Mongolia, Inner Mongolia in China and the Buryatia Republic of the Russian Federation. The Mongols are the principal member ...
, and Indians as early as the 13th century. All rockets used some form of solid or powdered
propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the ...
up until the 20th century, when
liquid-propellant rocket A liquid-propellant rocket or liquid rocket utilizes a rocket engine that uses liquid propellants. Liquids are desirable because they have a reasonably high density and high specific impulse (''I''sp). This allows the volume of the propellant ta ...
s offered more efficient and controllable alternatives. Solid rockets are still used today in military armaments worldwide,
model rocket A model rocket are small rockets designed to reach low altitudes (e.g., for model) and be recovered by a variety of means. According to the United States National Association of Rocketry (NAR) Safety Code, model rockets are constructed of ...
s,
solid rocket booster A solid rocket booster (SRB) is a large solid propellant motor used to provide thrust in spacecraft launches from initial launch through the first ascent. Many launch vehicles, including the Atlas V, SLS and space shuttle, have used SRBs to gi ...
s and on larger applications for their simplicity and reliability. Since solid-fuel rockets can remain in storage for an extended period without much propellant degradation and because they almost always launch reliably, they have been frequently used in military applications such as
missile In military terminology, a missile is a guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously unguided rocket ...
s. The lower performance of solid propellants (as compared to liquids) does not favor their use as primary propulsion in modern medium-to-large launch vehicles customarily used to orbit commercial satellites and launch major space probes. Solids are, however, frequently used as strap-on boosters to increase payload capacity or as spin-stabilized add-on upper stages when higher-than-normal velocities are required. Solid rockets are used as light launch vehicles for
low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never m ...
(LEO) payloads under 2 tons or escape payloads up to .


Basic concepts

A simple solid
rocket motor A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordance ...
consists of a casing,
nozzle A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe. A nozzle is often a pipe or tube of varying cross sectional area, ...
, grain (
propellant charge A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...
), and
igniter In pyrotechnics, a pyrotechnic initiator (also initiator or igniter) is a device containing a pyrotechnic composition used primarily to ignite other, more difficult-to-ignite materials, such as thermites, gas generators, and solid-fuel rockets. T ...
. The solid grain mass burns in a predictable fashion to produce exhaust gases, the flow of which is described by
Taylor–Culick flow In fluid dynamics, Taylor–Culick flow describes the axisymmetric flow inside a long slender cylinder with one end closed, supplied by a constant flow injection through the sidewall. The flow is named after Geoffrey Ingram Taylor and F. E. C. Culic ...
. The
nozzle A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe. A nozzle is often a pipe or tube of varying cross sectional area, ...
dimensions are calculated to maintain a design
chamber Chamber or the chamber may refer to: In government and organizations *Chamber of commerce, an organization of business owners to promote commercial interests *Legislative chamber, in politics *Debate chamber, the space or room that houses deliber ...
pressure, while producing
thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that ...
from the exhaust gases. Once ignited, a simple solid rocket motor cannot be shut off, because it contains all the ingredients necessary for combustion within the chamber in which they are burned. More advanced solid rocket motors can be
throttle A throttle is the mechanism by which fluid flow is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases (by the use of a throttle), but usually decreased. The term ''throttle' ...
d, and also be extinguished, and then re-ignited by control of the nozzle geometry, or through the use of vent ports. Further,
pulsed rocket motors A pulsed rocket motor is typically defined as a multiple pulse solid-fuel rocket motor. This design overcomes the limitation of solid propellant motors being unable to be easily shut down and reignited. The pulse rocket motor allows the motor to ...
that burn in segments, and that can be ignited upon command are available. Modern designs may also include a steerable nozzle for guidance,
avionics Avionics (a blend of ''aviation'' and ''electronics'') are the electronic systems used on aircraft. Avionic systems include communications, navigation, the display and management of multiple systems, and the hundreds of systems that are fit ...
, recovery hardware (
parachute A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, w ...
s),
self-destruct A self-destruct is a mechanism that can cause an object to destroy itself or render itself inoperable after a predefined set of circumstances has occurred. Self-destruct mechanisms are typically found on devices and systems where malfunction could ...
mechanisms,
APUs Apus is a small constellation in the southern sky. It represents a bird-of-paradise, and its name means "without feet" in Greek because the bird-of-paradise was once wrongly believed to lack feet. First depicted on a celestial globe by Pet ...
, controllable tactical motors, controllable divert and
attitude control Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle ...
motors, and thermal management materials.


History

The medieval
Song dynasty The Song dynasty (; ; 960–1279) was an imperial dynasty of China that began in 960 and lasted until 1279. The dynasty was founded by Emperor Taizu of Song following his usurpation of the throne of the Later Zhou. The Song conquered the res ...
Chinese invented a very primitive form of solid-propellant rocket. Illustrations and descriptions in the 14th century Chinese military treatise ''
Huolongjing The ''Huolongjing'' (; Wade-Giles: ''Huo Lung Ching''; rendered in English as ''Fire Drake Manual'' or ''Fire Dragon Manual''), also known as ''Huoqitu'' (“Firearm Illustrations”), is a Chinese military treatise compiled and edited by Jiao ...
'' by the Ming dynasty military writer and philosopher
Jiao Yu Jiao Yu () was a Chinese military general, philosopher, and writer of the Yuan dynasty and early Ming dynasty under Zhu Yuanzhang, who founded the dynasty and became known as the Hongwu Emperor. He was entrusted by Zhu as a leading artillery ...
confirm that the Chinese in 1232 used proto solid propellant rockets then known as "
fire arrows Fire arrows were one of the earliest forms of weaponized gunpowder, being used from the 9th century onward. Not to be confused with earlier incendiary arrow projectiles, the fire arrow was a gunpowder weapon which receives its name from the tra ...
" to drive back the Mongols during the
Mongol siege of Kaifeng In the Mongol siege of Kaifeng from 1232 to 1233, the Mongol Empire captured Kaifeng, the capital of the Jurchen-led Jin dynasty. The Mongol Empire and the Jin dynasty had been at war for nearly two decades, beginning in 1211 after the Jin dy ...
. Each arrow took a primitive form of a simple, solid-propellant rocket tube that was filled with gunpowder. One open end allowed the gas to escape and was attached to a long stick that acted as a guidance system for flight direction control. The first rockets with tubes of cast iron were used by the
Kingdom of Mysore The Kingdom of Mysore was a realm in South India, southern India, traditionally believed to have been founded in 1399 in the vicinity of the modern city of Mysore. From 1799 until 1950, it was a princely state, until 1947 in a subsidiary allia ...
under
Hyder Ali Hyder Ali ( حیدر علی, ''Haidarālī''; 1720 – 7 December 1782) was the Sultan and ''de facto'' ruler of the Kingdom of Mysore in southern India. Born as Hyder Ali, he distinguished himself as a soldier, eventually drawing the att ...
and
Tipu Sultan Tipu Sultan (born Sultan Fateh Ali Sahab Tipu, 1 December 1751 – 4 May 1799), also known as the Tiger of Mysore, was the ruler of the Kingdom of Mysore based in South India. He was a pioneer of rocket artillery.Dalrymple, p. 243 He i ...
in the 1750s. These rockets had a reach of targets up to a mile and a half away. These were extremely effective in the Second Anglo-Mysore War that ended in a humiliating defeat for the
British Empire The British Empire was composed of the dominions, colonies, protectorates, mandates, and other territories ruled or administered by the United Kingdom and its predecessor states. It began with the overseas possessions and trading posts e ...
. Word of the success of the Mysore rockets against the British Imperial power triggered research in England, France, Ireland and elsewhere. When the British finally conquered the fort of Srirangapatana in 1799, hundreds of rockets were shipped off to the
Royal Arsenal The Royal Arsenal, Woolwich is an establishment on the south bank of the River Thames in Woolwich in south-east London, England, that was used for the manufacture of armaments and ammunition, proofing, and explosives research for the Britis ...
near London to be reverse-engineered. This led to the first industrial manufacture of military rockets with the
Congreve rocket The Congreve rocket was a type of rocket artillery designed by British inventor Sir William Congreve in 1808. The design was based upon the rockets deployed by the Kingdom of Mysore against the East India Company during the Second, Third, ...
in 1804. In 1921 the
Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
research and development laboratory
Gas Dynamics Laboratory Gas Dynamics Laboratory (GDL) (russian: Газодинамическая лаборатория) was the first Soviet research and development laboratory to focus on rocket technology. Its activities were initially devoted to the development ...
began developing solid-propellant rockets, which resulted in the first launch in 1928, that flew for approximately 1,300 metres. These rockets were used in 1931 for the world's first successful use of rockets to assist take-off of aircraft. The research continued from 1933 by the
Reactive Scientific Research Institute Reactive Scientific Research Institute (commonly known by the joint initialism RNII; russian: Реактивный научно-исследовательский институт, Reaktivnyy nauchno-issledovatel’skiy institut) was one of the ...
(RNII) with the development of the RS-82 and RS-132 rockets, including designing several variations for ground-to-air, ground-to-ground, air-to-ground and air-to-air combat. The earliest known use by the
Soviet Air Force The Soviet Air Forces ( rus, Военно-воздушные силы, r=Voyenno-vozdushnyye sily, VVS; literally "Military Air Forces") were one of the air forces of the Soviet Union. The other was the Soviet Air Defence Forces. The Air Forces ...
of aircraft-launched unguided anti-aircraft rockets in combat against heavier-than-air aircraft took place in August 1939, during the
Battle of Khalkhin Gol The Battles of Khalkhin Gol (russian: Бои на Халхин-Голе; mn, Халхын голын байлдаан) were the decisive engagements of the undeclared Soviet–Japanese border conflicts involving the Soviet Union, Mongolia, ...
. In June 1938, the RNII began developing a multiple rocket launcher based on the RS-132 rocket. In August 1939, the completed product was the BM-13 / Katyusha rocket launcher. Towards the end of 1938 the first significant large scale testing of the rocket launchers took place, 233 rockets of various types were used. A salvo of rockets could completely straddle a target at a range of . By the end of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
total production of rocket launchers reached about 10,000. with 12 million rockets of the RS type produced for the Soviet armed forces. In the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
modern castable composite solid rocket motors were invented by the American aerospace engineer
Jack Parsons John Whiteside Parsons (born Marvel Whiteside Parsons; October 2, 1914 – June 17, 1952) was an American Aerospace engineering, rocket engineer, chemist, and Thelema, Thelemite occultist. Associated with the California Institute of Technology ...
at
Caltech The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...
in 1942 when he replaced double base propellant with roofing
asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...
and
potassium perchlorate Potassium perchlorate is the inorganic salt with the chemical formula K Cl O4. Like other perchlorates, this salt is a strong oxidizer although it usually reacts very slowly with organic substances. This, usually obtained as a colorless, crysta ...
. This made possible slow-burning rocket motors of adequate size and with sufficient shelf-life for jet-assisted take off applications.
Charles Bartley Charles E. Bartley () was an American scientist, known for developing the first elastomeric solid rocket propellant formula, at the Jet Propulsion Laboratory (JPL), now part of NASA, in Pasadena, California, in the late 1940s. Bartley founded ...
, employed at JPL (Caltech), substituted curable
synthetic rubber A synthetic rubber is an artificial elastomer. They are polymers synthesized from petroleum byproducts. About 32-million metric tons of rubbers are produced annually in the United States, and of that amount two thirds are synthetic. Synthetic rubb ...
for the gooey asphalt, creating a flexible but geometrically stable load-bearing propellant grain that bonded securely to the motor casing. This made possible much larger solid rocket motors. Atlantic Research Corporation significantly boosted composite propellant Isp in 1954 by increasing the amount of powdered aluminium in the propellant to as much as 20%. Solid-propellant rocket technology got its largest boost in technical innovation, size and capability with the various mid-20th century government initiatives to develop increasingly capable military missiles. After initial designs of
ballistic missile A ballistic missile is a type of missile that uses projectile motion to deliver warheads on a target. These weapons are guided only during relatively brief periods—most of the flight is unpowered. Short-range ballistic missiles stay within t ...
military technology designed with
liquid-propellant rocket A liquid-propellant rocket or liquid rocket utilizes a rocket engine that uses liquid propellants. Liquids are desirable because they have a reasonably high density and high specific impulse (''I''sp). This allows the volume of the propellant ta ...
s in the 1940s and 1950s, both the
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nationa ...
and the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
embarked on major initiatives to develop solid-propellant
local Local may refer to: Geography and transportation * Local (train), a train serving local traffic demand * Local, Missouri, a community in the United States * Local government, a form of public administration, usually the lowest tier of administrat ...
,
regional In geography, regions, otherwise referred to as zones, lands or territories, are areas that are broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and the interaction of humanity and t ...
, and
intercontinental Intercontinental is an adjective to describe something which relates to more than one continent. Intercontinental may also refer to: * Intercontinental ballistic missile, a long-range guided ballistic missile * InterContinental Hotels Group (I ...
ballistic missiles, including solid-propellant missiles that could be launched from
air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...
or
sea The sea, connected as the world ocean or simply the ocean, is the body of salty water that covers approximately 71% of the Earth's surface. The word sea is also used to denote second-order sections of the sea, such as the Mediterranean Sea, ...
. Many other governments also developed these military technologies over the next 50 years. By the later 1980s and continuing to 2020, these government-developed highly-capable solid rocket technologies have been applied to
orbital spaceflight An orbital spaceflight (or orbital flight) is a spaceflight in which a spacecraft is placed on a trajectory where it could remain in space for at least one orbit. To do this around the Earth, it must be on a free trajectory which has an altit ...
by many government-directed programs, most often as
booster rockets A booster rocket (or engine) is either the first stage of a multistage rocket, multistage launch vehicle, or else a shorter-burning rocket used in parallel with longer-burning sustainer engine, sustainer rockets to augment the space vehicle's t ...
to add extra thrust during the early ascent of their primarily liquid rocket
launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload ( spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and sys ...
s. Some designs have had solid rocket upper stages as well. Examples flying in the 2010s include the European
Ariane 5 Ariane 5 is a European heavy-lift space launch vehicle developed and operated by Arianespace for the European Space Agency (ESA). It is launched from the Centre Spatial Guyanais (CSG) in French Guiana. It has been used to deliver payloads in ...
, US
Atlas V Atlas V is an expendable launch system and the fifth major version in the Atlas launch vehicle family. It was originally designed by Lockheed Martin, now being operated by United Launch Alliance (ULA), a joint venture between Lockheed Mart ...
and
Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program n ...
, and Japan's H-II. The largest solid rocket motors ever built were Aerojet's three monolithic solid motors cast in Florida. Motors 260 SL-1 and SL-2 were in diameter, long, weighed , and had a maximum thrust of . Burn duration was two minutes. The nozzle throat was large enough to walk through standing up. The motor was capable of serving as a 1-to-1 replacement for the 8-engine
Saturn I The Saturn I was a rocket designed as the United States' first medium lift launch vehicle for up to low Earth orbit payloads.Terminology has changed since the 1960s; back then, 20,000 pounds was considered "heavy lift". The rocket's first st ...
liquid-propellant first stage but was never used as such. Motor 260 SL-3 was of similar length and weight but had a maximum thrust of and a shorter duration.


Design

Design begins with the total
impulse Impulse or Impulsive may refer to: Science * Impulse (physics), in mechanics, the change of momentum of an object; the integral of a force with respect to time * Impulse noise (disambiguation) * Specific impulse, the change in momentum per uni ...
required, which determines the
fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy b ...
and
oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...
mass. Grain geometry and chemistry are then chosen to satisfy the required motor characteristics. The following are chosen or solved simultaneously. The results are exact dimensions for grain, nozzle, and case geometries: * The grain burns at a predictable rate, given its surface area and chamber pressure. * The chamber pressure is determined by the nozzle throat diameter and grain burn rate. * Allowable chamber pressure is a function of casing design. * The length of burn time is determined by the grain "web thickness". The grain may or may not be bonded to the casing. Case-bonded motors are more difficult to design, since the deformation of the case and the grain under flight must be compatible. Common modes of failure in solid rocket motors include fracture of the grain, failure of case bonding, and air pockets in the grain. All of these produce an instantaneous increase in burn surface area and a corresponding increase in exhaust gas production rate and pressure, which may rupture the casing. Another failure mode is casing
seal Seal may refer to any of the following: Common uses * Pinniped, a diverse group of semi-aquatic marine mammals, many of which are commonly called seals, particularly: ** Earless seal, or "true seal" ** Fur seal * Seal (emblem), a device to imp ...
failure. Seals are required in casings that have to be opened to load the grain. Once a seal fails, hot gas will erode the escape path and result in failure. This was the cause of the Space Shuttle ''Challenger'' disaster.


Grain geometry

Solid rocket fuel
deflagrates Deflagration (Lat: ''de + flagrare'', "to burn down") is subsonic combustion in which a pre-mixed flame propagates through a mixture of fuel and oxidizer. Deflagrations can only occur in pre-mixed fuels. Most fires found in daily life are diffu ...
from the surface of exposed propellant in the combustion chamber. In this fashion, the geometry of the propellant inside the rocket motor plays an important role in the overall motor performance. As the surface of the propellant burns, the shape evolves (a subject of study in internal ballistics), most often changing the propellant surface area exposed to the combustion gases. Since the propellant volume is equal to the
cross sectional area In geometry and science, a cross section is the non-empty intersection of a solid body in three-dimensional space with a plane, or the analog in higher-dimensional spaces. Cutting an object into slices creates many parallel cross-sections. ...
A_s times the fuel length, the
volumetric Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). The def ...
propellant consumption rate is the cross section area times the linear burn rate \dot, and the instantaneous
mass flow rate In physics and engineering, mass flow rate is the mass of a substance which passes per unit of time. Its unit is kilogram per second in SI units, and slug per second or pound per second in US customary units. The common symbol is \dot ('' ...
of combustion gases generated is equal to the volumetric rate times the fuel density \rho: :\dot = \rho \cdot A_s \cdot \dot Several geometric configurations are often used depending on the application and desired
thrust curve A thrust curve, sometimes known as a "performance curve" or "thrust profile" is a graph of the thrust of an engine or motor, (usually a rocket) with respect to time. Most engines do not produce linear thrust (thrust which increases at a constant ...
: Image:circ ex.jpg, Circular bore simulation Image:cslot ex.jpg, C-slot simulation Image:moon ex.jpg, Moon burner simulation Image:fino ex.jpg, 5-point finocyl simulation * Circular bore: if in
BATES Bates may refer to: Places * Bates, Arkansas, an unincorporated community * Bates, Illinois. an unincorporated community in Sangamon County * Bates, Michigan, a community in Grand Traverse County * Bates, New York, a hamlet in the town of Elli ...
configuration, produces progressive-regressive thrust curve. * End burner: propellant burns from one axial end to other producing steady long burn, though has thermal difficulties, center of gravity (CG) shift. * C-slot: propellant with large wedge cut out of side (along axial direction), producing fairly long regressive thrust, though has thermal difficulties and asymmetric CG characteristics. * Moon burner: off-center circular bore produces progressive-regressive long burn, though has slight asymmetric CG characteristics * Finocyl: usually a 5- or 6-legged star-like shape that can produce very level thrust, with a bit quicker burn than circular bore due to increased surface area.


Casing

The casing may be constructed from a range of materials. Cardboard is used for small
black powder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). T ...
model motors, whereas aluminium is used for larger composite-fuel hobby motors. Steel was used for the space shuttle boosters. Filament-wound graphite epoxy casings are used for high-performance motors. The casing must be designed to withstand the pressure and resulting stresses of the rocket motor, possibly at elevated temperature. For design, the casing is considered a
pressure vessel A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure. Construction methods and materials may be chosen to suit the pressure application, and will depend on the size o ...
. To protect the casing from corrosive hot gases, a sacrificial thermal liner on the inside of the casing is often implemented, which ablates to prolong the life of the motor casing.


Nozzle

A convergent-divergent design accelerates the exhaust gas out of the nozzle to produce thrust. The nozzle must be constructed from a material that can withstand the heat of the combustion gas flow. Often, heat-resistant carbon-based materials are used, such as amorphous
graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...
or carbon-carbon. Some designs include directional control of the exhaust. This can be accomplished by gimballing the nozzle, as in the Space Shuttle SRBs, by the use of jet vanes in the exhaust as in the
V-2 The V-2 (german: Vergeltungswaffe 2, lit=Retaliation Weapon 2), with the technical name ''Aggregat 4'' (A-4), was the world’s first long-range guided ballistic missile. The missile, powered by a liquid-propellant rocket engine, was develope ...
rocket, or by liquid injection thrust vectoring (LITV). LITV consists of injecting a liquid into the exhaust stream after the nozzle throat. The liquid then vaporizes, and in most cases chemically reacts, adding mass flow to one side of the exhaust stream and thus providing a control moment. For example, the
Titan III Titan was a family of United States expendable rockets used between 1959 and 2005. The Titan I and Titan II were part of the US Air Force's intercontinental ballistic missile (ICBM) fleet until 1987. The space launch vehicle versions contribut ...
C solid boosters injected
nitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russia rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...
for LITV; the tanks can be seen on the sides of the rocket between the main center stage and the boosters. An early
Minuteman Minutemen were members of the organized New England colonial militia companies trained in weaponry, tactics, and military strategies during the American Revolutionary War. They were known for being ready at a minute's notice, hence the name. Mi ...
first stage used a single motor with four
gimbal A gimbal is a pivoted support that permits rotation of an object about an axis. A set of three gimbals, one mounted on the other with orthogonal pivot axes, may be used to allow an object mounted on the innermost gimbal to remain independent of ...
led nozzles to provide pitch, yaw, and roll control.


Performance

A typical, well-designed
ammonium perchlorate composite propellant Ammonium perchlorate composite propellant (APCP) is a solid-propellant rocket fuel. It differs from many traditional solid rocket propellants such as black powder or zinc-sulfur, not only in chemical composition and overall performance but als ...
(APCP) first-stage motor may have a vacuum
specific impulse Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse is ...
(''I'') as high as (Titan IVB SRMU). This compares to for RP1/LOX (RD-180) and for LH2/LOX (Block II
RS-25 The Aerojet Rocketdyne RS-25, also known as the Space Shuttle Main Engine (SSME), is a liquid-fuel cryogenic rocket engine that was used on NASA's Space Shuttle and is currently used on the Space Launch System (SLS). Designed and manufactu ...
) bipropellant engines. Upper stage specific impulses are somewhat greater: as much as for APCP (Orbus 6E), for RP1/LOX (RD-0124) and for LH2/LOX (RL10B-2). Propellant fractions are usually somewhat higher for (non-segmented) solid propellant first stages than for upper stages. The Castor 120 first stage has a propellant mass fraction of 92.23% while the Castor 30 upper stage developed for Orbital Science's Taurus II COTS(Commercial Off The Shelf) (International Space Station resupply) launch vehicle has a 91.3% propellant fraction with 2.9% graphite epoxy motor casing, 2.4% nozzle, igniter and thrust vector actuator, and 3.4% non-motor hardware including such things as payload mount, interstage adapter, cable raceway, instrumentation, etc. Castor 120 and Castor 30 are in diameter, respectively, and serve as stages on the Athena IC and IIC commercial launch vehicles. A four-stage Athena II using Castor 120s as both first and second stages became the first commercially developed launch vehicle to launch a lunar probe (''
Lunar Prospector ''Lunar Prospector'' was the third mission selected by NASA for full development and construction as part of the Discovery Program. At a cost of $62.8 million, the 19-month mission was designed for a low polar orbit investigation of the Moon ...
'') in 1998. Solid rockets can provide high thrust for relatively low cost. For this reason, solids have been used as initial stages in rockets (for example the
Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program n ...
), while reserving high specific impulse engines, especially less massive hydrogen-fueled engines, for higher stages. In addition, solid rockets have a long history as the final boost stage for satellites due to their simplicity, reliability, compactness and reasonably high mass fraction. A spin-stabilized solid rocket motor is sometimes added when extra velocity is required, such as for a mission to a comet or the outer solar system, because a spinner does not require a guidance system (on the newly added stage). Thiokol's extensive family of mostly titanium-cased ''Star'' space motors has been widely used, especially on Delta launch vehicles and as spin-stabilized upper stages to launch satellites from the cargo bay of the Space Shuttle. ''Star'' motors have propellant fractions as high as 94.6% but add-on structures and equipment reduce the operating mass fraction by 2% or more. Higher performing solid rocket propellants are used in large strategic missiles (as opposed to commercial launch vehicles).
HMX HMX, also called octogen, is a powerful and relatively insensitive nitroamine high explosive, chemically related to RDX. Like RDX, the compound's name is the subject of much speculation, having been variously listed as High Melting Explosive, Her ...
, C4H8N4(NO2)4, a nitramine with greater energy than ammonium perchlorate, was used in the propellant of the Peacekeeper ICBM and is the main ingredient in NEPE-75 propellant used in the Trident II D-5 Fleet Ballistic Missile. It is because of explosive hazard that the higher energy military solid propellants containing HMX are not used in commercial launch vehicles except when the LV is an adapted ballistic missile already containing HMX propellant (Minotaur IV and V based on the retired Peacekeeper ICBMs). The Naval Air Weapons Station at China Lake, California, developed a new compound, C6H6N6(NO2)6, called simply
CL-20 Hexanitrohexaazaisowurtzitane, also called HNIW and CL-20, is a polycyclic nitroamine explosive with the formula C6H6N12O12. In the 1980s, CL-20 was developed by the China Lake facility, primarily to be used in propellants. It has a better oxid ...
(China Lake compound #20). Compared to HMX, CL-20 has 14% more energy per mass, 20% more energy per volume, and a higher oxygen-to-fuel ratio.http://www.navair.navy.mil/techTrans/index.cfm?map=local.ccms.view.aB&doc=crada.13 One of the motivations for development of these very high
energy density In physics, energy density is the amount of energy stored in a given system or region of space per unit volume. It is sometimes confused with energy per unit mass which is properly called specific energy or . Often only the ''useful'' or extrac ...
military solid propellants is to achieve mid-course exo-atmospheric ABM capability from missiles small enough to fit in existing ship-based below-deck vertical launch tubes and air-mobile truck-mounted launch tubes. CL-20 propellant compliant with Congress' 2004 insensitive munitions (IM) law has been demonstrated and may, as its cost comes down, be suitable for use in commercial launch vehicles, with a very significant increase in performance compared with the currently favored APCP solid propellants. With a specific impulse of 309 s already demonstrated by Peacekeeper's second stage using HMX propellant, the higher energy of CL-20 propellant can be expected to increase specific impulse to around 320 s in similar ICBM or launch vehicle upper stage applications, without the explosive hazard of HMX. An attractive attribute for military use is the ability for solid rocket propellant to remain loaded in the rocket for long durations and then be reliably launched at a moment's notice.


Propellant families


Black powder (gunpowder) propellant

Black powder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). T ...
(gunpowder) is composed of
charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, ...
(fuel),
potassium nitrate Potassium nitrate is a chemical compound with the chemical formula . This alkali metal nitrate salt is also known as Indian saltpetre (large deposits of which were historically mined in India). It is an ionic salt of potassium ions K+ and ...
(oxidizer), and
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...
(fuel and catalyst). It is one of the oldest
pyrotechnic Pyrotechnics is the science and craft of creating such things as fireworks, safety matches, oxygen candles, explosive bolts and other fasteners, parts of automotive airbags, as well as gas-pressure blasting in mining, quarrying, and demolition. ...
compositions with application to rocketry. In modern times, black powder finds use in low-power model rockets (such as
Estes Estes is an English-language surname said to derive from Old English and have the meaning "of the East" (literally, "East's"). As a surname, it has been traced to southern Kent, as early as the mid-15th century, Nicholas Estes (Ewstas, Esteuzi) b. ...
and Quest rockets), as it is cheap and fairly easy to produce. The fuel grain is typically a mixture of pressed fine powder (into a solid, hard slug), with a burn rate that is highly dependent upon exact composition and operating conditions. The
specific impulse Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse is ...
of black powder is low, around . The grain is sensitive to fracture and, therefore, catastrophic failure. Black powder does not typically find use in motors above thrust.


Zinc–sulfur (ZS) propellants

Composed of powdered
zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
metal and powdered sulfur (oxidizer), ZS or "micrograin" is another pressed propellant that does not find any practical application outside specialized amateur rocketry circles due to its poor performance (as most ZS burns outside the combustion chamber) and fast linear burn rates on the order of 2 m/s. ZS is most often employed as a novelty propellant as the rocket accelerates extremely quickly leaving a spectacular large orange fireball behind it.


"Candy" propellants

In general, rocket candy propellants are an oxidizer (typically potassium nitrate) and a sugar fuel (typically
dextrose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, usin ...
,
sorbitol Sorbitol (), less commonly known as glucitol (), is a sugar alcohol with a sweet taste which the human body metabolizes slowly. It can be obtained by reduction of glucose, which changes the converted aldehyde group (−CHO) to a primary alcoho ...
, or
sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refine ...
) that are cast into shape by gently melting the propellant constituents together and pouring or packing the
amorphous In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid, glassy solid) is a solid that lacks the long-range order that is characteristic of a crystal. Etymology The term comes from the Greek language, Gr ...
colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...
into a mold. Candy propellants generate a low-medium specific impulse of roughly and, thus, are used primarily by amateur and experimental rocketeers.


Double-base (DB) propellants

DB propellants are composed of two
monopropellant Monopropellants are propellants consisting of chemicals that release energy through exothermic chemical decomposition. The molecular bond energy of the monopropellant is released usually through use of a catalyst. This can be contrasted with bipro ...
fuel components where one typically acts as a high-energy (yet unstable) monopropellant and the other acts as a lower-energy stabilizing (and gelling) monopropellant. In typical circumstances,
nitroglycerin Nitroglycerin (NG), (alternative spelling of nitroglycerine) also known as trinitroglycerin (TNG), nitro, glyceryl trinitrate (GTN), or 1,2,3-trinitroxypropane, is a dense, colorless, oily, explosive liquid most commonly produced by nitrating g ...
is dissolved in a
nitrocellulose Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid and ...
gel and solidified with additives. DB propellants are implemented in applications where minimal smoke is required yet a medium-high Isp of roughly is required. The addition of metal fuels (such as
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
) can increase performance to around , though
metal oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...
nucleation In thermodynamics, nucleation is the first step in the formation of either a new thermodynamic phase or structure via self-assembly or self-organization within a substance or mixture. Nucleation is typically defined to be the process that deter ...
in the exhaust can turn the smoke opaque.


Composite propellants

A powdered oxidizer and powdered metal fuel are intimately mixed and immobilized with a rubbery binder (that also acts as a fuel). Composite propellants are often either
ammonium nitrate Ammonium nitrate is a chemical compound with the chemical formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, although it does not form hydrates. It is ...
-based (ANCP) or
ammonium perchlorate Ammonium perchlorate ("AP") is an inorganic compound with the formula Ammonium, NH4perchlorate, ClO4. It is a colorless or white solid that is soluble in water. It is a powerful oxidizer. Combined with a fuel, it can be used as a rocket propella ...
-based (APCP). Ammonium nitrate composite propellant often uses
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...
and/or
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
as fuel and delivers medium performance (Isp of about ) whereas
ammonium perchlorate composite propellant Ammonium perchlorate composite propellant (APCP) is a solid-propellant rocket fuel. It differs from many traditional solid rocket propellants such as black powder or zinc-sulfur, not only in chemical composition and overall performance but als ...
often uses aluminium fuel and delivers high performance: vacuum Isp up to with a single piece nozzle or with a high area ratio telescoping nozzle. Aluminium is used as fuel because it has a reasonable specific energy density, a high volumetric energy density, and is difficult to ignite accidentally. Composite propellants are cast, and retain their shape after the rubber binder, such as
Hydroxyl-terminated polybutadiene Hydroxyl-terminated polybutadiene (HTPB) is an oligomer of butadiene terminated at each end with a hydroxyl functional group. It reacts with isocyanates to form polyurethane polymers. HTPB is a translucent liquid with a color similar to wax paper ...
(HTPB),
cross-links In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...
(solidifies) with the aid of a curative additive. Because of its high performance, moderate ease of manufacturing, and moderate cost, APCP finds widespread use in space rockets, military rockets, hobby and amateur rockets, whereas cheaper and less efficient ANCP finds use in amateur rocketry and
gas generator A gas generator is a device for generating gas. A gas generator may create gas by a chemical reaction or from a solid or liquid source, when storing a pressurized gas is undesirable or impractical. The term often refers to a device that uses a ...
s.
Ammonium dinitramide Ammonium dinitramide (ADN) is the ammonium salt of dinitraminic acid. ADN decomposes under heat to leave only nitrogen, oxygen, and water. The ions are the ammonium ion NH4+ and the dinitramide N(NO2)2−. It makes an excellent solid rocket oxi ...
, NH4N(NO2)2, is being considered as a 1-to-1 chlorine-free substitute for ammonium perchlorate in composite propellants. Unlike ammonium nitrate, ADN can be substituted for AP without a loss in motor performance. Polyurethane-bound aluminium-APCP solid fuel was used in the submarine launched Polaris missiles. APCP used in the
space shuttle Solid Rocket Boosters The Space Shuttle Solid Rocket Booster (SRB) was the first solid-propellant rocket to be used for primary propulsion on a vehicle used for human spaceflight. A pair of these provided 85% of the Space Shuttle's thrust at liftoff and for the first ...
consisted of ammonium perchlorate (oxidizer, 69.6% by weight), aluminium (fuel, 16%), iron oxide (a catalyst, 0.4%), polybutadiene acrylonitrile (PBAN) polymer (a non-urethane rubber binder that held the mixture together and acted as secondary fuel, 12.04%), and an epoxy curing agent (1.96%). It developed a specific impulse of 242 seconds (2.37 km/s) at sea level or 268 seconds (2.63 km/s) in a vacuum. The 2005-2009
Constellation Program The Constellation program (abbreviated CxP) was a crewed spaceflight program developed by NASA, the space agency of the United States, from 2005 to 2009. The major goals of the program were "completion of the International Space Station" and a ...
was to use a similar PBAN-bound APCP. In 2009, a group succeeded in creating a propellant of
water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...
and nanoaluminium (
ALICE Alice may refer to: * Alice (name), most often a feminine given name, but also used as a surname Literature * Alice (''Alice's Adventures in Wonderland''), a character in books by Lewis Carroll * ''Alice'' series, children's and teen books by ...
).


High-energy composite (HEC) propellants

Typical HEC propellants start with a standard composite propellant mixture (such as APCP) and add a high-energy explosive to the mix. This extra component usually is in the form of small crystals of RDX or
HMX HMX, also called octogen, is a powerful and relatively insensitive nitroamine high explosive, chemically related to RDX. Like RDX, the compound's name is the subject of much speculation, having been variously listed as High Melting Explosive, Her ...
, both of which have higher energy than ammonium perchlorate. Despite a modest increase in specific impulse, implementation is limited due to the increased hazards of the high-explosive additives.


Composite modified double base propellants

Composite modified double base propellants start with a nitrocellulose/nitroglycerin double base propellant as a binder and add solids (typically
ammonium perchlorate Ammonium perchlorate ("AP") is an inorganic compound with the formula Ammonium, NH4perchlorate, ClO4. It is a colorless or white solid that is soluble in water. It is a powerful oxidizer. Combined with a fuel, it can be used as a rocket propella ...
(AP) and powdered
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
) normally used in composite propellants. The ammonium perchlorate makes up the oxygen deficit introduced by using
nitrocellulose Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid and ...
, improving the overall specific impulse. The aluminium improves specific impulse as well as combustion stability. High performing propellants such as
NEPE-75 A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses solid propellants (fuel/oxidizer). The earliest rockets were solid-fuel rockets powered by gunpowder; they were used in warfare by the Arabs, Chinese, Persians ...
used to fuel the
Trident II A trident is a three- pronged spear. It is used for spear fishing and historically as a polearm. The trident is the weapon of Poseidon, or Neptune, the God of the Sea in classical mythology. The trident may occasionally be held by other marine ...
D-5,
SLBM A submarine-launched ballistic missile (SLBM) is a ballistic missile capable of being launched from submarines. Modern variants usually deliver multiple independently targetable reentry vehicles (MIRVs), each of which carries a nuclear warhea ...
replace most of the AP with
polyethylene glycol Polyethylene glycol (PEG; ) is a polyether compound derived from petroleum with many applications, from industrial manufacturing to medicine. PEG is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its molecular we ...
-bound
HMX HMX, also called octogen, is a powerful and relatively insensitive nitroamine high explosive, chemically related to RDX. Like RDX, the compound's name is the subject of much speculation, having been variously listed as High Melting Explosive, Her ...
, further increasing specific impulse. The mixing of composite and double base propellant ingredients has become so common as to blur the functional definition of double base propellants.


Minimum-signature (''smokeless'') propellants

One of the most active areas of solid propellant research is the development of high-energy, minimum-signature propellant using C6H6N6(NO2)6 CL-20 nitroamine (
China Lake Naval Air Weapons Station China Lake is a United States military facility in California. China Lake may also refer to: Places in the United States * China Lake, Kern County, California, an unincorporated community named for a nearby dry lake *Ch ...
compound #20), which has 14% higher energy per mass and 20% higher energy density than HMX. The new propellant has been successfully developed and tested in tactical rocket motors. The propellant is non-polluting: acid-free, solid particulates-free, and lead-free. It is also smokeless and has only a faint shock diamond pattern that is visible in the otherwise transparent exhaust. Without the bright flame and dense smoke trail produced by the burning of aluminized propellants, these smokeless propellants all but eliminate the risk of giving away the positions from which the missiles are fired. The new CL-20 propellant is shock-insensitive (hazard class 1.3) as opposed to current HMX smokeless propellants which are highly detonable (hazard class 1.1). CL-20 is considered a major breakthrough in solid rocket propellant technology but has yet to see widespread use because costs remain high.


Electric solid propellants

Electric solid propellants (ESPs) are a family of high performance
plastisol A plastisol is a colloidal dispension of small polymer particles, usually polyvinyl chloride (PVC), in a liquid plasticizer. When heated to around , the plastic particles absorb the plasticizer, causing them to swell and fuse together forming a ...
solid propellants that can be ignited and throttled by the application of electric current. Unlike conventional rocket motor propellants that are difficult to control and extinguish, ESPs can be ignited reliably at precise intervals and durations. It requires no moving parts and the propellant is insensitive to flames or electrical sparks.


Hobby and amateur rocketry

Solid propellant rocket motors can be bought for use in
model rocket A model rocket are small rockets designed to reach low altitudes (e.g., for model) and be recovered by a variety of means. According to the United States National Association of Rocketry (NAR) Safety Code, model rockets are constructed of ...
ry; they are normally small cylinders of black powder fuel with an integral
nozzle A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe. A nozzle is often a pipe or tube of varying cross sectional area, ...
and optionally a small charge that is set off when the propellant is exhausted after a time delay. This charge can be used to trigger a
camera A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with ...
, or deploy a
parachute A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, w ...
. Without this charge and delay, the motor may ignite a second
stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Sta ...
(black powder only). In mid- and
high-power rocketry High-power rocketry is a hobby similar to model rocketry. The major difference is that higher impulse range motors are used. The National Fire Protection Association (NFPA) definition of a high-power rocket is one that has a total weight of more ...
, commercially made APCP motors are widely used. They can be designed as either single-use or reloadables. These motors are available in impulse ranges from "A" (1.26 Ns– 2.50 Ns) to "O" (20.48 kNs – 40.96 kNs), from several manufacturers. They are manufactured in standardized diameters and varying lengths depending on required impulse. Standard motor diameters are 13, 18, 24, 29, 38, 54, 75, 98, and 150 millimeters. Different propellant formulations are available to produce different thrust profiles, as well as special effects such as colored flames, smoke trails, or large quantities of sparks (produced by adding
titanium Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion i ...
sponge to the mix).


Use


Sounding rockets

Almost all
sounding rocket A sounding rocket or rocketsonde, sometimes called a research rocket or a suborbital rocket, is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight. The rockets are used to ...
s use solid motors. *
Astrobee Astrobee is the designation of series of American sounding rockets with 1 - 3 stages. Aerojet-designed family of sounding rockets conceived as a lower-cost replacement of the liquid-propellant Aerobee. Several versions were realized: * The th ...
*
Black Brant The brant or brent goose (''Branta bernicla'') is a small goose of the genus ''Branta''. There are three subspecies, all of which winter along temperate-zone sea-coasts and breed on the high-Arctic tundra. The Brent oilfield was named after t ...
*
S-310 S-Series is a fleet of sounding rockets funded by the JAXA, Japan Aerospace Exploration Agency (JAXA) that have been in service since the late 1960s. Manufactured by IHI Aerospace and operated by the Institute of Space and Astronautical Science ( ...
,
S-520 S-Series is a fleet of sounding rockets funded by the Japan Aerospace Exploration Agency (JAXA) that have been in service since the late 1960s. Manufactured by IHI Aerospace and operated by the Institute of Space and Astronautical Science (ISAS) ...
*
Skylark (rocket) Skylark was a family of British sounding rockets. It was operational between 1957 and 2005. Development of the Skylark begun during the early 1950s at the Royal Aircraft Establishment (RAE), which approached the Royal Society with an offer ...
*
Terrier-Orion The Terrier Orion sounding rocket is a combination of the Terrier booster rocket with the Orion rocket used as a second stage. This spin stabilized configuration is most often used by the Goddard Space Flight Center, who operate out of the Wall ...
,
Terrier-Malemute The Terrier Malemute is a two-stage American sounding rocket typically used for smaller payloads (less than ). Both the RIM-2 Terrier, Terrier first stage and the Malemute second stage use solid fuel. The Terrier burns for approximately 5.2 second ...
* VSB-30


Missiles

Due to reliability, ease of storage and handling, solid rockets are used on missiles and ICBMs. * Air-to-air missiles:
AIM-9 Sidewinder The AIM-9 Sidewinder (where "AIM" stands for "Air Intercept Missile") is a short-range air-to-air missile which entered service with the US Navy in 1956 and subsequently was adopted by the US Air Force in 1964. Since then the Sidewinder has prove ...
* Ballistic missiles:
Jericho Jericho ( ; ar, أريحا ; he, יְרִיחוֹ ) is a Palestinian city in the West Bank. It is located in the Jordan Valley, with the Jordan River to the east and Jerusalem to the west. It is the administrative seat of the Jericho ...
, Sejjil * ICBMs:
LGM-30 Minuteman The LGM-30 Minuteman is an American land-based intercontinental ballistic missile (ICBM) in service with the Air Force Global Strike Command. , the LGM-30G Minuteman III version is the only land-based ICBM in service in the United States and ...
,
UGM-133 Trident II The UGM-133A Trident II, or Trident D5 is a submarine-launched ballistic missile (SLBM), built by Lockheed Martin Space in Sunnyvale, California, and deployed with the American and British navies. It was first deployed in March 1990, and rema ...
,
LGM-118 Peacekeeper The LGM-118 Peacekeeper, originally known as the MX for "Missile, Experimental", was a MIRV-capable intercontinental ballistic missile (ICBM) produced and deployed by the United States from 1985 to 2005. The missile could carry up to twelve Mark ...
,
RT-2PM Topol The RT-2PM Topol (russian: РТ-2ПМ Тополь ("Poplar"); NATO reporting name SS-25 Sickle; GRAU designation: 15Ж58 ("15Zh58"); START I designation: RS-12M Topol) is a mobile intercontinental ballistic missile designed in the Soviet Union a ...
,
DF-41 The Dongfeng-41 (DF-41, CSS-20) () is a fourth-generation Chinese solid-fuelled road-mobile intercontinental ballistic missile operated by the People's Liberation Army Rocket Force (formerly the Second Artillery Corps). DF-41 is the fourth and ...
, M51 SLBM


Orbital rockets

Solid rockets are suitable for launching small payloads to orbital velocities, especially if three or more stages are used. Many of these are based on repurposed ICBMs. *
Scout Scout may refer to: Youth movement *Scout (Scouting), a child, usually 10–18 years of age, participating in the worldwide Scouting movement ** Scouts (The Scout Association), section for 10-14 year olds in the United Kingdom **Scouts BSA, secti ...
*
Athena Athena or Athene, often given the epithet Pallas, is an ancient Greek goddess associated with wisdom, warfare, and handicraft who was later syncretized with the Roman goddess Minerva. Athena was regarded as the patron and protectress of v ...
* Mu *
Pegasus Pegasus ( grc-gre, Πήγασος, Pḗgasos; la, Pegasus, Pegasos) is one of the best known creatures in Greek mythology. He is a winged divine stallion usually depicted as pure white in color. He was sired by Poseidon, in his role as hor ...
* Taurus *
Minotaur In Greek mythology, the Minotaur ( , ;. grc, ; in Latin as ''Minotaurus'' ) is a mythical creature portrayed during classical antiquity with the head and tail of a bull and the body of a man or, as described by Roman poet Ovid, a being "p ...
*
Start-1 Start-1 is a Russian satellite launch vehicle based on the RT-2PM Topol, a Soviet intercontinental ballistic missile developed by Moscow Institute of Thermal Technology. History The Start-1 launch vehicle derives its name from the Strategic ...
*
PSLV The Polar Satellite Launch Vehicle (PSLV) is an expendable medium-lift launch vehicle designed and operated by the Indian Space Research Organisation (ISRO). It was developed to allow India to launch its Indian Remote Sensing (IRS) satellites ...
- alternating solid and liquid stages *
Shavit Shavit ( he, שביט, link=no, meaning ''comet'') may refer to: People Surname * Ari Shavit (born 1957), Israeli reporter and writer * Bradley Shavit Artson (born 1959), American rabbi * Dorit Shavit (born 1949), Israeli ambassador * Edna Sh ...
*
Vega Vega is the brightest star in the northern constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated Alpha Lyr or α Lyr. This star is relatively close at only from the Sun, a ...
*
Long March 11 The Long March 11 (), or Chang Zheng 11 as in pinyin, abbreviated LM-11 for export or CZ-11 within China (and designated 11H when launched from sea), is a Chinese four stage solid-propellant carrier rocket of the Long March family, which is ...
*
OmegA Omega (; capital: Ω, lowercase: ω; Ancient Greek ὦ, later ὦ μέγα, Modern Greek ωμέγα) is the twenty-fourth and final letter in the Greek alphabet. In the Greek numeric system/ isopsephy ( gematria), it has a value of 800. The ...
Larger liquid-fueled orbital rockets often use solid rocket boosters to gain enough initial thrust to launch the fully fueled rocket. *
Delta II Delta II was an expendable launch system, originally designed and built by McDonnell Douglas. Delta II was part of the Delta rocket family and entered service in 1989. Delta II vehicles included the Delta 6000, and the two later Delta 7000 va ...
*
Titan IV Titan IV was a family of heavy-lift space launch vehicles developed by Martin Marietta and operated by the United States Air Force from 1989 to 2005. Launches were conducted from Cape Canaveral Air Force Station, Florida and Vandenberg Air Forc ...
*
Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program n ...
*
Space Launch System The Space Launch System (SLS) is an American super heavy-lift expendable launch vehicle developed by NASA. As of 2022, SLS has the highest payload capacity of any rocket in operational service, as well as the greatest liftoff thrust of any ...
*
Ariane 5 Ariane 5 is a European heavy-lift space launch vehicle developed and operated by Arianespace for the European Space Agency (ESA). It is launched from the Centre Spatial Guyanais (CSG) in French Guiana. It has been used to deliver payloads in ...
*
Atlas II Atlas II was a member of the Atlas family of launch vehicles, which evolved from the successful Atlas missile program of the 1950s. The Atlas II was a direct evolution of the Atlas I, featuring longer first stage tanks, higher-performing engine ...
*
Atlas V Atlas V is an expendable launch system and the fifth major version in the Atlas launch vehicle family. It was originally designed by Lockheed Martin, now being operated by United Launch Alliance (ULA), a joint venture between Lockheed Mart ...
(optionally 1-5 boosters) *
Delta IV Delta IV is a group of five expendable launch systems in the Delta rocket family introduced in the early 2000s. Originally designed by Boeing's Defense, Space and Security division for the Evolved Expendable Launch Vehicle (EELV) program, th ...
(optionally 2 or 4 boosters) *
H-IIA H-IIA (H-2A) is an active expendable launch system operated by Mitsubishi Heavy Industries (MHI) for the Japan Aerospace Exploration Agency. These liquid fuel rockets have been used to launch satellites into geostationary orbit; lunar o ...
,
H-IIB H-IIB (H2B) was an expendable space launch system jointly developed by the Japanese government's space agency JAXA and Mitsubishi Heavy Industries. It was used to launch the H-II Transfer Vehicle (HTV, or ''Kōnotori'') cargo spacecraft for ...
*
PSLV The Polar Satellite Launch Vehicle (PSLV) is an expendable medium-lift launch vehicle designed and operated by the Indian Space Research Organisation (ISRO). It was developed to allow India to launch its Indian Remote Sensing (IRS) satellites ...
- optional solid boosters to lift heavier payloads *
GSLV Mk III The Launch Vehicle Mark-3 (LVM 3), previously referred to as the Geosynchronous Satellite Launch Vehicle Mark III (GSLV Mk3), is a three-stage medium-lift launch vehicle developed by the Indian Space Research Organisation (ISRO). Primarily desi ...
Solid fuel is also used for some upper stages, particularly the
Star 37 The Star is a family of US solid-propellant rocket motors originally developed by Thiokol and used by many space propulsion and launch vehicle stages. They are used almost exclusively as an upper stage, often as an apogee kick motor. Three Star ...
(sometimes referred to as the "Burner" upper stage) and the
Star 48 The Star 48 is the largest of a family of solid rocket motors used by many space propulsion and launch vehicle stages. It is used almost exclusively as an upper stage. It was developed primarily by Thiokol Propulsion and is now, after several ...
(sometimes referred to as the "
Payload Assist Module The Payload Assist Module (PAM) is a modular upper stage designed and built by McDonnell Douglas (now Boeing), using Thiokol Star-series solid propellant rocket motors. The PAM was used with the Space Shuttle, Delta, and Titan launchers and carri ...
", or PAM), both manufactured originally by
Thiokol Thiokol (variously Thiokol Chemical Corporation(/Company), Morton Thiokol Inc., Cordant Technologies Inc., Thiokol Propulsion, AIC Group, ATK Thiokol, ATK Launch Systems Group; finally Orbital ATK before becoming part of Northrop Grumman) was ...
, and today by
Northrop Grumman Northrop Grumman Corporation is an American multinational aerospace and defense technology company. With 90,000 employees and an annual revenue in excess of $30 billion, it is one of the world's largest weapons manufacturers and military tech ...
. They are used to lift large payloads to intended orbits (such as the
Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite ...
satellites), or smaller payloads to interplanetary—or even interstellar—trajectories. Another solid-fuel upper stage, used by the
Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program n ...
and the
Titan IV Titan IV was a family of heavy-lift space launch vehicles developed by Martin Marietta and operated by the United States Air Force from 1989 to 2005. Launches were conducted from Cape Canaveral Air Force Station, Florida and Vandenberg Air Forc ...
, was the
Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and ...
-manufactured
Inertial Upper Stage The Inertial Upper Stage (IUS), originally designated the Interim Upper Stage, was a two-stage, solid-fueled space launch system developed by Boeing for the United States Air Force beginning in 1976 for raising payloads from low Earth orbit to ...
(IUS). * ''
Pioneer 10 ''Pioneer 10'' (originally designated Pioneer F) is an American space probe, launched in 1972 and weighing , that completed the first mission to the planet Jupiter. Thereafter, ''Pioneer 10'' became the first of five artificial objects to ac ...
'' and ''
Pioneer 11 ''Pioneer 11'' (also known as ''Pioneer G'') is a robotic space probe launched by NASA on April 5, 1973, to study the asteroid belt, the environment around Jupiter and Saturn, solar winds, and cosmic rays. It was the first probe to encoun ...
'' were both sent out of the solar system by Star 37E upper stages from
Atlas-Centaur The Atlas-Centaur was a United States expendable launch vehicle derived from the SM-65 Atlas D missile. Launches were conducted from Launch Complex 36 at the Cape Canaveral Air Force Station (CCAFS) in Florida. Early development Convair, ...
rockets. * ''
Voyager 1 ''Voyager 1'' is a space probe launched by NASA on September 5, 1977, as part of the Voyager program to study the outer Solar System and interstellar space beyond the Sun's heliosphere. Launched 16 days after its twin '' Voyager 2'', ''V ...
'' and ''
Voyager 2 ''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, '' Voyager 1'', ...
'' were both sent out of the solar system by Star 37E upper stages from
Titan IIIE The Titan IIIE or Titan 3E, also known as the Titan III-Centaur, was an American expendable launch system. Launched seven times between 1974 and 1977, it enabled several high-profile NASA missions, including the Voyager and Viking planetary prob ...
rockets. * ''
Magellan Ferdinand Magellan ( or ; pt, Fernão de Magalhães, ; es, link=no, Fernando de Magallanes, ; 4 February 1480 – 27 April 1521) was a Portuguese explorer. He is best known for having planned and led the 1519 Spanish expedition to the East ...
'' was sent to Venus on an IUS after being deployed from Space Shuttle ''Atlantis'' on STS-30. * ''
Galileo Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Commonly referred to as Galileo, his name was pronounced (, ). He was ...
'' was sent to Jupiter on an IUS after being deployed from Space Shuttle ''Atlantis'' on STS-34. * '' Ulysses'' was sent to Jupiter on an IUS and a Star 48 PAM after being deployed from Space Shuttle ''Discovery'' on STS-41. It then was placed in a polar orbit around the Sun following a
gravity assist In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the p ...
around Jupiter. * ''
New Horizons ''New Horizons'' is an interplanetary space probe that was launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institute (SwRI), with a ...
'' was sent out of the solar system on a Star 48 PAM from an
Atlas V Atlas V is an expendable launch system and the fifth major version in the Atlas launch vehicle family. It was originally designed by Lockheed Martin, now being operated by United Launch Alliance (ULA), a joint venture between Lockheed Mart ...
rocket. Some rockets, like the
Antares Antares is the brightest star in the constellation of Scorpius. It has the Bayer designation α Scorpii, which is Latinised to Alpha Scorpii. Often referred to as "the heart of the scorpion", Antares is flanked by σ Scorpii and τ ...
(manufactured by Northrop Grumman), have mandatory solid-fuel upper stages. The Antares rocket uses the
Northrop Grumman Northrop Grumman Corporation is an American multinational aerospace and defense technology company. With 90,000 employees and an annual revenue in excess of $30 billion, it is one of the world's largest weapons manufacturers and military tech ...
-manufactured
Castor 30 The Castor family of solid-fuel rocket stages and boosters built by Thiokol (now Northrop Grumman) and used on a variety of launch vehicles. They were initially developed as the second-stage motor of the Scout rocket. The design was based on the ...
as an upper stage.


Advanced research

* Environmentally sensitive fuel formulations such as ALICE propellant *
Ramjet A ramjet, or athodyd (aero thermodynamic duct), is a form of airbreathing jet engine that uses the forward motion of the engine to produce thrust. Since it produces no thrust when stationary (no ram air) ramjet-powered vehicles require an ass ...
s with solid fuel * Variable thrust designs based on variable nozzle geometry *
Hybrid rocket A hybrid-propellant rocket is a rocket with a rocket motor that uses rocket propellants in two different phases: one solid and the other either gas or liquid. The hybrid rocket concept can be traced back to the early 1930s. Hybrid rockets avo ...
s that use solid fuel and throttleable liquid or gaseous oxidizer


See also

*
Comparison of solid-fuelled orbital launch systems This article contains the lift launch systems constructed by some solid fuel stages except the final stage. All stages solid fueled :* Including suborbital mission All stages solid fueled except uppermost stage See also * Comparison of o ...
*
Comparison of orbital launch systems This comparison of orbital launch systems lists the attributes of all individual rocket configurations designed to reach orbit. A first list contains rockets that are operational or in development as of 2022; a second list includes all retired roc ...
*
Comparison of orbital launchers families This article compares different orbital launcher families (although many launchers that are significantly different from other members of the same 'family' have their own separate entries). The article is organized into two tables: the first tabl ...
* List of space launch system designs *
List of missiles Below is a list of missiles, sorted alphabetically into large categories and subcategories by name and purpose. Other missile lists Types of missiles: * Conventional guided missiles ** Air-to-air missile ** Air-to-surface missile ** Anti-rad ...
*
List of orbital launch systems This is a list of conventional orbital launch systems. This is composed of launch vehicles, and other conventional systems, used to place satellites into orbit. Argentina *ORBIT II – ''Retired'' * TRONADOR – ''Under Development'' Australia ...
*
List of sounding rockets This is a list of sounding rockets used for suborbital research flights. Argentina *Gamma Centauro *Gradicom-1 *Proson-M1 *Rigel series **Canopus-1, Canopus 2, **Castor (A) **Centenario * Orión series **Orión-1, Orión-2 Australia *Aeolus *Ae ...
* List of military rockets *
Fireworks Fireworks are a class of low explosive pyrotechnic devices used for aesthetic and entertainment purposes. They are most commonly used in fireworks displays (also called a fireworks show or pyrotechnics), combining a large number of devices ...
*
Pyrotechnic composition A pyrotechnic composition is a substance or mixture of substances designed to produce an effect by heat, light, sound, gas/smoke or a combination of these, as a result of non-detonative self-sustaining exothermic chemical reactions. Pyrotechnic s ...
*
Intercontinental ballistic missile An intercontinental ballistic missile (ICBM) is a ballistic missile with a range greater than , primarily designed for nuclear weapons delivery (delivering one or more thermonuclear warheads). Conventional, chemical, and biological weapo ...
*
Jetex engine The Jetex motor is a miniature solid-fuel rocket motor produced for use as a powerplant for flying model aircraft. Its production led to a number of imitators and, after its demise, successors of similar type. __FORCETOC__ Original Jetex motors ...
*
Space Shuttle Solid Rocket Booster The Space Shuttle Solid Rocket Booster (SRB) was the first solid-propellant rocket to be used for primary propulsion on a vehicle used for human spaceflight. A pair of these provided 85% of the Space Shuttle's thrust at liftoff and for the first ...
*
Crawford burner A Crawford burner is a device used to test burn rate (chemistry) of solid propellants. It is also known as a strand burner. A Crawford burner consists of a small pressure vessel in which a thin bar of propellant to be tested is mounted on a stand. ...
* Nano-thermite *
Skyrocket A skyrocket is a type of firework that uses a solid-fuel rocket to rise quickly into the sky; a bottle rocket is a small skyrocket. At the apex of its ascent, it is usual for a variety of effects (stars, bangs, crackles, etc.) to be emitted. S ...


References


Further reading

*


External links


Robert A. Braeunig rocket propulsion page





Amateur High Power Rocketry Association

Nakka-Rocketry (Design Calculations and Propellant Formulations)






{{DEFAULTSORT:Solid-Fuel Rocket American inventions Chinese inventions Indian inventions Rocket engines Rocket propulsion Rocket engines by propellant Solid fuels