
A solid-propellant rocket or solid rocket is a
rocket
A rocket (from , and so named for its shape) is a vehicle that uses jet propulsion to accelerate without using any surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely ...
with a
rocket engine
A rocket engine is a reaction engine, producing thrust in accordance with Newton's third law by ejecting reaction mass rearward, usually a high-speed Jet (fluid), jet of high-temperature gas produced by the combustion of rocket propellants stor ...
that uses
solid propellants (
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 (physics), work. The concept was originally applied solely to those materials capable of releasing chem ...
/
oxidizer). 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, charcoal (which is mostly carbon), and potassium nitrate, potassium ni ...
. The inception of gunpowder rockets in warfare can be credited to the ancient Chinese, and in the 13th century, the Mongols played a pivotal role in facilitating their westward adoption.
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 another motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicle ...
until the 20th century, when
liquid-propellant rocket
A liquid-propellant rocket or liquid rocket uses a rocket engine burning liquid rocket propellant, liquid propellants. (Alternate approaches use gaseous or Solid-propellant rocket , solid propellants.) Liquids are desirable propellants because th ...
s offered more efficient and controllable alternatives. Because of their simplicity and reliability, solid rockets are still used today in military armaments worldwide,
model rocket
A model rocket is a small rocket designed to reach low altitudes (e.g., for a model) and #Model rocket recovery methods, be recovered by a variety of means.
According to the United States National Association of Rocketry, National Associati ...
s,
solid rocket boosters and on larger applications.
Since solid-fuel rockets can remain in storage for an extended period without much propellant degradation, and since they almost always launch reliably, they have been frequently used in military applications such as
missile
A missile is an airborne ranged weapon capable of self-propelled flight aided usually by a propellant, jet engine or rocket motor.
Historically, 'missile' referred to any projectile that is thrown, shot or propelled towards a target; this ...
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 for commercial satellites and 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 geocentric orbit, orbit around Earth with a orbital period, period of 128 minutes or less (making at least 11.25 orbits per day) and an orbital eccentricity, eccentricity less than 0.25. Most of the artificial object ...
(LEO) payloads under 2 tons or escape payloads up to .
Basic concepts

A simple solid
rocket motor consists of a casing,
nozzle, grain (
propellant charge), and
igniter.
The solid grain mass
burns in a predictable fashion to produce exhaust gases, the flow of which is described by
Taylor–Culick flow. The
nozzle dimensions are calculated to maintain a design
chamber 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, as it contains all the ingredients necessary for combustion within the chamber in which they are burned. More advanced solid rocket motors can be
throttled, or extinguished and re-ignited, by control of the nozzle geometry or through the use of vent ports. Further,
pulsed rocket motors 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 portmanteau of ''aviation'' and ''electronics'') are the Electronics, electronic systems used on aircraft. Avionic systems include communications, Air navigation, navigation, the display and management of multiple systems, and the ...
, recovery hardware (
parachute
A parachute is a device designed to slow an object's descent through an atmosphere by creating Drag (physics), drag or aerodynamic Lift (force), lift. It is primarily used to safely support people exiting aircraft at height, but also serves va ...
s),
self-destruct mechanisms,
APUs, controllable tactical motors, controllable divert and
attitude control motors, and thermal management materials.
History

The medieval
Song dynasty
The Song dynasty ( ) was an Dynasties of China, imperial dynasty of China that ruled from 960 to 1279. The dynasty was founded by Emperor Taizu of Song, who usurped the throne of the Later Zhou dynasty and went on to conquer the rest of the Fiv ...
Chinese invented a very primitive form of solid-propellant rocket. Illustrations and descriptions in the 14th century Chinese military treatise ''
Huolongjing'' by the Ming dynasty military writer and philosopher
Jiao Yu confirm that the Chinese in 1232 used proto solid propellant rockets then known as "
fire arrows" to drive back the Mongols during the
Siege of Kaifeng (1232).
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 geopolitical realm in southern India founded in around 1399 in the vicinity of the modern-day city of Mysore and prevailed until 1950. The territorial boundaries and the form of government transmuted substantially ...
under
Hyder Ali and
Tipu Sultan
Tipu Sultan (, , ''Sultan Fateh Ali Sahab Tipu''; 1 December 1751 – 4 May 1799) commonly referred to as Sher-e-Mysore or "Tiger of Mysore", was a ruler of the Kingdom of Mysore based in South India. He was a pioneer of rocket artillery ...
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 East India Company
The East India Company (EIC) was an English, and later British, joint-stock company that was founded in 1600 and dissolved in 1874. It was formed to Indian Ocean trade, trade in the Indian Ocean region, initially with the East Indies (South A ...
. Word of the success of the Mysore rockets against the British 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 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, 2nd Baronet, Sir William Congreve in 1808.
The design was based upon Mysorean rockets, the rockets deployed by the Kingdom of Mysore against ...
in 1804.
In 1921 the
Soviet
The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
research and development laboratory
Gas Dynamics Laboratory 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 (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 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.
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 (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
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 (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
modern castable composite solid rocket motors were invented by the American aerospace engineer
Jack Parsons at
Caltech
The California Institute of Technology (branded as Caltech) is a private university, private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small g ...
in 1942 when he replaced double base propellant with roofing
asphalt and
potassium perchlorate. This made possible slow-burning rocket motors of adequate size and with sufficient shelf-life for jet-assisted take off applications.
Charles Bartley, employed at JPL (Caltech), substituted curable
synthetic rubber
A synthetic rubber is an artificial elastomer. They are polymers synthesized from petroleum byproducts. About of rubber is produced annually in the United States, and of that amount two thirds are synthetic. Synthetic rubber, just like natural ru ...
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 I
sp 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 powered only during relatively brief periods—most of the flight is unpowered. Short-range ballistic missiles (SRBM) typic ...
military technology designed with
liquid-propellant rocket
A liquid-propellant rocket or liquid rocket uses a rocket engine burning liquid rocket propellant, liquid propellants. (Alternate approaches use gaseous or Solid-propellant rocket , solid propellants.) Liquids are desirable propellants because th ...
s in the 1940s and 1950s, both the
Soviet Union
The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
and the
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
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
Arts, entertainment, and media
* ''Local'' (comics), a limited series comic book by Bria ...
,
regional
In geography, regions, otherwise referred to as areas, zones, lands or territories, are portions of the Earth's surface that are broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and ...
, and
intercontinental ballistic missiles, including solid-propellant missiles that could be launched from
air or
sea
A sea is a large body of salt water. There are particular seas and the sea. The sea commonly refers to the ocean, the interconnected body of seawaters that spans most of Earth. Particular seas are either marginal seas, second-order section ...
. 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 to add extra thrust during the early ascent of their primarily liquid rocket
launch vehicle
A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage ...
s. Some designs have had solid rocket upper stages as well. Examples flying in the 2010s include the European
Ariane 5, US
Atlas V and
Space Shuttle
The Space Shuttle is a retired, partially reusable launch system, 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. ...
, 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 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 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 (physics), work. The concept was originally applied solely to those materials capable of releasing chem ...
and
oxidizer 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 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 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 times the fuel length, the
volumetric propellant consumption rate is the cross section area times the linear burn rate
, and the
instantaneous mass flow rate of combustion gases generated is equal to the volumetric rate times the fuel density
:
:
Several geometric configurations are often used depending on the application and desired
thrust curve:
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 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, charcoal (which is mostly carbon), and potassium nitrate, potassium ni ...
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 Crystallinity, crystalline allotrope (form) of the element carbon. It consists of many stacked Layered materials, layers of graphene, typically in excess of hundreds of layers. Graphite occurs naturally and is the most stable ...
or
reinforced 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 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 IIIC solid boosters injected
nitrogen tetroxide for LITV; the tanks can be seen on the sides of the rocket between the main center stage and the boosters.
An early
Minuteman first stage used a single motor with four
gimballed nozzles to provide pitch, yaw, and roll control.
Performance

A typical, well-designed
ammonium perchlorate composite propellant (APCP) first-stage motor may have a vacuum
specific impulse
Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine, such as a rocket engine, rocket using propellant or a jet engine using fuel, generates thrust. In general, this is a ratio of the ''Impulse (physics), ...
(''I'') as high as (Titan IVB SRMU). This compares to for RP1/LOX (RD-180) and for LH
2/LOX (Block II
RS-25) bipropellant engines. Upper stage specific impulses are somewhat greater: as much as for APCP (Orbus 6E),
for RP1/LOX (RD-0124) and for LH
2/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'') 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 launch system, 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. ...
), 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, C
4H
8N
4(NO
2)
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, C
6H
6N
6(NO
2)
6, called simply
CL-20 (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.
[navy.mil](_blank)
/ref> One of the motivations for development of these very high energy density
In physics, energy density is the quotient between the amount of energy stored in a given system or contained in a given region of space and the volume of the system or region considered. Often only the ''useful'' or extractable energy is measure ...
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, charcoal (which is mostly carbon), and potassium nitrate, potassium ni ...
(gunpowder) is composed of charcoal (fuel), potassium nitrate (oxidizer), and sulfur
Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
(fuel and catalyst). It is one of the oldest pyrotechnic compositions with application to rocketry. In modern times, black powder finds use in low-power model rockets (such as Estes 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, such as a rocket engine, rocket using propellant or a jet engine using fuel, generates thrust. In general, this is a ratio of the ''Impulse (physics), ...
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; it has symbol Zn and atomic number 30. It 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 periodic tabl ...
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 sugar with the molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae during photosynthesis from water an ...
, 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 alco ...
, 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 refined ...
) 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) is a solid that lacks the long-range order that is a characteristic of a crystal. The terms "glass" and "glassy solid" are sometimes used synonymousl ...
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 exte ...
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 biprop ...
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 nitroglycerine), also known as trinitroglycerol (TNG), nitro, glyceryl trinitrate (GTN), or 1,2,3-trinitroxypropane, is a dense, colorless or pale yellow, oily, explosive liquid most commonly produced by ...
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 (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
) can increase performance to around , though metal oxide nucleation
In thermodynamics, nucleation is the first step in the formation of either a new Phase (matter), thermodynamic phase or Crystal structure, structure via self-assembly or self-organization within a substance or mixture. Nucleation is typically def ...
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-based (ANCP) or ammonium-perchlorate-based (APCP). Ammonium nitrate composite propellant often uses magnesium
Magnesium is a chemical element; it has Symbol (chemistry), 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 ...
and/or aluminium
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
as fuel and delivers medium performance (Isp of about ) whereas ammonium perchlorate composite propellant 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 (HTPB), cross-links (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, military, and amateur rockets, whereas cheaper and less efficient ANCP finds use in amateur rocketry and gas generators. Ammonium dinitramide, 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 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 is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
and nanoaluminium ( ALICE).
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
RDX (Research Department Explosive or Royal Demolition Explosive) or hexogen, among other names, is an organic compound with the formula (CH2N2O2)3. It is white, odorless, and tasteless, widely used as an explosive. Chemically, it is classified ...
or HMX, 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 (AP) and powdered aluminium
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
) 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 Rocket propellant#Solid chemical propellants, solid propellants (fuel/oxidizer). The earliest rockets were solid-fuel rockets powered by gunpowder. The incepti ...
used to fuel the Trident II D-5 SLBM 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 wei ...
-bound HMX, 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 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 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 is a small rocket designed to reach low altitudes (e.g., for a model) and #Model rocket recovery methods, be recovered by a variety of means.
According to the United States National Association of Rocketry, National Associati ...
ry; they are normally small cylinders of black powder fuel with an integral nozzle 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 instrument used to capture and store images and videos, either digitally via an electronic image sensor, or chemically via a light-sensitive material such as photographic film. As a pivotal technology in the fields of photograp ...
, or deploy a parachute
A parachute is a device designed to slow an object's descent through an atmosphere by creating Drag (physics), drag or aerodynamic Lift (force), lift. It is primarily used to safely support people exiting aircraft at height, but also serves va ...
. Without this charge and delay, the motor may ignite a second stage (black powder only).
In mid- and high-power rocketry, 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; it has 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 in ...
sponge to the mix).
Use
Sounding rockets
Almost all sounding rockets use solid motors.
* Astrobee
* 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-520
* Skylark (rocket)
* Terrier-Orion, Terrier-Malemute
* 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 is a short-range air-to-air missile. Entering service with the United States Navy in 1956 and the Air Force in 1964, the AIM-9 is one of the oldest, cheapest, and most successful air-to-air missiles. Its latest variants rema ...
, AIM-54 Phoenix, Fakour-90, Meteor
A meteor, known colloquially as a shooting star, is a glowing streak of a small body (usually meteoroid) going through Earth's atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere,
creating a ...
, R-33, PL-15
* Ballistic missiles: Jericho
Jericho ( ; , ) is a city in the West Bank, Palestine, and the capital of the Jericho Governorate. Jericho is located in the Jordan Valley, with the Jordan River to the east and Jerusalem to the west. It had a population of 20,907 in 2017.
F ...
, Sejjil, 9K720 Iskander, Fateh-110, ATACMS, DF-21
* ICBMs: LGM-30 Minuteman, UGM-133 Trident II, LGM-118 Peacekeeper
The LGM-118 Peacekeeper, originally known as the MX for "Missile, Experimental", was a Multiple independently targetable reentry vehicle, MIRV-capable intercontinental ballistic missile (ICBM) produced and deployed by the United States from 1986 ...
, RT-2PM Topol, DF-41, 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, sect ...
* Athena
Athena or Athene, often given the epithet Pallas, is an ancient Greek religion, ancient Greek goddess associated with wisdom, warfare, and handicraft who was later syncretism, syncretized with the Roman goddess Minerva. Athena was regarde ...
* Mu
* Pegasus
* Taurus
* Minotaur
In Greek mythology, the Minotaur (, ''Mīnṓtauros''), also known as Asterion, 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 "par ...
* Start-1
* PSLV - alternating solid and liquid stages
* SSLV - all lower 3 stages are solid stages
* SFDR
* Shavit
* Vega
* Long March 11
* OmegA
Omega (, ; uppercase Ω, lowercase ω; Ancient Greek ὦ, later ὦ μέγα, Modern Greek ωμέγα) is the twenty-fourth and last letter in the Greek alphabet. In the Greek numerals, Greek numeric system/isopsephy (gematria), it has a value ...
(project was cancelled in 2020, rocket unflown)
* Qaem 100
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, and sometimes known as the Thorad Delta 1. Delta II was part of the Delta rocket family, derived directly from the Delta 3000, and entered service in ...
* Titan IV
* Space Shuttle
The Space Shuttle is a retired, partially reusable launch system, 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. ...
* Space Launch System
* Ariane 5
* Atlas II
* Atlas V (optionally 1-5 boosters)
* Delta IV (optionally 2 or 4 boosters)
* H-IIA, H-IIB
* PSLV - optional solid boosters to lift heavier payloads
* GSLV Mk III
Solid fuel is also used for some upper stages, particularly the Star 37 (sometimes referred to as the "Burner" upper stage) and the Star 48 (sometimes referred to as the " Payload Assist Module", or PAM), both manufactured originally by Thiokol, and today by Northrop Grumman
Northrop Grumman Corporation is an American multinational Aerospace manufacturer, aerospace and Arms industry, defense company. With 97,000 employees and an annual revenue in excess of $40 billion, it is one of the world's largest Arms industry ...
. They are used to lift large payloads to intended orbits (such as the Global Positioning System
The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide ge ...
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 launch system, 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. ...
and the Titan IV, was the Boeing
The Boeing Company, or simply Boeing (), is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, and missiles worldwide. The company also provides leasing and product support s ...
-manufactured Inertial Upper Stage (IUS).
* ''Pioneer 10
''Pioneer 10'' (originally designated Pioneer F) is a NASA space probe launched in 1972 that completed the first mission to the planet Jupiter. ''Pioneer 10'' became the first of five artificial objects to achieve the escape velocity needed ...
'' and ''Pioneer 11
''Pioneer 11'' (also known as ''Pioneer G'') is a NASA robotic space probe launched on April 5, 1973, to study the asteroid belt, the environment around Jupiter and Saturn, the solar wind, and cosmic rays. It was the first probe to Exploration ...
'' were both sent out of the Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
by Star 37E upper stages from Atlas-Centaur 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 the interstellar medium, interstellar space beyond the Sun's heliosphere. It was launched 16 days afte ...
'' and ''Voyager 2
''Voyager 2'' is a space probe launched by NASA on August 20, 1977, as a part of the Voyager program. It was launched on a trajectory towards the gas giants (Jupiter and Saturn) and enabled further encounters with the ice giants (Uranus and ...
'' were both sent out of the Solar System by Star 37E upper stages from Titan IIIE rockets.
* '' Magellan'' 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), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...
'' 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
A gravity assist, gravity assist maneuver, swing-by, or generally a gravitational slingshot in orbital mechanics, is a type of spaceflight flyby (spaceflight), flyby which makes use of the relative movement (e.g. orbit around the Sun) and gra ...
around Jupiter.
* ''New Horizons
''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institut ...
'' was sent out of the Solar System on a Star 48 PAM from an Atlas V rocket.
Some rockets, like the Antares (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 manufacturer, aerospace and Arms industry, defense company. With 97,000 employees and an annual revenue in excess of $40 billion, it is one of the world's largest Arms industry ...
-manufactured Castor 30 as an upper stage.
Advanced research
* Environmentally sensitive fuel formulations such as ALICE propellant
* Ramjets with solid fuel
* Variable thrust designs based on variable nozzle geometry
* Hybrid rockets that use solid fuel and throttleable liquid or gaseous oxidizer
See also
* Comparison of solid-fuelled orbital launch systems
* Comparison of orbital launch systems
* Comparison of orbital launcher families
* List of canceled launch vehicle designs
* List of missiles
* List of orbital launch systems
* List of sounding rockets
* List of military rockets
* Fireworks
Fireworks are Explosive, low explosive Pyrotechnics, 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 numbe ...
* 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 reaction, exothermic chemical reac ...
* Intercontinental ballistic missile
An intercontinental ballistic missile (ICBM) is a ballistic missile with a range (aeronautics), range greater than , primarily designed for nuclear weapons delivery (delivering one or more Thermonuclear weapon, thermonuclear warheads). Conven ...
* Jetex
* Space Shuttle Solid Rocket Booster
* Crawford burner
* Nano-thermite
* Skyrocket
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
Chinese inventions
Rocket engines
Rocket propulsion
Rocket engines by propellant
Solid fuels