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 ...

rocket (or "monochemical 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 ...

that uses a single

chemical A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combin ...

as its

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 ...

. Monopropellant rockets are commonly used as small attitude and trajectory control rockets in satellites, rocket upper stages, crewed spacecraft, and spaceplanes.

Chemical-reaction based monopropellant rockets

The simplest monopropellant rockets depend on the

chemical decomposition Chemical decomposition, or chemical breakdown, is the process or effect of simplifying a single molecular entity, chemical entity (normal molecule, reaction intermediate, etc.) into two or more fragments. Chemical decomposition is usually regarded ...

of a storable propellant after passing it over a catalyst bed. The power for the thruster comes from the high pressure gas created during the decomposition reaction that allows a

rocket nozzle A rocket engine nozzle is a propelling nozzle (usually of the de Laval type) used in a rocket engine to expand and accelerate combustion products to high supersonic velocities. Simply: propellants pressurized by either pumps or high pressure u ...

to speed up the gas to create thrust. The most commonly used monopropellant is

hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly hazardous unless handled in solution as, for example, hydraz ...

(), a compound unstable in the presence of a

catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

and which is also a strong

reducing agent In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are common reducing agents include hydrogen, carbon ...

. The most common catalyst is granular

alumina Aluminium oxide (or aluminium(III) oxide) is a chemical compound of aluminium and oxygen with the chemical formula . It is the most commonly occurring of several aluminium oxides, and specifically identified as aluminium oxide. It is commonly ...

(aluminum oxide, ) coated with

iridium Iridium is a chemical element; it has the symbol Ir and atomic number 77. This very hard, brittle, silvery-white transition metal of the platinum group, is considered the second-densest naturally occurring metal (after osmium) with a density ...

. These coated granules are usually under the commercial labels Aerojet S-405 (previously made by

Shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses Science Biology * Seashell, a hard outer layer of a marine ani ...

) or W.C. Heraeus H-KC 12 GA (previously made by Kali Chemie). There is no igniter with hydrazine. Aerojet S-405 is a spontaneous catalyst, that is, hydrazine decomposes on contact with the catalyst. The

decomposition Decomposition is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is ess ...

is highly

exothermic In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e ...

and produces a gas that is a mixture of

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

and

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

. The main limiting factor of the monopropellant rocket is its life, which mainly depends on the life of the catalyst. The catalyst may be subject to catalytic poisoning and catalytic attrition which results in the catalyst failure. Another monopropellant is

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...

, which, when purified to 90% or higher concentration, is self-decomposing at high temperatures or when a catalyst is present. Most chemical-reaction monopropellant rocket systems consist of a

fuel tank A fuel tank (also called a petrol tank or gas tank) is a safe container for Flammability, flammable fluids, often gasoline or diesel fuel. Though any storage tank for fuel may be so called, the term is typically applied to part of an engine sys ...

, usually a

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 ...

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 ...

sphere, with an ethylene-propylene rubber container or a

surface tension Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension (physics), tension is what allows objects with a higher density than water such as razor blades and insects (e.g. Ge ...

propellant management device A propellant management device (PMD) provides a way to expel propellant in a low-gravity environment. Devices can use surface tension as the primary expulsion device with a combination of baffles, fins, and vanes. The main goal of the PMD is to prov ...

filled with the fuel. The tank is then pressurized with

helium Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...

, which pushes the fuel out to the motors. A pipe leads from the tank to a

poppet valve A poppet valve (also sometimes called mushroom valve) is a valve typically used to control the timing and quantity of petrol (gas) or vapour flow into or out of an engine, but with many other applications. It consists of a hole or open-ended ch ...

, and then to the decomposition chamber of the rocket motor. Typically, a

satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...

will have not just one motor, but two to twelve, each with its own valve. The

attitude control Spacecraft attitude control is the process of controlling the orientation of a spacecraft (vehicle or satellite) with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, ...

rocket motors for satellites and

space probe Uncrewed spacecraft or robotic spacecraft are spacecraft without people on board. Uncrewed spacecraft may have varying levels of autonomy from human input, such as remote control, or remote guidance. They may also be autonomous, in which th ...

s are often very small, or so in

diameter In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...

, and mounted in groups that point in four directions (within a plane). The rocket is fired when the

computer A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...

sends

direct current Direct current (DC) is one-directional electric current, flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor (material), conductor such as a wire, but can also flow throug ...

through a small

electromagnet An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire (likely copper) wound into a electromagnetic coil, coil. A current through the wire creates a magnetic ...

that opens the poppet valve. The firing is often very brief, a few

millisecond A millisecond (from '' milli-'' and second; symbol: ms) is a unit of time in the International System of Units equal to one thousandth (0.001 or 10−3 or 1/1000) of a second or 1000 microseconds. A millisecond is to one second, as one second i ...

s, and — if operated in air — would sound like a pebble thrown against a metal trash can; if on for long, it would make a piercing hiss. Chemical-reaction monopropellants are not as efficient as some other propulsion technologies. Engineers choose monopropellant systems when the need for simplicity and reliability outweigh the need for high delivered impulse. If the propulsion system must produce large amounts of thrust, or have a high

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), ...

, as on the main motor of an interplanetary spacecraft, other technologies are used.

Solar-thermal based monopropellant thrusters

A concept to provide

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)

propellant depot An orbital propellant depot is a cache of propellant that is placed in orbit around Earth or another body to allow spacecraft or the transfer stage of the spacecraft to be fueled in space. It is one of the types of space resource depots that ha ...

s that could be used as way-stations for other spacecraft to stop and refuel on the way to beyond-LEO missions has proposed that waste gaseous

—an inevitable byproduct of long-term

liquid hydrogen Liquid hydrogen () is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecule, molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point (thermodynamics), critical point of 33 Kelvins, ...

storage in the radiative heat environment of

space Space is a three-dimensional continuum containing positions and directions. In classical physics, physical space is often conceived in three linear dimensions. Modern physicists usually consider it, with time, to be part of a boundless ...

—would be usable as a monopropellant in a solar-thermal propulsion system. The waste hydrogen would be productively utilized for both

orbital station-keeping In astrodynamics, orbital station-keeping is keeping a spacecraft at a fixed distance from another spacecraft or celestial body. It requires a series of orbital maneuvers made with thruster burns to keep the active craft in the same orbit as its ...

and attitude control, as well as providing limited propellant and thrust to use for

orbital maneuvers Orbital may refer to: Sciences Chemistry and physics * Atomic orbital * Molecular orbital * Orbital hybridisation, Hybrid orbital Astronomy and space flight * Orbit ** Geocentric orbit, Earth orbit Medicine and physiology * Orbit (anatomy), als ...

to better

rendezvous Rendezvous or rendez-vous may refer to: Arts and entertainment Film and television * ''The Rendezvous'' (1923 film), a silent film adventure melodrama * ''Rendezvous'' (1930 film), a German musical directed by Carl Boese * ''Rendezvous ...

with other spacecraft that would be inbound to receive fuel from the depot. Solar-thermal monopropellant thrusters are also integral to the design of a next-generation cryogenic

upper stage A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own Rocket engine, engines and Rocket propellant, propellant. A ''tandem'' or ''serial'' stage is mounted on top of anoth ...

proposed by U.S. company

United Launch Alliance United Launch Alliance, LLC (ULA) is an American launch service provider formed in December 2006 as a joint venture between Lockheed Martin Space and Boeing Defense, Space & Security. The company designs, assembles, sells and launches rockets ...

(ULA). The Advanced Common Evolved Stage (ACES) is intended as a lower-cost, more-capable and more-flexible upper stage that would supplement, and perhaps replace, the existing ULA

Centaur A centaur ( ; ; ), occasionally hippocentaur, also called Ixionidae (), is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse that was said to live in the mountains of Thessaly. In one version o ...

and ULA

Delta Cryogenic Second Stage The Delta Cryogenic Second Stage (DCSS) is a family of cryogenic-fuelled rocket stages used on the Delta III, Delta IV, and on the Space Launch System Block 1 launch vehicles. The DCSS employs a unique two-tank architecture where the cylind ...

(DCSS) upper stage vehicles. The ACES Integrated Vehicle Fluids option eliminates all

and

from the space vehicle—normally used for attitude control and station keeping—and depends instead on solar-thermal monopropellant thrusters using waste hydrogen.Zegler and Kutter, 2010, p. 5.

History

Soviet designers had begun experimenting with monopropellant rockets as early as 1933. They believed their monopropellant mixes of

nitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russian rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...

with gasoline, or toluene, and kerosene would lead to an overall simpler system; however, they ran into problems with violent explosions with pre-mixed fuel and oxidizer serving as a monopropellant that led the designers to abandon this approach.

Helmuth Walter Helmuth is both a masculine German given name and a surname. Notable people with the name include: __NOTOC__ Given name *Helmuth Theodor Bossert Helmuth Theodor Bossert (11 September 1889 – 5 February 1961) was a German and Turkish history of ...

was a German engineer an early pioneer of monopropellant rockets using hydrogen peroxide as fuel. Although his initial work was on submarine propulsion the same jets of oxygen produced by for combustion in gas turbines could be directed through a nozzle to generate thrust. The rocket Walter developed was used in the German ME-163 fighter aircraft in 1944, the first aircraft to break the 1000 km/h (635 mph). After World War Two the British would continue to experiment with hydrogen peroxide monopropellants. They would develop the

de Havilland Sprite The de Havilland Sprite is a British rocket engine that was built by de Havilland Engine Company, de Havilland in the early-1950s for use in RATO (Rocket-assisted take off) applications. A developed engine with slightly less thrust but a long ...

a hydrogen peroxide rocket that could produce 5000lbf of thrust over 16 seconds. Not intended for space flight the rocket would provide hot and high takeoff capability to the

de Havilland Comet 1 The de Havilland DH.106 Comet is the world's first commercial jet airliner. Developed and manufactured by de Havilland in the United Kingdom, the Comet 1 prototype first flew in 1949. It features an aerodynamically clean design with four ...

the first commercial jet airliner. In the United States, when NASA began studying monopropellants at the Jet Propulsion Laboratory (JPL) the properties of the existing propellants demanded that the thrusters be impractically large. The addition of a catalyst and pre-heating propellant made them more efficient, but raised concerns over safety and handling of hazardous propellants like anhydrous

. However the simplicity of the thrusters designed around early monopropellants offered many simplicities and were first tested in 1959 on the Able-4 mission. This test allowed for the Ranger and

Mariner A sailor, seaman, mariner, or seafarer is a person who works aboard a watercraft as part of its crew, and may work in any one of a number of different fields that are related to the operation and maintenance of a ship. While the term ''sailor' ...

missions to use a similar thruster for correction maneuvers and in the orbital insertion of

Telstar Telstar refers to a series of communications satellites. The first two, Telstar 1 and Telstar 2, were experimental and nearly identical. Telstar 1 launched atop of a Thor-Delta rocket on July 10, 1962, successfully relayed the first televisi ...

, considered by the National Air and Space Museum to be the most significant communications satellite in the beginning of the space race. Centaur rocket stage

In 1964, NASA began use of the

Lunar Landing Research Vehicle The Bell Aerosystems Lunar Landing Research Vehicle (LLRV, nicknamed the Flying Bedstead) was a Apollo program, Project Apollo era program to build a simulator for the Moon landings. The LLRVs were used by the FRC, now known as the NASA Armstron ...

to train Apollo astronauts in piloting the Lunar Excursion Module (LEM) using an attitude control system consisting of 16 hydrogen peroxide monopropellant thrusters to steer the LEM to the lunar surface. Upper stage vehicles began using monopropellant thrusters as a convenient control device in the early 1960s when General Dynamics proposed the Centaur upper stage to the United States Airforce of which versions are still in use in

Atlas An atlas is a collection of maps; it is typically a bundle of world map, maps of Earth or of a continent or region of Earth. Advances in astronomy have also resulted in atlases of the celestial sphere or of other planets. Atlases have traditio ...

and Vulcan rockets.

New developments

NASA is developing a new monopropellant propulsion system for small, cost-driven spacecraft with

delta-v Delta-''v'' (also known as "change in velocity"), symbolized as and pronounced , as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as launching from or l ...

requirements in the range of 10–150 m/s. This system is based on a hydroxylammonium nitrate (HAN)/water/fuel monopropellant blend which is extremely dense, environmentally benign, and promises good performance and simplicity. The EURENCO Bofors company produced LMP-103S as a 1-to-1 substitute for hydrazine by dissolving 65%

ammonium dinitramide Ammonium dinitramide (ADN) is an inorganic compound with the chemical formula . It is the ammonium salt (chemistry), salt of dinitraminic acid . It consists of ammonium cations and dinitramide anions . ADN decomposes under heat to leave only nitr ...

, NH₄N(NO₂)₂, in 35% water solution of

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...

and ammonia. LMP-103S has 6% higher specific impulse and 30% higher impulse density than hydrazine monopropellant. Additionally, hydrazine is highly toxic and carcinogenic, while LMP-103S is only moderately toxic. LMP-103S is UN Class 1.4S allowing for transport on commercial aircraft, and was demonstrated on the Prisma satellite in 2010. Special handling is not required. LMP-103S could replace hydrazine as the most commonly used monopropellant.

References

External links

Technical Reports on Hydrogen Peroxide as a Monopropellant for Rockets

USPAT 20090133788 Nitrous oxide fuel blend monopropellants
{{DEFAULTSORT:Monopropellant Rocket Rocket propulsion Rocket engines by propellant Rocket engines pt:Foguete monopropulsor