User:Tylerd24/Monopropellant rocket

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A monopropellant rocket (or "monochemical rocket") is a rocket that uses a single chemical as its propellant.

Chemical-reaction monopropellant rockets
For monopropellant rockets that depend on a chemical reaction, the power for the propulsive reaction and resultant thrust is provided by the chemical itself. That is, the energy needed to propel the spacecraft is contained within the chemical bonds of the chemical molecules involved in the reaction.

The most commonly used monopropellant is hydrazine (N2H4, or H2N\sNH2), a compound unstable in the presence of a catalyst and which is also a strong reducing agent. The most common catalyst is granular alumina (aluminum oxide, Al2O3) coated with iridium. These coated granules are usually under the commercial labels Aerojet S-405 (previously made by Shell) 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 is highly exothermic and produces a 1000 C gas that is a mixture of nitrogen, hydrogen and ammonia. 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, 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, usually a titanium or aluminium sphere, with an ethylene-propylene rubber container or a surface tension propellant management device filled with the fuel. The tank is then pressurized with helium or nitrogen, which pushes the fuel out to the motors. A pipe leads from the tank to a poppet valve, and then to the decomposition chamber of the rocket motor. Typically, a satellite will have not just one motor, but two to twelve, each with its own valve.

The attitude control rocket motors for satellites and space probes are often very small, 25 mm or so in diameter, and mounted in groups that point in four directions (within a plane).

The rocket is fired when the computer sends direct current through a small electromagnet that opens the poppet valve. The firing is often very brief, a few milliseconds, 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, as on the main motor of an interplanetary spacecraft, other technologies are used.

Solar-thermal monopropellant thrusters
A concept to provide low Earth orbit (LEO) propellant depots 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 hydrogen—an inevitable byproduct of long-term liquid hydrogen storage in the radiative heat environment of space—would be usable as a monopropellant in a solar-thermal propulsion system. The waste hydrogen would be productively utilized for both orbital stationkeeping and attitude control, as well as providing limited propellant and thrust to use for orbital maneuvers to better rendezvous with other spacecraft that would be inbound to receive fuel from the depot.

Solar-thermal monoprop thrusters are also integral to the design of a next-generation cryogenic upper stage rocket proposed by U.S. company United Launch Alliance (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 and ULA Delta Cryogenic Second Stage (DCSS) upper stage vehicles. The ACES Integrated Vehicle Fluids option eliminates all hydrazine and helium from the space vehicle—normally used for attitude control and station keeping—and depends instead on solar-thermal monoprop thrusters using waste hydrogen.

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

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 hydrazine. 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 missions to use a similar thruster for correction maneuvers and in the orbital insertion of Telstar, considered by the National Air and Space Museum to be the most significant communications satellite in the beginning of the space race.

In 1964, NASA began use of the Lunar Landing Research Vehicle to train Apollo astronauts in piloting the Lunar Excursion Module (LEM) utilizing an attitude control system comprised of 16 hydrogen peroxide monopropellant thrusters to steer the LEM to the lunar surface.

On May 4th, 1974 Yvonne C. Brill, a woman engineer at RCA, was granted a patent for a monopropellant rocket to be used for unmanned satellite attitude control or orbit maneuvering.

End of additions March 2024

Responding to Mnbkv6's Peer Review

Thank you for your review! We could definitely add some more context as to why they are important. I made an attempt on mine but could definitely flesh it out more and maybe add some pictures to help visualize what exactly it is that is being discussed. Similarly, I can add links to the important missions that are mentioned. I can certainly try to find some sources from maybe other government space programs like ESA or JAXA (or maybe even the Soviet Union); however, many rocket technologies researched and invested in by private companies is held as proprietary technology and is not available to the public or is protected by ITAR. NASA, being a government agency, has everything they invent and develop themselves in the public domain and even most of the technology developed for them by private companies is somewhat available. So I can certainly try, but understand there is a bit of limitation there as far as the availability of information. NASA technical reports are peer reviewed typically to remove bias and are typically not opinion pieces and are reliable documents; however, there is certainly more value to be added from a breadth of sources.

Responding to Atghmb's Peer Review

Thank you for the review! I can go back through my work and make sure that I am keeping a breadth of sources throughout the history section. Images can definitely help, but there is a limit to what we should add in the history section about the actual function of the technology and the propellants. This article is not about the propellants, and the history section is unfortunately not the place to get into the details of the actual function of the technology. I do agree that some more context to their origin and necessity would certainly help. I will also definitely review my article to make sure it is friendly to readers who are unfamiliar with any rocket technology.

New developments
NASA is developing a new monopropellant propulsion system for small, cost-driven spacecraft with delta-v 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, NH4N(NO2)2, in 35% water solution of methanol 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.