Editing Hydrazine (section)

===Rocket fuel===
[[File:Hypergolic Fuel for MESSENGER.jpg|thumb|upright|[[Anhydrous]] (pure, not in solution) hydrazine being loaded into the ''[[MESSENGER]]'' space probe (orbital reconnaissance mission of the planet [[Mercury (planet)|Mercury]]). The technician is wearing a safety suit in overpressure with an external air supply.]]
Hydrazine was first used as a component in [[rocket fuel]]s during [[World War II]]. A 30% mix by weight with 57% [[methanol]] (named [[List of stoffs|M-Stoff]] in the German [[Luftwaffe]]) and 13% water was called [[C-Stoff]] by the Germans.<ref name=Clark2018>{{cite book |isbn = 978-0-8135-9918-2 |title = Ignition!: An Informal History of Liquid Rocket Propellants |last1 = Clark |first1 = John Drury |author-link=John Drury Clark |date = 23 May 2018 |publisher = Rutgers University Press |url=https://books.google.com/books?id=BdU4DwAAQBAJ&q=C-Stoff  |pages=302}}</ref> The mixture was used to power the [[Messerschmitt Me 163#Me 163 B|Messerschmitt Me 163B]] rocket-powered fighter plane, in which the German [[high test peroxide]] ''[[T-Stoff]]'' was used as an oxidizer. Unmixed hydrazine was referred to as [[List of stoffs|B-Stoff]] by the Germans, a designation also used later for the ethanol/water fuel for the [[V-2 missile]].<ref>{{cite report |author1=T. W. Price|author2=D. D. Evans|date= |title=Technical Report 32-7227 The Status of Monopropellant Hydrazine Technology| url=https://ntrs.nasa.gov/api/citations/19680006875/downloads/19680006875.pdf|publisher=National Aeronautics and Space Administration (NASA) |page=1|access-date=22 February 2022}}</ref>

Hydrazine is used as a low-power [[monopropellant]] for the maneuvering (RCS/Reaction control system) thrusters of spacecraft, and was used to power the [[Space Shuttle]]'s auxiliary power units (APUs). In addition, mono-propellant hydrazine-fueled rocket engines are often used in terminal descent of spacecraft. Such engines were used on the [[Viking program]] landers in the 1970s as well as the Mars landers ''[[Phoenix (spacecraft)|Phoenix]]'' (May 2008), ''[[Curiosity rover|Curiosity]]'' (August 2012), and ''[[Perseverance (rover)|Perseverance]]'' (February 2021).

During the [[Soviet space program]], [[unsymmetrical dimethylhydrazine]] (also discovered by Fischer in 1875) was used instead of hydrazine. Together with nitric oxidizers it became known as "[[devil's venom]]" due to its highly dangerous nature.<ref>{{Cite web|url=http://www.spacesafetymagazine.com/space-disasters/nedelin-catastrophe/historys-launch-padfailures-nedelin-disaster-part-1/|title=The Nedelin Catastrophe, Part 1|date=28 October 2014|archive-url=https://archive.today/20220215233340/http://www.spacesafetymagazine.com/space-disasters/nedelin-catastrophe/historys-launch-padfailures-nedelin-disaster-part-1/|access-date=15 February 2022|archive-date=15 February 2022|url-status=live}}</ref>

In all hydrazine mono-propellant engines, the hydrazine is passed over a [[catalyst]] such as [[iridium]] metal supported by high-surface-area [[alumina]] (aluminium oxide), which causes it to decompose into [[ammonia]] ({{chem2|NH3}}), nitrogen gas ({{chem2|N2}}), and hydrogen ({{chem2|H2}}) gas according to the three following reactions:<ref name="Haws">{{cite journal|vauthors=Haws JL, Harden DG|date=1965|title=Thermodynamic Properties of Hydrazine|journal= Journal of Spacecraft and Rockets |volume=2|issue=6|pages=972–974|bibcode=1965JSpRo...2..972H|doi=10.2514/3.28327}}</ref>

: Reaction 1: {{chem2|N2H4 → N2 + 2 H2}}
: Reaction 2: {{chem2|3 N2H4 → 4 NH3 + N2}}
: Reaction 3: {{chem2|4 NH3 + N2H4 → 3 N2 + 8 H2}}

The first two reactions are extremely [[exothermic]] (the catalyst chamber can reach 800&nbsp;°C in a matter of milliseconds,<ref name="Vieira">{{cite journal|vauthors=Vieira R, Pham-Huu C, Kellera N, Ledouxa MJ|year=2002|title=New carbon nanofiber/graphite felt composite for use as a catalyst support for hydrazine catalytic decomposition|journal=[[Chemical Communications|Chem. Comm.]]|volume=44|issue=9|pages=954–955|doi=10.1039/b202032g|pmid=12123065}}</ref>) and they produce large volumes of hot gas from a small volume of liquid,<ref name="Chen">{{cite journal|vauthors=Chen X, Zhang T, Xia L, Li T, Zheng M, Wu Z, Wang X, Wei Z, Xin Q, Li C|date=Apr 2002|title=Catalytic Decomposition of Hydrazine over Supported Molybdenum Nitride Catalysts in a Monopropellant Thruster|journal=[[Catalysis Letters]]|volume=79|pages=21–25|doi=10.1023/A:1015343922044|s2cid=92094908}}</ref> making hydrazine a fairly efficient thruster propellant with a vacuum [[specific impulse]] of about 220 seconds.<ref>{{Cite web|url=https://www.eso-io.com/my.logout.php3?errorcode=20|archive-url=https://web.archive.org/web/20080623224048/http://cs.astrium.eads.net/sp/SpacecraftPropulsion/MonopropellantThrusters.html|title=BIG-IP logout page|archive-date=June 23, 2008|website=www.eso-io.com|access-date=May 20, 2020}}</ref> Reaction 2 is the most exothermic, but produces a smaller number of molecules than that of reaction 1. Reaction 3 is [[endothermic]] and reverts the effect of reaction 2 back to the same effect as reaction 1 alone (lower temperature, greater number of molecules). The catalyst structure affects the proportion of the {{chem2|NH3}} that is dissociated in reaction 3; a higher temperature is desirable for rocket thrusters, while more molecules are desirable when the reactions are intended to produce greater quantities of gas.<ref>{{Cite journal |last1=Valera-Medina |first1=A |last2=Xiao |first2=H |last3=Owen-Jones |first3=M |last4=David |first4=W. I. F. |last5=Bowen |first5=P. J. |date=2018-11-01 |title=Ammonia for power |journal=Progress in Energy and Combustion Science |language=en|volume=69 |pages=63–102 |doi=10.1016/j.pecs.2018.07.001 |s2cid=106214840 |issn=0360-1285|doi-access=free|bibcode=2018PECS...69...63V }}</ref>

Since hydrazine is a solid below 2&nbsp;°C, it is not suitable as a general purpose rocket propellant for military applications. Other [[Hydrazines|variants of hydrazine]] that are used as rocket fuel are [[monomethylhydrazine]], {{chem2|CH3NHNH2}}, also known as MMH (melting point −52&nbsp;°C), and [[unsymmetrical dimethylhydrazine]], {{chem2|(CH3)2NNH2}}, also known as UDMH (melting point −57&nbsp;°C). These derivatives are used in two-component rocket fuels, often together with [[dinitrogen tetroxide]], {{chem2|N2O4}}. A 50:50 mixture by weight of hydrazine and UDMH was used in the engine of the service propulsion system of the [[Apollo command and service module]], both the ascent and descent engines of the [[Apollo Lunar Module]] and [[Titan II]] [[Intercontinental ballistic missile|ICBMs]] and is known as [[Aerozine 50]].<ref name=Clark2018/> These reactions are extremely exothermic, and the burning is also [[Hypergolic propellant|hypergolic]] (it starts burning without any external ignition).<ref name="Mitchell">{{cite journal |vauthors=Mitchell MC, Rakoff RW, Jobe TO, Sanchez DL, Wilson B |date=2007 |title=Thermodynamic analysis of equations of state for the monopropellant hydrazine |journal= Journal of Thermophysics and Heat Transfer |volume=21 |issue=1 |pages=243–246 |doi=10.2514/1.22798}}</ref>

There are ongoing efforts in the aerospace industry to find a replacement for hydrazine, given its potential ban across the European Union.<ref>{{Cite web |date=2017-10-25 |title=Hydrazine ban could cost Europe's space industry billions |url=https://spacenews.com/hydrazine-ban-could-cost-europes-space-industry-billions/ |access-date=2022-08-19 |website=SpaceNews |language=en-US}}</ref><ref>{{Cite web |title=International research projects {{!}} Ministry of Business, Innovation & Employment |url=https://www.mbie.govt.nz/science-and-technology/space/nzspacetalk/international-research-projects/ |access-date=2022-08-19 |website=www.mbie.govt.nz}}</ref><ref>{{Cite web |last=Urban |first=Viktoria |date=2022-07-15 |title=Dawn Aerospace granted €1.4 million by EU for green propulsion technology |url=https://spacewatch.global/2022/07/dawn-aerospace-granted-e1-4-million-by-eu-for-green-propulsion-technology/ |access-date=2022-08-19 |website=SpaceWatch.Global |language=en-US}}</ref> Promising alternatives include [[nitrous oxide]]-based propellant combinations, with development being led by commercial companies [[Dawn Aerospace]], [[Impulse Space]],<ref>{{Cite web |last=Berger |first=Eric |date=2022-07-19 |title=Two companies join SpaceX in the race to Mars, with a launch possible in 2024 |url=https://arstechnica.com/science/2022/07/relativity-and-impulse-space-say-theyre-flying-to-mars-in-late-2024/ |access-date=2022-08-19 |website=Ars Technica |language=en-us}}</ref> and [[Launcher (company)|Launcher]].<ref>{{Cite web |date=2021-06-15 |title=Launcher to develop orbital transfer vehicle |url=https://spacenews.com/launcher-to-develop-orbital-transfer-vehicle/ |access-date=2022-08-19 |website=SpaceNews |language=en-US}}</ref> The first nitrous oxide-based system ever flown in space was by [[D-Orbit]] onboard their [[ION Satellite Carrier]] in 2021, using six Dawn Aerospace B20 thrusters.<ref>{{Cite web |title=Dawn Aerospace validates B20 Thrusters in space – Bits&Chips |date=6 May 2021 |url=https://bits-chips.nl/artikel/dawn-aerospace-validates-b20-thrusters-in-space/ |access-date=2022-08-19 |language=en-US}}</ref><ref>{{Cite web |title=Dawn B20 Thrusters Proven In Space |url=https://www.dawnaerospace.com/latest-news/b20-thrusters-proven-in-space |access-date=2022-08-19 |website=Dawn Aerospace |language=en-US}}</ref> Another alternative is more safe blends of hydrazine with much lower [[vapor pressure]], hence reduced inhalation hazard. [[Aerojet Rocketdyne]] has developed HPB-G28 blend that have 150 times lower vapor pressure, same specific impulse, and 35% higher density specific impulse than neat hydrazine. HPB-G28 can be used with same thrusters and catalysts as hydrazine, but has freezing point of -55°C, making propellant line heating unnecessary. It contains 65% (by mol) hydrazine, 27% hydroxyethylhydrazinuim nitrate (HEHN) and 8% [[hydrazinium nitrate]].<ref>{{Cite conference |last=Masse |first=Robert K. |last2=Glassy |first2=Benjamin A. |last3=Spores |first3=Ronald A. |last4=Vuong |first4=Andrew T. |last5=Zhu |first5=Zhenghao |last6=Pourpoint |first6=Timothee L. |date=January 2024 |title=Hydrazine-Based Green Monopropellant Blends |conference=AIAA SCITECH 2024 Forum |language=en |publisher=AIAA |doi=10.2514/6.2024-1619 |isbn=978-1-62410-711-5}}</ref>