Editing Hydrazine (section)

==Applications==
===Gas producers and propellants===
The largest use of hydrazine is as a precursor to [[blowing agent]]s. Specific compounds include [[azodicarbonamide]] and [[azobisisobutyronitrile]], which produce {{nowrap|100–200 mL}} of gas per gram of precursor. In a related application, [[sodium azide]], the gas-forming agent in [[Airbag|airbags]], is produced from hydrazine by reaction with [[sodium nitrite]].<ref name=Ullmann/>

Hydrazine is also used as a long-term [[storable propellant]] on board [[outer space|space]] vehicles, such as the [[Dawn (spacecraft)#Propulsion system|''Dawn'']] mission to Ceres and Vesta, and to both reduce the concentration of dissolved oxygen in and control pH of water used in large industrial boilers. The [[General Dynamics F-16 Fighting Falcon|F-16]] fighter jet,<ref>https://schultzairshows.com/wp-content/uploads/2020/05/usaf-f-16-emergency-extraction-card.pdf</ref> [[Space Shuttle]], and [[Lockheed U-2|U-2]] spy plane use hydrazine to fuel their Emergency Start System in the event of an engine stall.<ref>{{Cite web |url=http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA065595 |title=Exhaust Gas Composition of the F-16 Emergency Power Unit |last1=Suggs |first1=HJ|last2=Luskus|first2=LJ|date=1979|publisher=[[United States Air Force|USAF]]|type=technical report |id=SAM-TR-79-2|archive-url=https://web.archive.org/web/20160304084802/http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA065595 |archive-date=4 March 2016|access-date=23 Jan 2019 |last3=Kilian|first3=HJ|last4=Mokry|first4=JW}}</ref>

===Precursor to pesticides and pharmaceuticals===
[[Image:Fluconazole skeletal formula.svg|thumb|left|180 px|[[Fluconazole]], synthesized using hydrazine, is an [[antifungal]] medication.]]

Hydrazine is a precursor to several pharmaceuticals and pesticides. Often these applications involve conversion of hydrazine to [[Heterocyclic compound|heterocyclic rings]] such as [[pyrazole]]s and [[pyridazine]]s. Examples of commercialized bioactive [[Hydrazines|hydrazine derivatives]] include [[cefazolin]], [[rizatriptan]], [[anastrozole]], [[fluconazole]], metazachlor, metamitron, [[metribuzin]], [[paclobutrazol]], diclobutrazole, [[propiconazole]], [[hydrazine sulfate]],<ref name="OrgSynth"/> [[diimide]], [[triadimefon]],<ref name="Ullmann"/> and the [[Diacylhydrazine insecticide|diacylhydrazine]] insecticides.

Hydrazine compounds can be effective as active ingredients in insecticides, miticides, [[nematicide]]s, fungicides, antiviral agents, attractants, herbicides, or plant growth regulators.<ref>{{Cite web|url=https://patents.google.com/patent/US5304657A/en|title=Hydrazine compounds useful as pesticides|last1=Toki|first1=T|last2=Koyanagi|first2=T|date=1994|type=US patent|others=Ishihara Sangyo Kaisha Ltd (original assignee)|id=US5304657A|last3=Yoshida|first3=K|last4=Yamamoto|first4=K|last5=Morita|first5=M}}</ref>

===Small-scale, niche, and research===
[[File:Puch MS 25 with hydrazine-air fuel cell, Technisches Museum Wien.jpg|thumb|Puch Ms 25 motorcycle with a hydrazine-air fuel cell, arguably the world's first ever fuel cell motorcycle, developed by [[Karl Kordesch]]]]
The Italian [[catalyst]] manufacturer Acta (chemical company) has proposed using hydrazine as an alternative to [[hydrogen]] in [[fuel cell]]s. The chief benefit of using hydrazine is that it can produce over 200 m[[watt|W]]/cm<sup>2</sup> more than a similar hydrogen cell without requiring (expensive) [[platinum]] catalysts.<ref name=":0">{{Cite news|url=https://www.theengineer.co.uk/liquid-asset-3/|title=Liquid asset|date=15 Jan 2008|work=[[The Engineer (UK magazine)|The Engineer]]|access-date=23 Jan 2019|publisher=Centaur Media plc}}</ref> Because the fuel is liquid at room temperature, it can be handled and stored more easily than hydrogen. By storing the hydrazine in a tank full of a double-bonded [[carbon]]-[[oxygen]] [[carbonyl]], the fuel reacts and forms a safe solid called [[hydrazone]]. By then flushing the tank with warm water, the liquid hydrazine hydrate is released. Hydrazine has a higher [[electromotive force]] of 1.56 [[volt|V]] compared to 1.23 V for hydrogen. Hydrazine breaks down in the cell to form [[nitrogen]] and [[hydrogen]] which bonds with oxygen, releasing water.<ref name=":0" /> Hydrazine was used in fuel cells manufactured by [[Allis-Chalmers|Allis-Chalmers Corp.]], including some that provided electric power in space satellites in the 1960s.

A mixture of 63% hydrazine, 32% [[hydrazine nitrate]] and 5% water is a standard propellant for experimental [[Bulk loaded liquid propellants|bulk-loaded liquid propellant artillery]]. The propellant mixture above is one of the most predictable and stable, with a flat pressure profile during firing. Misfires are usually caused by inadequate ignition. The movement of the shell after a mis-ignition causes a large bubble with a larger ignition surface area, and the greater rate of gas production causes very high pressure, sometimes including catastrophic tube failures (i.e. explosions).<ref name=":1">{{Cite web|url=https://apps.dtic.mil/dtic/tr/fulltext/u2/a263143.pdf|archive-url=https://web.archive.org/web/20200307105240/https://apps.dtic.mil/dtic/tr/fulltext/u2/a263143.pdf|url-status=live|archive-date=March 7, 2020|title=A Review of the Bulk-Loaded Liquid Propellant Gun Program for Possible Relevance to the Electrothermal Chemical Propulsion Program|last1=Knapton|first1=JD|last2=Stobie|first2=IC|date=Mar 1993|publisher=Army Research Laboratory|id=[https://apps.dtic.mil/docs/citations/ADA263143 ADA263143]|last3=Elmore|first3=L}}</ref> From January–June 1991, the [[U.S. Army Research Laboratory]] conducted a review of early bulk-loaded liquid propellant gun programs for possible relevance to the electrothermal chemical propulsion program.<ref name=":1" />

The [[United States Air Force]] (USAF) regularly uses H-70, a 70% hydrazine 30% water mixture, in operations employing the [[General Dynamics F-16 Fighting Falcon]] fighter aircraft and the [[Lockheed U-2|Lockheed U-2 "Dragon Lady"]] reconnaissance aircraft. The single jet engine F-16 utilizes hydrazine to power its [[Emergency Power Unit]] (EPU), which provides emergency electrical and hydraulic power in the event of an engine flame out. The EPU activates automatically, or manually by pilot control, in the event of loss of hydraulic pressure or electrical power in order to provide emergency flight controls. The single jet engine U-2 utilizes hydrazine to power its Emergency Starting System (ESS), which provides a highly reliable method to restart the engine in flight in the event of a stall.<ref>{{Cite web|url=https://www.robins.af.mil/Portals/59/documents/technicalorders/00-25-172.pdf?ver=2016-08-22-142719-060|title=Ground Servicing of Aircraft and Static Grounding/Bonding|date=13 Mar 2017|website=[[United States Air Force|USAF]]|type=technical manual|id=TO 00-25-172|access-date=23 Nov 2018}}</ref>

===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>