Editing Liquid-propellant rocket (section)

==Propellants==
{{main article|Liquid rocket propellant}}
Thousands of combinations of fuels and oxidizers have been tried over the years. Some of the more common and practical ones are:

===Cryogenic===
* Liquid oxygen ([[LOX]], O<sub>2</sub>) and liquid [[hydrogen]] ([[LH2|LH{{sub|2}}]], H<sub>2</sub>) – [[Space Shuttle]] main engines, [[Space Launch System]] [[Space Launch System core stage|core stage]], [[Ariane 5]] main stage and the Ariane 5 ECA second stage, the [[BE-3]] of Blue Origin's New Shepard, the first and second stage of the [[Delta IV rocket|Delta IV]], the upper stages of the [[Ares I]], [[Saturn V (rocket)|Saturn V]]'s [[S-II|second]] and [[S-IVB|third stages]], [[Saturn IB (rocket)|Saturn IB]], and [[Saturn I (rocket)|Saturn I]] as well as [[Centaur (rocket stage)|Centaur]] rocket stage, the upper stages of the [[Long March 3]], [[Long March 5]], [[Long March 8]], the first stage and second stage of the [[H-II]], [[H-IIA]], [[H-IIB]], and the upper stage of the [[Geosynchronous Satellite Launch Vehicle|GSLV Mk-II]] and [[Geosynchronous Satellite Launch Vehicle Mark III|GSLV Mk-III]]. The main advantages of this mixture are a clean burn (water vapor is the only combustion product) and high performance.<ref name="jaxa-lng">{{cite web |url=https://global.jaxa.jp/projects/engineering/components/lng/index.html |title=About LNG Propulsion System |work=[[JAXA]] |access-date=2020-08-25}}</ref>
* Liquid oxygen (LOX) and [[liquid methane rocket fuel|liquid methane]] (CH<sub>4</sub>, [[liquefied natural gas]], LNG) – the [[Raptor (rocket engine family)|Raptor]] (SpaceX) and [[BE-4]] (Blue Origin) engines. (See also [[Propulsion Cryogenics & Advanced Development]] project of NASA, and [[Project Morpheus]].)

One of the most efficient mixtures, [[oxygen]] and [[hydrogen]], suffers from the extremely low temperatures required for storing liquid hydrogen (around {{cvt|20|K|disp=or}}) and very low fuel density ({{cvt|70|kg/m3|lb/ft3|disp=or}}, compared to RP-1 at {{cvt|820|kg/m3|lb/ft3|disp=or}}), necessitating large tanks that must also be lightweight and insulating. Lightweight foam insulation on the [[Space Shuttle external tank]] led to the {{OV|102}}'s [[Space Shuttle Columbia disaster|destruction]], as a piece broke loose, damaged its wing and caused it to break up on [[atmospheric reentry]].

Liquid methane/LNG has several advantages over LH{{sub|2}}. Its performance (max. [[specific impulse]]) is lower than that of LH{{sub|2}} but higher than that of RP1 (kerosene) and solid propellants, and its higher density, similarly to other hydrocarbon fuels, provides higher thrust to volume ratios than LH{{sub|2}}, although its density is not as high as that of RP1.<ref name="airbus"/>  This makes it specially attractive for [[reusable launch system]]s because higher density allows for smaller motors, propellant tanks and associated systems.<ref name="jaxa-lng" /> LNG also burns with less or no soot (less or no coking) than RP1, which eases reusability when compared with it, and LNG and RP1 burn cooler than LH{{sub|2}} so LNG and RP1 do not deform the interior structures of the engine as much. This means that engines that burn LNG can be reused more than those that burn RP1 or LH{{sub|2}}. Unlike engines that burn LH{{sub|2}}, both RP1 and LNG engines can be designed with a shared shaft with a single turbine and two turbopumps, one each for LOX and LNG/RP1.<ref name="airbus">{{cite web|title=LOX/Methane The Future is Green |first=Dr. Gerald |last=Hagemann |date=November 4, 2015|url=http://www.academie-air-espace.com/upload/doc/ressources/Launchers/slides/hagemann.pdf|access-date=November 29, 2022}}</ref> In space, LNG does not need heaters to keep it liquid, unlike RP1.<ref>{{cite web|title=Methane Engine Just for Future Space Transportation |url=https://www.ihi.co.jp/var/ezwebin_site/storage/original/application/c947f865f960ed20f82895dcaa4bbbb1.pdf|publisher=IHI Corporation|access-date=November 29, 2022}}</ref><!--less soot eases fuel injector unclogging and refurbishment for reusability. and methane can also be used to autogenously pressurize rocket fuel tanks, eliminating the need for Helium, which is normally used to provide additional structural stability to the rocket. --> LNG is less expensive, being readily available in large quantities. It can be stored for more prolonged periods of time, and is less explosive than LH{{sub|2}}.<ref name="jaxa-lng"/>

===Semi-cryogenic===
* Liquid oxygen (LOX) and [[RP-1]] (kerosene) – [[Saturn V (rocket)|Saturn V]]'s [[S-IC|first stage]], [[Zenit rocket]], [[R-7 Semyorka|R-7]]-derived vehicles including [[Soyuz (rocket family)|Soyuz]], [[Delta rocket|Delta]], [[Saturn I (rocket)|Saturn I]], and [[Saturn IB (rocket)|Saturn IB]] first stages, [[Titan (rocket family)|Titan I]] and [[Atlas rocket]]s, [[Falcon 1]] and [[Falcon 9]], [[Long March 5]], [[Long March 6]], [[Long March 7]] and [[Long March 8]] first stages. 
* Liquid oxygen (LOX) and alcohol ([[ethanol]], C<sub>2</sub>H<sub>5</sub>OH) – early liquid rockets, like [[Germany|German]] ([[World War II]]) A4, aka [[V-2]], and [[Redstone (rocket)|Redstone]]
* Liquid oxygen (LOX) and [[gasoline]] – [[Robert Goddard (scientist)|Robert Goddard]]'s first liquid rocket
* Liquid oxygen (LOX) and [[carbon monoxide]] (CO) – proposed for a Mars ''hopper'' vehicle (with a specific impulse of approximately 250{{nbsp}}s), principally because carbon monoxide and oxygen can be straightforwardly produced by [[Zirconia]] electrolysis from the Martian atmosphere without requiring use of any of the Martian water resources to obtain Hydrogen.<ref name="landis2001">{{cite journal |last=Landis |title=Mars Rocket Vehicle Using In Situ Propellants |journal=Journal of Spacecraft and Rockets |date=2001 |volume=38 |issue=5 |pages=730–735 |doi=10.2514/2.3739 |url=http://arc.aiaa.org/doi/abs/10.2514/2.3739?journalCode=jsr |bibcode=2001JSpRo..38..730L |url-access=subscription }}</ref>

=== Non-cryogenic/storable/hypergolic ===
[[File:Messerschmitt Me 163B USAF.jpg|thumb|left| The [[NMUSAF]]'s Me 163B ''Komet'' rocket plane]]

Many non-cryogenic bipropellants are [[hypergolic propellant|hypergolic]] (self igniting).
* [[T-Stoff]] (80% hydrogen peroxide, H<sub>2</sub>O<sub>2</sub> as the oxidizer) and [[C-Stoff]] (methanol, {{chem2|CH3OH}}, and hydrazine hydrate, {{chem2|N2H4*''n''(H2O)}} as the fuel) – used for the Hellmuth-Walter-Werke [[HWK 109-509]]A, -B and -C engine family used on the [[Messerschmitt Me 163]]B Komet, an operational rocket fighter plane of [[World War II]], and [[Bachem Ba 349|Ba 349 ''Natter'']] crewed [[Takeoff#Vertical takeoff|VTO]] interceptor prototypes.
* [[Nitric acid]] (HNO<sub>3</sub>) and kerosene – [[Soviet Union|Soviet]] [[Bereznyak-Isayev BI-1|BI-1]] and [[Mikoyan-Gurevich I-270|MiG I-270]] rocket fighter prototypes, [[Scud]]-A, aka [[SS-1]] [[SRBM]]
* Inhibited red fuming nitric acid (I[[RFNA]], HNO<sub>3</sub> + N<sub>2</sub>O<sub>4</sub>) and unsymmetric dimethyl hydrazine ([[UDMH]], (CH<sub>3</sub>)<sub>2</sub>N<sub>2</sub>H<sub>2</sub>) – Soviet [[Scud]]-C, aka [[SS-1]]-c,-d,-e
* Nitric acid 73% with [[dinitrogen tetroxide]] 27% (AK27) and kerosene/gasoline mixture (TM-185) – various Russian (USSR) cold-war ballistic missiles ([[R-12 Dvina|R-12]], [[Scud]]-B,-D), [[Iran]]: [[Shahab-5]], [[North Korea]]: [[Taepodong-2]]
* [[High-test peroxide]] (H<sub>2</sub>O<sub>2</sub>) and kerosene – [[United Kingdom|UK]] (1970s) [[Black Arrow]], [[United States|USA]] Development (or study): BA-3200
* [[Hydrazine]] (N<sub>2</sub>H<sub>4</sub>) and [[red fuming nitric acid]] – [[MIM-3 Nike Ajax]] Anti-aircraft missile
* Unsymmetric dimethylhydrazine ([[UDMH]]) and [[dinitrogen tetroxide]] (N<sub>2</sub>O<sub>4</sub>) – [[Proton rocket|Proton]], [[Rokot]], [[Long March 2 (rocket family)|Long March 2]] (used to launch [[Shenzhou (spacecraft)|Shenzhou]] crew vehicles.)
* [[File:LGM-25C Titan II Test Launch.jpg|thumb|Titan II]][[Aerozine 50]] (50% UDMH, 50% hydrazine) and [[dinitrogen tetroxide]] (N<sub>2</sub>O<sub>4</sub>) – [[Titan (rocket family)|Titans 2–4]], Apollo [[lunar module]], Apollo [[service module]], interplanetary probes (Such as [[Voyager 1]] and [[Voyager 2]])
* [[Monomethylhydrazine]] (MMH, (CH<sub>3</sub>)HN<sub>2</sub>H<sub>2</sub>) and dinitrogen tetroxide (N<sub>2</sub>O<sub>4</sub>) – [[Space Shuttle orbiter]]'s [[orbital maneuvering system]] (OMS) engines and [[Reaction control system]] (RCS) thrusters. [[SpaceX]]'s [[Draco (rocket engine)|Draco]] and SuperDraco engines for the [[Dragon spacecraft]].

For [[storable propellant|storable]] [[ICBM]]s and most spacecraft, including crewed vehicles, planetary probes, and satellites, storing cryogenic propellants over extended periods is unfeasible. Because of this, mixtures of [[hydrazine]] or its derivatives in combination with nitrogen oxides are generally used for such applications, but are toxic and [[carcinogenic]]. Consequently, to improve handling, some crew vehicles such as [[Dream Chaser]] and [[Space Ship Two]] plan to use [[hybrid rocket]]s with non-toxic fuel and oxidizer combinations.