Editing Propellant (section)

===Chemically powered===
====Solid propellant====
{{Further|Solid fuel|Solid-fuel rocket}}
* [[Composite propellant]]s made from a solid [[oxidizer]] such as [[ammonium perchlorate]] or [[ammonium nitrate]], a [[synthetic rubber]] such as [[HTPB]], [[Polybutadiene acrylonitrile|PBAN]], or [[Polyurethane]] (or energetic polymers such as [[polyglycidyl nitrate]] or [[polyvinyl nitrate]] for extra energy), optional high-explosive fuels (again, for extra energy) such as [[RDX]] or [[nitroglycerin]], and usually a powdered [[metal]] [[fuel]] such as [[aluminum]].
* Some [[amateur rocketry|amateur]] propellants use [[potassium nitrate]], combined with [[sugar]], [[epoxy]], or other fuels and binder compounds.
* [[Potassium perchlorate]] has been used as an oxidizer, paired with [[Bitumen|asphalt]], [[epoxy]], and other binders.

Propellants that explode in operation are of little practical use currently, although there have been experiments with [[Pulse Detonation Engine]]s. Also the newly synthesized bishomocubane based compounds are under consideration in the research stage as both solid and liquid propellants of the future.<ref>{{cite journal|last1=Lal|first1=Sohan|last2=Rajkumar|first2=Sundaram|last3=Tare|first3=Amit|last4=Reshmi|first4=Sasidharakurup|last5=Chowdhury|first5=Arindrajit|last6=Namboothiri|first6=Irishi N. N.|title=Nitro-Substituted Bishomocubanes: Synthesis, Characterization, and Application as Energetic Materials|journal=Chemistry: An Asian Journal|date=December 2014|volume=9|issue=12|pages=3533–3541|doi=10.1002/asia.201402607|pmid=25314237|doi-access=free}}</ref><ref>{{cite journal|last1=Lal|first1=Sohan|last2=Mallick|first2=Lovely|last3=Rajkumar|first3=Sundaram|last4=Oommen|first4=Oommen P.|last5=Reshmi|first5=Sasidharakurup|last6=Kumbhakarna|first6=Neeraj|last7=Chowdhury|first7=Arindrajit|last8=Namboothiri|first8=Irishi|title=Synthesis and energetic properties of high-nitrogen substituted bishomocubanes|journal=J. Mater. Chem. A|volume=3|issue=44|pages=22118–22128|date=2015|doi=10.1039/C5TA05380C|url=http://uu.diva-portal.org/smash/get/diva2:878740/FULLTEXT01|doi-access=free}}</ref>

=====Grain=====
Solid fuel/propellants are used in forms called [[Solid-fuel rocket#Grain geometry|grains]]. A grain is any individual particle of fuel/propellant regardless of the size or shape. The shape and size of a grain determines the burn time, amount of gas, and rate of produced energy from the burning of the fuel and, as a consequence, thrust vs time profile.

There are three types of burns that can be achieved with different grains.
; Progressive burn: Usually a grain with multiple perforations or a star cut in the center providing a lot of surface area.
; Degressive burn: Usually a solid grain in the shape of a cylinder or sphere.
; Neutral burn: Usually a single perforation; as outside surface decreases the inside surface increases at the same rate.

=====Composition=====
There are four different types of solid fuel/propellant compositions:
; Single-based fuel/propellant: A single based fuel/propellant has nitrocellulose as its chief explosives ingredient. Stabilizers and other additives are used to control the chemical stability and enhance its properties.
; Double-based fuel/propellant: Double-based fuel/propellants consist of nitrocellulose with nitroglycerin or other liquid organic nitrate explosives added. Stabilizers and other additives are also used. Nitroglycerin reduces smoke and increases the energy output. Double-based fuel/propellants are used in small arms, cannons, mortars and rockets.
; Triple-based fuel/propellant: Triple-based fuel/propellants consist of nitrocellulose, nitroguanidine, nitroglycerin or other liquid organic nitrate explosives. Triple-based fuel/propellants are used in [[cannon]]s.
; Composite: Composites do not utilize nitrocellulose, nitroglycerin, nitroguanidine or any other organic nitrate as the primary constituent. Composites usually consist of a fuel such as metallic aluminum, a combustible binder such as synthetic rubber or [[HTPB]], and an oxidizer such as ammonium perchlorate. Composite fuel/propellants are used in large rocket motors.  In some applications, such as the US SLBM Trident II missile, nitroglycerin is added to the aluminum and ammonium perchlorate composite as an energetic plasticizer.

====Liquid propellant====
{{Further|liquid fuel|liquid-propellant rocket}}
In rockets, three main liquid bipropellant combinations are used:  cryogenic oxygen and hydrogen, cryogenic oxygen and a hydrocarbon, and storable propellants.<ref name=sutton2001>
{{cite book |last=Sutton|first=George |author2=Biblarz, Oscar  |title=Rocket Propulsion Elements |year=2001 |publisher=Willey |isbn=9781601190604 |oclc=75193234 }}</ref>
; [[Cryogenic]] [[liquid oxygen|oxygen]]-[[liquid hydrogen|hydrogen]] combination system: Used in upper stages and sometimes in booster stages of space launch systems. This is a nontoxic combination. This gives high [[specific impulse]] and is ideal for high-velocity missions.
; Cryogenic oxygen-hydrocarbon propellant system: Used for many booster stages of space [[launch vehicle]]s as well as a smaller number of [[second stage]]s. This combination of fuel/oxidizer has high density and hence allows for a more compact booster design.
; Storable propellant combinations: Used in almost all bipropellant low-thrust, auxiliary or [[reaction control system|reaction control]] rocket engines, as well as in some in large rocket engines for first and second stages of ballistic missiles. They are instant-starting and suitable for long-term storage.

Propellant combinations used for [[bipropellant rocket|liquid propellant rocket]]s include:
* [[Liquid oxygen]] and [[liquid hydrogen]]<ref name=ars20130414a>
{{cite news|last=Hutchinson|first=Lee |title=New F-1B rocket engine upgrades Apollo-era design with 1.8 M lbs of thrust |url=https://arstechnica.com/science/2013/04/new-f-1b-rocket-engine-upgrades-apollo-era-deisgn-with-1-8m-lbs-of-thrust/ |access-date=2013-04-15 |newspaper=ARS technica |date=2013-04-14 |quote=''The most efficient fuel and oxidizer combination commonly used today for chemical liquid rockets is hydrogen (fuel) and oxygen (oxidizer)," continued Coates. The two elements are relatively simple and they burn easily when combined—and even better, the result of their reaction is simple water.''}}</ref>
* [[Liquid oxygen]] and [[kerosene]] or [[RP-1]]<ref name=ars20130414b>
{{cite news|last=Hutchinson|first=Lee |title=New F-1B rocket engine upgrades Apollo-era design with 1.8 M lbs of thrust |url=https://arstechnica.com/science/2013/04/new-f-1b-rocket-engine-upgrades-apollo-era-deisgn-with-1-8m-lbs-of-thrust/2/ |page=2 |access-date=2013-04-15 |newspaper=ARS technica |date=2013-04-14 |quote=''Refined petroleum is not the most efficient thrust-producing fuel for rockets, but what it lacks in thrust production it makes up for in density. It takes less volume of RP-1 to impart the same thrust force on a vehicle, and less volume equates to reduced stage size. ... A smaller booster stage means much less aerodynamic drag as the vehicle lifts off from near sea-level and accelerates up through the more dense (thicker) part of the atmosphere near the earth. The result of a smaller booster stage is it allows a more efficient ascent through the thickest part of the atmosphere, which helps improve the net mass lifted to orbit.''}}</ref>
* [[Liquid oxygen]] and [[ethanol]]
* Liquid oxygen and [[methane]]
* [[High-test peroxide|Hydrogen peroxide]] and mentioned above alcohol or [[RP-1]]
* [[Red fuming nitric acid]] (RFNA) and [[kerosene]] or [[RP-1]]
* RFNA and [[Unsymmetrical dimethylhydrazine]] (UDMH)
* [[Dinitrogen tetroxide]] and UDMH, [[monomethylhydrazine|MMH]], and/or [[hydrazine]]

Common monopropellant used for [[liquid-propellant rocket|liquid rocket engines]] include:
* Hydrogen peroxide
* [[Hydrazine]]
* Red fuming nitric acid (RFNA)