Ajay Kumar at 06:59, 23 August 2023

2023-08-23T06:59:25Z

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{{Short description|Type of rocket engine which uses liquid fuel stored at very low temperatures}}
[[File:Moteur-Vulcain.jpg|thumb|150px|''[[Vulcain (rocket engine)|Vulcain]]'' engine of [[Ariane 5]] rocket]]

A '''cryogenic rocket engine''' is a [[rocket engine]] that uses a [[cryogenic fuel]] and [[oxidizer]]; that is, both its fuel and oxidizer are [[gas]]es which have been [[Liquefied gas|liquefied]] and are stored at [[Cryogenics|very low temperatures]].<ref name="saturn">{{cite book|author=Bilstein, Roger E.
|title=Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicles (NASA SP-4206) (The NASA History Series)
|publisher=NASA History Office
|year=1995
|pages=[https://archive.org/details/bub_gb_JnoZTbVLx0MC/page/n109 89]–91
|isbn=0-7881-8186-6
|url=https://archive.org/details/bub_gb_JnoZTbVLx0MC
}}</ref> These highly efficient engines were first flown on the US [[Atlas-Centaur]] and were one of the main factors of [[NASA]]'s success in reaching the Moon by the [[Saturn V]] rocket.<ref name="saturn"/>

Rocket engines burning cryogenic propellants remain in use today on high performance [[Multistage rocket|upper stages]] and [[Booster (rocketry)|boosters]]. Upper stages are numerous. Boosters include [[European Space Agency|ESA's]] [[Ariane 5]], [[JAXA]]'s [[H-II (rocket family)|H-II]], and the [[United States]] [[Delta IV]] and [[Space Launch System]]. The [[United States]], [[Russia]], [[Japan]], [[India]], [[France]] and [[China]] are the only countries that have operational cryogenic rocket engines.

== History ==
{{Empty section|date=August 2022}} 

==Cryogenic propellants==
[[File:RL-10 rocket engine.jpg|thumb|300px|[[RL-10]] is an early example of cryogenic rocket engine.]]

Rocket engines need high [[mass flow rate]]s of both oxidizer and fuel to generate useful thrust. Oxygen, the simplest and most common oxidizer, is in the [[gas phase]] at [[standard temperature and pressure]], as is hydrogen, the simplest fuel. While it is possible to store propellants as pressurized gases, this would require large, heavy tanks that would make achieving [[orbital spaceflight]] difficult if not impossible. On the other hand, if the propellants are cooled sufficiently, they [[phase diagram|exist]] in the [[liquid phase]] at higher density and lower pressure, simplifying tankage. These [[cryogenic]] temperatures vary depending on the propellant, with [[liquid oxygen]] existing below {{convert|-183|C|F K}} and [[liquid hydrogen]] below {{convert|-253|C|F K}}. Since one or more of the propellants is in the liquid phase, all cryogenic rocket engines are by definition [[Liquid-propellant rocket|liquid-propellant rocket engines]].<ref name="isbn0-470-08024-8">{{cite book
|author1=Biblarz, Oscar |author2=Sutton, George H. |title=Rocket Propulsion Elements
|publisher=Wiley
|location=New York
|year=2009
|page=[https://archive.org/details/Rocket_Propulsion_Elements_8th_Edition_by_Oscar_Biblarz_George_P._Sutton/page/n614 597]
|isbn=978-0-470-08024-5
|url=https://archive.org/details/Rocket_Propulsion_Elements_8th_Edition_by_Oscar_Biblarz_George_P._Sutton
}}</ref>

Various cryogenic fuel-oxidizer combinations have been tried, but the combination of liquid hydrogen ([[LH2]]) fuel and the liquid oxygen ([[LOX]]) oxidizer is one of the most widely used.<ref name="saturn"/><ref>The liquefaction temperature of oxygen is 89 [[kelvin]]s, and at this temperature it has a density of 1.14 kg/L. For hydrogen it is 20 K, just above [[absolute zero]], and has a density of 0.07 kg/L.</ref> Both components are easily and cheaply available, and when burned have one of the highest [[enthalpy]] releases in [[combustion]],<ref name="isbn0-7923-5813-9">{{cite book|author=Biswas, S.
|title=Cosmic perspectives in space physics
|publisher=Kluwer
|location=Bruxelles
|year=2000
|page=23
|isbn=0-7923-5813-9
|url=https://books.google.com/books?id=lZ-qFK0pkfAC&pg=PA23
}} "... [LH2+LOX] has almost the highest specific impulse."</ref> producing a [[specific impulse]] of up to 450 s at an [[effective exhaust velocity]] of {{convert|4.4|km/s|mi/s Mach}}.

==Components and combustion cycles==
The major components of a cryogenic rocket engine are the [[combustion chamber]], [[pyrotechnic initiator]], fuel injector, fuel and oxidizer [[turbopump]]s, cryo valves, regulators, the fuel tanks, and [[rocket engine nozzle]]. In terms of feeding propellants to the combustion chamber, cryogenic rocket engines are almost exclusively [[Pump-fed engine|pump-fed]]. Pump-fed engines work in a [[gas-generator cycle (rocket)|gas-generator cycle]], a [[Staged combustion cycle (rocket)|staged-combustion cycle]], or an [[expander cycle]]. Gas-generator engines tend to be used on booster engines due to their lower efficiency, staged-combustion engines can fill both roles at the cost of greater complexity, and expander engines are exclusively used on upper stages due to their low thrust.{{citation_needed|date=July 2019}}

==LOX+LH2 rocket engines by country==
[[File:YF-77 at CSTM.jpg|thumb|160px|alt=Chinese YF-77 engine used by Long March 5|Chinese [[YF-77]] engine used by [[Long March 5]]]]
Currently, six countries have successfully developed and deployed cryogenic rocket engines:
{| class="wikitable"
!Country
!Engine
!Cycle
!Use
!Status
|-
| rowspan="7" |{{USA}}
|[[RL-10]]
|[[Expander cycle|Expander]]
|Upper stage
|Active
|-
|[[Rocketdyne J-2|J-2]]
|[[Gas-generator cycle|Gas-generator]]
|lower stage

|Retired
|-
|[[Space Shuttle main engine|SSME (aka RS-25)]]
|[[Staged combustion cycle|Staged combustion]]
|Booster
|Active
|-
|[[RS-68]]
|[[Gas-generator cycle|Gas-generator]]
|Booster
|Active
|-
|[[BE-3]]
|[[Combustion tap-off cycle|Combustion tap-off]]
|[[New Shepard]]
|Active
|-
|[[BE-7]]
|[[Combustion tap-off cycle|Combustion tap-off]]
|[[Blue Moon (spacecraft)]]
|Active
|-
|[[J-2X]]
|[[Gas-generator cycle|Gas-generator]]
|Upper stage
|Developmental
|-
| rowspan="3" |{{RUS}}
|[[RD-0120]]
|[[Staged combustion cycle|Staged combustion]]
|Booster
|Retired
|-
|[[KVD-1]]
|[[Staged combustion cycle|Staged combustion]]
|Upper stage
|Retired
|-
|[[RD-0146]]
|[[Expander cycle|Expander]]
|Upper stage
|Developmental
|-
| rowspan="3" |{{FRA}}
|[[Vulcain (rocket engine)|Vulcain]]
|[[Gas-generator cycle|Gas-generator]]
|Booster
|Active
|-
|[[HM7B]]
|[[Gas-generator cycle|Gas-generator]]
|Upper stage
|Active
|-
|[[Vinci (rocket engine)|Vinci]]
|[[Expander cycle|Expander]]
|Upper stage
|Developmental
|-
| rowspan="2" |{{IND}}
|[[CE-7.5]]
|[[Staged combustion cycle|Staged combustion]]
|Upper stage
|Active
|-
|[[CE-20]]
|[[Gas-generator cycle|Gas-generator]]
|Upper stage
|Active
|-
| rowspan="4" |{{CHN}}
|[[YF-73]]
|[[Gas-generator cycle|Gas-generator]]
|Upper stage
|Retired
|-
|[[YF-75]]
|[[Gas-generator cycle|Gas-generator]]
|Upper stage
|Active
|-
|[[YF-75D]]
|[[Expander cycle]]
|Upper stage
|Active
|-
|[[YF-77]]
|[[Gas-generator cycle|Gas-generator]]
|Booster
|Active
|-
| rowspan="2" |{{JAP}}
|[[LE-7|LE-7 / 7A]]
|[[Staged combustion cycle|Staged combustion]]
|Booster
|Active
|-
|[[LE-5|LE-5 / 5A / 5B]]
|[[Gas-generator cycle|Gas-generator]](LE-5) [[Expander cycle|Expander]](5A/5B)
|Upper stage
|Active
|}

==Comparison of first stage cryogenic rocket engines==
{| class="wikitable"
!style="background:#FFDEAD"|model!!style="background:#FFDEAD"|[[Space Shuttle main engine|SSME/RS-25]]!!style="background:#FFDEAD"|[[LE-7A]]!!style="background:#FFDEAD"|[[RD-0120]]!!style="background:#FFDEAD"|[[Vulcain (rocket engine)|Vulcain 2]]!!style="background:#FFDEAD"|[[RS-68]]!!style="background:#FFDEAD"|[[YF-77]]
|- align=center
!align=left|Country of origin
|{{USA}}||{{JPN}}||{{URS}}||{{FRA}}||{{USA}}||{{CHN}}
|- align=center
!align=left|Cycle
|[[Staged combustion cycle|Staged combustion]]||[[Staged combustion cycle|Staged combustion]]||[[Staged combustion cycle|Staged combustion]]||[[Gas-generator cycle|Gas-generator]]||[[Gas-generator cycle|Gas-generator]]||[[Gas-generator cycle|Gas-generator]]
|- align=center
!Length
|4.24 m||3.7 m||4.55 m||3.00 m||5.20 m||2.6 m
|- align=center
!Diameter
|1.63 m||1.82 m||2.42 m||1.76 m||2.43 m||1.5 m
|- align=center
!Dry weight
|3,177 kg||1,832 kg||3,449 kg||1,686 kg||6,696 kg||1,054 kg
|- align=center
!Propellant
|[[LOX]]/[[LH2]]||[[LOX]]/[[LH2]]||[[LOX]]/[[LH2]]||[[LOX]]/[[LH2]]||[[LOX]]/[[LH2]]||[[LOX]]/[[LH2]]
|- align=center
!Chamber pressure
|18.9 MPa||12.0MPa||21.8 MPa||11.7 MPa||9.7 MPa||10.1 MPa
|- align=center
!Isp (vac.)
|453 sec||440 sec||454 sec||433 sec||409 sec||428 sec
|- align=center
!Thrust (vac.)
|2.278MN||1.098MN||1.961MN||1.120MN||3.37MN||0.7MN
|- align=center
!Thrust (SL)
|1.817MN||0.87MN||1.517MN||0.800MN||2.949MN||0.518MN
|- align=center
!Used in
|[[Space Shuttle]] [[Space Launch System]]||[[H-IIA]] [[H-IIB]]||[[Energia (rocket)|Energia]]||[[Ariane 5]]||[[Delta IV]]||[[Long March 5]]
|}

==Comparison of upper stage cryogenic rocket engines==

{| class="wikitable" style="text-align:center;"
|+ '''Specifications'''
!　
![[RL-10]]
![[HM7B]]
![[Vinci (rocket engine)|Vinci]]
![[KVD-1]]
![[CE-7.5]]
![[CE-20]]
![[YF-73]]
![[YF-75]]
![[YF-75D]]
![[RD-0146]]
!ES-702
!ES-1001
![[LE-5]]
![[LE-5A]]
![[LE-5B]]
|-
!Country of origin
|{{USA}}
|{{FRA}}
|{{FRA}}
|{{USSR}}
|{{IND}}
|{{IND}}
|{{CHN}}
|{{CHN}}
|{{CHN}}
|{{RUS}}
|{{JPN}}
|{{JPN}}
|{{JPN}}
|{{JPN}}
|{{JPN}}
|-
!Cycle
|[[Expander cycle|Expander]]
|[[Gas-generator cycle|Gas-generator]]
|[[Expander cycle|Expander]]
|[[Staged combustion cycle|Staged combustion]]
|[[Staged combustion cycle|Staged combustion]]
|[[Gas-generator cycle|Gas-generator]]
|[[Gas-generator cycle|Gas-generator]]
|[[Gas-generator cycle|Gas-generator]]
|[[Expander cycle|Expander]]
|[[Expander cycle|Expander]]
|[[Gas-generator cycle|Gas-generator]]
|[[Gas-generator cycle|Gas-generator]]
|[[Gas-generator cycle|Gas-generator]]
|[[Expander cycle#Expander bleed cycle (open cycle)|Expander bleed cycle]] （Nozzle Expander）
|[[Expander cycle#Expander bleed cycle (open cycle)|Expander bleed cycle]] （Chamber Expander）
|-
!Thrust (vac.)
|66.7 kN (15,000 lbf)
|62.7 kN
|180 kN
|69.6 kN
|73 kN
|186.36 kN
|44.15 kN
|83.585 kN
|88.36 kN
|98.1 kN (22,054 lbf)
|68.6 kN (7.0 tf)<ref>without nozzle 48.52kN (4.9 tf)</ref>
|98 kN (10.0 tf)<ref>without nozzle 66.64kN (6.8 tf)</ref>
|102.9 kN (10.5 tf)
|r121.5 kN (12.4 tf)
|137.2 kN (14 tf)
|-
!Mixture ratio
|5.5:1 or 5.88:1
|5.0
|5.8
|
|
|5.05
|5.0
|5.2
|6.0
|
|5.2
|6.0
|5.5
|5
|5
|-
!Nozzle ratio
|40
|83.1
|
|
|
|100
|40
|80
|80
|
|40
|40
|140
|130
|110
|-
![[Specific impulse|Isp]] (vac.)
|433
|444.2
|465
|462
|454
|442
|420
|438
|442.6
|463
|425<ref>without nozzle 286.8</ref>
|425<ref>without nozzle 291.6</ref>
|450
|452
|447
|-
!Chamber pressure :MPa
|2.35
|3.5
|6.1
|5.6
|5.8
|6.0
|2.59
|3.68
|4.1
|5.9
|2.45
|3.51
|3.65
|3.98
|3.58
|-
!LH2 TP rpm
|
|
|90,000
|
|
|
|
|42,000
|65,000
|125,000
|41,000
|46,310
|50,000
|51,000
|52,000
|-
!LOX TP rpm
|
|
|18,000
|
|
|
|
|
|
|
|16,680
|21,080
|16,000
|17,000
|18,000
|-
!Length m
|1.73
|1.8
|2.2~4.2
|2.14
|2.14
|
|1.44
|2.8
|
|2.2
|
|
|2.68
|2.69
|2.79
|-
!Dry weight kg
|135
|165
|550
|282
|435
|558
|236
|245
|265
|242
|255.8
|259.4
|255
|248
|285
|}

==References==
{{Reflist}}

==External links==
*[https://web.archive.org/web/20120204144940/http://www.astronautix.com/engines/rl10b2.htm USA's Cryogenic Rocket engine RL10B-2]
*[http://www.lpre.de/energomash/RD-170/index.htm Russian Cryogenic Rocket Engines]

{{Rocket engines}}
{{Spacecraft propulsion}}

{{DEFAULTSORT:Cryogenic Rocket Engine}}
[[Category:Rocket propulsion]]
[[Category:Rocket engines]]
[[Category:Cryogenics|Rocket]]
[[Category:Rocket engines using hydrogen propellant| ]]
[[Category:Hydrogen technologies]]

Cryogenic rocket engine - Revision history

Ajay Kumar at 06:59, 23 August 2023