Cryogenic rocket engine

Short description: Type of rocket engine which uses liquid fuel stored at very low temperatures

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 gases which have been liquefied and are stored at very low temperatures.[1] 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.[1]

Rocket engines burning cryogenic propellants remain in use today on high performance upper stages and boosters. Upper stages are numerous. Boosters include ESA's Ariane 6, ISRO's GSLV, LVM3, JAXA's H-II, NASA's Space Launch System. The United States, Russia, India, Japan, France and China are the only countries that have operational cryogenic rocket engines.

## Contents

* 1 Cryogenic propellants
* 2 Components and combustion cycles
* 3 LOX+LH2 rocket engines by country
* 4 Comparison of first stage cryogenic rocket engines
* 5 Comparison of upper stage cryogenic rocket engines
* 6 References
* 7 External links

## Cryogenic propellants

RL-10 is an early example of cryogenic rocket engine.

Rocket engines need high mass flow rates 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 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 −183 °C (−297.4 °F; 90.1 K) and liquid hydrogen below −253 °C (−423.4 °F; 20.1 K). Since one or more of the propellants is in the liquid phase, all cryogenic rocket engines are by definition liquid-propellant rocket engines.[2]

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.[1][3] Both components are easily and cheaply available, and when burned have one of the highest enthalpy releases in combustion,[4] producing a specific impulse of up to 450 s at an effective exhaust velocity of 4.4 kilometres per second (2.7 mi/s; Mach 13).

## Components and combustion cycles

The major components of a cryogenic rocket engine are the combustion chamber, pyrotechnic initiator, fuel injector, fuel and oxidizer turbopumps, 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. Pump-fed engines work in a gas-generator cycle, a 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]

## LOX+LH2 rocket engines by country

Chinese YF-77 engine used by Long March 5

Currently, six countries have successfully developed and deployed cryogenic rocket engines:

Country  | Engine  | Cycle  | Use  | Status

|
|
|
|

United States  | RL-10  | Expander | Upper stage  | Active
J-2 | Gas-generator | lower stage  | Retired
SSME (aka RS-25) | Staged combustion | Booster  | Active
RS-68  | Gas-generator | Booster  | Retired
BE-3  | Combustion tap-off | New Shepard | Active
BE-7  | Dual Expander | Blue Moon (spacecraft) | Active
J-2X  | Gas-generator | Upper stage  | Developmental
Russia  | RD-0120  | Staged combustion | Booster  | Retired
KVD-1  | Staged combustion | Upper stage  | Retired
RD-0146  | Expander | Upper stage  | Developmental
France  | Vulcain | Gas-generator | Booster  | Active
HM7B | Gas-generator | Upper stage  | Retired
Vinci  | Expander | Upper stage  | Active
India  | CE-7.5  | Staged combustion | Upper stage  | Active
CE-20  | Gas-generator | Upper stage  | Active
China  | YF-73  | Gas-generator | Upper stage  | Retired
YF-75  | Gas-generator | Upper stage  | Active
YF-75D  | Expander cycle | Upper stage  | Active
YF-77  | Gas-generator | Booster  | Active
Japan  | LE-7 / 7A[5] | Staged combustion | Booster  | Active
LE-5 / 5A / 5B[6] | Gas-generator(LE-5)
Expander bleed(5A/5B)  | Upper stage  | Active
LE-9[7] | Expander bleed | Booster  | Active

## Comparison of first stage cryogenic rocket engines

model | SSME/RS-25 | LE-7A | RD-0120 | Vulcain 2 | RS-68 | YF-77

|
|
|
|
|
|

Country of origin  |  United States |  Japan |  Soviet Union |  France |  United States |  China
Cycle  | Staged combustion | Staged combustion | Staged combustion | Gas-generator | Gas-generator | Gas-generator
Length  | 4.24 m | 3.7 m | 4.55 m | 3.00 m | 5.20 m | 2.6 m
Diameter  | 1.63 m | 1.82 m | 2.42 m | 1.76 m | 2.43 m | 1.5 m
Dry weight  | 3,177 kg | 1,832 kg | 3,449 kg | 1,686 kg | 6,696 kg | 1,054 kg
Propellant  | LOX/LH2 | LOX/LH2 | LOX/LH2 | LOX/LH2 | LOX/LH2 | LOX/LH2
Chamber pressure  | 18.9 MPa | 12.0MPa | 21.8 MPa | 11.7 MPa | 9.7 MPa | 10.1 MPa
Isp (vac.)  | 453 sec | 440 sec | 454 sec | 433 sec | 409 sec | 428 sec
Thrust (vac.)  | 2.278MN | 1.098MN | 1.961MN | 1.120MN | 3.37MN | 0.7MN
Thrust (SL)  | 1.817MN | 0.87MN | 1.517MN | 0.800MN | 2.949MN | 0.518MN
Used in  | Space Shuttle
Space Launch System | H-IIA
H-IIB | Energia | Ariane 5 | Delta IV | Long March 5

## Comparison of upper stage cryogenic rocket engines

Specifications | RL-10  | HM7B | 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

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Country of origin  |  United States  |  France  |  France  |  Soviet Union  |  India  |  India  |  China  |  China  |  China  |  Russia  |  Japan  |  Japan  |  Japan  |  Japan  |  Japan
Cycle  | Expander | Gas-generator | Expander | Staged combustion | Staged combustion | Gas-generator | Gas-generator | Gas-generator | Expander | Expander | Gas-generator | Gas-generator | Gas-generator | Expander bleed cycle
（Nozzle Expander）  | 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)[8] | 98 kN (10.0 tf)[9] | 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
Isp (vac.)  | 433  | 444.2  | 465  | 462  | 454  | 442  | 420  | 438  | 442.6  | 463  | 425[10] | 425[11] | 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

1. ↑ 1.0 1.1 1.2 Bilstein, Roger E. (1995). Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicles (NASA SP-4206) (The NASA History Series). NASA History Office. pp. 89–91. ISBN 0-7881-8186-6. https://archive.org/details/bub_gb_JnoZTbVLx0MC.
2. ↑ Biblarz, Oscar; Sutton, George H. (2009). Rocket Propulsion Elements. New York: Wiley. p. 597. ISBN 978-0-470-08024-5. https://archive.org/details/Rocket_Propulsion_Elements_8th_Edition_by_Oscar_Biblarz_George_P._Sutton.
3. ↑ The liquefaction temperature of oxygen is 89 kelvins, 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.
4. ↑ Biswas, S. (2000). Cosmic perspectives in space physics. Bruxelles: Kluwer. p. 23. ISBN 0-7923-5813-9. https://books.google.com/books?id=lZ-qFK0pkfAC&pg=PA23. "... [LH2+LOX] has almost the highest specific impulse."
5. ↑ "Le-7A｜エンジン｜H-Iiaロケット｜ロケット｜Jaxa 宇宙輸送技術部門". https://www.rocket.jaxa.jp/rocket/engine/le7/.
6. ↑ "Le-5B｜エンジン｜H-Iiaロケット｜ロケット｜Jaxa 宇宙輸送技術部門". https://www.rocket.jaxa.jp/rocket/engine/le5b/.
7. ↑ "Le-9｜エンジン｜H3ロケット｜ロケット｜Jaxa 宇宙輸送技術部門". https://www.rocket.jaxa.jp/rocket/engine/le9/.
8. ↑ without nozzle 48.52kN (4.9 tf)
9. ↑ without nozzle 66.64kN (6.8 tf)
10. ↑ without nozzle 286.8
11. ↑ without nozzle 291.6

## External links

* USA's Cryogenic Rocket engine RL10B-2
* Russian Cryogenic Rocket Engines
* [1]

* v
* t
* e

Rocket engines and solid motors for orbital launch vehicles

* Comparison of orbital rocket engines

Liquid fuel|

| Cryogenic (hydrolox)
(LH2 / LOX)|

* China
* YF-73
* YF-75
* YF-75D
* YF-77
* Europe
* HM7B
* Vinci
* Vulcain
* India
* CE-7.5
* CE-20
* Japan
* LE-5
* LE-7
* LE-9
* Russia
* KVD-1 (RD-56)
* RD-0120
* RD-0146
* USA
* BE-3U
* BE-7
* J-2
* RL10
* RS-25 (SSME)
* RS-68

|

Cryogenic (methalox)
(CH4 / LOX)|

* USA
* BE-4
* Raptor
* Europe
* Prometheus
* Italy (with Russia)
* Mira (LM-10)

Semi-cryogenic (kerolox)
(RP-1 / LOX)|

* China
* YF-100
* YF-115
* India
* SCE-200
* Russia
* NK-15
* NK-33 NK-44
* RD-58
* RD-0105, 0109
* RD-0107, 0108, 0110
* RD-0110R
* RD-0124
* RD-107, 108, 117, 118
* RD-120
* RD-170, 171
* RD-180
* RD-191, 151, 181
* RD-193
* S1.5400
* Ukraine
* RD-8
* RD-801
* RD-810
* USA
* F-1
* H-1
* Kestrel
* LR-79
* LR-89
* LR-105
* LR70-NA , S-3D
* Merlin 1
* RS-27
* RS-27A
* RS-56
* S-3D
* Rutherford
* XLR50

Storable (hypergolic)
(UDMH, UH 25,
Aerozine or MMH
reacting with NTO N2O4,
MON or HNO3)|

* China
* YF-1, 2, 3
* YF-20, 21, 22, 24, 25
* YF-23
* YF-40
* YF-50D
* Europe
* Aestus
* Astris
* Vexin
* Viking
* India
* PS4
* Vikas
* Israel
* LK-4
* North Korea
* Paektusan LRE along other LREs
* Russia
* 17D61
* RD-0202 to 0206, 0208 to 0213
* RD-0207, 0214
* RD-0216, 0217, 0235
* RD-0233, 0234
* RD-0236
* RD-0237
* RD-0243 to 0245
* RD-0255 to 0257
* RD-215, 216
* RD-250 to 252, 261, 262
* RD-253, 275
* RD-263, 268, 273
* RD-270
* RD-854, 861
* RD-855
* RD-856
* RD-864, 869
* S5.92
* S5.98M
* Ukraine
* RD-843
* USA
* AJ10
* LR-87
* LR-91
* TR-201

Other propellants|

* Europe
* Gamma
* Russia
* RD-109, 119
* RD-211 to 214
* USA
* XLR81
* Curie

Solid fuel|

* China
* FG-02
* FG-36
* FG-46
* FG-47
* SpaB-65
* SpaB-140C
* Europe
* Mage 1
* P-4
* P-6
* PAP
* P80
* P120
* P230
* Topaze
* Waxwing
* Zefiro 9
* Zefiro 23
* Zefiro 40
* India
* S7
* S9
* S12
* S139
* S200
* Israel
* LK-1
* RSA-3
* Japan
* KM-V1
* KM-V2b
* M-14
* M-24
* M-34
* M-34c
* SRB-A
* USA
* AJ-60A
* Algol
* Castor 30
* GEM
* Orbus-6
* Orbus-21
* Orion
* Space Shuttle SRB
* Star 37
* Star 48
* UA120
* SRMU
* X-248
* X-254

* Engines under development are in italics.

* v
* t
* e

Spacecraft propulsion

Chemical
rockets|

| State|

* Liquid-propellant rocket
* Solid-propellant rocket
* Hybrid-propellant rocket

|

Propellants|

* Liquid propellant
* Cryogenic
* Hypergolic
* Monopropellant
* Bipropellant
* Staged combustion cycle
* Expander cycle
* Gas-generator cycle
* Tap-off cycle
* Pressure-fed engine
* Pump-fed engine
* Electric-pump-fed engine
* Tripropellant

Electrical
thrusters|

| Electrostatic|

* Colloid thruster
* Ion thruster
* Gridded
* Hall-effect thruster
* Field-emission electric propulsion

|

Electromagnetic|

* Pulsed inductive thruster
* Magnetoplasmadynamic thruster
* Electrodeless plasma thruster

Electrothermal|

* Pulsed plasma thruster
* Helicon double-layer thruster
* Arcjet rocket
* Resistojet rocket
* VASIMR

Other|

* Atmosphere-breathing electric propulsion
* High Power Electric Propulsion
* MagBeam
* Mass driver

Nuclear
propulsion|

| Closed system|

* Direct Fusion Drive
* Nuclear electric rocket
* Nuclear thermal rocket
* Radioisotope
* Salt-water
* Gas core
* "Lightbulb"

|

Open system|

* Nuclear pulse propulsion
* Antimatter-catalyzed
* Pulsed nuclear thermal rocket‎
* Fusion rocket
* Bussard ramjet
* Fission-fragment rocket
* Fission sail
* Nuclear photonic rocket

Other|

* Anti-gravity
* Beam-powered propulsion
* Cold gas thruster
* Gravity assist
* Solar sail
* Electric sail
* Magnetic sail
* Solar thermal rocket
* Tethers
* Steam thruster

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