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AJ10

Hypergolic rocket engine manufactured by Aerojet

Field	Value
country_of_origin	United States
image	Delta II second stage.jpg
caption	AJ10-118K
name	AJ10
date	1957–present
manufacturer	Aerojet
Aerojet Rocketdyne
purpose	Upper stage
status	In use
cycle	Pressure-fed
combustion_chamber	1
thrust(Vac)	43.7 kN
specific_impulse_vacuum	270-319 isp
chamber_pressure	7-9 bar
diameter	0.84 m
dry_weight	90–100 kg
type	liquid
fuel	{{Plainlist
* {{Chem2	HNO3	link	Nitric acid}} / UDMH
* {{Chem2	HNO3	link	Nitric acid}} / Aniline
* {{Chem2	N2O4	link	Dinitrogen tetroxide}} / Aerozine-50
* {{Chem2	N2O4	link	Dinitrogen tetroxide}} /
used_in	{{plainlist

Aerojet Rocketdyne | thrust(Vac) = 43.7 kN

/ UDMH
/ Aniline
/ Aerozine-50
/
Vanguard (Delta-A)
Thor/Atlas (Able)
Thor-Delta/Delta A-N, Super-Six (Stage 2)
Thor-Ablestar (Ablestar)
Delta 0100/1000/2000/3000 (Delta-F)
Delta 4000/5000/II (Delta-K)
Titan III (Transtage)
Apollo (service module)
Space Shuttle (Orbital Maneuvering System)
Orion (service module)}} The AJ10 is a hypergolic rocket engine manufactured by Aerojet Rocketdyne (previously Aerojet). It has been used to propel the upper stages of several launch vehicles, including the Delta II, Titan III and Orion MPCV. Variants were and are used as the service propulsion engine for the Apollo command and service module, in the Space Shuttle Orbital Maneuvering System, and on the European Service Module – part of NASA's Orion spacecraft.

Variants

Many AJ10 engine variations were developed over the years, summarized on the following table:

Model	Propellant	Used on	First flight	Notes	Ref
AJ10	/ UDMH	Vanguard			last=McDowell	first=Jonathan C.	date=Aug 13, 2025	title=Engines	url=https://planet4589.org/space/gcat/data/tables/engines.html	access-date=2025-08-13	website=GCAT: General Catalog of Artificial Space Objects}}
AJ1011B	/ UDMH
AJ1021	/ Aniline	Aerobee RV-N-13b			title=Aerojet General PWN-2 Aerobee-Hi	url=https://www.designation-systems.net/dusrm/n-2.html	access-date=2025-08-13	website=www.designation-systems.net}}
AJ1024	/ Aniline	Aerobee RTV-N-10b
AJ1025	/ Aniline	Aerobee RTV-A-1a, RTV-A-1c, RTV-N-10a, Aerobee AJ10-25
AJ1027	/ Aniline	Aerobee AJ10-27
AJ1034	/ Aniline	Aerobee RTV-N-10c, Aerobee AJ10-34
AJ1037	/ UDMH	Vanguard	1958	Vanguard second stage
AJ1040	/ UDMH	Thor-Able	1958	Able stage
AJ1041	/ UDMH	Thor-Able I	1958	Able stage
AJ1042	/ UDMH	Thor-Able II	1959	Able stage
AJ10101	/ UDMH	Atlas-Able, Thor-Able	1958	ABLE-1 lunar probes
AJ10101A	/ UDMH	Atlas-Able IV, V; Thor-Able III, IV	1959
AJ10104	/ UDMH	Thor-Ablestar	1960	Ablestar
AJ10104D	/ UDMH	Thor-Ablestar	1963	Ablestar
AJ10118	/ UDMH	Delta A, Thor/ASSET	1960	Long Tank Able stage for Delta
AJ10118A	/ UDMH	Delta B
AJ10118D	/ UDMH	Delta B, C, D	1962
AJ10118E	/ UDMH	Delta E, G, J, L, M, N	1965
AJ10118F	/ UDMH	Delta 0100, 1000	1972	Transtage derived
AJ10118G	/ UDMH	Delta G	1965
AJ10118H	/ UDMH	Delta H
AJ10118FJ	/ UDMH	N-II	1981	Transtage derived
AJ10118K	/ Aerozine-50	Delta 4000, 5000, II	1982	Pressure-fed, altitude-optimized
AJ10131	/ Aerozine-50			Subscale Apollo Service Propulsion System
AJ10137	/ Aerozine-50	Apollo Service Module		Pressure-fed
AJ10138	/ Aerozine-50	Titan IIIC, Titan IIIA, Titan 34D, Titan 3C7	1964	Originally developed for Vanguard and Able, flown as Transtage
AJ10138A	/ Aerozine-50	Titan IIIC, Titan IIIA, Titan 34D, Titan 3C7		Transtage
AJ10190	/	Shuttle OMS, European Service Module	1981	Also called the Orbital Maneuvering Engine (OME). Refurbished shuttle engines used on ESM. Only reusable variant in the AJ10 family.
AJ10198				Kick stage engine
AJ10196				Liquid throttling engine.
Transtar	/	Transtar		Pump-fed upper stage engine based on Shuttle OMS components.

AJ10-37

The AJ10 engine was first used in the Delta-A/Able second stage of the Vanguard rocket, in the AJ10-37 configuration. It was initially fueled by and UDMH. An AJ10 engine was first fired in flight during the third Vanguard launch, on 17 March 1958, which successfully placed the Vanguard 1 satellite into orbit.

AJ10-101

The AJ10-101 engine was used on an uprated version of the Able stage, used on Atlas-Able and Thor-Able rockets. The first AJ10-101 flight, with a Thor-Able, occurred on 23 April 1958; however, the Thor failed before the upper Able stage fired. The second flight, which saw the first in flight firing of an AJ10-101 engine, occurred on 10 July 1958.

AJ10-138

The AJ10-138 engine was originally developed for Vanguard and Able, and was flown from 1964 to 1980. Two of these engines were used in the Titan III GTO Transtage, with thrust uprated from 7800 lbf to 8000 lbf, and with a higher specific impulse of 311 isp.

AJ10-137

The AJ10-137 engine (20,500 lbf (91 kN) of thrust) was used in the Apollo service module's service propulsion system from first flight in 1966. Trans-Earth injection, from lunar orbit, was the most critical usage of this engine during the Apollo program. This version used Aerozine 50 (a 1:1 mix of UDMH and hydrazine) as fuel and nitrogen tetroxide (N2O4) as oxidizer, rather than the previous nitric acid/UDMH.

AJ10-118F

The AJ10-118F engine produced 9000 lbf of thrust and was derived from the AJ10-138 engine used on the Transtage. It was used by the Delta-F upper stage of the Delta 1000 Straight Eight series rocket, starting in 1972. This version also used Aerozine 50 as fuel and nitrogen tetroxide (N2O4) as oxidizer.

AJ10-190

The AJ10-190 engine was used on the Space Shuttle Orbital Maneuvering System (OMS) for orbital insertion, on-orbit maneuvers, and de-orbiting, first flown in 1981. They produced 26.7 kN of thrust with a specific impulse (Isp) of 316 seconds. Following the retirement of the Shuttle, these engines were repurposed for use on the Orion spacecraft's service module. This variant uses as fuel, with nitrogen tetroxide (N2O4) as oxidizer.

AJ10-118K

The AJ10-118K engine was used on the Delta II rocket's upper stage, Delta-K. It used Aerozine 50 as fuel and nitrogen tetroxide (N2O4) as oxidizer. The AJ10-118K engine variant was used from 1989 and retired at the conclusion of the ICESat-2 launch on 15 September 2018.

References

"AJ10-118".
"Aerojet liquid motors".
Wade. "AJ10".
McDowell, Jonathan C.. (Aug 13, 2025). "Engines".
"Aerojet General PWN-2 Aerobee-Hi".
Aircraft Industries Association, Inc.. (1959). "The Aircraft Year Book". Wayne W. Parrish.
Wade, Mark. "AJ10-118". Encyclopedia Astronautica.
Wade, Mark. "Thor-Able". Encyclopedia Astronautica.
(October 1968). "APOLLO BLOCK II SPS ENGINE (AJ10-137) - ENVIRONMENTAL TESTS AND MOD I-C BIPROPELLANT - VALVE QUALIFICATION TESTS - (PHASE VI, PART I)". ROCKET TEST FACILITY, ARNOLD ENGINEERING DEVELOPMENT CENTER AIR FORCE SYSTEMS COMMAND, ARNOLD AIR FORCE STATION, TENNESSEE.
Kyle, Ed. (8 April 2010). "Long Tank Thor-Delta". Space Launch Report.
The First Space Race: Launching the World's First Satellites, By Matt Bille, Erika Lishock, page 163 and page 174
Wade. (2009). "OME".
Bergin, Chris. (20 June 2015). "Plum Brook prepped for EM-1 Orion Service Module testing". NASASpaceFlight.com.
"Aerojet Rocketdyne - In-Space Propulsion Data Sheets".
"Delta II Stage 2 Engine". [[Aerojet Rocketdyne]].

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