Not to be confused with RL10.
AJ10
liquid
Country of originUnited States
Date1957–present
ManufacturerAerojet
Aerojet Rocketdyne
PurposeUpper stage
StatusIn use
CyclePressure-fed
Combustion chamber1
Thrust(vac)43.7 kN (9,800 lbf)
Specific impulse vacuum270-319 isp
Chamber pressure7-9 bar[1]
Diameter0.84 m (2.8 ft)
Dry weight90–100 kg
Fuel
Used in

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 and Titan III. 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.[2]

Variants

Many AJ10 engine variations were developed over the years, summarized on the following table:[2][3]

ModelPropellantUsed onFirst flightNotesRef
AJ10‑11BHNO3 / UDMH[4]
AJ10‑21HNO3 / AnilineAerobee RV-N-13b[5]
AJ10‑24HNO3 / AnilineAerobee RTV-N-10b[4][5]
AJ10‑25HNO3 / AnilineAerobee RTV-A-1a, RTV-A-1c, RTV-N-10a, Aerobee AJ10-25[4][5]
AJ10‑27HNO3 / AnilineAerobee AJ10-27[4]
AJ10‑34HNO3 / AnilineAerobee RTV-N-10c, Aerobee AJ10-34[4][5]
AJ10‑37HNO3 / UDMHVanguard1958Vanguard second stage[4][6]
AJ10‑40HNO3 / UDMHThor-Able1958Able stage[4]
AJ10‑41HNO3 / UDMHThor-Able I1958Able stage[4]
AJ10‑42HNO3 / UDMHThor-Able II1959Able stage[4]
AJ10‑101HNO3 / UDMHAtlas-Able, Thor-Able1958ABLE-1 lunar probes[4]
AJ10‑101AHNO3 / UDMHAtlas-Able IV, V; Thor-Able III, IV1959[4]
AJ10‑104HNO3 / UDMHThor-Ablestar1960Ablestar[4]
AJ10‑104DHNO3 / UDMHThor-Ablestar1963Ablestar
AJ10‑118HNO3 / UDMHDelta A, Thor/ASSET1960Long Tank Able stage for Delta[4]
AJ10‑118AHNO3 / UDMHDelta B[4]
AJ10‑118DHNO3 / UDMHDelta B, C, D1962[4]
AJ10‑118EHNO3 / UDMHDelta E, G, J, L, M, N1965[4]
AJ10‑118FHNO3 / UDMHDelta 0100, 10001972Transtage derived[4]
AJ10‑118FJHNO3 / UDMHN-II1981Transtage derived[4]
AJ10‑118KN2O4 / Aerozine-50Delta 4000, 5000, II1982Pressure-fed, altitude-optimized[4][7]
AJ10‑131N2O4 / Aerozine-50Subscale Apollo Service Propulsion System
AJ10‑137N2O4 / Aerozine-50Apollo Service ModulePressure-fed[4][8]
AJ10‑138N2O4 / Aerozine-50Titan IIIC, Titan IIIA, Titan 34D, Titan 3C71964Originally developed for Vanguard and Able, flown as Transtage[4]
AJ10‑138AN2O4 / Aerozine-50Titan IIIC, Titan IIIA, Titan 34D, Titan 3C7Transtage[4]
AJ10‑190N2O4 / CH6N2Shuttle OMS, European Service Module1981Also called the Orbital Maneuvering Engine (OME). Refurbished shuttle engines used on ESM. Only reusable variant in the AJ10 family.[4][9][10]
AJ10‑198Kick stage engine
AJ10‑196Liquid throttling engine.
TranstarN2O4 / CH6N2TranstarPump-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.[2][6] It was initially fueled by HNO3 and UDMH.[11] 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.[12]

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 7,800 lbf (35 kN) to 8,000 lbf (36 kN), and with a higher specific impulse of 311 isp.[11]

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.[8] 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.[13][14]

AJ10-118F

The AJ10-118F engine produced 9,000 lbf (40 kN) 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 kilonewtons (6,000 lbf) of thrust with a specific impulse (Isp) of 316 seconds.[15] Following the retirement of the Shuttle, these engines were repurposed for use on the Orion spacecraft's service module.[10] This variant uses CH6N2 as fuel, with nitrogen tetroxide (N2O4) as oxidizer.[9]

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.[7] The AJ10-118K engine variant was used from 1989 and retired at the conclusion of the ICESat-2 launch on 15 September 2018.

References

  1. ^ "AJ10-118". Encyclopedia Astronautica. Archived from the original on 2008-07-06. Retrieved 2008-06-22.
  2. ^ "Aerojet liquid motors". www.planet4589.org. Retrieved 2025-06-16.
  3. ^ Wade. "AJ10". Encyclopedia Astronautica. Archived 2016-12-28 at the Wayback Machine. Retrieved 2025-06-14.
  4. ^ McDowell, Jonathan C. (Aug 13, 2025). "Engines". GCAT: General Catalog of Artificial Space Objects. Retrieved 2025-08-13.
  5. ^ "Aerojet General PWN-2 Aerobee-Hi". www.designation-systems.net. Retrieved 2025-08-13.
  6. ^ Aircraft Industries Association, Inc. (1959). The Aircraft Year Book. Wayne W. Parrish. p. 370.
  7. ^ "Delta II Stage 2 Engine". Aerojet Rocketdyne. Archived from the original on 14 March 2017. Retrieved 22 January 2017.
  8. ^ 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. October 1968.
  9. ^ "Aerojet Rocketdyne - In-Space Propulsion Data Sheets". Archived from the original on 2020-01-11. Retrieved 2019-12-07.
  10. ^ Bergin, Chris (20 June 2015). "Plum Brook prepped for EM-1 Orion Service Module testing". NASASpaceFlight.com. Retrieved 28 July 2015.
  11. ^ Wade, Mark. "AJ10-118". Encyclopedia Astronautica. Archived from the original on 6 July 2008. Retrieved 2008-06-22.
  12. ^ Wade, Mark. "Thor-Able". Encyclopedia Astronautica. Archived from the original on February 28, 2002. Retrieved 2008-05-24.
  13. ^ Kyle, Ed (8 April 2010). "Long Tank Thor-Delta". Space Launch Report. Retrieved 6 June 2012.
  14. ^ The First Space Race: Launching the World's First Satellites, By Matt Bille, Erika Lishock, page 163 and page 174
  15. ^ Wade (2009). "OME". Encyclopedia Astronautica. Archived from the original on 13 January 2010. Retrieved 4 January 2010.