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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. It is intended for use as the main engine of NASA's Orion service module.

Delta II second stage.jpg
Country of originUnited States
ManufacturerAerojet, Aerojet Rocketdyne
ApplicationUpper stage/spacecraft propulsion
StatusIn use
Liquid-fuel engine
PropellantN2O4 / Aerozine 50
CyclePressure-fed engine
Thrust (vac.)43.7 kN
Chamber pressure7–9 bar[1]
Isp (vac.)319 s[2]
Diameter0.84 m
Dry weight90–100 kg
Used in
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)


It was first used in the Delta-A/Able second stage of the Vanguard rocket, in the AJ10-118 configuration. It was initially fueled by nitric acid and UDMH.[3] 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.

The AJ10-101 engine was used on an uprated version of the Able, used on Atlas-Able and Thor-Able rockets. The first flight, of a Thor-Able, occurred on 23 April 1958, however, the Thor failed before the upper stage fired. The second flight, which saw the first firing of an AJ10-101 engine, occurred on 10 July 1958.[4]

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 3540 kgf to 3628 kgf, with higher specific impulse, Isp = 311 s.

The AJ10-137 engine 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 also used Aerozine 50 as fuel and nitrogen tetroxide (N2O4) as oxidizer.

The AJ10-118F engine produces 4.08 tonnes of thrust and was derived from the AJ10-138 engine used on Transtage. Used in Delta 1000 ("Straight Eight") series on Delta-F upper stage starting in 1972. 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.[5]

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. Following the retirement of the Shuttle, these engines will be repurposed for use on the Orion spacecraft's service module.[6]

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.

See alsoEdit


  1. ^ "Archived copy". Archived from the original on 2008-07-06. Retrieved 2008-06-22.CS1 maint: Archived copy as title (link)
  2. ^ "Delta II Design". Gunter's Space Page. Retrieved 6 June 2012.
  3. ^ Wade, Mark. "AJ10-118". Encyclopedia Astronautica. Archived from the original on 6 July 2008. Retrieved 2008-06-22.
  4. ^ Wade, Mark. "Thor-Able". Encyclopedia Astronautica. Retrieved 2008-05-24.
  5. ^ Kyle, Ed (8 April 2010). "Long Tank Thor-Delta". Space Launch Report. Retrieved 6 June 2012.
  6. ^ Bergin, Chris (20 June 2015). "Plum Brook prepped for EM-1 Orion Service Module testing". Retrieved 28 July 2015.
  7. ^ "Delta II Stage 2 Engine". Aerojet Rocketdyne. Retrieved 22 January 2017.