| United States|
N2O4 / Aerozine 50
| Aerojet, Aerojet Rocketdyne|
Upper stage/Spacecraft propulsion
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.
It was first used in the Able second stage of the Vanguard rocket, in the AJ10-118 configuration. It was initially fueled by nitric acid 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.
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.
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.
This version used Aerozine 50 (a 50-50 mix of UDMH and hydrazine) as fuel and nitrogen tetroxide (N2O4) as oxidizer, rather than the previous nitric acid/UDMH.
The AJ10-118K engine is currently in use on the Delta II rocket's upper stage. It uses Aerozine 50 as fuel and nitrogen tetroxide (N2O4) as oxidizer.
The AJ10-137 engine was used in the Apollo Service Module's Service Propulsion System. 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 AJ10-138 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=311s.
The AJ10-190 engine was used on the Space Shuttle Orbital Maneuvering System (OMS) for orbital insertion, on-orbit maneuvers, and de-orbiting. Following the retirement of the Shuttle, these engines will be repurposed for use on the Orion spacecrafts Service Module.