The engine used in Shuttle Orbiter Orbital Maneuvering System (OMS). The Shuttle Orbiter carried two OMS pods (name coined by Aerojet), each housing a single Aerojet OM Engine for orbit insertion, maneuvering, and re-entry initiation. The astronauts had great faith in these engines, unlike other shuttle hardware, due to their simplicity. This did not stop NASA studying several times replacing them with complex pump-fed or cryogenic engines in order to get (unnecessarily) improved performance.

The engines never failed and never required replacement during the life of the shuttle program. They were designed to be capable of 100 missions and 500 starts in space. Rocketdyne built the shuttle SSME main engines which were supposed to have similar reliability. They didn't come close, and Rocketdyne was rewarded with billions of dollars over the decades in SSME repair, refurbishment, and improvement contracts. Aerojet's engines didn't need any of that, and the reliable designs required no further suport.

First Flown: April 12th, 1981, on the Orbiter Columbia. Mounting: gimballed ( 7 degrees yaw, 6 pitch by two electromechanical actuators for thrust vector control. Engine Cycle: pressure-fed (improvement underway for pump-fed). Oxidizer: 6743 kg nitrogen tetroxide in each pod (pods can be cross-linked). Fuel: 4087 kg of monomethyl hydrazine in each pod (pods can be cross-linked). Mixture Ratio: 1.65:1. Cooling Method: fuel regenerative for chamber, radiative for nozzle. Burn Time: qualified for 500 starts, 15 hr/100 mission life, longest firing 1250 sec, de-orbit. burn typically 150-250 secs.