High Quality Content by WIKIPEDIA articles! The Space Shuttle Orbital Maneuvering System, or OMS (pronounced /omz/), is a system of rocket engines designed and manufactured by Aerojet for use on the space shuttle orbiter for orbital injection and modifying its orbit. It consists of two "packs" at the back of the Shuttle, the large lumps on either side of the vertical stabilizer. Each pack contains a single hypergolic OME engine (AJ10-190)., based on the Service Propulsion System on the Apollo Service Module, with a thrust of 6,000 lbf (27 kN) and a Specific impulse of 313 seconds, which can be reused for 100 missions and is capable of 1,000 starts and 15 hours of firing. The OMS pods also contain the rear set of reaction control system (RCS) engines as well, which are referred to as the OMS/RCS. The fuel used is monomethylhydrazine (MMH), which is oxidized with nitrogen tetroxide (N2O4). The Shuttle has enough fuel, 8,174 kilograms (18,020 lb) of MMH and 13,486 kilograms (29,730 lb) of oxydizer, for about 1,000 feet per second (300 m/s) of delta-V using the OMS.