 The underside of a left OMS/RCS pod onSpace Shuttle Endeavour | |
| Manufacturer | Aerojet |
|---|---|
| Country of origin | United States |
| Used on | Space Shuttle/OrionEuropean Service Module |
| General characteristics | |
| Length | 21.8 ft (6.6 m) |
| Width |
|
| Launch history | |
| Status | Pod: Retired Engines: Active |
| Total launches | Space Shuttle: 135 Orion: 1 |
| Successes (stage only) | Space Shuttle: 134 Orion: 1 |
| Lower stage failed | 1 (STS-51-L) |
| First flight | 12 April 1981 (STS-1) |
| Last flight | |
| OMS Engine | |
| Powered by | 1 ×AJ10-190 |
| Maximum thrust | 26.7 kN (6,000 lbf) |
| Specific impulse | 316 s (3.10 km/s) |
| Burn time |
|
| Propellant | MMH/MON-3 |
| Aft Primary RCS | |
| Powered by | Primary RCS engines |
| Maximum thrust | 3.87 kN (870 lbf) |
| Burn time |
|
| Propellant | MMH/MON-3 |
| Aft Vernier RCS | |
| Powered by | Vernier RCS engines |
| Maximum thrust | 106 N (24 lbf) |
| Burn time | Up to 125 seconds (each burn) |
| Propellant | MMH/MON-3 |
TheOrbital Maneuvering System (OMS) is a system ofhypergolicliquid-propellantrocket engines used on theSpace Shuttle and theOrion spacecraft. Designed and manufactured in the United States byAerojet,[1] the system allowed theorbiter to perform variousorbital maneuvers according to requirements of each mission profile:orbital injection aftermain engine cutoff, orbital corrections during flight, and the final deorbit burn forreentry.[2] From STS-90 onwards the OMS were typically ignited part-way into the Shuttle's ascent for a few minutes to aid acceleration to orbital insertion. Notable exceptions were particularly high-altitude missions such as those supporting theHubble Space Telescope (STS-31) or those with unusually heavy payloads such asChandra (STS-93). An OMS dump burn also occurred onSTS-51-F, as part of the Abort to Orbit procedure.[3]
The OMS consists of two pods mounted on the orbiter's aft fuselage, on either side of thevertical stabilizer.[2] Each pod contains a singleAJ10-190 engine,[4] based on theApollo Service Module's Service Propulsion System engine,[5] which produces 26.7 kilonewtons (6,000 lbf) of thrust with aspecific impulse (Isp) of 316 seconds.[4] The oxidizer-to-fuel ratio is 1.65-to-1, The expansion ratio of the nozzle exit to the throat is 55-to-1, and the chamber pressure of the engine is 8.6 bar.[2] The dry weight of each engine is 118kg (260lb). Each engine could be reused for 100 missions and was capable of a total of 1,000 starts and 15 hours of burn time.[2]
These pods also contained the Orbiter's aft set ofreaction control system (RCS) engines, and so were referred to asOMS/RCS pods. The OM engine and RCS both burnedmonomethylhydrazine (MMH) as fuel, which was oxidized with MON-3 (mixed oxides of nitrogen, 3% nitric acid), with the propellants being stored in tanks within the OMS/RCS pod, alongside other fuel and engine management systems.[6] When full, the pods together carried around 4,087 kilograms (9,010 lb) of MMH and 6,743 kilograms (14,866 lb) of MON-3, allowing the OMS to produce a totaldelta-v of around 305 metres per second (1,000 ft/s) with a 29,000-kilogram (64,000 lb) payload.[6][7]
It was never built, but to augment the OMS an OMS Payload Bay Kit was proposed.[8] It would have used one, two or three sets of OMS tanks, installed in the payload bay, to provide an extra 150 m/s, 300 m/s or 450 m/s( (500 ft, 1000 ft/s or 1500 ft/s) of delta-V to the orbiter.[8] The orbiter control panels had related switches and gauges but they were nonfunctional.[9]: 1–2
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Following the retirement of theShuttle, these engines were repurposed for use on theOrion spacecraft'sservice module.[10] This variant usesMonomethylhydrazine as fuel, with MON-3Mixed Oxides of Nitrogen as oxidizer.[11] It is planned to be used for the first six flights of theArtemis program, afterwards it would be replaced by a new "Orion Main Engine" starting Artemis 7.[12]
