Space Shuttle Orbital Maneuvering System

The Space Shuttle Orbital Maneuvering System (OMS) is a system of hypergolic liquid-propellant rocket engines used on the Space Shuttle. Designed and manufactured in the United States by Aerojet,[1] the system allowed the orbiter to perform various orbital maneuvers according to requirements of each mission profile: orbital injection after main engine cutoff, orbital corrections during flight, and the final deorbit burn for reentry.[2] Rarely the OMS were actually ignited part-way into the Shuttle's main ascent for a few minutes to aid acceleration to orbital insertion (usually while carrying heavy ISS payloads). This occurred on STS-51-F, STS-124, STS-128 and STS-135.

"Orbital Maneuvering System" redirects here, but can refer to any system used to modify a spacecraft's orbit. For the similarly-named Gemini component, see Orbit Attitude and Maneuvering System.

Space Shuttle OMS/RCS Pod
The underside of a left OMS/RCS pod.
ManufacturerAerojet
Country of originUnited States
Used onSpace Shuttle
General characteristics
Length21.8 feet (6.6 m)
Width
  • 11.37 feet (3.47 m) (aft)
  • 8.14 feet (2.48 m) (forward)
Launch history
StatusRetired
Total launches135
Successes
(stage only)		134
Lower stage
failed		1 (STS-51-L)
First flightSTS-1 (12 April 1981)
Last flightSTS-135 (8 July 2011)
OMS Engine
Powered by1 AJ10-190
Maximum thrust26.7 kilonewtons (6,000 lbf)
Specific impulse316 seconds (vacuum)
Burn time
  • 15 hours (maximum service life)
  • 1250 seconds (deorbit burn)
  • 150–250 seconds (typical burn)
PropellantMMH/N
2O
4
Aft Primary RCS
Powered byPrimary RCS engines
Maximum thrust3.87 kilonewtons (870 lbf)
Burn time
  • 1–150 seconds (each burn)
  • 800 seconds (total)
PropellantMMH/N
2O
4
Aft Vernier RCS
Powered byVernier RCS engines
Maximum thrust106 newtons (24 lbf)
Burn time1–125 seconds (each burn)
PropellantMMH/N
2O
4

The OMS consists of two pods mounted on the orbiter's aft fuselage, on either side of the vertical stabilizer.[2] Each pod contains a single AJ10-190 engine,[3] based on the Apollo Service Module's Service Propulsion System engine, which produces 26.7 kilonewtons (6,000 lbf) of thrust with a specific impulse (Isp) of 316 seconds.[3] The oxidizer-to-fuel ratio is 1.65-to-1, The expansion ratio of the nozzle exit to the throat is 55-to-1, The chamber pressure of the engine is 8.6 bar.[2] The dry weight of each engine is 260 pounds. 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 of reaction control system (RCS) engines, and so were referred to as OMS/RCS pods. The OM engine and RCS both burned monomethylhydrazine (MMH) as fuel, which was oxidized with dinitrogen tetroxide (N
2O
4), with the propellants being stored in tanks within the OMS/RCS pod, alongside other fuel and engine management systems.[4] When full, the pods together carried around 4,087 kilograms (9,010 lb) of MMH and 6,743 kilograms (14,866 lb) of N
2O
4, allowing the OMS to produce a total delta-v of around 1,000 feet per second (300 m/s) with a 65,000-pound (29,000 kg) payload.[4][5]

  • Diagram of OMS pod components
  • An OMS pod detached from an orbiter for maintenance

Proposed OMS Payload Bay Kit

It was never built, but to augment the OMS an OMS Payload Bay Kit was proposed.[6] It would have used one, two or three sets of OMS tanks, installed in the payload bay, to provide an extra 500 ft/s, 1000 ft/s or 1500 ft/s of delta-V to the orbiter.[6] The orbiter control panels had related switches and gauges but they were nonfunctional.[7]: 1–2 

References
  1. D. Craig Judd (1992). "Capability and flight record of the versatile space shuttle OMS engine". Space Technology and Science. NASA. Bibcode:1992spte.symp..107J.
  2. "Orbital Maneuvering System". NASA. 1998. Archived from the original on 29 June 2011.
  3. Encyclopedia Astronautica (2009). "OME". Encyclopedia Astronautica. Archived from the original on 27 August 2016. Retrieved 16 September 2021.
  4. NASA (1998). "Propellant Storage and Distribution". NASA. Archived from the original on 10 February 2001. Retrieved 8 February 2008.
  5. David Palmer, Allie Cliffe and Tim Kallman (9 May 1997). "Spacecraft Fuel". NASA.
  6. SHUTTLE PERFORMANCE ENHANCEMENTS USING AN OMS PAYLOAD BAY KIT 1991
  7. Orbital Maneuvering System Workbook 2006

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