Space Shuttle Orbital Maneuvering System

Summary

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.[citation needed]

Space Shuttle OMS/RCS Pod
OMS Pod removal.png
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
2
O
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
2
O
4
Aft Vernier RCS
Powered byVernier RCS engines
Maximum thrust106 newtons (24 lbf)
Burn time1–125 seconds (each burn)
PropellantMMH/N
2
O
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,[citation needed] 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
2
O
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
2
O
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]

Proposed OMS Payload Bay KitEdit

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 

ReferencesEdit

  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. ^ a b c d "Orbital Maneuvering System". NASA. 1998. Archived from the original on 29 June 2011.
  3. ^ a b Encyclopedia Astronautica (2009). "OME". Encyclopedia Astronautica. Archived from the original on 27 August 2016. Retrieved 16 September 2021.
  4. ^ a b 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. ^ a b SHUTTLE PERFORMANCE ENHANCEMENTS USING AN OMS PAYLOAD BAY KIT 1991
  7. ^ Orbital Maneuvering System Workbook 2006