Orion Service Module

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Orion spacecraft including the ATV-derived Service Module

The Orion Service Module serves as the primary power and propulsion component of the Orion spacecraft, and can be discarded at the end of each mission. In January 2013, an ATV-based service module was announced.[1]

It is intended to support the crew module from launch through separation prior to reentry. It provides in-space propulsion capability for orbital transfer, attitude control, and high altitude ascent aborts. When mated with the crew module, it provides the water and oxygen needed for a habitable environment, generates and stores electrical power while on-orbit, and maintains the temperature of the vehicle's systems and components. This module can also transport unpressurized cargo and scientific payloads.


Old design[edit]

Pre-ATV Service Module design

Roughly cylindrical in shape, the original American-designed Orion service module, would, like the crew module, have been constructed of Al-Li alloy (to keep weight down), and feature a pair of deployable circular solar panels, similar in design to the panels used on the Mars Phoenix lander. The panels, the first to be used on a U.S. manned spacecraft (except for a 10-year period, the Soviet/Russian Soyuz spacecraft has used them since the first mission in 1967), would allow NASA to eliminate the need to carry malfunction-prone fuel cells, and their associated hardware (mainly LH2 tanks) in the service module, resulting in a shorter, yet more maneuverable spacecraft. Successful initial testing of an Orion solar array design using full-scale "UltraFlex wing" hardware was reported in October, 2008.[2]

The Orion Main Engine (OME) is a 7500-pound thrust, pressure-fed, regeneratively cooled, storable bi-propellant rocket engine made by Aerojet. The OME is an increased performance version of the 6000-pound thrust rocket engine used by the Space Shuttle for its Orbital Maneuvering System (OMS). The SM Reaction Control System (RCS), the spacecraft's maneuvering thrusters (originally based on the Apollo "quad" system, but currently resembles that used on Gemini), will also be pressure-fed, and will use the same propellants. NASA believes the SM RCS would be able to act as a backup for a trans-Earth injection (TEI) burn in case the main SM engine fails.

A pair of LOX tanks (similar to those used in the Apollo SM) will provide, along with small tanks of nitrogen, the crew with breathing air at sea-level or "cruising altitude" pressure (14.7 or 10.2 psi), with a small "surge tank" providing necessary life support during reentry and touchdown. Lithium hydroxide (LiOH) cartridges will recycle the spacecraft's environmental system by "scrubbing" the carbon dioxide (CO2) exhaled by the astronauts from ship's air and adding fresh oxygen and nitrogen, which is then cycled back out into the system loop. Because of the switch from fuel cells to solar panels, the service module will have an onboard water tank which will provide drinking water for the crew, and (when mixed with glycol), cooling water for the spacecraft's electronics. Unlike the practice during Apollo of dumping both water and urine overboard during the flight, the Orion will have an onboard recycling system, identical to that used on the International Space Station, that will convert both waste water and urine into both drinking and cooling water.

The Service Module also mounts the spacecraft's waste heat management system (its radiators) and the aforementioned solar panels. These panels, along with backup batteries located in the Orion CM, will provide in-flight power to the ship's systems. The voltage, 28 volts DC, is similar to that used on the Apollo spacecraft during flight.

The Orion service module would be encapsulated by fiberglass shrouds jettisoned at the same time as the LES/Boost Protective Cover, which would take place roughly 2½ minutes after launch (30 seconds after the solid rocket first stage is jettisoned). Prior to the "Orion 606" redesign, the Orion SM resembled a squat, enlarged version of the Apollo Service Module. The new "Orion 606" SM design retains the 5-meter width for the attachments of the Orion SM with the Orion CM, but utilizes a Soyuz-like service module design that allows Lockheed Martin to make the vehicle lighter in weight and permitting the attachment of the circular solar panels at the module's midpoints, instead of at the base near the spacecraft/rocket adapter, which may subject the panels to damage.

The Orion service module (SM) is projected comprising a cylindrical shape, having a diameter of 5.03 m (16 ft 6 in) and an overall length (including thruster) of 4.78 m (15 ft 8 in). With solar panels extended, span is either 17.00 m (55.77 ft) or 55.00 ft (16.76 m)[clarification needed]. The projected empty mass is 3,700 kg (8,000 lb), fuel capacity is 8,300 kg (18,000 lb).[3][4]

ATV-based module[edit]

Edoardo Amaldi ATV approaches the International Space Station

In May 2011 the European Space Agency (ESA) Director General announced a possible collaboration with NASA to work on a successor to ESA's Automated Transfer Vehicle (ATV).[5] On 21 June 2012, Astrium announced that it had been awarded two separate studies, each worth €6.5 million, to evaluate the possibilities of using technology and experience gained from ATV and Columbus related work for future missions. The first looked into the possible construction of a service module which would be used in tandem with the Orion capsule.[6] The second examined the possible production of a versatile multi purpose orbital vehicle.[7]

On November 21, 2012, ESA decided they will construct an ATV-derived Service Module ready to support the Orion capsule on the maiden flight of the Space Launch System in 2017.[8] The service module will likely be manufactured by Airbus Defence and Space in Bremen, Germany.[9]

Service Module shown with the Crew Module and adapters

NASA announced on January 16, 2013, that ESA will construct the service module for Exploration Mission 1 in 2017.[1] They will use hardware from their current Automated Transfer Vehicle to construct a compatible service module to the spacecraft.

On 17 November 2014 ESA signed a €390 million contract with Airbus Defence and Space for the development and construction of the service module. The first Orion mission to use the module is expected to be Exploration Mission 1 Scheduled for launch at the end of 2018.[10]

See also[edit]


  1. ^ a b NASA Signs Agreement for a European-Provided Orion Service Module
  2. ^ "NASA and ATK Successfully Deploy 18-Foot Diameter Solar Array for ST8 Program". ATK. 9 October 2008. 
  3. ^ "The Orion Service Module". NASA. 4 August 2008. Retrieved 2008-08-19. 
  4. ^ "Orion". Encyclopedia Astronautica. Retrieved 2013-05-11. 
  5. ^ "US and Europe plan new spaceship". BBC News. 5 May 2011. Archived from the original on 6 May 2011. Retrieved 2011-05-14. 
  6. ^ "ATV evolution studies look at exploration, debris removal". Spaceflight Now. 21 June 2012. Retrieved 2012-06-23. 
  7. ^ "Astrium awarded two ATV evolution studies from ESA". Astrium. 21 June 2012. Retrieved 2012-06-23. 
  8. ^ Bergin, Chris (November 21, 2012). "UK steps up, as ESA commit to ATV Service Module on NASA’s Orion". NASASpaceFlight.com. NASA. Retrieved 2013-05-06. 
  9. ^ Clark, Stephen (November 21, 2012). "ESA member states fund Orion service module". Spaceflight Now. Retrieved 2013-05-06. 
  10. ^ "ESA Commissions Airbus Defence and Space as Prime Contractor for US Space Capsule Orion Service Module". spaceref business. 17 November 2014. Retrieved 18 November 2014. 

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