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The service module designed for Orion will serve as the primary power and propulsion component of the spacecraft system, and like its predecessors, will be discarded at the end of each mission. Roughly cylindrical in shape, the Orion service module, like the crew module, will be constructed of Al-Li alloy (to keep weight down), and will 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), will allow NASA to eliminate the need to carry malfunction-prone fuel cells, and its associated hardware (mainly LH₂ tanks) from 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.

- - - The spacecraft's main propulsion system is an Aerojet AJ-10 rocket engine, derived from the second stage of the Delta II rocket, powered by hypergolic fuels, that are kept in helium pressured fuel cells. 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 (10.2 to 14.7 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.

- - Like the Orion crew module, the Orion service module will be encapsulated by a fiberglass shroud that would be 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 mid-points, like that of the Soyuz, 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). The projected empty mass is 3,700 kg (8,000 lb), fuel capacity is 8,300 kg (18,000 lb).