Orion Service Module
NASA and the European Space Agency (ESA) signed an agreement in 2013 for the Orion Exploration-1 Service Module to be provided by ESA. The Service Module houses Orion’s power, thermal and propulsion systems in order to provide orbital transfer, attitude control and high-altitude abort capability; power generation and storage; thermal control; and water and air for the astronauts.
Aerojet Rocketdyne will provide eight Auxiliary Engine thrusters to support the 2018 launch for the Exploration Mission-1 flight. The Auxiliary engines are 110-pound-thrust bipropellant thrusters, designated as R-4D with a 164:1 area ratio.