European Service Module

The European Service Module (ESM) is the service module component of the Orion spacecraft, serving as its primary power and propulsion component until it is discarded at the end of each mission. In January 2013, the National Aeronautics and Space Administration (NASA) announced that the European Space Agency (ESA) will contribute the service module for Artemis I, based on ESA's Automated Transfer Vehicle (ATV). It was delivered by Airbus Defence and Space from Bremen, Germany, to NASA at the end of 2018. After approval of the first module, ESA provided the ESM for Artemis II with current plans to continue the provision up to Artemis VI.

The module's first flight was Artemis I, the first major milestone in NASA's Artemis program to return humans to the Moon, on November 16, 2022. The Space Launch System launched Orion toward the Moon, where the ESM placed the spacecraft into distant retrograde orbit around the Moon, and subsequently extracted it from that orbit and sent it back to Earth.

The service module (SM) supports the crew module (CM) from launch through to separation prior to reentry. It provides in-space propulsion capability for orbital transfer, attitude control, and high altitude ascent aborts. It provides the water and oxygen needed for a habitable environment, generates and stores electrical power, and maintains the temperature of the vehicle's systems and components. This module can also transport unpressurized cargo and scientific payloads.

Unlike the Apollo command and service module, the ESM does not have the delta-v necessary to return to Earth from low lunar orbit. This limitation motivates the larger size of Artemis's Human Landing Systems, and previously the Lunar Gateway.