European Service Module

The European Service Module (ESM) is the propulsion, power, thermal control, and life-support unit attached to NASA's Orion capsule. ESM-2, which flew on Artemis II, was built by Airbus Defence and Space in Bremen from components supplied by 13 ESA member states. It provides 24 kilonewtons of main-engine thrust (a heritage Space Shuttle OMS-E), 8 auxiliary thrusters, and 24 attitude control thrusters. ESM-2 delivered translunar injection so precisely that two planned trajectory correction burns were unnecessary. However, its O2 manifold pressurisation valve leaked at 10 times the rate ground tests predicted throughout the mission; crew were not at risk because the system ran in blowdown mode, but a redesigned valve is non-negotiable before Artemis IV. ESM-2 burned up on re-entry on 10 April, destroying in-flight performance evidence before any post-mission data extraction was possible.

ESM-3, built for Artemis III, arrived at KSC from Bremen in August 2024 and is inside the Neil A. Armstrong Operations and Checkout Building. It has joined the crew module adapter and completed initial power-up. Whether ESM-3 incorporates corrected valve hardware is publicly unanswered. ESA deferred the performance review to the June 2026 ESA Council, a ministerial setting rather than an engineering forum.

The ESM is ESA's largest single contribution to a US crewed spaceflight programme since the Columbus laboratory. Without it, Orion cannot fly to the Moon. That dependency gives ESA structural leverage in Artemis access negotiations, even as Gateway cancellation has disrupted the wider cooperation framework.