European Service Module

On 10 April, POST-mission analysis found a valve on the module's oxygen manifold leaking at ten times the ground-test prediction. Artemis II remained SAFE because its propulsion system could operate in blowdown mode, but that workaround cannot support a full lunar-orbit mission.

By 16 April, the pressurisation valves were one of five open Orion items without public fix dates. ESM-3 had already reached Kennedy Space Center before the anomaly became public, leaving its valve configuration and any needed rework unconfirmed. For the European Service Module, the issue is now whether its next flight unit can clear a hardware question exposed by its predecessor.

On 2 April, the module's OMS-E main engine fired for five minutes and 50 seconds to send Orion and four astronauts towards a lunar flyby. NASA described the translunar injection burn as flawless, making the European Service Module the propulsion unit that committed the crew to the free-return trajectory.

On 3 April, NASA cancelled the first planned trajectory correction burn because Orion's PATH remained sufficiently precise after injection. That result mattered directly to the module: its main-engine burn had delivered a course accurate enough to preserve propellant for later corrections or contingencies.