Airbus is advancing its ambitious ZEROe program, targeting a significant ground test in 2027 for the core components of its hydrogen-electric aircraft engine. This milestone marks a critical step towards realizing zero-emission commercial aviation, despite a revised timeline for passenger service entry, now anticipated between 2040 and 2045.

The European aerospace giant has selected a hydrogen-electric design, driven by four engines, as the preferred propulsion system for its future 100-passenger airliner, aiming for a range of 1,850 kilometers. This decision, announced in March after nearly five years of concept assessment, prioritizes fuel cells to convert liquid hydrogen and atmospheric oxygen into electricity, which then powers an electric motor and propeller. Gregg Llewellyn, who leads the ZEROe project, emphasized that fuel cells offer advantages over direct hydrogen combustion, including the elimination of nitrogen oxide emissions and potential contrails, both significant contributors to atmospheric warming.

Initial testing has already led to design optimizations, reducing the engine count from six to four, as each unit demonstrated higher power output per kilogram than initially projected. Mathias Andriamisaina, head of testing for ZEROe technologies, noted that fewer engines will also contribute to cost reduction. However, the original 2035 entry-to-service target has been pushed back to 2040-2045, primarily due to the anticipated slow development of a global hydrogen supply network, as stated by Bruno Fichefeux, head of future programs.

Engineers face substantial technical hurdles, including transforming bulky industrial hydrogen-electric components into lightweight, compact systems suitable for aircraft. Key challenges before the 2027 demo include boosting engine power per kilogram, efficiently managing the significant heat generated by fuel cells (up to 1.2 megawatts of heat for every 2 megawatts of power), and developing sophisticated software for precise engine power control during flight. Current ground tests, which have accumulated over 500 hours, utilize industrial gaseous hydrogen and off-the-shelf components, but plans call for integrating aircraft-specific fuel cells, electric motors, and gearboxes by year-end. The transition to lighter materials and innovative tank designs capable of maintaining liquid hydrogen at minus-253 degrees Celsius is also underway, with collaborations like that with Air Liquide Advanced Technologies exploring aluminum alloys and carbon-reinforced plastics.

Heat management remains a critical design consideration. Unlike conventional jet engines that eject heat, fuel cell systems require robust heat exchangers. Airbus is bench-testing various prototypes, focusing on reducing the size and cooling liquid requirements to improve engine power density. Additionally, optimizing the air intake channel to direct airflow through the heat exchanger without significant drag is being refined through wind tunnel tests. The control software, responsible for managing the complex interplay of fuel cells, motor control units, and electric motors, must also ensure safe flight and landing even in the event of component failures, adding another layer of engineering complexity to this pioneering project.