While Rolls-Royce and other European partners including Safran continue to drive toward full-scale hydrogen-fueled propulsion testing, there is far less equivalent research activity underway at GE Aerospace and Pratt & Whitney.

The picture reflects the disproportionate national research priorities on both sides of the Atlantic. Major investments into hydrogen for aerospace are underway in Europe under a slew of centrally backed efforts such as the Clean Aviation initiative, while in the U.S. smaller and fewer hydrogen-propulsion study efforts are funded by the FAA and NASA.

The growing rift is a worry to Airbus which, according to industry sources, is quietly moving behind the scenes to encourage a more serious level of U.S. industry interest in hydrogen-related propulsion research. The focus for its concern is believed to be in the regional and single-aisle sectors where Airbus is targeting development of a potential new series of hydrogen-enabled airliners under its ZEROe initiative.

In the near term, Airbus sees fuel-cell based hybrid propulsion will be better suited to the 100-200 passenger aircraft under study in the current “pre-program”—while it envisages direct hydrogen combustion will likely be the preferred zero-carbon option for larger aircraft.

Why does Airbus want greater U.S. research involvement? The likely answer is in three parts—one of which may seem surprising.

First, encouraging U.S. involvement will add significant weight to solving the harder challenges facing hydrogen propulsion—some of which extend beyond the many technical and certification-related issues such as the management of cryogenic fuel in aircraft systems and engines. Bigger picture challenges include the development of major fuel production and distribution system infrastructures as well as the regulatory environment surrounding it.

In May, Airbus upped the ante by signing multiple agreements to study the feasibility of established hydrogen hubs at major airports in North America to support the deployment of zero-emission airliners in the mid-2030s. The agreements added to multiple studies already underway with airports and airlines in Europe and Asia-Pacific to support its planned decision on whether to launch development of a hydrogen-powered commercial aircraft for service entry in 2035 under its ZEROe initiative.

The North America deals included memorandum of understanding (MOUs) to conduct hydrogen infrastructure feasibility studies with Hartsfield-Jackson Atlanta International Airport, the world’s busiest, and Houston’s George Bush Intercontinental Airport. Airbus, with hydrogen-electric propulsion startup ZeroAvia, has also signed MOUs with Canada’s three largest airports: Montreal-Trudeau International Airport, Toronto Pearson International Airport, and Vancouver International Airport. These are Airbus’ first such MOUs to include another aircraft OEM.

Secondly, widening the net to include GE Aerospace and Pratt will open up its propulsion system options and help reduce the company’s long-term reliance on Rolls-Royce—its de facto exclusive engine provider for all its current widebody civil programs. Although both MTU Aero Engines and Safran have growing involvement in hydrogen propulsion research work through Clean Aviation and other initiatives, neither is directly part of any potential hydrogen-specific commercial engine plan under roadmaps with existing partners Pratt and GE, respectively.

MTU Aero Engines recently tested a liquid-hydrogen tank for its Flying Fuel Cell (FFC) propulsion system and has begun installing test cells for the zero-emission powertrain at its facility in Munich. Developed in cooperation with German aerospace center DLR, which plans to use the 600-kW hydrogen-electric drivetrain to replace one of the turboprops on its Dornier 228 flying testbed, MTU aims to have the FFC available for the commuter and regional markets by the mid-2030s.

Building on FFC under Clean Aviation, MTU is also leading the three-year HEROPS (Hydrogen-Electric Zero Emission Propulsion Systems) project to ground-test a 1.2-megawatt fuel cell powertrain which will be scalable to 2-4 megawatts for powering larger regional aircraft.

Safran meanwhile completed tests in 2023 of hydrogen combustion sub-systems for a turbine engine as part of the European HyPERION project—a French acronym for “hydrogen for environmentally responsible aviation propulsion.” The three-year project involved Airbus and the ArianeGroup, the two companies’ joint venture in space launchers, and built on decades of experience in liquid-hydrogen handling and combustion.

Third—and perhaps the most unexpected reason—is that Airbus sources say that U.S. powerplant makers pay too little attention to hydrogen at their peril. In particular, some strategists within the company believe U.S. propulsion providers could become dangerously complacent in the face of growing ambitions in China to develop non-conventional hydrogen and hybrid-based propulsion systems which bypass traditional gas turbine-based turbomachinery routes altogether.

While China itself has publicly stated a national goal of net-zero emissions by 2060, the government released details in October 2023 of a plan to develop a green-aviation manufacturing industry by 2035. The planning document from the Civil Aviation Administration of China and the ministries of industry, science and technology, and finance, outlined—among other things—plans to accelerate developments in battery-electric, hybrid-electric, hydrogen-electric and hydrogen propulsion as well as sustainable aviation fuel. As virtually none of these areas necessarily rely on a deep heritage of commercial propulsion developments, sources say the U.S. should be alert to the longer-term potential challenges this move could represent.

Pilot-E – The World’s First Hydrogen-Powered Work Vessel