Disruptive ideas needed to achieve sustainable flight by 2050

Aerospace engineers don’t know the exact configuration and performance of a jet airplane powered by liquid hydrogen, but they do know that getting there by 2050 will take some big shifts from the conventional ways we design aircraft today.

A recent study at the University of Illinois Urbana-Champaign considered the aircraft configuration impact of a liquid hydrogen/fuel cell electric propulsion system when integrated into a single-aisle, transport-class aircraft—having the consistent performance capability of a Boeing 737-800.

The researchers have what they believe to be a feasible replacement of narrow-body transport aircraft to help meet climate goals set for the aviation industry.

“The aircraft industry is looking at alternative fuels and developing new technologies, but we needed a platform to project them onto so that when we select a new power and energy system for an airplane, we can learn how it will change the various design components and parameters. This is the first time we’ve shown what one of a host of solutions for hydrogen-electric applications might look like in the future,” said Phillip Ansell, associate professor in the Department of Aerospace Engineering at Illinois.

Ansell said he and his team used a mix of conventional design methods from the industry and new processes. They used models to generate maps of how key performance metrics of an aircraft and sizing aspects will change as a function of some design variables.

But the computer can only go so far.

“We know the faults, foibles, and pitfalls that crop up, so we use our engineering judgment to make decisions about design details such as the placement of liquid hydrogen tanks on an aircraft. The configuration is the result of a balance between trying to be visionary, while also being realistic,” he said, recognizing that for air transport to be a lot more sustainable 30 years from now, disruptive ideas are needed, rather than merely incremental steps.

“We made visionary changes, but ones that meet certain limitations and constraints that the incumbent systems abide by. We don't want to advance things so far that there's no way that they'll be produced because they're impractical,” he said.

Ansell leads the Center for High-Efficiency Electrical Technologies for Aircraft at Illinois and is co-chair of the 2022 IEEE/AIAA Transportation Electrification Conference and Electric Aircraft Technologies Symposium, held in Anaheim, California in mid-June.

“One thing we’ve done in this research is to show that with this new liquid hydrogen power plant, there are ways in which it can be more efficient than typical jet engines that burn kerosene and still meet the same mission requirements, but with less energy expenditure than in today’s systems,” Ansell said. “Creatively engineering this aircraft, we’ve made it more aerodynamically efficient by distributing fuel cells across wing surfaces, for example.”

According to Ansell, the configuration study is a synthesis of input from numerous Illinois partners.

“We have collected different motor and power system designs to develop this conceptual design configuration. It’s a clean sheet design,” he said. “We took a lot of knowledge about how airplanes have been historically designed, then identified how the design needs to change when starting with a new power and energy system.”

Ansell realizes that what there are developing today will look very different 30 years from now.

“The lifecycle of these types of systems is extremely long,” he said. “I like to think creatively about what we can do if we push some fundamental boundary conditions of how we think about aircraft systems, but I’m 100 percent sure that even this early work is going to look extremely different than what we're anticipating here today. That said, I do see this as a rewarding contribution, because it is the starting point toward making a market impact on environmental sustainability of this industry.”

The study, “Impact of LH2 Fuel Cell-Electric Propulsion on Aircraft Configuration and Integration,” written by Elias G. Waddington, Jason M. Merret, and Phillip J. Ansell, is published in the AIAA Aviation Forum. DOI: 10.2514/6.2021-2409

This work was supported by NASA under award number 80NSSC19M0125 as part of the Center for High-Efficiency Electrical Technologies for Aircraft (CHEETA). Special thanks is extended to Chellappa Balan and James Falcone of the Boeing Company and Wolfgang Stautner of General Electric Global Research for their contributions to hydrogen fuel cell and liquid hydrogen storage, respectively.

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