A day after Airbus endeavored to boost its environmental credentials with Monday’s announcement of a commitment to bringing to market a hydrogen-powered airliner by 2035, Boeing Commercial Airplanes vice president of product development Mike Sinnett expressed what some might consider a more sober view of the prospects for such modes of propulsion. While participating in a briefing with reporters to recap Boeing’s recent completion of the latest phase of its ecoDemonstrator program, Sinnett cautioned about the limitations of electrical power as well, noting that battery technology—even as far as it has advanced in the laboratory—won’t soon reach a level of maturity to allow for real-world application in narrowbodies.

Although he didn’t completely reject the potential of hydrogen power and acknowledged its “unique promise,” Sinnett noted the challenge of immature regulatory and infrastructure framework.

“The difficulty is always around the practical implementation and engines and how you ensure that the regulatory environment and the technical environment [are] progressing together and maturing at the same time,” said Sinnett. “We have come to enjoy a significant level of safety that’s improved dramatically over the course of the last 70 years of the jet age. And we know a lot about how kerosene is burned and how it can be stored safely and how it can be transported and how engines use that fuel in all environments, from the arctic to the desert.

“As we transition to more sustainable fuels, we have to ensure that there’s no backpedaling in those levels of safety...I do believe we see promise in a transition to more hydrogen-based fuels over time. However, I would caution that it’s not something I believe is right around the corner.”

In terms of electric propulsion, Sinnett sounded more optimistic about the level of battery maturity within the next five years for application in small airplanes flying at relatively short ranges. However, he said, the energy and power densities of batteries engineers have developed so far wouldn’t allow for application in long-haul airliners in particular.

“When you think about energy densities and how they may apply to aviation, it’s almost like I described with how long it took us to get to the levels of safety that we enjoy today with jet fuel,” explained Sinnett. “When you look at battery technologies, even technologies that are in labs today, it takes a while for those to get to the point where they would meet the safety requirements of our industry…So we can demonstrate cell-level technologies, but getting them into a battery package with a battery management unit [and] a battery charger that can meet our rigorous requirements for safe charging and safe discharging at all temperature ranges that you’re likely to see in aviation, that takes a lot more work than just having a cell that works in a laboratory.”