The propeller — a relic from the dawn of powered flight more than a century ago — is making a comeback as an emblem of aviation’s greener future.
Rotors are proliferating on futuristic air taxis and plane prototypes powered by hydrogen and electricity. The old-school feature is also central to a radical new engine that could one day replace the turbofans on today’s jetliners as climate change pushes the industry to innovate its way out of fossil fuel dependence.
That design, developed…