H3 Dynamics (formerly HES – Horizon Energy Systems) has flown a small example of its hydrogen-electric nacelle that could power many craft now in the concept phase. H3 headlines its web page with the words, “Dreaming Big,” followed by the premise, “The future of aviation is hydrogen-electric, autonomous, and digital.” Their press release declares, “The future of hydrogen aviation powered by H3 Dynamics’ distributed hydrogen propulsion nacelles has taken flight for the very first time in France.” Hydrogen could be a dream fuel, clean burning and leaving only a little water vapor in its wake. It has a few drawbacks, though. H2 takes up four times the space of gasoline or kerosene for a roughly equivalent amount of energy. In something sizeable like a semi-truck or a seagoing ship, such space requirements can be accommodated. Airplanes need to be streamlined and svelte, so trying to carry enough energy for long ranges and endurance can spoil otherwise beautiful lines. H3 claims its …