Its shape is distinctive: two blades twist together so that the tip of the leading blade curves and joins into the trailing blade. The structure forms a closed loop, shaped like a torus (ring). “This propeller eliminates a number of attributes. It is quieter than conventional propellers,” says Thibaud Frossard, Capgemini’s Director of Defence and Security.

By drastically reducing vortices, this geometry cuts drag and therefore diminishes the propeller’s acoustic signature, a particular advantage as electric and hybrid propulsion systems become more widespread. When submerged, the toroidal propeller limits cavitation — the formation of noisy bubbles — an advantage for marine drones and sensitive marine ecosystems, according to the French fishing industry association, France Filière Pêche.