Innovation: toroidal propellers
Recently, the famous Massachusetts Institute ofTechnology (M.I.T.) developed a new type of propellers for remotely piloted air systems (RPAS): toroidal propellers.
‘‘The toroidal propeller allows a small multirotor unpiloted aircraft, or drone, to operate more quietly than current drones that use propeller forms unchanged since the beginning of aviation. By enabling a drone that is less of an acoustic annoyance, this propeller may accelerate the acceptance of such aircraft for a wide range of uses—for example, aerial deliveries, cinematography, industrial or infrastructure inspections, and agricultural monitoring.’’
What is a toroidal propeller?
² Quiet toroidal propeller [developed by M.I.T.] consists of two blades loopingtogether so that the tip of one blade curves back into the other. This closed-form structure minimizes the drag effects of swirling air tunnels (i.e.,vortices) created at the tips of blades and streng thens the overall stiffnessof the propeller. These features reduce the propeller’s acoustic signature.Tests of prototype toroidal propellers on commercial quadcopters demonstrated thrust levels comparable to those of conventional propellers at similar power levels. Reduced sound levels allowed toroidal propeller equipped drones to operate without taxing human hearing at a distance half that of typical operation.’’
To see these propellers inaction: https://www.youtube.com/watch?v=UWoXFdRhPKc