Toroidal Propellers May Quietly Pave the Way to UAM Package Deliveries and More

One of the most significant challenges to the widespread adoption of unmanned aerial vehicles (UAVs) for commercial purposes, such as package delivery, is the noise UAVs create. Most of that noise is made by the rotation of the aircraft’s propellers. Dr. Thomas Sebastian, a senior staff member in the Structural and Thermal-Fluids Engineering Group at MIT Lincoln Laboratory, believes toroidal propellers are the solution.

Time to Make the Donuts?

What is a toroidal propeller? Glad you asked. A toroidal propeller is a closed-form propeller design (similar to a doughnut shape) which produces significantly less noise than a conventional propeller while generating comparable thrust.

Graphic illustration demonstrating the substantial noise reduction MIT researchers achieved by attaching toroidal propellers to a commercial drone. (Image copyright and courtesy MIT)

There has been little to no advancement in propeller design since the dawn of aviation. The adoption of toroidal propellers could hasten the adoption of UAVs for package delivery, industrial and infrastructure inspection, cinematography, and agronomic monitoring.

Sebastian’s toroidal propeller loops two blades together so they curve into each other. The result minimizes vortices (swirling air tunnels) and stiffens the propellers to make them stronger. It also allows for operations approximately twice as close to those currently possible because they are so much quieter.

Stop Droning On

Psychoacoustic experiments conducted in 2017 by NASA Langley Research Center showed that humans reported a higher level of sensitivity to noise produced by small multirotor drones than to noise from other traffic. Thus, quieter propellers could accelerate public acceptance and commercial adoption of drones.

Dr. Thomas Sebastian explains his process and rationale for developing the use of toroidal propellers in this video.

If the commercial adoption of drones is to make some noise in operator’s profits, they will need to make less noise in residential neighborhoods.