Researchers at MIT have done some tinkering and may have revolutionized propeller design. Almost on a scientific whim, a team at the Lincoln Laboratory whipped up a few batches of “toroidal” propellers for a drone on a 3D printer and discovered they were not only much quieter than the OEM props but they put out more thrust at the same power level. The new props were a side project to their real job creating an entirely new form of silent aircraft propulsion using an ion drive.
The result is a closed loop design that looks like a couple of opposed inclined boomerangs joined at the tips. Researcher Dr. Tom Sebastian told New Atlas the prop design was inspired by some obscure “ring wing” aircraft prototyped in the early 20th century. He’s not even sure why they work but theorized their odd shape greatly reduces the noise-creating vortices that come off the tips of regular props.
“The key thing that we thought was making the propellers quieter, was the fact that you’re now distributing the vortices that are being generated by the propeller across the whole shape of it, instead of just at the tip,” Sebastian said in a video. “Which then makes it effectively dissipate faster in the atmosphere. That vortex doesn’t propagate as far, so you’re less likely to hear it.”
He said they haven’t spent much time optimizing the design but it shows promise, particularly for eVTOLs and drones. It also works remarkably well for marine propulsion, and there are already commercially available toroidal boat props on the market that boost power, flatten out the acceleration pitch of boats and markedly reduce noise.
As for Sebastian’s real job, the Lincoln Lab has already flown a small model plane that generates an “ionic wind” for propulsion. The plane has no moving parts and doesn’t use fossil fuels. “This has potentially opened new and unexplored possibilities for aircraft which are quieter, mechanically simpler, and do not emit combustion emissions,” spokesman Steven Barrett said. Again, drones will likely be the first application for the new power source but Barrett foresees hybrid designs that could create more fuel-efficient airliners and cargo planes.