

I remember reading about these a little while ago. Supposedly toroidal propellers aren’t that good for high RPM and high speeds, but they’re really good for things like submarines and they also create no bubbles/sound. Another big benefit is they don’t harm wildlife such as manatees because they don’t have blades.
The places I see them gaining traction are areas with manatees and wildlife that can be harmed by conventional propellers. If the local government enacts legislation that requires the use of them to protect wildlife for instance.