What is the downside of toroidal propellers?

Toroidal propellers, also known as rim-driven thrusters, have a few potential downsides when compared to traditional propellers:

1. Reduced efficiency: Toroidal propellers may be less efficient than traditional propellers, especially at higher speeds. This is because they generate less thrust per unit of power input.
2. Higher cost: Toroidal propellers can be more expensive to manufacture than traditional propellers, due to their more complex design and the use of specialized materials.
3. Lower durability: The rim of the toroidal propeller can be more susceptible to damage than a traditional propeller due to its position and exposure to potential impacts or debris.
4. Limited power output: Toroidal propellers may not be suitable for larger vessels or those requiring higher power outputs. This is because their design limits the size of the propeller and the amount of thrust that can be generated.
5. Limited availability: Toroidal propellers are a relatively new technology and may not be widely available in all regions. This can make them more difficult and expensive to source and maintain compared to traditional propellers.

Overall, toroidal propellers offer some potential advantages in terms of reduced noise and vibration, as well as improved maneuverability in certain situations. However, their downsides should also be considered when evaluating their suitability for a particular application.