Voith Schneider Propeller

The coolest recent development in marine propellers is toroidal propellers which are now commercially available and seem to perform significantly better than standard propellers: https://www.sharrowmarine.com/

Cool, similar to helicopters which can also control direction indepentendent of thrust, which leads to RC helicopters being able to pull of crazy, physics-defying moves like here: https://www.youtube.com/watch?v=QSiwyoQldfo

This reads a lot like an advertisement. The linked page [[Cyclorotor]] is more neutral and has more information on the design and applications outside of marine vessels:

https://en.wikipedia.org/wiki/Cyclorotor

See a tug showing off here: https://www.youtube.com/watch?v=u6uNECa_X8Q Voith is the only company producing those, even though the patent has expired.

I recommend this video with animations : https://www.youtube.com/watch?v=QrBF9BWYAZY

From a resilience POV, my guess would be that failure of any one blade would botch the system overall. Maybe that is why many diagrams show them installed in pairs. (I would guess each operates in a different direction for angular momentum reasons.) I have no idea about overall reliability.

See also https://news.ycombinator.com/item?id=26339421