The Lockheed XFV Salmon was the less successful of the two designs, due mainly to the lack of a suitably powerful engine.

The new contra-rotating version Sharrow’s earlier propeller design (a finalist in the 2023 Innovation by Design awards) rotated the blades go in a single direction.

Serious engineering work on contra-rotating open rotors for aircraft propulsion dates back to the late 1940s, particularly as a means to enhance fuel efficiency and extend the endurance of long-range ...

Technology Aviation A Completely New Kind of Aircraft Propulsion System, Made of Rotating Cylinders No wings, no rotors, no jets By Rebecca Boyle Published Jun 22, 2011 7:58 PM EDT ...