Seiko Epson created a miniature flying robot, claimed to be the world's lightest. The robot, about the size of a playing card, uses contra-rotating propellers and weighs 0.4 ounces. Designed for ...

Using two propellers spinning in opposite directions, the genius contra-rotating propeller system is used on marine vessels ...

Sharrow's extraordinary looped propellers were already some 30% more efficient than traditional designs – and now the company has put two of them together into a coaxial, contra-rotating prop that ...