For nine months the ship Transocean Discoverer Spirit used 360-degree rotatingpropellers to hold itself steady in the 3, 500-foot-deep water as diamond-tipped bits cut the deepest oil well ever--6.5 miles down.
One way to increase the efficiency of a high-bypass jet engine is to turn the fan into an open rotor, a bit like returning to propellers, but using two rings of stubby counter-rotating blades.