The WS-15 is a mini-helicopter built in 1974 by Vincent Seremet. It is powered by a 35 hp engine. Vincent Seremet was a Danish aeronautical experimenter who had built 37 hanggliders, autogyros, gyrogliders, flexwing ultralights, paramotors, helicopters and strap-on wings with a rocket engine. At the age of 88 he jumped from a C-130 at 4 km altitude to fly such a rocket wing. After that he stopped with experimenting.