Abstract: A pair of sealed, concentric metal tanks define a high pressure air storage chamber between the tanks, while the inner of the two tanks forms an air expansion chamber and carries a plurality of axially spaced impellers fixed to a shaft mounted for rotation coaxially through both concentric tanks. A plurality of tubular inductor nozzles are fixedly mounted to the motor and project at circumferentially and axially spaced positions into the inner chamber and carry high pressure expansion nozzles which receive air from the high pressure storage chamber and induce recirculated, low pressure air from the inner chamber to flow through the tubular inductor nozzles for impingement on the respective impellers. Planetary gearing couples the impellers to the shaft to effect high velocity rotation of the output shaft of the motor.