The research presents a novel approach for propelling high-speed, submerged, marine vehicles. The operating principle is based on the operation of a ram-rocket (ducted-rocket) motor (solid or hybrid), where water is introduced through an inlet due to the vehicle motion, and mixed with the hot propellant gases. Theoretical predictions reveal specific impulse increase as high as 70% for non-water-reactive propellants, and over 100% for water-reactive propellants containing aluminum or magnesium, relatively to a parallel non-water-breathing motor. The increase in specific impulse means a substantial increase in range and operating time. Static firing tests of hybrid motors without and with water addition revealed major increase in thrust and standard specific impulse, reaching a peak of 485 s due to water addition when using polyester fuel containing 30% magnesium (twice the specific impulse of a solid rocket). A series of underwater tests of hybrid ram-rockets in the lab pool at cruise speeds as high as 25 m/s (90 km/h) demonstrated ignition, sustained combustion, and noticeable pressure build-up in the combustion chamber due to incoming water through the nose inlet. Such underwater experiments are unique and had never been published before in the open literature.
The presentation will include video clips of underwater operation of a water-breathing ducted-rocket vehicle.