STATUS OF THE WATER-PISTON PROPULSOR

The mission of future Marine Corps amphibious vehicles may include transits from ship to shore, shore to shore, and shore to ship. If an assault is made on a fortified shore, it may be necessary that the ships launching the amphibious remain well offshore to achieve an over the horizon launch. Preliminary design and performance analyses have shown that the concept of a eater piston propulsor system is well suited to propel a 20 ton Marine Corps amphibious vehicle at a speed of over 20 miles per hours over water. Four 16 inch diameter propulsors located in a transom flap on the vehicle will provide the required in-water propulsive thrust to achieve this speed. The propulsion system offers large weight and volume savings because of the elimination of a large diesel or gas turbine engine with its associated drive train. Of primary concern to the viability of the concept to date, is the gas water interface of 3000 degree F gas and 70 degree F water. The water piston design described has the potential for greatly reducing the volume and weight required to propel an amphibian (as well as other marine craft) for the same fuel efficiency as conventional propulsion if heat loss and leakage in the propulsor are not excessive and if the gas-water interface in nearly piston-like. Based on full scale single channel water piston propulsor testing at 800degF, nothing to date has indicated that this interface will yield an unacceptable efficiency or that the concept is not viable.