Waterjet Propulsion

Waterjet propulsion, also called a pump-jet or hydrojet, is a marine propulsion system that draws in water from beneath a vessel hull, pressurizes it with a ducted axial-flow, centrifugal or mixed-flow pump, and expels it through a nozzle to produce thrust, with a reversing bucket giving reverse thrust with no gear change and a steering nozzle redirecting the jet the way a rudder redirects a propeller wash, so a jet-driven vessel steers the same way whether moving forward or in reverse. The underlying idea dates to 1661, when Toogood and Hayes described ships propelled by a central water channel driven by a plunger or centrifugal pump, and James Rumsey demonstrated a steam-powered water-jet boat on the Potomac River on December 3, 1787; John Howard Kyan patented a jet-propulsion design in 1833, and Secondo Campini water-jet craft reached 28 knots in a 1932 Venice demonstration. New Zealand engineer Sir William Hamilton built the first modern jetboat in the mid-1950s, work that established the pump-jet as a practical propulsion system, particularly for shallow or debris-filled water where an exposed propeller is vulnerable.