Pump-jet

A pump-jet, hydrojet, or water jet is a marine system that creates a jet of water for propulsion. The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal pump and nozzle.

Invention

The Italian inventor Secondo Campini showed the first functioning man-made pump-jet engine in Venice in 1931. However, he never applied for a patent, and since the device suffered from material problems resulting in a short life-span, it never became a commercial product. The first person to achieve that was New Zealand inventor Sir William Hamilton in 1954.

Typical use

Pump-jets were once limited to high-speed pleasure craft (such as jet skis and jet boats) and other small vessels, but since 2000 the desire for high-speed vessels has increased and thus the pump-jet is gaining popularity on larger craft, military vessels and ferries. On these larger craft, they can be powered by diesel engines or gas turbines. Speeds of up to 40 knots can be achieved with this configuration, even with a conventional hull.