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A pump-jet, hydrojet, or water jet is a marine system that produces a jet of water for propulsion. The mechanical arrangement may be a ducted propeller ( axial-flow pump ), a centrifugal pump , or a mixed flow pump which is a combination of both centrifugal and axial designs.
Marine propulsion is the mechanism or system used to generate thrust to move a watercraft through water. While paddles and sails are still used on some smaller boats , most modern ships are propelled by mechanical systems consisting of an electric motor or internal combustion engine driving a propeller , or less frequently, in pump-jets , an ...
A water jet, or pump-jet, is a marine propulsion system that uses a jet of water. The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal compressor and nozzle. The pump-jet must be driven by a separate engine such as a Diesel or gas turbine. A pump jet schematic.
When the jet ski and the floating rider move with the water, the 20+ meter long hose can hang up on underwater obstructions. This can pull the rider, and potentially the jet ski under water as the hose becomes taut. Deaths have occurred in this manner and hydroflight in moving water is strongly recommended against.
Jet drives are inefficient in low speed vessels, but may have other advantages that make them suitable for a given application. Internal drive propulsion was originally designed by Sir William Hamilton (who invented the waterjet in 1954) for operation in the fast-flowing and shallow rivers of New Zealand, specifically to overcome the problem of ...
Jet propulsion is produced by some reaction engines or animals when thrust is generated by a fast moving jet of fluid in accordance with Newton's laws of motion.It is most effective when the Reynolds number is high—that is, the object being propelled is relatively large and passing through a low-viscosity medium.
Yamato 1 on display in Kobe, Japan.The first working full-scale MHD ship. A magnetohydrodynamic drive or MHD accelerator is a method for propelling vehicles using only electric and magnetic fields with no moving parts, accelerating an electrically conductive propellant (liquid or gas) with magnetohydrodynamics.
Water jets are best suited to fast vessels and are thus used often by the military. Water jet propulsion has many advantages over other forms of marine propulsion, such as stern drives, outboard motors, shafted propellers and surface drives. [11]