U. S. Submarine Propeller Design
1862 to Present
Propellers have been used on American submarines since 1862 when the 16 hand-powered paddles in the original design of the Alligator, the U. S. Navy’s first submarine, were replaced with a simple four-blade propeller.
The technology advanced, and in 1900, the USS Holland (SS-1), the U. S. Navy’s first commissioned submarine, was equipped with a familiar-looking 3-bladed propeller.
While these early propellers were effective in pushing submarines around, they made a lot of noise in the process due to cavitation (the formation and collapse of vapor-filled bubbles on the low-pressure side of the propeller), turbulence caused by the propeller slicing through violently swirling water, mechanical vibration, and several other more complex hydrodynamic mechanisms.
Following development of an operational passive sonar system after WW1, an all-out effort was made to reduce propeller noise, an effort that continues today. Newer designs included better blade curvature and streamlined surfaces.
Throughout the 1950s and 1960s, naval engineers worked tirelessly to develop quieter propellers. One significant breakthrough was the development of “skewback” propeller blades, a design that spread the load across the blades more evenly and reduced cavitation. These blades, shaped more like twisted fans than traditional propellers, offered significant noise reduction and were incorporated into the growing fleet of nuclear submarines.
Another turbulence-reducing innovation was the shrouded or ducted propeller, which added a ring surrounding the propeller blades.
The latest development was the pump-jet propeller first employed in Ohio-class ballistic missile submarines in the 1980s. Instead of traditional blades, pump-jets feature multiple shorter blades encased in a ducted housing, reducing cavitation and creating a more efficient and quieter thrust.
U.S. submarine propellers will continue to evolve toward even quieter and more efficient designs. New materials, advanced hydrodynamics, and possibly even non-traditional propulsion methods, such as electromagnetic or jet propulsion systems, could be on the horizon.
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