“If it is well-built, a rim-driven pump jet would be a quieter propulsion system than traditional propellers, and could be quieter than shaft-driven pump jets like those on some U.S. submarines,” Bryan Clark, a retired U.S. Navy undersea warfare officer and analyst the Center for Strategic and Budgetary Assessments, told The National Interest. “The question is whether the Chinese can build one with the fine machining necessary to achieve the degree of quieting possible. The article doesn't address that. The basic technology is straightforward, but building a good one is hard. Manufacturing precision equipment like turbines has been a challenge for China’s shipbuilding industry.”… “A rim-driven pump jet would use an electric motor that is installed in the rim around the propulsor. Like any electric motor, it would generate a magnetic field. Because it’s outside the hull, it might be easier to detect with magnetic anomaly detection, but it could be designed to shield some of the field,” Clark said. “It again comes down to how well they build the propulsion system. In any event, magnetic anomaly detection does not work at long ranges, and is not useful as a search capability. It is generally used to target a submarine once it has been located and tracked.”…“If China can put a well-built rim-driven pump jet on a submarine, the next question is how much thrust it provides,” Clark said. “With submarine propulsion, one of the tradeoffs is quietness versus speed. Most changes to the propulsion architecture that reduce noise also reduce sprint speed. One of the concerns I have heard from engineers is whether a rim-driven pump jet can deliver the horsepower needed to reach high sprint speeds for torpedo evasion or repositioning.”
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