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Marine Log

March 25, 2008

ONR begins testing Rimjet propulsor

The Office of Naval Research (ONR) has begun testing of a revolutionary Rimjet propulsion system on its technology demonstrator at a Navy testing facility in Idaho.

On March 14, Computer Sciences Corporation (CSC) returned the Navy's Advanced Electric Ship Demonstrator, nicknamed the Sea Jet, with a new modified stern contained Rimjet to the custody of the ONR.

The 133-foot Sea Jet was christened in August 2005 at the Naval Surface Warfare Center's Bayview facility at Lake Pond Oreille, Idaho, and has served as a technology demonstrator for hull and bow designs as well as a test bed for new propulsion technologies. Sea Jet is owned by the ONR and operated for testing activities by the Naval Surface Warfare Center Carderock Division. The Naval Surface Warfare Center is now taking Sea Jet through a series of hydrodynamic, electromagnetic, and acoustic tests.

The Rimjet propulsor is an external podded propulsor manufactured for ONR by General Dynamics Electric Boat with a control system provided by Rolls-Royce. It is a rim-driven permanent magnet integrated motor propulsor. The Rimjet differs from other external propulsors in that the pod's motor resides within the shroud of the propulsor itself, rather in a separate part of the pod.

Rimjet testing will provide experimental assessments of podded electric propulsion systems and will serve to validate the computational and predictive capabilities of the ONR External Engine Room initiative, which is exploring different technology options for podded propulsion. External pods, common on today's cruise ships but rare in warships, allow propulsion machinery to be placed outside of the hull, freeing up space within the ship.

The scale of the Rimjet unit minimizes scaling artifacts. The testing of the motor on Sea Jet will provide the first wetted measurement of an external podded propulsion unit on a Navy vessel and will allow study of the effects of hull interactions on signatures.


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