Research Summaries

Back Assessment of Ghost Swimmer Performance in Shallow Water with Marine Growth and the Surf Zone

Fiscal Year 2020
Division Research & Sponsored Programs
Department NPS Naval Research Program
Investigator(s) Klamo, Joseph
Sponsor NPS Naval Research Program (Navy)
Summary Typical existing unmanned undersea vehicles (UUVs) use conventional propellers for propulsion and rotating foils as control surfaces for stability and maneuvering. High concentrations of marine vegetation, such as seaweed or kelp, has the potential to entangle these rotating components and severely limit their effectiveness. This in turn would dramatically impact the mission effectiveness of the UUV. Boston Engineeringâ¿¿s GhostSwimmer is an autonomous underwater vehicle shaped like a large tuna fish. The GhostSwimmer uses a moving tailfin for propulsion and rotating side fins for roll, pitch, and depth control. An analysis is needed to see if this bio-inspired propulsion, stability, and maneuvering scheme proves advantageous over traditional UUV designs in shallow water with high concentrations of marine vegetation to support management decisions.

This research proposes to study a traditional UUV design and a bio-inspired UUV design operating in identical shallow water environments with marine vegetation. The marine vegetation environment will be created in the shallow water tow tank with wave making capability at the Experimental Naval Hydrodynamics Lab at the Naval Postgraduate School. Both vehicles will propel themselves the length of the tank and through the marine vegetation. The propensity of the propulsion mechanism and stability devices to become entangled in marine growth will be noted. The density of the marine growth will be varied to determine operational concentration limits for each vehicle. Pending successful laboratory analysis and if wave environments and local Coast Guard unit support resources allow, a follow-on in-field analysis will be conducted in the kelp field in Monterey Bay or Point Magu to validate the laboratory analysis.

The research deliverable of this work is a technical report that describes the operating procedures, contains the analysis, and provides design guidance for operating UUVs in areas of marine vegetation. This work directly supports technology assessment in support of Explosive Ordnance Disposalâ¿¿s (EODâ¿¿s) very shallow water mine hunting mission. It also supports technology used in ocean survey missions.
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