The efforts to discover the world’s oceans — even in extremely deep-sea environments — have grown more and more in the past years. In this context, unmanned underwater vehicles play a central role. Underwater systems that are not tethered need to provide an apparatus to ensure a safe return to the surface. Therefore, positive buoyancy is required and can be achieved by either losing weight or expanding volume. A conservative method is the dropping of ballast weight. However, nowadays this method is not appropriate due to the environmental impact.

This paper presents a ballast system for an automated ascent of a deep-sea seabed station in up to 6000 m depth. The ballast system uses a DC motor driven modified hydraulic pump and a compressed air auxiliary system inside a pressure vessel. With regard to the environmental contamination in case of a leakage, only water is used as ballast fluid. The modification of an ordinary oil-hydraulic radial piston pump and the set-up of the ballast system is introduced.

Results from sea trials in the Atlantic Ocean are presented to verify the functionality of the ballast system.

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