Unmanned Systems Technology 023 I Milrem Multiscope I Wireless charging I Logistics insight I InterGeo, CUAV London & USA show reports I VideoRay Defender I OS Engines GR400U-FI I Ultrabeam Hydrographic Ultra-2 I IMUs

40 Focus | Wireless charging The magnetisable concrete can be produced in exactly the same way as conventional concrete, without needing a pressurised process. It is created by mixing ferrite particles in cement, and controlling the magnetic parameters of the aggregate precisely for use in concrete tiles. The tiles act as primary and secondary coils, resonating at 85 kHz. At a distance of 20 cm, the technique can achieve an efficiency of 95%. Underwater Researchers at the US Navy have developed a way to use wireless charging technology underwater to recharge UUVs. Getting power down into the ocean is the first part of the challenge. One system, called a Subsea Power Node, uses what is called an ejector-driven reactant hydrogen fuel cell system to generate 8 kW of power, with hydrogen as the fuel and oxygen as the reactant, both stored in canisters. All of this is housed in a shipping container that can be installed at depth. The node is designed to be slightly buoyancy-negative when full so that it sinks slowly to the ocean bed, and when spent, it is slightly buoyancy- positive and can be brought up at a controlled speed, for example using cabled buoys. Around 260 litres of fuel provide 100 kWh of energy, and a standard 40 ft shipping container can house three fuel cell modules to provide 20 MWh of energy. That can be boosted to 40 MWh if solid-state hydrogen materials are used for the fuel cells. The output from the fuel cell powers the charging dock, which uses inductive charging pads on the outside of the container. The UUVs communicate with the power node via acoustic modems that have a range of 300 m. This connection is used to log and communicate data on critical parameters such as the state of charge and health of the battery in the UUV. However, data also has to be transferred, so connectors are still necessary. These ‘wet mate’ connectors carry the data back into the pod to be stored. December/January 2019 | Unmanned Systems Technology The concrete tiles act as primary and secondary coils. At 20 cm distance the technique can achieve an efficiency of 95% A forest of carbon nanotubes on a conducting substrate is used to covert laser light to electricity to charge a UAV in flight (Courtesy of Georgia Institute of Technology)