Unmanned Systems Technology 007 | UMEX 2016 report | Navya ARMA | Launch & recovery systems | AIE 225CS | AUVs | Electric motors | Lethal autonomous weapons

61 Seafloor mining More than 1.2 million sq km of ocean floor now have permits to be mined, and AUVs are a key tool for the analysis of the seabed for oil and gas as well as rare earth elements such as neodymium and yttrium, key constituents in magnets and computer screens for example. A major challenge with deep sea mining is the lack of light, which limits the use of traditional cameras, so researchers at the Helmholtz Centre for Ocean Research in Kiel, Germany, have developed a payload called a self-potential (SP) sensor, which uses a combination of a magnetometer and a second sensor that measures weak electrical currents produced by chemical reactions occurring between mineral deposits and seawater. It has been designed to fit into the Helmholtz Centre’s Abyss AUV. A first trial at Kiel tested the feasibility of collecting SP data using two electrodes mounted to the frame of the AUV at different positions. The greater the distance between the electrodes, the more precise the measurements and the better the detection limit. The front electrode was positioned on an outrigger near the nose of the vehicle, as this is the working position for the magnetometer during seafloor surveys, while the rear electrode was tested in various positions along the AUV. Results indicate that, as expected, the data is clearly affected by the rotating magnetic fields generated by the propellers, but measurements capable of detecting sulphide deposits should be possible if the back electrode is more than 1 m away from the propellers. However, trials in the Atlantic in late 2015 found that using the outrigger placed too much stress on the craft’s buoyancy foam, so installing the SP sensor and data logger together with the magnetometer onto the outrigger needs to be rethought, and the tests are continuing. Another approach to prospecting on the seabed is to use a hyperspectral camera that can look across a wide range of frequencies, not just visible light. Ecotone, a spin-off company from the Norwegian University of Science and Technology in Trondheim, has developed the first underwater hyperspectral imager designed to go as deep as 6000 m, and this was tested on a research expedition in the Pacific in autumn 2015. The 35 kg camera was mounted on a remotely operated vehicle to detect nodules of rock on the seabed by measuring 100 separate frequencies at a depth of 4200 m to create a profile of the response of the rocks on the seabed. “Hyperspectral imaging has been implemented successfully by planes Autonomous underwater vehicles | Insight Unmanned Systems Technology | April/May 2016 Another approach to prospecting on the seabed is to use a hyperspectral camera that can look across a wide range of frequencies Category Diameter (in) Weight (lb) Payload volume (cu ft) Man-portable 3-9 Less than 100 Less than 0.25 Lightweight 12.75 About 500 1-3 Heavyweight 21 (US Navy Less than 3000 4-6 torpedo tube diameter) Large More than 36 Up to 20,000 15-30 (plus external stores) The US Navy classifies UUVs and AUVs in four categories