Unmanned Systems Technology 033 l SubSeaSail Gen6 USSV l Servo actuators focus l UAVs insight l Farnborough 2020 update l Transforma XDBOT l Strange Development REVolution l Radio telemetry focus

35 SubSeaSail Gen6 USSV | Dossier strength, low weight, durability, low visual and radar signatures, and cost, with marine paint applied for extra protection from the environment. The wingsail is made from a combination of CFRP and polycarbonate, and the float module is formed from PVC foam covered with a combination of CFRP and Kevlar. The structural keel is aircraft plywood and CFRP, the stabiliser is also CFRP and the cylindrical hull is ABS, with multi-jet 3D-printed nylon for the modular nose section for payloads. SubSeaSail does most of its manufacturing in-house at the moment, having built its prototypes on its own workshop equipment, which includes 3D-printing capabilities. It outsources printed circuit board assembly and CNC machining of the foam and wood components. Testing and service entry Most of the testing has taken place using real hardware, in the sea off San Diego, with some carried out off the coast of New Zealand. The company also used a PC-based virtual simulator for some tasks early and late in the autopilot development process. “The simulator was very good at the beginning of the autopilot system’s development and at the end, when we were working on remote command & control, when you don’t need the boat to sail but just need to know it’s doing the right thing,” Todter says. “In between, I think it is easier to use the real hardware on the water and observe it. To me that’s a lot more fun anyway!” At the time of writing, the project had resulted in one (non-submersible) Gen6 entering service with SubSeaSail’s first customer, the US Army Corps of Engineers (USACE). The Engineer Research and Development Center (ERDC), a division of the USACE, successfully tested the vessel in the waters off Puerto Rico, ERDC reported in April. The chosen location was Bahia Salina del Sur, a bay used by the US Navy for gunnery and aerial bombing practice from 1941 until 2003, and the vessel was fitted with sensors to detect and measure chemicals leaking from deteriorating unexploded ordnance. The Gen6 was tested at three places in the bay, with between eight and 20 waypoints programmed into each search area. The principal sensor, which SubSeaSail integrated, was a polar organic compounds integrative sampler (POCIS) calibrated to look for traces of explosives including 2,4,6-trinitrotoluene and 1,3,5-trinitro-1,3,5-triazine. A set of five POCIS elements was strapped to the Gen6 vessel’s submerged hull. It also carried a multi-function water quality sensor package from Sontek/ Xylem to measure temperature, salinity, depth and turbidity. Future developments SubSeaSail is also developing unique sensors to take advantage of the platform’s compactness and extreme quietness. For example, it and partner company Applied Ocean Sciences have applied for a provisional patent on a reconfigurable, rigid acoustic array. This can be mounted on one or multiple Gen6 boats working together to produce a cooperative system with capabilities much greater than any single platform and sensor combination. While this raises the question of swarming technology, Todter believes that a virtual array capability can be achieved more simply by commanding the boats individually without requiring each to communicate with the others and automatically prioritise and apportion tasks among themselves. Integrating sonar signals received by different boats to generate reliable locations for underwater targets requires each signal to have accurate time and location stamps. These can be provided by GPS, particularly with the aid of a real-time kinematic (RTK) system to boost accuracy. “There are now RTK GPS systems that are almost chip size, and if one of the boats carries the base station, the others will know where they are relative to that to within a few centimetres,” Todter says. “So the technology is there to do that; we just need to demonstrate it.” Plans for further tests are focused on missions of longer range, while future developments are to include an integrated payload bay, improved data-handling facilities, refining the submersible version and producing a catamaran variant for a sponsor. Unmanned Systems Technology | August/September 2020 Before setting up SubSeaSail, company principals Michael Jones and Mark Ott were co-founders of Ocean Aero. SubSeaSail’s third co-founder, Chris Todter, joined Ocean Aero and co-authored Ocean Aero’s patents for the folding wing mechanism and retractable thruster used by the Submaran S-10 (detailed in UST 9, September/October 2016). Ott and Todter have many years of experience in ocean- going yacht racing. Todter is also the lead technical partner at SubSeaSail, and has been involved in every America’s Cup since 1983, except the most recent one in 2017. He has been responsible for performance enhancement, and winning the cup in 2010 with the Oracle trimaran. “That involved understanding what the guys do that makes the boat go faster and how to guide them,” he says. “I have spent many years developing the analytical tools to understand the subtlety of acceleration and the forces, the aerodynamics and hydrodynamics, and how they interact with each other.” The company