Unmanned Systems Technology 038 l Skyeton Raybird-3 l Data storage l Sea-Kit X-Class USV l USVs insight l Spectronik PEM fuel cells l Blue White Robotics UVIO l Antennas l AUVSI Xponential Virtual 2021 report

48 crew casts it off, an evolution that Sea-Kit has demonstrated on many occasions, Simpson emphasises. Once the X-Class reaches the operating area and the location at which the AUV is to be launched, there are more checks to go through for the AUV and the LRS. As well as status feedback from switches and other sensors integrated into the LRS, the remote operations crew always has eyes on the system via an extensive camera suite. As Simpson explains, “We have multiple CCTV cameras on the boat so you can see that the safety cages are in place. Then, when you are ready to launch, you can open them up so that the vessel is free to go. Finally there is a countdown that ends with the pressing of the launch button. “It takes about 10 seconds to get clear of the back of the boat and then, when you have visual confirmation that it is clear, the AUV can dive. When it does, it will lose its GPS position, so it has to do a handshake with the HIPAP underneath. That’s when the mission starts.” Power and propulsion Power comes from a diesel-electric series hybrid system with two 18 kW, 48 V generators that charge a set of marine battery banks that power the thrusters, service loads and payloads. The inverter/converter system provides electrical outputs at 48, 24 and 12 V DC and 220 V three-phase AC. With a total capacity of 140 kW/h, the banks consist of 56 x 12 V gel and absorbent glass mat (AGM) valve- regulated lead-acid (VRLA) batteries plus four dry-cell AGM VRLA dual-purpose batteries for propulsion. Primary propulsion comes from a pair of 10 kW directional electric thrusters set in fixed skegs at the stern, supplemented by a single 12 kW, 360 º Aziprop thruster mounted under the forward part of the hull that aids position holding and target tracking. There is also a tunnel thruster at the bow for close-quarters manoeuvring in port. Designed to run at 1-6 knots, in station-keeping mode the X-Class can ‘weather vane’ around its Aziprop thruster for long periods, pointing its bow into the current or the prevailing wind, whichever is strongest, to minimise energy consumption. “You can either track a slow-moving target like an ROV or a Hugin, or you can stay in the same position to a very high accuracy for as long as you like,” Simpson says. The vessel burns just 100 litres of fuel per operational day, a figure that falls significantly during station-keeping or slow running, enabling it to remain at sea for 3 months. How far it can travel in that time depends on the environmental conditions and the speeds required for the mission. “Our UTAS [Uncrewed Trans-Atlantic Survey] project last year proved that the X-Class was capable of transiting 2880 nm across the Atlantic Ocean with plenty of fuel left afterwards,” Simpson says. He stresses that the USV is proven in ocean environments and is designed to stand up to severe weather. For example, it can survive in winds of up to force 9 on the Beaufort scale and up to sea state 5. It also has a self-righting capability. Control monitoring and autonomy According to the UK Maritime Autonomous Systems Regulatory Working Group autonomy rating, the X-Class is at autonomy level (AL) 2, or June/July 2021 | Unmanned Systems Technology Graphic illustrating twin thrusters in skegs, the transverse thruster at the bow and the gondola under the keel that houses sensors and underwater acoustic comms systems (Courtesy of Sea-Kit) Seabed mapping sensors integrated so far include Kongsberg sonar systems such as the EM2040 high-resolution multi-beam echo sounder that produced this image (Courtesy of Kongsberg)