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

46 Digest | Sea-Kit X-Class commanding the stern doors to close. The LRS can also be used to recover a ‘dead’ AUV on the surface by backing onto it and scooping it up, which has been demonstrated on a number of occasions, Simpson says. Much of the development and testing of this system took place in Norway, in cooperation with Ocean Floor Geophysics, which supplied a Hugin for the work. Any launch and recovery operation, particularly in less than glassy seas, carries the risk of damage, but the ‘kid gloves’ approach majoring in soft surfaces seems to have reduced that risk appreciably. “We’ve never put a scratch on a Hugin, despite completing more than 40 operations,” Simpson says. Sea- Kit has also developed the LRS for other ROVs and AUVs of up to 1.5 t. Gauging satcom bandwidth Sea-Kit’s solution to the satcom bandwidth problem began with working out what the minimum requirements for safe navigation were and assessing whether services available around the world could meet those needs. Systems have different abilities depending on the vessel’s position in a satellite’s coverage footprint, particularly when relying on very small aperture terminal (VSAT) antennas. “If you’re at the heart of that footprint, the suppliers can focus more bandwidth on you,” Simpson explains. “It really depends where you are in the world, because a lot of satellites are focused on high population areas, so if you push out to the extremities the signal gets weaker and the data rate lower.” Satcom user equipment is still developing rapidly though. Simpson says Sea-Kit has a USV operating in Australian waters that uses a much larger antenna to bring the data rate up, but since the start of the operation a few new systems have come on line that work with much smaller deck-mounted equipment that has higher data rates and less latency. “We are currently testing a new system with Inmarsat,” he says. In addition to VSAT, the long-range comms systems that have been integrated into the X-Class include Iridium, Inmarsat Fleet Broadband, 4G/5G LTE and Kongsberg’s Maritime Broadband Radio. A further data rate challenge presents itself during comms between the USV and the AUV when it is running deep, as the amount of information that can be exchanged is tiny. Communication is limited to short strings of code that denote simple status reports or commands. Underwater comms are via an acoustic ultra-short baseline system that is also used for positioning, while on the surface the two vehicles communicate over RF links including wi-fi, with a handover between the acoustic and RF systems during launch and recovery. Dockside preparations Before the USV can launch the AUV, however, they must get to a port from which they can reach their operating area, and must be assembled on the dockside and checked over. The system is transported to the port in containers, one for the X-Class and its support equipment and assembly tools, and another for the AUV and its LRS. Packed for transport, the X-Class fills its 40 ft container with just an inch to spare on each side, Simpson says, so the dockside assembly and launch crew, which could be just two people, slide it out slowly, attaching a crane hook to each of the vessel’s integral lifting points as it emerges. The vessel is then lifted by an on-site crane onto a pair of cradles that enable the crew to work safely underneath, attaching the thrusters and skegs (stability- enhancing longitudinal keel extensions) and bolting on large items such as a high- precision acoustic positioning (HIPAP) system or multi-beam sonar. Next, the mast is lifted into position with the crane and bolted on, after which the vessel is ready to enter the water. Launch is followed by a pre-departure systems check. Depending on the rules laid down by the port, the X-Class can then be driven out to sea under local remote control before being handed over to the remote operations crew via satcom once it is clear of traffic. Alternatively, the crew can take control as soon as the dockside June/July 2021 | Unmanned Systems Technology Sea-Kit has integrated several satellite comms systems to maximise available bandwidth, which varies between satellite services and geographical position within satellite coverage footprints (Courtesy of Fugro)