30 “Things like our electrical racks, fuel-cell skids or battery skids can all be built at a separate location, moved to the Isle of Wight and dropped into a H-USV hull, so there’s no conflict of activities that might happen if welding and hotworks were co-occurring with electrical outfitting, plumbing, piping and so on,” Mike says. “Traditional shipbuilding is long and laborious, whereas modularity of internal systems means things can be quickly rack-mounted and dropped in. It also means repairs don’t entail taking Pioneer out of the water for weeks; a damaged rack or section can simply be removed and a purpose-built one slotted in its place. That increases MRO efficiency and reduces operation downtime.” In tandem with AMC building USV Pioneer, ACUA Ocean recruited two naval architects from Babcock International Group to handle the integration and optimisation of subsystems, which sparked a noteworthy expansion of ACUA’s staff. As of December 2024, they number 22 people, up from seven in December 2023. Naval architecture The SWATH configuration gives Pioneer a distinctly square shape when viewed from above, sacrificing speed in favour of stability – an apt trade, given this USV’s operating speed of 4 knots (industry-standard ROV survey speeds are 1-3 knots). The shape and high ratio of below-surface displacement to abovesurface displacement keep Pioneer’s pitching and heaving to an absolute minimum, giving sonar imagery great consistency and sharpness (as well as camera, Lidar, and other geospatial and hydrographic sensor data). “Test data has shown we can deploy an ROV amid waves of at least 4 m in height,” Mike adds. The USV’s deck features a few hatched compartments. One, within the aft transverse beam, houses an electrical rack with all of the control and intelligence systems (behind which is a mast mounting all of the communications systems, as well as some navigation and survey systems). For redundancy’s sake, a forward electrical rack in the forward transverse beam has redundant systems for communications, power and controllers. The forward rack offers capacity for dedicated payload computers, such as user-defined or -supplied programmable logic controllers (PLCs). Each of the longitudinal beams holds two additional, smaller, hatched compartments. The two forward ones contain racks for Pioneer’s batteries (supplied by Kreizel in Austria), while the aft starboard one has a fuel-cell rack, as will the aft port hatch in future (a single fuel cell being sufficient for initial demonstrations and deployments). “For the purposes of the CMDC, we were a hydrogen-electric vessel, and in the long term we think hydrogen will play a huge role in the route to net zero, but for a lot of prospective operators of Pioneer, hydrogen is a foreign entity. They’re interested in what it could mean in the future, but they’re not comfortable with it at the moment,” Mike explains. “So there will be diesel-electric variants of Pioneer, although still saving hugely on emissions over diesel crewed vessels by eliminating all the extra weight and space needed for sustaining crews onboard. We will provide whatever fuels customers are comfortable with, but, whatever the fuel, it will always be an electric powertrain with a hybrid-fuel range extender.” Much of the powertrain engineering has been led by Charles Anuyagu, senior robotics engineer at ACUA Ocean, who previously worked on software for Mercedes F1’s power unit development division, enhancing its performance and reliability for the Mercedes-AMG Petronas F1 and Mercedes’ customer teams. “We’ve two thrusters, one at the back of each pontoon, with rudders mounted behind each for steering,” Anuyagu says. SWATH vessels It may seem odd that SWATH vessels are not more prevalent. However, as indicated, their hydrodynamics are not optimal for speed due to factors such as the increased surface drag inherent to their design compared with conventional catamarans, and their inability to plane; the Pioneer thus has a maximum recommended speed of 6.5 knots. Any higher and efficiency losses become significant. So, SWATHs can move adequately for a survey mission, but not so much for, say, sea rescue, interdictions or racing. “But, more crucially, SWATHs are very difficult to engineer, because they’re incredibly trim-sensitive,” explains Oliver Mulcahy, CTO of ACUA Ocean. Trim refers to the balance of a vessel in its longitudinal axis between bow and stern, and potential changes in that balance during operation. February/March 2025 | Uncrewed Systems Technology Dossier | ACUA Ocean Pioneer-class H-USV The final build of USV Pioneer took place at ACUA’s harbourside facility in Plymouth in late 2024
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