Issue 37 Unmanned Systems Technology April/May 2021 Einride next-gen Pod l Battery technology l Dive Technologies AUV-Kit l UGVs insight l Vanguard EFI/ETC vee twins l Icarus Swarms l Transponders l Sonobot 5 l IDEX 2021 report

45 conventional manufacturing tooling, given what that would mean in terms of expense and being ‘locked in’ to a specific vehicle form factor. Instead the company investigated large-format AM to meet its development budget and schedule, seeing it as the ideal prototyping solution at the time. “We needed to design, develop and integrate high-end core subsystems into the Dive-LD, but we didn’t realise that these parallel efforts were defining a product offering that we now call the Dive Technologies AUV-Kit,” Russo says. The kit consists of a set of standard subsystems, hull components and design templates which the company can move around, swap or modify, to produce a different customised AUV architecture to suit the operational targets of one end- user’s application or another’s. The Dive-LD is the first manifestation of this kit. It is rated to 6000 m, has a flooded hull measuring 5.8 x 1.2 m, and is battery-powered for mission endurances of up to 10 days. Concept design for the system began in late 2018, with detailed design work following through 2019 and long-lead material procured later that year. Benchtop lab testing was then carried out through mid-2020, with design and procurement concluding in July 2020. The custom electronics build was finished in August 2020, and sea testing was completed by October 2020. “Once its AUV-Kit was ready for integration, in August 2020, the Dive-LD went from an inventory of parts – core subsystems and electrical, mechanical and software architectures with the additively printed hull form – to a fully integrated AUV in four days, complete with a low- drag 3D-printed skin,” explains Lebo. “The hull pieces are produced as single components up to 4 ft [1.22 m] long and over 4 ft in diameter through a proprietary process, and have been successfully tested down to 6000 m. The process has never been used in the subsea environment, and it is now our go-to method for producing easily customisable AUVs,” he says. With the speed at which the Dive-LD has been created, Dive Technologies has surmised that it does not matter what its other AUVs will look like. The process can output AUVs scaled and tailored to meet any mission requirement in a matter of weeks, whether that means a vehicle with a diameter of 30 cm or 300. AUV-Kit construction Large-format AM naturally calls for a large printer, and Lebo says, “The printer, which comes from Additive Engineering Solutions, is called the Cincinnati BAAM [Big Area Additive Manufacturing]. It can print pieces up to 6 ft in diameter and 6 ft tall, and we use it in a proprietary way to manufacture prints that can survive the pressures at ocean depths.” Russo adds, “Many of our 3D prints are made from ABS plastic, and for the external skin of the vehicle we apply a proprietary coating for hydrodynamic efficiency. In total, the Dive-LD has 86 printed parts.” Once the prints are complete, Dive uses a proprietary process for smoothing and coating the AUV’s fairings. The coating is vital to filling in the ‘valleys’ of the print and producing a smooth outer surface, which is important for reducing hydrodynamic drag. Looking through the fairings, it can be seen that Dive has used standard ship-building materials to create a low- cost skeleton for mounting the core subsystems. The company typically sources stock sheets of marine-grade aluminium, which are then waterjet-cut and assembled with tab- and slot-based self- aligning weldments. The overall process and materials list keeps production costs low and build schedules short. “The vehicle’s structure also allows it to be picked out of the water at a single point on the top, or towed from the nose after a pier-launched deployment,” Sgobbo adds. For buoyancy, the kit has syntactic foams that are supplied in standardised blocks that Dive refers to as ‘cards’. A buoyancy simulation tool created in-house tells the team where to install the cards, and how many to fit in each part of the AUV. This also enables the buoyancy to be rapidly altered to accommodate changes in each AUV’s payload contents or configuration of subsystems while maintaining the centre of buoyancy. “This too is a quick, cheap, and now proven approach that uses stock Dive Technologies AUV-Kit | Digest Unmanned Systems Technology | April/May 2021 The Dive-LD is designed around a flooded hull, with internal pressure vessels from Prevco housing its electronics