Unmanned Systems Technology 042 | Mayflower Autonomous Ship | Embedded Computing | ElevonX Sierra VTOL | UUVs insight | Flygas Engineering GAS418S | Ocean Business 2021 report | Electric motors | Priva Kompano

69 UUVs | Insight been designed around simplicity and user-friendliness, and serves as a front end to COLA2 for comms, mission waypoint planning and real-time position monitoring. COLA2 meanwhile executes pre-programmed commands for navigation, payloads, lights and so on. Iqua also produces SoundTiles, a standalone post-processing software solution for assembling mosaic maps from sonar imagery that has been ‘stitched’ together, even when no positioning is available. The software complements the needs of customers who have an AUV for mapping, while also serving other UUV market segments such as users of ROVs for infrastructure inspection. “We have gained a lot of information about how our customers use our AUVs, and what technologies they want most, so we’re now planning the design phases of our next-generation vehicles, probably for development in the next few years,” Carreras says. Renewable energy from underwater When pursuing more sustainable forms of long-term autonomous mobility, exploring new sources of energy for powering unmanned systems is paramount. UUVs present a particular problem in this regard. USVs for example can sail using wind or tidal energy, and all autonomous vehicles above the water’s surface can use PV panels to harvest solar energy. For obvious reasons though, these are all more challenging for UUVs. Advanced Cooling Technologies (ACT) however is investigating ways of circumventing this issue. A recent study funded by the US Office of Naval Research enabled the company to develop and trial a system for harvesting thermal energy from the ocean, using the latent energy storage capabilities of phase-change materials (PCMs). The company developed a small benchtop prototype to serve as a vehicle- like testing platform, and tested it in the lab with water temperatures that simulated different depths. The principle of the energy harvesting system is that the PCMs will melt near the warmer ocean surface levels, and freeze at the colder, deeper levels, with these temperature differentials causing power to be generated using thermoelectric converters installed between the PCMs. “The energy intake through this method fluctuates over mission durations, but tends to mean two big pulses of energy towards the beginning and end of a dive cycle,” explains Nathan Van Velson, senior engineer for r&d at ACT. “The test vehicle itself had a glider-type configuration.” The lab results found an energy density of around 30 J/kg/cycle, with peaks in power generation of roughly 112 mW. While not enough for a commercial range-extender system just yet, the overall system concept could theoretically provide much higher energy density with next-generation PCMs, or with a larger, longer UUV with more internal storage volume. “It’s also worth noting that with all its heat pipes, thermo-electrics and PCMs, this is a completely passive system, so unlike say an IC engine there are no moving parts,” Van Velson adds. “That could be hugely important for long underwater missions where you need minimal vibration and points of failure on the vehicle.” Defence The proliferation of UUVs (from micro- AUVs to XLUUVs) in our oceans will no doubt enhance our understanding of subsea geographies and ecosystems. However, unmanned systems are far from failure-proof – more UUVs means more accidents and collisions below the water, and more wreckages that could litter the seafloor with plastics, battery chemicals and other materials harmful to aquatic life. Advances in underwater obstacle avoidance capabilities will be critical for keeping the oceans as accident-free as our typically aircraft-filled skies. While many strides in sense & avoid have been commercially driven, the defence industry has an additional strategic imperative for ensuring its UUVs stay out of the way – and out of sight – of foreign assets, for example during reconnaissance operations. With this in mind, MSubs (see our cover story on page 24) recently provided one of its XLUUVs for a successful demonstration of Vigilant, a new forward-looking sonar developed by Wavefront and manufactured by Sonardyne for obstacle avoidance. The Vigilant has a 120 º FoV, a range of 600 m in 2D/3D ‘depth modes’ and 1500 m in ‘sonar mode’, and emits pulses on an operating frequency of 70 kHz. It consumes up to 150 W of power and can function in temperatures of -2 C to +40 C. Unmanned Systems Technology | February/March 2022 The use of phase-change materials could one day allow UUVs to recharge their batteries using thermal energy from the oceans (Courtesy of Advanced Cooling Technologies)