100 In operation | Arkeocean’s Inca & Maya anti-sub warfare UUVs maritime industry’s traditional, torpedotype AUVs, with their long, thin bodies and singular propeller screws, which cannot hover or hold position effectively. “Plus, in the near future, industry regulations are going to come out that require AUVs longer than 1 m to be registered, along with other compliance needs. All our AUVs are less than 1 m in length, so we will avoid such constraints,” Brizard says. The Inca is 70 cm in length, with a thick body (slightly similar in shape to a shark), and it weighs 16 kg in air. It is typically engineered to be neutrally buoyant – except in some niche applications where it is made negatively buoyant to sink down to the seafloor (with some altered navigation firmware to account for the change in weight) – and remain stationary there to form a surveillance barrier on the seabed. It is designed with two pairs of thrusters: two vertically oriented in tunnels along the Inca’s hull length, one near the nose and one behind an antenna fin, with the other two being ducted and mounted near the back, one on the left and one on the right. The vertical thrusters enable the Inca to hover and maintain a particular altitude in the water, while the horizontal thrusters can hold a given horizontal position; differential thrust between the horizontal thrusters enables turning with zero radius to compensate for currents running sideways to the direction the Incas face. “We have worked especially hard to keep them as low-cost as possible. Our end-users may need dozens of Incas to form their swarm, so Proteus absolutely would not work if each unit cost $2 million to $3 million, like long-endurance work-class AUVs do,” Brizard adds. “The Incas don’t leave the water: they need to hold position and keep surveying, or else they would create a gap in the antenna swath. So, as you can’t use radio underwater nor acoustic modems for detailed data transfer, we need a second AUV to ‘mule’ the data from the Incas to the navy crews surface-side.” Maya uses a similar thruster configuration to Inca, with two vertical and two horizontal propellers, but otherwise it is physically quite different. Maya has a rounded, almost disc-like frame body, with its hydrodynamics optimised for thrusting up and down (while the Inca is designed for thrusting forwards and backwards to hold position against currents). Maya integrates an RF antenna, extending vertically upwards from its top side, as well as a RTK-GNSS antenna, and at its lower side there is a SEAKER, which is a very small Arkeocean ultra short baseline (USBL) for automatically docking with the Inca and collecting its survey data. The SEAKER plays a critical role in the operation that follows. On deck First, the Incas and Mayas must be transported to the ASW survey location by a support vessel. Before lowering them into the water, which can be done by simply dropping them in by hand, some pre-launch steps must take place onboard. All AUVs have a wi-fi connection, so the operators at the ship’s command and control centre can interface with the Mayas and Incas remotely. “The AUVs must be powered-on so that the C2 officers can affirm that their vital systems are functioning and then engage with the mission planning. The plans can be uploaded to the AUVs wirelessly,” Brizard explains. The planning software has been developed in-house, with particular elements focusing on the 2D or 3D shape that the swarm formation may take. Key tools used in its development from early on were C++ and Qt libraries common among programmers, although today, Arkeocean increasingly uses web-based application environments for creating its C2 software. The company will also integrate COTS software applications for key functions, such as displaying tactical information in formats familiar to some naval users when requested. April/May 2024 | Uncrewed Systems Technology The micro-AUVs can be hand-launched into the water after affirmation that they are functioning and their mission plans have been uploaded
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