Issue 41 Unmanned Systems Technology December/January 2022 PteroDynamics X-P4 l Sense & avoid l 4Front Robotics Cricket l Autonomous transport l NWFC-1500 fuel cell l DroneX report l OceanScout I Composites I DSEI 2021 report

98 PS | Extra-large naval UUVs W ith the 50-ton Orca eXtra Large Unmanned Underwater Vehicle (XLUUV) concept, the US Navy plans to move UUV operations into uncharted waters, figuratively speaking (writes Peter Donaldson). The Orca is intended to take on several roles, mostly unrevealed as yet but including minelaying, that at present are carried out by manned submarines. While that fits the established pattern of transferring ‘dull, dirty and dangerous’ missions to unmanned systems, it is remarkable for a number of reasons. First, it fits with the US Navy’s desire to shift to what it terms a more distributed fleet architecture, meaning one characterised by proportionally fewer aircraft carriers, resupply ships, cruisers and destroyers, and proportionally more of the smaller combatants such as frigates and corvettes, plus a new ‘third tier’ of large USVs and UUVs. This shift is in response to China’s growing ability to hold carrier battle groups at bay. A more distributed fleet architecture, the Navy argues, would complicate an adversary’s targeting challenge by presenting a larger number of smaller vessels to detect, identify and track, and would reduce the overall loss of capability from the destruction of an individual platform. Second, the US Navy doesn’t operate the kind of small, manoeuvrable and stealthy non-nuclear submarines that many navies task with the kind of close- in intelligence-gathering missions likely to fall into the Orca’s portfolio. Also, setting the Orca to lay mines will give it the ability to place the new Hammerhead ordnance, which might indicate that the job is becoming too risky for manned submarines, particularly large ones. The Hammerhead consists of a canister tethered to the seabed and equipped with a sensor suite capable of identifying target vessels and launching a lightweight torpedo. Third, the technical ambition of the Orca programme is remarkable, because minelaying and the other clandestine missions expected of the XLUUV are among the most complex given to any naval vessel. The Orca will have to avoid or negotiate natural and human-made hazards such as sea mounts, currents and fishing nets as well as, potentially, enemy minefields and defensive sensor networks. Those last two threats put a strong emphasis on stealth, and make both navigation and obstacle avoidance much more challenging, as the use of active sensors has to be kept to a minimum. The Orca’s design will be informed by but not identical to that of Boeing’s Echo Voyager, whose 51 ft length can be extended to 85 ft by installing its largest hull module. The Echo Voyager is square in cross-section, 8.5 ft on a side, and has a range of 6500 miles. Five Orcas are on order, with options for four more; first deliveries were first planned for 2022 but they have been delayed by production problems. Vice Admiral James W Kilby, Deputy Chief of Naval Operations responsible for war-fighting requirements and capabilities, told the US House Armed Services Committee in March 2021, “I’ve got to be able to communicate with it, sustain it. I’ve got to maybe be able to tell it to abort a mission, which means it has to come up to the surface and communicate, or get comms from its current depth. Those are all complexities we’ve got to work through with this vehicle.” Now, here’s a thing “ ” December/January 2022 | Unmanned Systems Technology I’ve got to be able to communicate with it, maybe be able to tell it to abort a mission, which means it has to be able to come to the surface or get comms from depth