XLUUV: THE UNMANNED EVOLUTION OF THE UNDERWATER COMPETITION

The underwater (almost) domain increasingly represents one of the most dynamic frontiers of the multisectoral and multilevel strategic competition that characterizes the contemporary international scenario, spanning the extremes of high-intensity conventional conflict. Concealed theatre not only of cross-cutting challenges for technological and information supremacy in the deep, but especially of a persistent hybrid struggle over the security of an ever-widening network of critical infrastructure, such as gas pipelines, power lines and telecommunications cables branching along the seabed (CUI – Critical Underwater Infrastructure). Indeed, the ongoing planning and conduct of demanding deep-sea patrolling and monitoring activities, including in the Mediterranean basin with the Italian Navy’s Fondali Sicuri and the French Marine Nationale’s Calliope operations, underscore the utter importance of the underwater dimension in promoting national and allied security interests and protection. In this context, significantly marked by new technical requirements and incremental operational demands, the synergic advancement of robotics and artificial intelligence (AI) is driving a profound capacitive transformation, hinging on the development, testing, acquisition, tactical-operational integration and deployment of a wide range of Unmanned Underwater Vehicle (UUV) systems.

Although conventional submarines, regardless of their specific characteristics and type of propulsion, nuclear or conventional, continue to be the mainstay of contemporary underwater fleets, UUVs constitute a complementary segment of increasing significance. Removing the implicit engineering limitations generated by the need to embark, protect and sustain operators in an inherently physically, chemically and thermally hostile environment such as the deep sea, unveils a broad spectrum of innovations pertaining both to the architecture of the individual platform and to its deployment. The potential reduction in size, combined with accentuated modularity of cargoes and coupled with the ability to operate longer and deeper underwater are indeed significant advantages, capable of broadly changing the character of submarine operations along the entire continuum-of-competition and their contribution to the broader maritime and multi-domain manoeuvring in the event of conflict. The incremental focus on UUVs is also not only reflected in a comparison of technologically advanced powers, but also extends to include an appreciation of similar, more simplified platforms as a tool for asymmetrical combat. As an example, the Ukrainian Armed Forces, in the context of the battle for the Black Sea aimed at denying freedom of movement to the Russian fleet, has complemented the effective use of unmanned surface vessels (USVs) with the experimental deployment of both a kind of loitering torpedo, named Toloka, and a larger UUV designated by the manufacturer AMMO Ukraine, the Marichka. The evaluation of the use of underwater explosive drones by Hamas and the Houthis as much as it represents a highly rudimentary attempt to emulate UUVs underscores the widespread perception, even among asymmetric actors, of the transformative effects brought about by the introduction and refinement of unmanned submersible vessels. Beyond marginal solutions closer to manoeuvring torpedoes or USVs capable of navigating on the water surface, the development and integration of UUVs within contemporary submarine fleets is expected to be functional for the implementation of more distributed operational approaches based on a mobile sensor and effector architecture, declining the Distributed Maritime Operations (DMO) concept into the more challenging subsurface environment. Indeed, the implementation of this is central as much to countering tactical asymmetry between areal defence requirements, especially with respect to CUIs compared to a point threat, as to generating persistent dilemmas in the eventuality of military confrontation, to adversary Anti-Submarine Warfare (ASW) capabilities. The underwater (almost) domain, however, presents significant technological challenges to the operational effectiveness of UUVs, with the water’s scarce penetrability to almost all electromagnetic waves undermining the utility of command-and-control systems generally employed in all other domains. From this perspective, the use of AI is even more crucial in enabling these systems to conduct a wider range of technical activities and tactical tasks. In particular, machine learning is central in the calculation and maintenance of the vessel’s course, in the data collection, processing and sharing phase by the on-board sensors, and as a tool for self-diagnostics and technical maintenance of the system. The use of software aimed at automatic recognition of potential static underwater targets (ATR – Automatic Target Recognition), such as naval mines, is then a good example of how AI can enable the attitude to proceed to perform its tasks autonomously without operator impulses. In light of the growing attention and relevance of the segment, both in terms of military capabilities and industrial opportunities for development, this Focus Report aims to systematize the analysis of UUVs, delving into their technical characteristics and potential uses, as well as mapping in detail prototypes and models currently in the defence market. Building on this foundation, it specifically addresses the state-of-the-art and perspectives related to the specific category of Extra Large UUVs (XLUUVs), outlining their evolutionary impact in the underwater competition.