Some Principles of Naval Autonomy

Naval warfare is in the nascent stages of another paradigm shift, the first time since the adoption of the aircraft carrier. The evidence of this upheaval is starkly illustrated in the Ukrainian conflict, where cruisers are now vulnerable to crudely assembled weapons. Global maritime freight is frozen by underequipped proxy regimes wielding inexpensive drones. These examples underpin a shift in the unit economics of war, where low-cost autonomous platforms are toppling conventional capabilities.

In Ukraine, the early stages of the conflict unveiled the unanticipated use of modest commercial platforms, like jet skis, modified to bear explosives. These rudimentary platforms have deterred the Russian Navy from the coast of Ukraine, and each new iteration has been marked by increased range, payload capacity, and economies of scale. The formidable Russian Navy has been struck deep in its territory with frequent attacks on the Sevastopol harbor and the notable sinking of the cruiser ‘Moskva.’

The shift is emblematic of a broader theme in contemporary warfare. Following the maturation of the precision warfare regime, abetted by the software revolution, the military focus has pivoted towards minimizing cost and accelerating the production of strikes, shifting weight from the operational to tactical levels. This development represents a recalibration of naval power projection and deterrence, with complex systems capable of denying conventional capacity being relatively easy to field, a boon to underfinanced states. The emergent theme is twofold, favoring autonomy and distribution over the floating fortresses characterizing modern navies.

UUVs/USVs and Current Market Leaders

Within this new naval paradigm, we can discern three classes of maritime systems: Unmanned Underwater Vehicles (UUVs), Unmanned Surface Vehicles (USVs), and Autonomous Underwater Vehicles (AUVs). It’s worth distinguishing large USVs like Overlord, Seahunter, or Seahawk, developed by the Navy, and the focus of our discourse: ‘fire and forget,’ distributed, and cost-effective systems. The former is developed to replicate conventional power and logistics, entailing large production and acquisition costs, while the latter allows for persistent asymmetric danger. The strikes in Ukraine have primarily used USVs, while UUVs and AUVs are climbing the technology readiness levels, with AUVs providing the majority of value in a new military paradigm.

Notwithstanding their category, these systems are presently used in versatile mission sets. The advent of the new class of attritable UUVs has significant advantages in ISR (intelligence, surveillance, reconnaissance), mine countermeasures, payload delivery, and loitering. The value of these systems in all of these use cases can be distilled to scale. When vast numbers of systems are deployed, their intended impact is amplified through collaboration. In the case of loitering, autonomous maritime swarms (AMS) can passively scan for combatant warships or be triggered remotely, denying access to large swaths of the ocean. Particularly interesting is the prospect of strengthening ‘porcupine’ or littoral defenses, where large quantities of small systems can deter conventional power. In this case, AMSs can be deployed to global chokepoints to deter invasion, like the scenario of a cross-strait assault.

The contemporary focus has honed in on aerial drones as the main cheap attritable system, with substantially less emphasis on the naval domain. The notable naval drone producers are Huntington Ingalls Industries, which produces the popular REMUS and Mk-18 mod 1 & 2, and General Dynamics, which builds the Bluefin and Knifefish. These systems are plagued by the same problem. They are all stand-alone multi-mission systems that are expensive and broad in scope. Building products that cover multiple divergent capabilities reduces the efficacy of each discrete capability. For example, the REMUS is built for both mine countermeasures and search and rescue, adding a substantial premium for each system built.

Knifefish

Luckily, as capital flows into defense tech, many startups are building products that can facilitate the age of large-scale AMS. First is Saronic, building collaborative AUVs led by a number of Navy veterans. Next is VATN systems, which builds swarm AUVs resilient to impaired navigation and comms. Finally, Saildrone is building cheap monitoring platforms. Anduril has naval capacity, but its Dive-LD is tailored for deep-water missions rather than the scaled solutions aforementioned. In all of these startups, the spoils of war will accrue to those who realize that asymmetric value is found in discrete mission sets at a fraction of the cost of what incumbents produce.

Technological Barriers

The largest risk to the Navy is the US’s deprecated industrial base, in which we are outcompeted in shipbuilding capacity by at least an order of magnitude. In the case of immediate conflict where upgrading our industrial base is untenable, large autonomous maritime systems are the only solution in which the Navy can leverage the unit economics game back in favor of the US. A couple of key innovations need to be made to enable AMS.

First is the navigation & localization issue. The transition from unmanned systems to autonomous systems means that AUVs need to locate themselves precisely and find optimal trajectories, a significant challenge in GPS-denied underwater environments. Reliance on existing navigation systems (dead-reckoning, inertial navigation systems) is fraught with cumulative errors over time. Acoustic navigation, while effective, demands a network of reference points that may not always be feasible. Geophysical navigation, utilizing environmental cues like magnetic fields, is still in its infancy and lacks precision. Optical systems, promising for close-range operations, struggle with murky waters and limited visibility.

Second is AUV collaboration & communication. For AMSs, achieving synchronized harmony for thousands of systems is fraught with hurdles. Effective communication underwater is hampered by the aquatic medium’s hostility to electromagnetic systems. Collaborative navigation, requiring precise synchronization among units, faces the compounded uncertainties of each AUV's navigation system. Acoustic communications are hampered by temperature, salinity, and pressure gradients but, most importantly, have limited bandwidth. These constraints are burdensome for the high-data-rate communication required for complex AMS operations.

Last is energy storage and efficiency. To maintain anti-access area denial for swaths of the ocean, AMSs or loitering munitions may be required to stay at sea for weeks. For swarm systems like AMS, individual units might be required to operate autonomously for extended periods covering hundreds of square miles. Developers must balance costly battery storage and mission time to maintain the unit economics asymmetries. However, a couple of innovations have been proposed, including hydrogen power, solar charging, and thermoelectric generators. The energy usage and storage of loitering maritime units need to get substantially more efficient to be fielded at scale.

Strategic Implications and Naval Force Composition

If these hurdles are overcome, the potential of autonomous maritime swarms in reshaping global naval strategy cannot be overstated. The dynamics of naval power would no longer be dictated by the size of fleets or the depth of a nation’s pockets but by the strategic deployment of advanced, cost-effective technologies. In this emerging paradigm, the ability to project power and exert control over crucial maritime zones would no longer be the exclusive domain of traditional naval superpowers. Smaller states, often overshadowed in the theater of global naval dominance, could now effectively assert their presence and interests on the world stage.

The preeminent naval strategist, Sir Julian Corbett, writes extensively about the limited form in unlimited war. The limited form entails pursuing smaller auxiliary objectives using constrained resources that act as a force multiplier on a whole campaign. The classic example Corbett cites is the Duke of Wellington in the Peninsular War, where a small invading force effectively immobilized multiple French divisions. Napoleon famously recites: ‘With 300 sail of transports and 500 men in the Downs, Englands can paralyze 300,00 of our troops and will reduce us to the rank of a second-class power.’ The advent of AMS in a new naval paradigm dictated by distributed autonomy would amplify Napoleon’s concerns. If wielded at scale, AMS would provide an even greater offensive burden at a more granular level. 

AMS could be wielded to disrupt or defend geopolitical chokepoints. Every congested strait worldwide, including Malacca, Hormuz, Bab al Mandab, Korea, Taiwan, Luzon, Panama, and Denmark, could see these systems deployed in both an offensive and defensive manner. The obvious applications include blockades, ‘porcupine’ deterrence, or maritime anti-access area denial. This is especially pertinent in the Pacific, peppered with archipelagoes that form chokepoints that would be easily clogged with AMS. Crucially, AMS systems, alongside conventional firepower, would signal the end of amphibious assaults. Invading forces would have to spend considerable resources to avoid or destroy thousands of drones. In the case of a cross-strait invasion, the PLAN and its considerable merchant navy of RoRo ferries could be deterred by such a capability, especially if they are cheap. 

Most important is the effect on small states. If technological hurdles are overcome, there won’t be high material costs to build these systems as each unit will be cheap. In the aggregate, autonomous solutions will democratize access to naval power, especially in defensive contexts. Deploying autonomous swarms will be trivially easy, with current small-scale systems used in lakes haphazardly thrown off the sides of commercial vessels. There is a large incentive for small states, especially those that don’t have exquisite military capability, to field these systems to level the playing field. Singapore and Taiwan best exemplify states that would benefit the most from an AMS paradigm, especially as naval environments become more contested and commercial incursions more frequent. The impact of this shift extends beyond mere defense. It represents a change in how small states engage in the maritime arena. With the ability to secure their maritime boundaries effectively, small states with control over important waterways (Panama, Egypt, Yemen, etc) won’t have to subsidize their security to external actors or, crucially, use access to the waterways as a diplomatic bargaining chip.

As autonomous maritime swarm systems mature, they necessitate reevaluating naval strategies, focusing on agile, distributed defense systems rather than large, expensive fleets. Just as the MQ-9 Reaper redefined aerial combat and surveillance, enabling unprecedented power projection without risking pilot lives, AMS promises to similarly revolutionize naval capabilities, offering states the ability to challenge conventional navies with low material cost.