There’s a growing trend for naval forces to acquire uncrewed surface vehicles (USVs) because of the potential advantages they offer, such as reduced risk and the ability to provide a persistent presence. In a medium-sized navy facing significant strategic challenges such as the Royal Australian Navy, it will be tempting for the upcoming surface combatant fleet review ^[1] to promote the rapid acquisition of USVs to achieve the required national security effects at a lower cost per unit than their crewed counterparts and with shorter delivery times.

This direction is being pursued by navies globally and represents, to some degree, an important trend in planning for future maritime operations ^[2]. However, before large-scale acquisition, naval forces must consider the unique operational challenges associated with USVs, such as their legal status ^[3], speed, vulnerability to interference by potential adversaries, sustainment and maintenance.

A comprehensive understanding of their intended concept of operations (CONOPS) that accounts for protection, maintenance, sustainment and ideal design criteria is necessary to exploit the benefits of USVs and avoid costly acquisition decisions based on a lack of understanding of how they can be employed effectively. The CONOPS would also allow for a detailed understanding of what the different classes of USVs offer and how they should be employed.

History has shown that being at the forefront of integrating new capabilities can provide a key military edge. In the past 18 months there have been significant developments in this area, such as the US Navy’s establishment of Task Force 59 ^[4], which is focused on the delivery of an intelligence, surveillance and reconnaissance (ISR) capability, and its recent attainment of full operational capability ^[5]. The US Navy’s Ghost Fleet Overlord program also deployed a fleet of USVs from San Diego to Hawaii to participate in RIMPAC 2022 ^[6].

Meanwhile, the Royal Navy demonstrated a missile firing ^[7] during NATO wargames in mid-2021 using its MADFOX (Maritime Demonstrator for Operational eXperimentation) vessel. In 2022, it acquired and began testing an mine countermeasures USV ^[8]. Closer to home, the RAN will acquire five Bluebottle USVs ^[9] and is working with Austal on the patrol boat autonomy trial ^[10]. The former HMAS Maitland will be renamed Sentinel and refurbished to allow for autonomous and remote operations. The RAN has also acquired and tested a maritime tactical systems catamaran ^[11], demonstrating a clear desire to expand its USV capabilities.

The successful integration of uncrewed aerial vehicles into almost all modern militaries indicates the potential benefits of fully integrating USVs. However, unique factors associated with surface capabilities present operational challenges that need to be fully considered through the development CONOPS before any large-scale acquisition.

USV capabilities span a vast array of sizes and functions ^[12], ranging from small ISR or oceanographic capabilities to large corvette-sized vessels for defensive and offensive operations. The reduction or elimination of crewing, the likely cost savings, and the ability to transit vast distances and provide a persistent presence while reducing the need to expose crewed capabilities to major threats are important benefits. However, the development of an effective CONOPS before any large-scale acquisition will highlight the challenges that must be worked through to provide an asymmetric advantage.

The legal status ^[13] of USVs is a grey area and is subject to debate ^[12], and so that must be a consideration in developing a CONOPS that covers where USVs will be deployed, how potential adversaries may react to their deployment, and the spectrum of options open to the operational commander once an adversary does react. Clarity in the international standing of USV capabilities would provide commanders with an indication of how adversarial actors might interact with those capabilities. In contrast, uncertainty or a lack of clarity creates potential flashpoints for escalation. In introducing any new capability, an operational commander must consider whether its introduction would fundamentally change the calculus for escalation.

This raises the question of a threshold test when introducing emerging disruptive technologies into a theatre of operations. What is the threshold for interference with the vehicle by adversary forces that would generate a reaction? What reaction would it generate? In the 2022 example of Iranian interference with US sail drones ^[14], the interference didn’t appear to provoke a kinetic reaction, nor did the 2016 Chinese interference with a US wave glider ^[15]; however, they could arguably be viewed as propaganda victories for both countries. Does this mean that militaries are unlikely to seek kinetic resolution with respect to interference with USV capabilities? If so, does this encourage adversaries to interfere knowing that it’s likely to be below the threshold at which a costly response is initiated? This may in turn make USVs more likely to be targeted than crewed capabilities, which may become costly and may well shape how they are operationally employed.

In developing a CONOPS for USVs, it’s challenging to group them, given the vast array of military capabilities available. However, when compared to the operation of uncrewed aerial vehicles, speed is a key factor. Most USVs operate at a speed that makes them an easy target for interference by adversarial actors, unless they are afforded protection. This vulnerability has been evident in several cases, including the attempted Iranian seizure of the US sail drones and the 2016 Chinese seizure of a US oceanographic wave glider in the South China Sea. An effective CONOPS would account for this vulnerability and provide protection through their intended employment or help articulate a key design specification of a required minimum speed or, if they’re considered attritable, a specification for acquisition at a necessary scale.

In the current era of competition, USV capabilities will remain an attractive target for physical or kinetic interference as their use proliferates. When developing a CONOPS, two key factors must be considered. If the capabilities are attritable, they need to be acquired and employed at low cost and at scale to avoid tying up additional assets to protect them. Employing crewed capabilities to provide protection or overwatch nullifies any benefits of the reduction in crew and cost.

And if the USVs are not considered attritable, and if it isn’t prudent to provide a crewed capability to protect them, they must either have the ability to protect themselves (which, at present, is a legal and technological quagmire) or be employed in areas where friendly forces have air and sea control. That would likely make them more effective for fleet logistics and sustainment roles rather than ISR and offensive operations during conflict. Such issues clearly need to be considered through the development of an effective CONOPS prior to acquisition.

Although one of the great advantages of USVs is their ability to loiter, this poses a question of how to sustain them in position, and whether they need to be maintained in position or brought home. If maintenance is done in position, how do you sustain and protect the maintainers? Do they stay on the vessels, or does this change the design? Is a ‘mothership’ capability needed, and how do you protect that vessel? How do you refuel USVs and how many do you need to employ them effectively?

The development of a comprehensive and effective CONOPS for USVs must take into account these and other factors unique to surface capabilities. By addressing these challenges up front, military leaders can ensure the successful integration of USVs into their operations, providing a valuable asset in modern naval warfare.