By Dr Tom Loveard and Dr Marcus Hellyer.
This article has been motivated by C2 Robotics’s internal company analysis of ongoing test and evaluation activities employing the Speartooth large uncrewed underwater vessel (LUUV).
Our assessment is that the Department of Defence and the broader Australian strategic policy community have underappreciated the potential impact of large numbers of LUUV systems on warfare. This is both an opportunity Australia can exploit and a threat we must be prepared for.
This article is an attempt to break the bounds of traditional understandings of the possible and paint a picture of the potential of LUUVs at the operational and strategic levels in order to provoke a wider, more informed discussion within the Australian and allied strategic policy communities.
How UUVs compare to USVs
Despite the hype around fast unmanned surface vessels (USVs), we believe that UUVs are the real future.
USVs have gained a lot of attention due to their spectacular sinking of a large proportion of the Russian Black Sea fleet.[1] This has been an incredible success story for Ukraine, but our view is that USVs’ disruptive effect is unlikely to be sustained, as the tactic is no longer novel and can be countered. Fast USVs, even in large numbers, are detectable at long ranges using simple technology (cameras can see them many kilometres away and the vessels have considerable thermal signatures). They can be effectively targeted and destroyed by low-cost counter-measures, whether air-launched munitions or uncrewed aerial vehicles (UAVs). Nevertheless, the fact that low-cost asymmetric systems have rendered a vastly larger and more powerful conventional force ineffective confirms that these approaches are already operationally effective and are no longer in the realm of science fiction or some distant future.
LUUVs are very different to USVs. While significantly slower, they are vastly more challenging to detect and track. They are even harder to localise to the accuracy level required for successful interception. The difficulty in targeting in the underwater environment is why submarines are such an important part of national defence capabilities. UUVs are no different in this regard, but unlike submarines they can be produced rapidly and in huge numbers. With their small signatures, UUVs are a technology that will not be easy to counter and as a result are likely to have much longer future applicability than USVs. Indeed, if the technology that can detect and destroy LUUVs is developed, it will likely also make crewed submarines obsolete.
This article uses C2 Robotics’ Speartooth LUUV as an exemplar of what LUUVs can achieve. Speartooth has been in the water for around three years, accumulating well over 1,000 hours of in-water test and evaluation (as well as many more hours of virtual test and evaluation).
Based on our experience, we are confident that LUUVs can operate over multiple thousand kilometres. This frees UUVs from the need to be transported to the area of operations by a crewed mothership; they can self-deploy from safe operating bases. As battery performance improvements flow across from the electric vehicle industry to other applications, range and endurance will increase further. Greater energy density and efficiency will also allow increased speed. Because autonomous systems have short development cycles (as the war in Ukraine has demonstrated), LUUVs will become more capable in relatively short timeframes.
The Operational Impact of LUUVs in Conflict
LUUVs have enormous potential to shape both the operational and strategic levels of major power conflict. While analysts have started to consider the operational aspects, the strategic aspects have received little or no scrutiny. We will start by examining the operational level, as this allows us to set out the capabilities of LUUVs. We can then consider their implications for the strategic level.
Combining flexibility and scalability for effective force-mass
Speartooth has been designed to be a long-range, payload-agnostic system that can deliver payloads with high accuracy, including in GPS-denied environments. This makes Speartooth – and other LUUVs with a similar design philosophy – an extremely flexible platform. When equipped with appropriate payloads, LUUVs can currently perform, or will be able to perform in the near term, the following missions:
- Strike on stationary maritime targets
- Strike on moving maritime targets
- Strike on land targets in the littoral
- Barrier operations in chokepoints
- Barrier operations off harbours (for example, preventing submarines from deploying)
- Trade blockade through threatened or actual strikes on merchant ships
- Spoofing/diversion/distraction
- Mine warfare
- Support to amphibious operations (for example, hydrography and rapid environmental assessment)
- Covert logistics
- Persistent intelligence, surveillance and reconnaissance (ISR) and electronic warfare.
Many of the payloads needed for these missions exist already. They are also benefiting from ongoing miniaturisation allowing more payloads (in both number and type) to be carried – every LUUV can be an ISR platform by default, regardless of its primary mission, as it has the space and power for multiple sensors. Moreover, integration into the LUUV host platform can be done much more rapidly than into a traditional crewed platform.
In addition to flexibility, the other key attribute of LUUV systems such as Speartooth is scalability. Speartooth has been designed to be manufactured cheaply and in large numbers using commercial, off-the-shelf components. Even small or medium-sized militaries will be able to acquire these types of LUUVs in the hundreds or thousands and stockpile them in large numbers in standard storage facilities at little cost.
Combining flexibility and scalability mean that small and medium-sized militaries will have sufficient LUUVs to conduct the missions listed above simultaneously in multiple locations, something that is not possible with small numbers of traditional crewed platforms. Moreover, with many nations’ industrial bases capable of producing multiple LUUVs every day, militaries will be able to sustain a high operational tempo across multiple locations, even in the face of attrition.
There are very valid concerns around the circumstances under which autonomous systems may be employed to deliver lethal effects. We are not suggesting Australia would or should use UUVs in ways that are contrary to the laws of armed conflict. But it is undeniable that potential adversaries will. For example, Yemen’s Houthis are currently attempting to enforce a blockade in the Red Sea by striking merchant shipping clearly in breach of international law. Moreover, when confronted with military threats, even responsible states that are signatories to arm control treaties will reconsider what they regard as justifiable. Finland, for example, is withdrawing from the Ottawa Treaty banning anti-personnel landmines.[2] Regardless of how Australia might employ LUUVs, it is difficult to prepare to counter an adversary’s potential use of UUVs if we are not familiar with what they can do, both now and in relatively near future.
LUUVs and anti-surface warfare
While all these missions have operational utility, we will focus on anti-surface warfare missions, which potentially have the greatest impact. ‘Minnow’ operations – whether midget submarines, manned torpedos, small watercraft or frogmen – have a long history and have been proven highly effective in targeting stationary maritime targets. They have realised disproportionate operational outcomes – for example, removing the threat posed by the German battleship Tirpitz to Arctic convoys supplying the Soviet Union. However, minnow operations have also had a high rate of failure, losing a high percentage of operators, who take a long time to train and are very difficult to replace. While the Krait raid by Australian and Allied special forces on Japanese shipping in Singapore harbour under Operation Jaywick in 1943 was successful, a subsequent mission in 1944, Operation Rimau, resulted in the entire raiding force of 23 men being killed in action or executed after capture.
We believe that LUUVs such as Speartooth already can conduct these sorts of operations but at a much larger scale (due to their low cost and high rate of production) and with much lower risk (as no human operators would be exposed to danger). What have been high risk, one-off operations conducted by small numbers of elite operators are repeatable at a high tempo. This means any adversary’s forward maritime operating bases in Australia’s near region are now at risk, including moored shipping, port infrastructure and even land-based assets near the coast.
However, LUUVs will also have the ability to strike moving surface vessels, whether military or commercial, in the near term. Attacking surface shipping and deterring surface ships has been a high-priority task for submarine fleets since World War I. But this is a high-risk task for a crewed submarine since target vessels are likely to be defended by anti-submarine systems, and the submarine’s location can be exposed when approaching or launching attacks on surface ships. Moreover, a submarine attack can be deterred or defeated if the submarine’s commander believes it has been detected, even if it is not destroyed.No such fear or constraint exists with LUUVs, because the loss of a cheap, mass-produced LUUV operating as part of a massed swarm is immaterial compared to the effect achieved. Indeed, the detection or loss of multiple UUVs may still achieve an operational effect – even if the UUVs do not inflict any damage – by forcing the adversary to alter or abandon a course of action.
Certainly current LUUVs are slower than surface ships, making open ocean interceptions difficult. However, submarine operations have traditionally occurred in key locations along sea lanes such as approaches to ports, strategic straits and similar predictable, high-traffic areas. Massing LUUV systems in these locations where shipping is channelled towards them mitigates their limitations and multiplies their ability to disrupt surface traffic. LUUVs also have the potential to interdict amphibious operations which by their nature occur close to shore and require amphibious ships to slow or stop. Moreover, once the land component of an amphibious task force has lodged, the location of its maritime component is well known.
Based on our experience, we believe that the step from existing LUUV systems to a capability that can target moving surface shipping would not be difficult, time-consuming or costly and could be achieved by integration of a range of existing propulsion systems and payloads. Therefore, this is a near-term capability. Should maritime conflict break out in our region, these developments would be rapidly accelerated as they have been in all areas of autonomous systems through the war in Ukraine.
Rewriting our understanding of distance
The National Defence Strategy acknowledges that the security provided to Australia by its distance from threats is being eroded due to the development of technologies such as long-range missiles.[3] While the National Defence Strategy does not name them, we assess that LUUVs are at the forefront of this technological revolution. Traditionally range has been proportional to a platform’s size; big things can go further. However, this rule is being rewritten by modern energy storage and propulsion technologies which provide smaller systems with great range and endurance.
Certainly LUUVs’ energy supply places limits on how far they can project power. Speartooth’s range is very considerable but it does have limits. However, by being small, very efficient and electrically powered, these systems can be recharged using basic infrastructure. A small vessel, autonomous craft or island base with a small generator and a diesel fuel supply (which LUUVs can deliver) would be all that is needed to cover thousands of kilometres around any forward location.[4] The ongoing rapid improvements in battery storage capacity will also improve LUUVs’ performance, allowing not only greater range and endurance but also speed which will enhance their anti-shipping capabilities. Hybrid propulsion systems are also feasible, either to allow recharging at sea, or to provide greater velocity for a final approach to the target.
Moreover, limitations in range and endurance can be addressed by forward deploying LUUVs, as they do not require significant infrastructure or support personnel. They can simply be ‘racked and stacked’ in shipping containers and stored in commercial storage facilities. With LUUVs’ constantly growing organic range capabilities and their ability to be forward deployed into theatre, considerations of range will not be the limiting factor on their employment.
Thinking in hundreds and thousands
Overall, we believe that the adoption of LUUVs will see far more sensors, weapons and processing power in the oceans than ever before. This will inevitably have a huge operational impact on maritime and archipelagic conflict in the very near future.
Therefore, it should be a high priority for the Department of Defence to model and analyse the operational impact of LUUVs both as an asset we can employ and a threat that will likely be deployed against us. This modelling should not be based on small numbers of vessels as is the case with traditional crewed vessels. Certainly a small number of autonomous systems can have a large asymmetric effect, as we have seen with Ukrainian USVs in the Black Sea, and this is clearly possible also with LUUVs conducting minnow operations. However, because of the simplicity and affordability of LUUVs, militaries will be able to deploy them at scale. Therefore operations analysis should be based on the employment of hundreds and even thousands of LUUVs.
The strategic impact of LUUVs
Much of the discussion of the potential threats to Australian and allied security interests focuses on traditional capabilities such as Chinese shipbuilding, fighter aircraft or long-range missiles. However, we believe that the single biggest relevant factor for force generation today is a country’s capacity for industrial mass production of autonomous systems.
In this regard China’s capabilities are vastly ahead of those of Australia and its allies, even the United States. China’s industrial capacity has achieved staggering dominance across consumer-grade, mass-produced electronics, drones, electric vehicles, batteries and propulsion systems. If C2 Robotics had been a Chinese company, building Speartooth would have been far easier due to the ability to access such a broad industrial base, and manufacturing at scale would be easier again. This is sobering to consider because Chinese companies are already developing LUUVs; we are not naïve enough to believe that other actors cannot develop comparable capabilities.
One Hundred Thousand LUUV Systems?
If hundreds or thousands of LUUVs can have disproportionate operational effects, could larger numbers have asymmetric strategic effects? As a thought exercise it is very useful to consider extreme cases and then assess the validity of assumptions in such cases. Let us consider an extremely large number of LUUV systems – 100,000 units. What does a world look like where a nation decides to build such a huge number?
First, is this even technically or economically possible? Australia might want to build thousands of F-35s but the costs and industrial requirements to build them, the personnel to fly and maintain them, and the runways to operate them make this unachievable.
This is not the case for LUUVs. Our experience shows that building LUUVs is of comparable complexity to building a large electric vehicle, and in fact it utilises many similar components. Both have their own unique requirements, but the fact that a small company has successfully designed and built numerous Speartooth LUUVs shows that this is the appropriate complexity level to assign to the system. Indeed, since a LUUV does not have to protect human occupants, it is simpler in many regards.
Economies of scale for 100,000 LUUVs would drive prices down. For reference, China produced over 10 million electric vehicles in 2024. We believe A$200,000 per unit for a highly capable LUUV would not be unrealistic at such quantities, and a country like China with a deep existing manufacturing capability could produce an equivalent capability for as low as A$100,000. The history of decreasing unit price for mass-manufactured electric vehicles and their key components such as batteries reinforces this view.
LUUVs will require payloads to deliver effects. These will vary in cost depending on their effect, but a reasonable assumption is a similar cost point to that of the vessel for several asymmetric payload systems. Some sophisticated sensors might cost more, but simple kinetic effectors would cost far less. Therefore, an average cost of between A$200,000 and $400,000 per unit equipped with payloads is reasonable. So, 100,000 LUUVs would cost A$20 billion to $40 billion to build. As a point of comparison, the approved budget for the first three Hunter-class frigates is $25.9 billion for the ships and a further $1.2 billion for other necessary inputs to capability.[5]
This would be the vast bulk of the lifecycle costs. Traditionally the materiel acquisition cost of a crewed system such as a major warship is only a third of its total lifecycle cost as it requires a large crew, is at sea for much of its life and will require maintenance, repair and upgrade. But for LUUVs this is not the case. They are more analogous to munitions. A Speartooth takes two people 10 minutes to launch from a small boat ramp and then it can stay at sea for months with little human interaction. It employs a ‘one operator to many systems’ model. Otherwise, when not in use it can be stored in a shipping container in a warehouse or even a field. Other operating costs such as electricity to recharge batteries are trivial. So through-life costs are minimal.
Overall, while the program cost would be huge, it would not be prohibitive. In fact, it might be quite attractive as an industry support program for a nation like China looking to soak up under-utilised manufacturing capacity in factories that are already built but are largely sitting idle (should, for example, other countries ban or place high tariffs on electric vehicle imports from China, which is no longer a hypothetical speculation).
Our assessment is that there is nothing fundamental in terms of industrial capacity, component or materials supply, budgets, workforce or facilities that suggests that the acquisition of 100,000 LUUVs is unachievable for a medium-sized nation. China could do it as a marginal exercise alongside commercial electric vehicle manufacturing systems and we might never notice. For a country such as China, a target of 1 million LUUVs could be achievable. Wars in Ukraine and Israel have shown how small economies can be mobilised in the face of threats to national survival. Even Australia, which once produced hundreds of thousands of cars per year, could do it unilaterally over several years if it were a national priority and the Australian Government wanted to mobilise our manufacturing sector.
What could you do with 100,000 LUUVs?
With 100,000 LUUVs it would be possible to disrupt all ocean-borne global trade. Released in huge numbers at the outset of a conflict (or indeed pre-emptively beforehand), LUUVs could swamp every major port in the world, every strategic strait and bottleneck. Even sea lines of communication crossing the open oceans could be filled with large numbers of LUUVs, supported by small recharging vessels keeping them at sea despite the distances involved. The oceans would be filled with sensors and weapons.
The Indo-Pacific region, which features numerous bottlenecks from the Red Sea across the Indian Ocean and through the Straits of Malacca to north Asia, is particularly vulnerable. It would become very difficult for any surface shipping to move, let alone enter or leave a port or chokepoint, without the approval of the country operating the LUUV fleet. This would allow it to control global trade.
The countries affected would of course seek to protect their shipping. But LUUVs are very hard to detect and defeat. Nets can be installed to protect moored vessels, but net-cutting devices can also be used by LUUVs, and moored vessels have to get underway eventually or become irrelevant. Command and control pathways can be attacked, but LUUVs use very low data rates, and communication links can take many alternative routes. An adversary unconcerned about rules of engagement or the laws of armed conflict would not need to exercise direct command and control, instead tasking LUUVs to target shipping completely autonomously regardless of the risk of collateral damage. And even if half of the total number of LUUVs sent on a mission were sunk, it would be of little concern to a state holding a stockpile of 100,000 vessels that could be rapidly replaced.
When attempting to defend against thousands of LUUVs, what would comparatively small numbers of crewed attack submarines or surface anti-submarine warfare assets even target, and with what weapons? In a world where one Javelin missile costs more than six or seven times the cost of a Tesla electric vehicle, it is likely that China could launch LUUVs much more quickly than the US and its allies could build torpedos or other countermeasures and get them to sea in submarines to counter those LUUVs.
Moreover, LUUVs could also influence any activity on land within proximity (for example, within 10 to 30 kilometres) of the ocean. All near-shore assets and activities – airports, ports, infrastructure, populations et cetera – would be at risk from LUUV-launched airborne munitions. LUUVs could be massed together to apply large simultaneous force effects to a specific area with very little warning time and could do so over huge sections of the coastline.
Australia would be vulnerable to such an attack and could be completely isolated, with maritime trade interdicted. Australia’s geography has often been seen as our greatest defensive asset, but in such a case it could become our greatest liability. If an adversary achieved control of shipping lanes by using massed LUUVs, it would be hard to break that control. Moreover, it would be extremely challenging to produce effective numbers of comparable systems to exercise an effective deterrent to such coercion without access to maritime trade.
LUUVs and the Strategic Balance
Finally, it is important to consider the global strategic impacts of scenarios in which nations employ massed LUUVs. If one country were able to control the world’s oceans, every other country would be forced to decide whether to forgo ocean access and trade or otherwise concede to the will of the nation with the LUUV fleet, likely resulting in exclusive trade with only that nation and its allies. Raw materials from the Middle East, Asia and Africa would either be forced to participate in the market controlled by the power controlling the oceans or have no market access. Each nation to capitulate would then bring more industrial capacity and raw materials exclusively to the side of the nation deploying the LUUV fleet. Any nation that resisted would be economically devastated.
In a scenario where one-sided deployment occurs, we do not see any long-term winning strategy for the nations that oppose such a deployment. We do not believe that any nation currently has a capability to counter this scale of LUUV activity; attempting to do so with crewed ships and submarines would incur a staggering cost while making very little dent in the adversary’s massive stockpile of LUUVs.
However, where both sides have huge numbers of such systems then we see a scenario of mutual denial of ocean access arising. Neither side could effectively defeat the other’s LUUVs, leading to a stalemate in which all maritime trade would cease since each side could interdict the other’s shipping at will. Unless major powers were happy to forgo maritime trade and its economic benefits, there would be a strong incentive to resolve the situation in favour of normalisation. In fact, the knowledge that an adversary had a mass LUUV fleet may serve as a strong deterrent against aggression.
As with all technologies that have offered the prospect of ending war because they potentially make its costs too great or would result in mutually assured destruction, we should carefully consider how this would work in practice. Many states have been willing to endure huge costs to achieve their aims or deny others, with Russia’s enduring war in Ukraine simply the latest in a long series of examples. Moreover, a global blockade could be highly escalatory: while the use of LUUVs against international trade would allow states to coerce without threatening to employ nuclear weapons, a state that lost access to the oceans and maritime trade might resort to a nuclear response to compel its adversary to give up the blockade.
These issues certainly require further analysis. Our fundamental point is that the simple and accessible technologies employed in LUUVs now offer many states, not just great powers, the ability to exercise strategic weight and reach far beyond what was previously possible. Moreover, this potential power is not currently constrained by any of the remaining international mechanisms governing nuclear weapons, other weapons of mass destruction or missile technologies.
Conclusion
One hundred thousand LUUVs may seem implausible, but there will likely be a saturation point at which a number of LUUVs well short of this can achieve the outcome of denying an adversary access to and the use of the oceans, whether unilaterally or mutually. What that number might be is beyond the remit of this article to consider.
The main point is that the scenarios presented here are within the realm of possible futures using existing technologies. The implications that flow from this are very significant, not just for naval operations but for the strategic balance. The first country that mobilises its industrial base to produce massive numbers of LUUVs will be at a major strategic advantage in the event of the current great power competition moving into open conflict.
[1] HI Sutton, ‘Uncrewed platforms have been critical to Ukraine’s success in the Black Sea,’ RUSI, 20 August 2024, https://www.rusi.org/explore-our-research/publications/commentary/uncrewed-platforms-have-been-critical-ukraines-success-black-sea. Vessels sunk include landing ships and landing craft, a missile corvette, a patrol ship and a minesweeper. Ukraine has also credibly claimed shoot down a helicopter from a USV as well a striking targets on land with guided weapons launched from USVs.
[2] Essi Lehto, Anne Kauranen, ‘Finland to exit landmines treaty, hike defence spending given Russia threat, PM says,’ Reuters, 1 April 2025, https://www.reuters.com/world/europe/finland-plans-withdraw-landmines-treaty-prime-minister-says-2025-04-01/.
[3] Department of Defence, 2024 National Defence Strategy, Australian Government, 2024, https://www.defence.gov.au/about/strategic-planning/2024-national-defence-strategy-2024-integrated-investment-program.
[4] While this may seem far-fetched to some, the technology to enable this is not science fiction. Indeed, the Australian Department of Defence’s Advanced Strategic Capabilities Accelerator recently awarded innovation funding to ‘explore the feasibility of two different technology options for underwater recharging stations for autonomous underwater vehicles.’ Department of Defence, ‘$3 million awarded to Defence research projects,’ Australian Government, 2 April 2025, https://www.defence.gov.au/news-events/releases/2025-04-02/3-million-awarded-defence-research-projects.
[5] Department of Defence, Defence Annual Report 2023–24, Australian Government, 2024, web table E.2, https://www.defence.gov.au/about/accessing-information/annual-reports.
Dr Tom Loveard is C2 Robotics’ Chief Technology Officer and Dr Marcus Hellyer is Director Strategy.
This article was originally published in the Australian Naval Review (2025 Issue 1) and is republished with permission of the authors.
Loveard, Tom and Marcus Hellyer, “Examining the True Force‑Mass Potential of Large Uncrewed Underwater Vessels,” Australian Naval Review, vol. X, no. 1, 2025.