What, exactly, is Australia’s intended fleet of nuclear-powered submarines supposed to do? It’s reasonable to ask the question, because the government has not spelled out the roles of the vessels.

Nonetheless, the answer is clear. Operating as part of a coalition in a major-power war to defend Taiwan against China, for example, their main function would be to undertake anti-submarine warfare (ASW) and anti-surface warfare (ASuW)—that is, to sink or repel enemy ships and submarines and help other forces do so as part of deterrence by denial. The submarines will also have a capability for land attack that could be seen as part of deterrence by punishment, but that will be secondary, not least because the small number of submarines on hand means any barrage of missiles won’t likely deliver unacceptable cost to China. 

The nuclear submarines (SSNs), which are due to begin entering the fleet in 2032, would act as apex predators of the seas to impose deterrence by denial. This is the basis for Australia’s military strategy set out in the 2023 Defence Strategic Review, and the SSNs are ideally suited for the role. 

The review defines deterrence by denial as ‘an approach designed to stop an adversary from succeeding in its goal to coerce states through force, or the threatened use of force, to achieve dominance.’ That contrasts with deterrence by punishment, in which an enemy is intended to be warded off by fear of retaliation. 

Narrowing the concept of deterrence by denial down to the Australian context, it means the SSNs must contribute to an anti-access and area denial capability. That’s one that is ‘designed to detect an adversary and prevent an advancing adversary from entering an operational area, and to limit an adversary’s freedom of action within a defined operational area.’ 

This would be the main application of the unique strengths of an SSN—superior stealth, speed and endurance—combined with weapons and advanced sensors for dealing with other submarines and ships.

Where they will operate is suggested (though not constrained) by the review’s declared area of primary strategic interest, which extends out from our immediate air and maritime approaches across a vast expanse of the Indo-Pacific: from the northeastern Indian Ocean through maritime Southeast Asia into the Pacific, including our northern approaches. Their high transit speed, long endurance on station and operational flexibility within these regions makes them ideal for long-range operations at sea, far more so than much slower diesel-electric submarines, which cannot stay on a station for long and do not have the speed for rapidly entering or escaping in the event of detection. 

Michael Clarke questions the utility of the future nuclear submarines in an 18 March 2024 article in the Lowy Interpreter, saying ‘how the SSNs contribute to a strategy of denial remains under-specified.’ He argues that in the context of a crisis in the Taiwan Strait, the submarines would be better suited to imposing costs on China as a form of deterrence by punishment. That would see them launching strike missiles against targets on the Chinese mainland. But he then argues that China is likely to be able to effectively defend against such attacks.

Clarke is correct to question the utility of nuclear submarines in carrying out strikes on the Chinese mainland, but not necessarily because China can potentially defeat such strikes. Rather, the limitation is that they just won’t be able to impose much punishment. 

Under the AUKUS Pillar 1 ‘Optimal Pathway’, Australia will first acquire three Virginia class SSNs. They will be two Block IV boats arriving in 2032 and 2035 and a Block VII Virginia in 2038. Australia also has an option to acquire two additional Virginia class SSNs before transitioning to the Anglo-Australian SSN-AUKUS class in the 2040s. 

Each of the two Block IVs will have vertical tubes for 12 Tomahawk land-attack missiles. (Two possible tube configurations would have the same Tomahawk capacity.) The Block VII boat probably will also be able to carry 12 Tomahawks. 

Block Vs can carry 36 Tomahawks, but unfortunately, there seem to be no plans for Australia to get Virginias of that version, not even as the two optional submarines. So, regardless of which configuration, each Australian Virginia will carry 12 Tomahawks, and the submarine fleet capacity will be 36 of those missiles for three submarines and 60 if the optional two, probably Block VIIs, are also acquired. 

A rule of thumb for submarine deployment tells us that, in peacetime, only a third of boats in a fleet are available for operational deployment. Even if we optimistically assume that more SSNs can be made available in a crisis—say, three from a maximum Virginia-class fleet of five—then only 36 Tomahawks would be available. That would hardly be a sufficient force for imposing deterrence by punishment on China. 

Rather than wasting the great strengths of SSNs on such a mission, a better role would be to use them against ships and submarines. That fits much more closely to the concept of deterrence by denial. 

Operating as part of a multi-national coalition, and in a manner that fully exploits an undersea warfare network, SSNs can quickly impose unacceptable losses on any Chinese naval forces supporting a cross straits invasion or operating in the South China Sea. China’s navy is a key element of its power and credibility. An ability to impose such cost on it would reinforce deterrence by denial, making Beijing consider a cost-benefit calculus on the use of force to achieve strategic ambitions.

The AUKUS pact promises to provide Australia with the first of its nuclear-powered submarines (SSNs) in the 2030s. But how will those boats, and the AUKUS SSNs to be delivered in the 2040s, fare in oceans whose soundscapes have been altered by ocean acidification and climate change?

A new study suggests that over the coming decades, soundwaves will travel further through a warmer, chemically different, less dense ocean—and it will be noisier underwater than ever.

Australia learned long ago that acquiring submarines is complex and always takes longer than expected. This was certainly the case with the Oberon class that Australia purchased from Britain in the 1960s—eight were ordered but only six delivered. And it held true for the Collins class that followed, which had problems that took almost 20 years to remediate.

Lengthy submarine design and delivery schedules create opportunities for adversaries to capitalise on fast-moving disruptive technologies such as artificial intelligence, quantum computing and autonomous systems. These technologies will change how underwater operations are conducted in ways that are difficult to predict and account for.

However, it is possible to predict with some confidence the ways in which the acoustic environment will change over the coming decades—and my simulator does just that. My research suggests that as the oceans become warmer and their chemical make-up changes, sound will travel further due to reduced transmission loss.

By 2100, ultrasonic sonar transmissions in the 30 kilohertz range (a frequency that might be used for mine hunting) will travel between 40% and 87% further than they do today, and sonar transmissions in the 10 kilohertz range (a frequency appropriate for hydrographic mapping) will travel between 15% and 25% further.

The effect will vary depending on latitude: colder polar oceans will experience more extreme variations than warmer coastal waters.

With sound traveling further, undersea stealth platforms such as submarines will find it more difficult to hide in the open ocean. But they may also find it easier to hide in coastal waters, as the ocean becomes noisier.

I modelled the effects of our changing oceans over time by bringing together predictions from the UN Intergovernmental Panel on Climate Change’s representative concentration pathway 8.5 climate model with data from ocean-going Argo data-collection robots that agencies such as the CSIRO use to monitor ocean parameters. I fed this data into a custom-built simulator, which generates a digital twin of the ocean to explore what these changes might look like.

The impact of changing hydroacoustics is far-reaching, extending to military, commercial and scientific applications. It will have significant effects on underwater technologies that rely on sound, such as active and passive sonar, hydrophones, echo sounders, fish finders and sub-seafloor profiling devices.

My findings suggest that the changed environment will have positives and negatives for submarines. Thermal layers are likely to have a greater density differential with the cooler water below them compared to today. This means that submarines will be harder to detect when such a layer is present. However, because sound will travel further, when there’s no thermal layer they may be easier to detect.

Even as it potentially becomes much more difficult to hide in the open ocean, increased noise across the full acoustic spectrum, as well as increasing sound intensity overall, will likely make hiding in coastal shallows, littoral waters and archipelagos much easier.

The time involved in taking a submarine from concept to operations means that the Australian Defence Force needs to start planning for a changing environment now. Naval architects will need to consider material choices for both anechoic plating and hull construction, while marine engineers will need to consider improved dampening for the mechanical components that generate noise. Electrical engineers will need to begin designing next-generation sonars, sensors, processors and filtering techniques to improve their ability to detect hostiles amid very loud ambient noise.

Future submarines will almost certainly use embedded artificial intelligence and machine learning to process acoustic signal intelligence. The developers of these systems will need to take future acoustic conditions into account when assembling training datasets, or they may train an AI with a keen ear for today that won’t be suitable for tomorrow.

Picture this scenario. An Australian frigate is on patrol in the Coral Sea around 100 kilometres off the north Queensland coast when it receives intelligence that an enemy submarine is in the area. It pings the warm waters at 3,500 hertz with its sonar. Under conditions recorded in October 2023 by an Argo robot in the area, that sonar ping would be audible to a range of 28.5 kilometres. In 2100, the same sonar ping, in the same location, would be audible at 37.5 kilometres. When considering the circular area covered by the sonar in this scenario, that’s an increase of about 73%, from 637 square kilometres scanned in 2023 to 1,104 square kilometres in 2100.

More research is needed on this subject to understand the changing world that awaits us under the sea—especially considering the recent joint statement of AUKUS defence ministers about the important work to come in areas such as trilateral anti-submarine warfare and undersea vehicle launch and recovery.

My pilot study is a significant step towards understanding the effects of climate change on ocean hydroacoustics, but it has its limitations. We need more data, and future work should look to expand the dataset and modify the 2100 model to better align with today’s most advanced oceanographic models. Changes to the sea surface will also need to be factored in. The information we gain may make a significant difference to how we approach future warfare in the Indo-Pacific and will be an important part of maintaining a maritime capability edge. It may also provide insights that help Australia address two existential problems—climate change and our geostrategic circumstances.

Anti-submarine warfare (ASW) has always been a game of hide and seek, with adversarial states looking to adopt and deploy emerging technologies in submarine stealth or detection to give them the strategic edge. The advantage has shifted back and forth, but, on the whole, it has proved easier to hide a submarine than find one: the oceans are wide, deep, dark, noisy, irregular and cluttered.

Technological change can alter the balance of military power, however, and parallel technological trends facilitated by the ‘digital revolution’ may gradually make submarine detection more reliable. Certain scientific or technical breakthroughs and investments may even prove to be game-changers for submarine detection—defined here as a combination of technologies that significantly reduce or even eliminate a state’s confidence that its submarines can elude tracking and remain undetected most of the time.

History cautions that there can be no jumping to conclusions, however. Truly game-changing ASW technologies have been awaited for decades and are by nature difficult to predict. This was clearly expressed in Western deterrence and arms-control literature in the 1970s and 1980s, which reflected fits of ‘transparent oceans anxiety’: a persistent and partially unfalsifiable disquiet that a technological innovation could make the oceans transparent and undermine strategic stability by making US nuclear-powered ballistic missile submarines (SSBNs) sitting ducks in a bolt-from-the-blue first-strike attack. Technologies available towards the end of the Cold War were insufficient to give seekers the advantage that some analysts predicted and, as Owen Cote notes, also contributed directly to the development of effective countermeasures that ensured the survivability of US SSBNs. After the Cold War, the notion that submarines (above all, SSBNs) were ‘invisible’ became politically unassailable.

Several articles and studies in recent years have revisited the survivability of SSBNs, for which game-changers would perhaps have the greatest consequences for international security. As Norman Friedman notes, ‘strategic submarines seem to be key to strategic stability’, providing what is generally believed to be the most survivable nuclear second-strike force. Friedman marshals some of the limited evidence available in the public sphere, but is deliberately cautious about making bold and certain predictions.

The technologies outlined here relate primarily to emerging ASW capabilities developed by the US, which has higher levels of transparency about its SSBN capabilities and nuclear strategy than other countries, but it may be assumed that similar technologies will proliferate to other navies.

Sensor platforms

ASW traditionally relies on a limited number of costly manned platforms such as attack submarines (SSNs and SSKs), frigates and maritime patrol aircraft fitted with a variety of sensors. Today, there’s evidence of a move away from this model towards unmanned aerial vehicles (UAVs), unmanned surface vehicles (USVs), and unmanned underwater vehicles (UUVs) fitted with equivalent sensors, which are more expendable and are becoming cheaper to develop, produce, modify and deploy at scale. Navies are indicating that this is the direction of travel; as Robert Brizzolara, a US Office of Naval Research program officer, states: ‘The U.S. military has talked about the strategic importance of replacing “king” and “queen” pieces on the maritime chessboard with lots of “pawns”.’

A prime example is the US Navy’s medium displacement USV, or MDUSV. The prototype launched in April 2016, Sea Hunter, was reported to have demonstrated autonomous SSK detection and tracking from the ocean surface from 3.2 kilometres away, requiring only sparse remote supervisory control for patrols of three months, using a combination of ‘advanced hydro-acoustics, pattern recognition and algorithms’. Since the range and resolution of acoustic sensors are highly variable according to oceanic conditions (such as depth, temperature and salinity), the range may well go further in favourable conditions; a Chinese estimate puts it at 18 kilometres. Since SSKs using air-independent propulsion or running on batteries are virtually silent, MDUSVs should theoretically be capable of pursuing SSNs and SSBNs (whose nuclear reactors continuously emit noise) at greater distances, and there are reports that they will be armed.

Whereas the new US FFG(X) frigate costs a sizeable US$1 billion per ship, MDUSV platforms are reported to cost only US$20 million each and so could conceivably be produced at scale to autonomously or semi-autonomously seek and trail submarines. Former US deputy defence secretary Robert Work has suggested as much: ‘These will be everywhere.’

Signal processing

ASW relies on separating tiny submarine signals from background ocean noise, primarily by using active and passive acoustic sensing (sonar) and magnetic anomaly detection (MAD), and it looks likely that these will remain the most important signals in the near future. However, the range of signals may grow as sensor resolution, processing power and machine autonomy reach the necessary thresholds to reliably separate other, ‘quieter’ kinds of signal. As Bryan Clark notes, ‘While the physics behind most [non-acoustic detection] techniques has been known for decades, they have not been exploitable until very recently because computer processors were too slow to run the detailed models needed to see small changes in the environment caused by a quiet submarine.’ However, he adds there’s now ‘the capability to run sophisticated oceanographic models in real time’.

No breakthroughs have been publicly disclosed, though an independent investigation by British Pugwash in 2016 identified light detection and ranging, or LIDAR, using blue–green lasers; anti-neutrino detection; and satellite wake detection as signal types that may merit further examination. Higher processing power can also enable digital sensor fusion, whereby different kinds of signal are synthesised and analysed together, and better simulations of the baseline ocean environment, which would show up anomalies in greater contrast.

Persistent observation

Tracking submarines across large areas of ocean remains a key challenge for ASW. Manned platforms have limited ranges, and while the US Navy’s passive sonar system, SOSUS, is still in operation in parts, it is geographically bounded and requires substantial modernisation to detect today’s quiet submarines. This gap has been partially filled by modern acoustic sensor arrays like the fixed reliable acoustic path, but in relative terms these cover very small areas of ocean.

Distributed remote sensing networks, however, which link interoperable manned and unmanned sensor platforms together as nodes in a larger system of systems, could be used to scale up persistent observation across wider areas. Networks in development include the US Defense Advanced Research Projects Agency (DARPA) distributed agile submarine hunting program, which is developing ‘a scalable number of collaborative sensor platforms to detect and track submarines over large areas’, and PLUSNet (persistent littoral undersea surveillance network), which aims to create ‘a semi-autonomous controlled network of fixed bottom and mobile sensors, potentially mounted on intelligent [unmanned platforms]’ in littoral zones.

Networks of this type could be greater than the sum of their parts, with nodes able to carry heterogeneous sensors, cross-reference positive signals from multiple directions and domains, and move and respond to get a better look at signals using real-time swarming. A video of a 56-strong ‘shark swarm’ of Chinese USVs conducting complex manoeuvres on the sea surface has demonstrated that USV swarming is already possible, and the size of swarms can be expected to grow considerably just as it has for UAVs. It’s easy to imagine fleets of MDUSVs being used in the same way, potentially much further apart. Some technical challenges remain, including scaling up to blue water and improving underwater communication, autonomous decision-making, self-location and battery life, but none appear insurmountable and some of the physical limitations felt by a single vehicle can be mitigated by swarming.

Sensor resolution

While it seems likely that the proliferation of distributed remote sensing networks could decrease the importance of extending sensor range and resolution as the quantity of platforms goes up, the two principal ASW sensor types (sonar and MAD) have, or are hoped to enjoy, significant improvements in resolution on their Cold War antecedents.

Acoustic sensing in peacetime relies mostly on passive sonar, as active sonar ‘pings’ of adversary submarines risk a hostile response and disrupt ocean fauna. Recent techniques under development at the Massachusetts Institute of Technology’s Laboratory for Undersea Remote Sensing, which use particular features of the ocean as acoustic waveguides for efficient long-range propagation, offer the potential for significantly greater ranges to detect and classify submarines under certain conditions. The POAWRS (passive ocean acoustic waveguide remote sensing) system was able to ‘detect, localise and classify vocalising [marine mammals] from multiple species instantaneously’ over a region of approximately 100,000 square kilometres, and detect quiet diesel-electric surface vessels ‘over areas spanning roughly 200 kilometres in diameter’ (30,000 square kilometres). The active variant (OAWRS) can localise manmade objects as short as 10 metres over areas 100 kilometres in diameter (8,000 square kilometres), provided the resonant frequencies scattered by the object are known. Crucially, by using many frequencies transmitted at once—multi-frequency measurements—the system can distinguish fish or seafloor clutter from manmade targets. POAWRS can also be mounted on unmanned vehicles and used to detect larger manmade objects like submarines, even if their signal is partially mitigated by acoustic cloaking.

Today’s MAD magnetometers can detect a submarine’s ferromagnetic hull at a maximum range of several hundred metres. The use of more sensitive magnetometers with a range around an order of magnitude higher, known as superconducting quantum interference devices, or SQUIDs, has been limited by their oversensitivity to background noise and their need for super-cooling.

However, in June 2017, an announcement by the Chinese Academy of Sciences, which was later taken down, claimed that a Chinese team had produced a ‘superconductive magnetic anomaly detection array’, which technical experts indicated could have ASW applications and could contribute to a wider strategy to create a ‘Great Underwater Wall’ to monitor underwater traffic in and out of the South China Sea. One expert in magnets estimated that such an array could have a range of 6 kilometres or further. If this technology can be proved to work and be mounted on unmanned platforms, it could have significant implications for shorter-range submarine detection, though these reports remain unverified in the public domain.

Data transmission speed

Most data can be transmitted in ‘nearly real time’ through air. Undersea communications are more challenging, as radio waves are heavily absorbed by water. While acoustic signals can be used, this has remained an expensive technique involving significant processing power. As a workaround, DARPA’s POSYDON (positioning system for deep ocean navigation) program looks to relay data between UUVs via low-frequency acoustic messages to USVs, and from them by radio to satellites, which can make use of radio waves.

Meanwhile, a team at Newcastle University in the UK has developed ultra-low-cost acoustic ‘nanomodems’, which can send data via sound up to 2 kilometres for use in short-range underwater networks. Improving the ‘intelligence’ of each node in the network so it can discriminate useful data and minimise data packets would also increase the speed of transmission.

Hurdles still remain, but it seems that low-cost workarounds can be found.

Conclusion

The introduction of autonomous, unmanned platforms mounted with improving and digitally fused sensors, integrated within cooperative systems, will enable wider surveillance of the ocean. One effect may be to elevate the reliability of submarine detection and, in some circumstances, these technologies could prove to be game-changers that tip the balance in the favour of ASW. Nevertheless, because the history of science and technology is littered with unforeseen obstacles and elusive breakthroughs, and because many of these technologies are currently classified, it’s difficult to offer any kind of firm timeline for game-changers in ASW.

According to James Clay Moltz at the US Naval Postgraduate School, writing in 2012, some ‘emerging autonomous-tracking technologies … are likely to be widely available within the next 20 years … [raising] the prospects for successful ASW against US forces’. If this proves correct, in spite of the United States’ world-leading stealth technologies, it would imply that nuclear-capable states in the Indo-Pacific deploying relatively noisy SSBNs might have even weaker prospects of survival by the early 2030s. This would have important implications for India’s first-generation Arihandt-class SSBN and China’s Type 094, for example.

As the technological picture becomes clearer, future work will need to continually evaluate the relative gains and losses in detection and survivability that these technologies could provide to each state, and offer tangible responses to reduce strategic nuclear risks both in the region and globally.

This piece was produced as part of the  Indo-Pacific Strategy: Undersea Deterrence Project, undertaken by the  ANU National Security College. This article is a modified version of chapter 19, ‘Prospects for game-changers in detection technology’, published in the 2020 edited volume  The future of the undersea deterrent: a global survey. Support for this project was provided by a grant from Carnegie Corporation of New York.

James Mugg’s recent piece made a convincing case that the anti-submarine warfare (ASW) capability of surface combatants is more about the aircraft they embark than about systems on the ships themselves. In this post I look at how those aircraft might go about their business.

A useful reference is a 2016 NATO publication, Alliance airborne anti-submarine warfare. It isn’t the lightest read going around, and it even includes a warning notice:

But it contains some useful analysis, provided you avoid head injuries while reading it. I read it so you don’t have to.

The take-home message is clear: the days of passively listening for noisy submarines are over. The report makes the following crucial observation: ‘As the ocean grows louder and warmer while submarines become quieter, Cold War methods of submarine detection have begun to falter in today’s ocean environment.’

The ocean environment is indeed getting steadily noisier. One of the interesting (and happy) reasons is the resurgence of whales, which fill the ocean with a cacophonous long-range noise as well as being false passive and active targets. Cargo shipping and deep-sea oil exploration also contribute, resulting in a doubling of background noise every decade or so over the past 50 years.

In the language of acoustics, that’s a 15 dB (decibel) increase. Submarines have quieted by a similar amount over that time. The report notes that a modern NATO nuclear submarine is 10 dB quieter than a Russian Kilo-class conventional boat, the design of which dates to the early 1980s. So, conservatively, the total change in the difference between submarine noise and the background signal has been 30 dB, or a factor of 1,000. Hence, ‘modern submarines, both nuclear and diesel, provide passive detection ranges better characterised as hundreds of yards rather than multiple miles’.

The NATO report somewhat simplifies Cold War ASW. In fact, there were two distinct types of ASW being routinely practised. Passive detection was the preferred technique for covertly tracking or trailing ballistic missile submarines, because it was important not to alert them that their location was known. The story is (partly) told in Blind man’s bluff. Always knowing where the enemy’s second-strike capability was mattered a lot.

ASW against attack submarines was a different story. Surface forces relied on brute force and ‘hunter-killer groups’ centred around aircraft carriers. A typical US Navy group had a carrier with dozens of ASW-capable aircraft, six surface vessels and two submarines. The NATO report says that, given a rough indication of a submarine’s position, back then a flock of helicopters or maritime patrol aircraft could sow dozens of passive buoys over hundreds of square miles and, theoretically, have a good chance of making contact on the first mission. (Though greybeards tell me it wasn’t that easy.)

Several decades and –30 dB later, the area that can be covered by those buoys with the same probability of detection has shrunk considerably. And for the ADF, the disappearance of the carriers in the 1980s means that there simply aren’t enough in-area aircraft to carry the buoys required for sufficient passive coverage. With reduced detection ranges, the same few dozen buoys would now cover less than 50 square miles. Carrying more buoys isn’t practicable, especially if we also want the helicopter to be able to engage a hostile submarine if it detects it. Even the ‘lightweight’ ASW torpedo carried by the RAN’s Seahawk ASW helicopters weighs 267 kilograms, which means that weapons come at a significant opportunity cost to the sensor payload.

The net result is that passive detection can’t be the sole tool of choice for modern ASW practitioners; there’s likely to be a much greater focus on active search systems. (In highly technical terms, they go ‘ping’, and a hydrophone listens for a return echo from the submarine and anything else that’s around.)

ASW practitioners have long regarded active systems with suspicion because they reveal the position of the emitter to the submarine. For ship-mounted systems that’s a rational concern: a submarine can detect the ping from a surface vessel long before the ship can hear the much weaker return signal. The dynamic is different for helicopters. It’s true that a submarine will generally hear a nearby ASW helicopter, but the aircraft’s speed means that it can stop and dip close enough for a probable detection relatively quickly.

Aircraft can make things even harder for a submarine by employing multi-static tactics. One technique is to sow a field of passive sonobuoys (which the submarine can’t detect unless it hears the splashes as the buoys are dropped) and then use an active dipper to create a source. Any echoes can be picked up not just by the dipping system, but by any of the buoys, which allows the sub’s position to be triangulated. If there are multiple helicopters around, any of which could be carrying weapons or additional sensors, life just got tough for the submarine. Done well, aggressive multi-static active sonar can intimidate submarine crews. NATO puts it this way:

[T]he submarine, should it determine that a multi-static source is being employed, cannot know which direction to turn to avoid the pattern. Multi-statics are still an emerging technology, but, based on analysis of classified briefs made available for this study, may address many of the challenges presented by quiet submarines operating in acoustically challenging operational environments.

In this loud new world full of quiet submarines, the RAN’s future ASW capability should be based on multiple helicopters operating multi-static active and passive systems, with the ability to work with RAAF patrol aircraft. In effect, the ‘emerging technology’ is a return to what the Cold War US Navy and the ADF did almost two generations ago, except that this time they’ll be better networked and have much more processing power, and will be able to better intimidate and hunt down threat submarines for further treatment.

 

Acknowledgement: I’d like to thank living national ASW treasure Daffy Donald for advice on this piece. You can still blame me for some of it.

Much has been made of the recent release of the report by the Center for Strategic and Budgetary Assessments (CSBA) into the emerging era of undersea warfare. The wide coverage that the report received in Australia (see here, for example) focussed largely on the assertion that ‘submersibles drones would make submarines obsolete’.

The report’s author Bryan Clark posits that ‘technological advancements, many of them driven by rapid increases in computer processing power, will likely spur a new round of dramatic changes in undersea warfare’. Those changes are expected to be new capabilities to find submarines, improvements to submarines that will improve stealth and submerged endurance, and new underwater weapon, sensor and communication systems.

Clark doesn’t advance a position as to whether these technological developments will fundamentally affect the current submarine/anti-submarine warfare (ASW) balance. He prefers to make the case for the US to continue research and engagement in this important area in order that the United States retains its technological and operational lead.

This report raises some interesting issues for Australia, for instance, how do we address the more than 300 submarines that are expected to be in the Indo-Pacific by 2030? How will maritime operations be affected into the future, and what are the implications for SEA 1000? In February 2000, at a conference on maritime warfare in the 21st century, I considered a number of the points now being made by CSBA; namely that advances in processing technology would allow the construction of large virtual arrays and hence improve submarine detection, and that the move to low frequency multi-static sonar would force the submarine to adopt noise-cancellation on a ‘pulse-by-pulse’ basis.

Advances in submarine detection have the potential to fundamentally change the way ASW is undertaken. The construction of large virtual arrays, coupled with the move to bi-static low frequency sonar, will dramatically increase sonar array sensitivity and submarine detection ranges. This will serve to inhibit a submarine aiming to engage a surface task group, and either push torpedo engagement ranges further out or force a reversion to long range anti-ship missile engagements. Either way, the submarine engagement dynamic will have changed.

A warship operating alone won’t be capable of achieving the same extended submarine detection range. An independent ship will have to rely on its own systems as there will be no cooperative platform with which to form the virtual array; although low frequency active sonar will provide some improvement in detection capabilities. The changed dynamic in task group engagements will therefore force submarines to become more ‘opportunistic’ with a greater focus on the interdiction of naval ships acting alone or on merchant shipping. The latter is a serious operational consideration for Australia.

However, one serious problem will remain, made worse by the increased array sensitivity and increased detection ranges, and requiring significant research effort in the coming years: identification. How will it be possible to positively identify a submerged submarine in Indo-Pacific waters prior to engagement, or to avoid engagement? How will it be possible to make the definitive call that a sonar contact is Indonesian, Singaporean, Malaysian, Vietnamese, Japanese, Russian, Chinese, Korean, Indian, Thai or some passing Frenchman? Some sonar techniques will assist—as will water space management arrangements to exchange submarine positional information between close allies—but identification will remain elusive. Declaration of exclusion zones will not solve the problem.

And what will be the impact on SEA 1000? Submarines will continue to have a valid role in the future Australian force structure due to their ongoing ability to exert psychological pressure on an adversary, and for anti-submarine operations, intelligence gathering, interdiction of shipping, and a range of other covert operations. Continuing relevance will however come at a cost, with improved stealth becoming increasingly expensive. As highlighted in the CSBA report, improved through-water communications will also see submerged submarines included in battlespace-wide area networks, and using a variety of underwater autonomous vehicles and sensors. The SEA 1000 solution needs to be cognisant of these trends in underwater warfare if the preferred solution is to be relevant long term.

Submarines and ASW are of high strategic importance to Australia. Investment in networked ASW—both for the detection of adversary submarines and the broader use of our own submerged submarines—is warranted to address strategic risks. Significant research into techniques for the identification of submerged platforms is also required. We cannot and should not just wait for the US to develop these techniques and expect to simply leverage off their investment.

Australia has a vibrant submarine and sonar processing industry—and success in the areas outlined above could be a game changer for Australia in both the operational and industrial sense. We need to be on the front foot for these technical challenges—even it has taken us 15 years to reach this point.