Underwater operations

An artist’s rendering of the future Columbia-class ballistic missile submarine. (Image: USN)

Boats of the future

The world’s submarine fleets face new but decidedly familiar mission sets as navies transition to prepare themselves for high-intensity conflicts.

Gerrard Cowan

Against a backdrop of rising great power-style competition, submarines are set to increasingly return to more traditional, Cold War-type roles, according to naval and industry experts, retaining their crucial advantage as stealth platforms despite improvements in detection technologies.

In the current geostrategic context, the submarine is more relevant than ever, a spokesperson for the French Navy told Shephard. The global fleet has increased by 6% since 2015, with the centre of gravity shifting to Asia. Over the next 20 years, there will be continued modernisation of ‘historic’ submarine forces in a range of roles, for example the UK RN’s new Dreadnought class or the US Columbia-class ballistic missile submarines, or the new versions of the USN’s Virginia-class boats.

The French Navy itself will soon have six new nuclear-powered attack submarines – the Suffren class – which the spokesperson said would have a range of conventional capabilities (supporting the oceanic component of nuclear deterrence, escorting other units, intelligence gathering and so on), as well as the capacity to launch precision strikes with naval cruise missiles and the increased capacity to deploy SF.

The spokesperson underlined this last task in particular, noting that France would now be only the third country – after the US and the UK – to have a dry deck shelter on its submarines to support infiltration of SOF operators.

The new boats will bring a range of other breakthroughs, the spokesperson added, pointing to greater autonomy, manoeuvrability, better detection capacities and more. Additionally, they highlighted the expanding submarine forces of a range of regional powers, along with the improving capacity of those boats, notably the rise of air-independent propulsion (AIP), better underwater and above-water detection capabilities and increased stealth.

Changing intensity

The role and importance of submarines has evolved over the past 20 years, said Eric Wertheim, a naval expert who edits the US Naval Institute’s (USNI’s) Combat Fleets of the World. In the years since the end of the Cold War, and particularly following the 9/11 terror attacks, the USN largely focused on the potential for low-intensity conflict – anti-terrorism most obviously, along with facing threats from small and mid-sized nations, counter-piracy and other smaller-scale tasks.

Against such a backdrop, the ISR role of submarines came to the forefront, with less focus on other more belligerent activities that were more common during the Cold War.

While ISR has always been a core mission of the underwater fleet and will continue to be so, Wertheim said the rise of near-peer competitors, with submarine and other maritime investments of their own, has led to a resurgent focus on anti-ship and anti-submarine warfare (ASW).


Global submarine procurement programmes currently in progress


🜂 Maritime powers are investing in acquiring new underwater warfare capabilities to meet growing threats. Of note are the large numbers of SSKs being procured by navies in the Asia-Pacific region. (Source: Shephard Defence Insight)


‘We’re not just emphasising terrorists and pirates any more, and we’re not just collecting intelligence, but we’re looking again at the role of the submarine encountering great navies,’ he said. ‘This is particularly true of high-technology, high-intensity types of conflict, where the role of surface ships and their ability to survive is doubted by many.’

Given the vulnerability of said vessel – particularly given the growing threat from hypersonic weapons – the less vulnerable submarine comes to the forefront, Wertheim continued.

‘It’s able to stay hidden, to provide any information needed and also engage the enemy while hidden, clearing a path for more vulnerable platforms to enter the fray later on,’ he said, also pointing to the growing land attack capacity of submarines, among other capabilities.

Cat and mouse

William Toti was the last captain of USS Indianapolis, a Los Angeles-class submarine, and previously commodore of Submarine Squadron 3 based at Pearl Harbor, Hawaii; he is now the CEO of Sparton Corporation, an undersea warfare company. He noted that while the Cold War is today remembered for ‘cat-and-mouse type activities’, ‘the real bread and butter was the ability to conduct ISR missions’. This remains true today.

There are two key ways in which submarines distinguish themselves in the ISR role, Toti observed. First, if an aircraft or surface ship attempts to conduct ISR missions – even over international waters offshore from an adversary country – that could be construed as being provocative and escalatory.

‘So, if the adversary wants an excuse to be agitated, the visible presence of intelligence-gathering forces near their country gives them the excuse they need to make an international incident, for example,’ Toti said. ‘A submarine unseen eliminates that opportunity because it’s not provocative, they don’t have to see it. If they want to get mad about something, they have to find another excuse.’

Secondly – and on a related note – if the adversary knows an intelligence-collecting asset is in an area, they can then ‘present to the collecting ship or plane what they want that ship or plane to see [and] that lends itself to misleading the folks that are doing the collecting’. This is much harder to accomplish against a submarine.

Depending on its capabilities, a boat could stay submerged for protracted periods of time, even months. This is another advantage in intelligence gathering, given the constantly shifting nature of the environment, Toti noted.

‘In the old days, when submarines fired torpedoes…, they were very capable platforms, but they could only threaten maritime assets,’ Toti said. ‘Now that submarine can non-provocatively collect intelligence in international waters without being seen while holding targets at risk a thousand miles inland.’

If a threat emerges, the submarine operator does not need to wait weeks to get another naval asset in the area to address it, or even wait hours for an aeroplane to be deployed, depending on local assets and infrastructure.

‘That’s important because oftentimes these targets are so transitory,’ he said. ‘They’re there for a few hours and then they’re gone, so it’s useful to have something that can sit and wait for months, without the enemy knowing whether it’s there or not, and unable to make assumptions about anything.’

Back to the future?

While ISR has always been an important role for submarines, Toti believes the rise of peer or near-peer adversaries has created ‘a bit of a back to the future scenario’. Over the past five years or so, more traditional, advanced national adversaries ‘are coming out to play again and increase their numbers… The adversaries’ submarine forces have not been more active since the end of the Cold War.’ So while ISR taskings have not reduced in importance, ‘sub-versus-sub missions have risen again’.

The return to this type of activity has involved ‘relearning old skills, but with a somewhat more challenging adversary’, he added. As the US and its allies were heavily engaged in the war on terror, shifting developmental funds from traditional naval missions to land-based wars against insurgents, big state adversaries were not stagnant and continued to develop maritime capability at a fast pace.


🜂 Assistant Secretary of the Navy for Manpower and Reserve Affairs Gregory J Slavonic discusses submarine missile capabilities with senior officers aboard the Virginia-class SSN USS John Warner in April 2019. (Photo: USN)


Toti argued that while submarine technological and operational development has continued to move forward for the US and its allies, ‘it has been at a lethargic pace, almost in order to keep the industry from dying… we have continued to invest to keep the pot simmering while other adversaries have kept their pots boiling because they weren’t distracted by the war on terror’. He warned that unless this pace accelerates, it could become ‘a fair fight, and we don’t want a fair fight’.

The scale of investment also differs from nation to nation, Toti said. For those with navies that ‘need to go from one end of the earth to the other’, such as France, the UK and the US, nuclear-powered submarines make sense because they can stay hidden for long periods and possess extensive range. For countries that only need to operate in short-range, localised environments, diesel submarines still make a great deal of sense.

However, AIP submarines are becoming an increasingly popular third option, Toti noted, functioning as a middle ground between diesel and nuclear, while not being as expensive to construct as the latter. This could have a major impact on the composition of submarine forces internationally in the coming years.

Seeing through it

There has long been speculation about the idea that sensors could become so advanced that they blunt or even negate the submarine’s key advantage. This is the scenario outlined by researcher and analyst Zachary Kallenborn in ‘If the Oceans Become Transparent’, a commentary recently published by the USNI, looking at the impact of transparency on sea-based nuclear deterrence.

Kallenborn writes that a broad range of emerging technologies is reducing the ocean’s opacity. UUVs offer cheap platforms for nanotechnology, 3D-printed sensors and anti-submarine weapons, while machine learning and big data tools boost analysis of this data. Additionally, the proliferation of UAVs and commercial satellite imagery allow for improved collection of activity at submarine ports, he notes.

Kallenborn said that such technologies reinforce each other, with improved AI boosting machine vision and allowing for faster decision-making and more complex behaviours, greater autonomy reducing the need for human control (which could potentially be disrupted) and additive manufacturing leading to cheaper and more easily customised drones.

‘Autonomy will allow drones to work together in swarms, coordinating among numerous systems, allowing much more efficient and broader searches,’ he writes. ‘Heterogeneous swarms could include surface, aerial and other undersea drones to form a massive antisubmarine drone network.’

Still, this transparency will not happen overnight, he notes, pointing to a range of challenges. For example, although distributed sensors will generate massive amounts of information, if states cannot effectively handle this data, they ‘risk seeing submarines that do not exist while missing those that do’. It is more likely that transparency will grow as technologies mature, but a total state of it may never occur. However, even a significant reduction in the ability of submarines to hide poses challenges for the role in nuclear deterrence.

Regardless of how clear the waters become, adversaries would still need to chase and kill a submarine. For nuclear-armed submarines, the latter must occur before the submarine can launch a retaliatory strike. The perceived risk of failure may prevent an attempt in the first place, Kallenborn notes. He also points to a number of other ways for states to offset transparency, such as improving speed, boosting the range of ballistic missiles and improving capacity to hide and fight back.

‘A transparent ocean does not mean the end of a sea-based second strike capability,’ Kallenborn concludes. ‘Every innovation can be countered. Improvements now can help ensure second strike remains reliable into the future.’

Unlikely prospect

The prospect of a fully transparent ocean remains far away, in the view of many. Andrew Davies, a senior fellow of the Australian Strategic Policy Institute and former director of its defence and strategy programme, notes that while detection technology is improving all the time, ‘the ocean is a very big place, and having enough sensors to cover all of it along with the ability to process all of the data is a big ask’.

He believes that submarines may have to avoid some key focal areas in future where discovery will be far more likely, so they will most often operate at stand-off range. However, ‘being under the water will always be preferable to being on top of it, as far as avoiding being located is concerned’, he added.

For his part, Wertheim said it is likely to remain ‘a cat-and-mouse game’. While adversary nations are likely to bolster ASW capacities and detection capabilities, there will likely be advances in stealth and other technologies to counterbalance this. Additionally, he noted that ‘there’s a lot we don’t know about the world’s oceans – we have better maps of the surfaces of Mars and the Moon than we do the bottom of the ocean’.

🜂 The future maritime environment is likely to involve a complex mix of assets, both above and below the water. (Image: Thales)


Against such a backdrop, submarines retain a key advantage. But conversely, they create a crucial vulnerability for less technologically advanced navies ‘because the ocean is so vast and the submarine is so small relatively’.

Toti has been involved with submarines for almost 40 years and says he has regularly heard predictions of a transparent ocean over that time period.

‘We’re not closer to that happening today because not only do the oceans change from moment to moment, but they’re just so vast… The architecture you would have to construct to [monitor] every potential location where a submarine could possibly be a risk is just so expensive.’

That is not to say ASW is a pointless task, Toti stressed. In fact, he believes that more work must be done to advance the ability to detect: ‘Allied nations have invested all this money in these [maritime patrol] planes, but it’s important that we chase the sensors as well.’

Speeding up

The number, accuracy and particularly the increasing speed and range of weapons – including hypersonics – now deployed by potential peer and near-peer adversaries underlines the need for greater sensing and effector ranges, said a spokesperson for Thales, which has developed a persistent underwater sensing solution installed on the seabed – a Seabed Sonar Barrier – to address such concerns.

Additionally, they said that as countries expand fleets of patrol vessels and corvettes – which are in use by increasing numbers of nations – so they require smaller sonar systems for those vessels. As these begin to proliferate, submarines will be forced to deliver their effects from greater distances. UUVs could be useful in this regard, it was added, working in conjunction with submarines for certain types of mission.

Toti said it is unlikely UUVs would replace manned submarines any time soon, for several reasons. First, smaller platforms are not capable of carrying larger sensors and may be restricted in range. ‘The size of a submarine gives you a lot more power storage capability,’ he noted.

Much larger UUVs could effectively operate as an unmanned diesel submarine, staying at sea for weeks or months at a time, ‘so they do have meaningful mission scenarios they can execute as far as long-endurance or long-duration missions’, Toti said.

However, the difficulty is configuring and planning for a mission in advance of it getting under way. This would be challenging without substantial advances in AI, he said, particularly if the system needs to quickly change its planned mission scenario. In that case, it would need to be repurposed or reprogrammed by human operators in order to prepare it for a new task.

‘But the more time you spend talking to the machine, the more vulnerable it is,’ he said. ‘With people on board a submarine you don’t have that problem.’

Maritime autonomy

Toti believes the world is still decades away from developing a true multi-mission capability in an autonomous, AI-dependent platform. However, he can envision a scenario where UUVs complement submarines, with rapidly reconfigurable systems operating from the manned boat, which is effectively a mothership.

‘The advantage is that [the UUV] can go places potentially where a submarine cannot, either because it’s too shallow or you just don’t want to send a manned platform because of the risk.’

Wertheim also pointed to the potential of the mothership scenario, noting that it could permit submarines to operate from greater stand-off distances, ‘potentially sending UUVs into areas where you would not want to risk a manned system, either because of the potential for capture or because it’s too difficult to navigate’.


🜂 A Dauntless-class patrol boat assigned to Coastal Riverine Squadron 1 transfers supplies to the Virginia-class USS Texas. (Photo: USN)


As UUVs get smaller and more capable, they can fit on a wider array of host submarines, Wertheim added, becoming ‘in many ways the intelligence-collection arm of the submarine force’. However, submarines would then face the challenge of protecting the data links that the UUVs rely upon. Improvements in AI could be a solution, allowing the system to operate autonomously even if a link is severed.

Kallenborn noted in an interview with Shephard that UUVs also face a considerable challenge of mastering undersea communications links. ‘Unmanned aerial vehicles typically use electromagnetic signals that do not propagate well underwater,’ he said. ‘Although acoustic signals are usable, they are much slower, have smaller bandwidths and higher risk of error. The challenge is particularly acute for UUV swarms because of the need to communicate and coordinate multiple UUVs.’

Sidharth Kaushal, research fellow, sea power – military sciences at the Royal United Services Institute, agreed that the rise of near-peer or peer adversaries means ‘it’s very much a return to tradition in some ways’. Submarine operators will face a range of challenges in the years ahead, he added, pointing to developments in low-frequency sonar.

While this has a greater range, it traditionally produces a less accurate picture. However, advances in oceanographic knowledge, AI and computer modelling are changing this and mean that ‘in the not-so-distant future it may well be possible to sift the feedback you receive from a low-frequency sonar away from general oceanographic clutter’. This would make it possible to detect submarines at increasingly large distances, ‘which opens up a whole host of avenues for ASW’.

Kaushal also pointed to UUVs as a potential threat to submarines, with large numbers of cheap, automated platforms substantially increasing the number of sensors at sea and providing updates on a boat’s whereabouts. These and other trends suggest that over the next ten to 15 years, ASW technology is likely to become a lot more effective.

However, Kaushal expects submarines to adapt to the changing environment, as they have done in the past. He pointed to the use of UUVs for specific missions, boosting the stand-off range of submarines, while designers will adapt quietening methods to respond to the trends as well. ‘A quiet SSN – or if you’re operating close to shore, a diesel-electric submarine – is and will remain a lethal platform.’

Evolving situation

Davies expects manned submarines ‘will be around for a while yet’ and expects to see them improve in evolutionary, rather than revolutionary ways.

‘Stealth will improve, as will sensors. Weapons aren’t likely to change that much, and torpedoes, missiles and mines will still be recognisably the same in 25 years’ time, although they will all be more capable, with more stealth and possibly autonomous decision-making.’

Submarines’ importance continues to grow, according to Wertheim. This process feeds on itself because ‘the best tool for hunting a submarine is in many ways another submarine, so as the proliferation… continues, they’re going to be needed more for ASW’.

There will also be more use of UUVs and aerial platforms in this evolution, he said. Yet the obvious strength of a submarine – its ability to remain hidden for long periods of time – is unlikely to fade any time soon.

‘A submarine is a true stealth platform and is very, very difficult to detect,’ Wertheim said. ‘Because of that, it has utility that other platforms lack.’