The Future of the Submarine - Emerging Threats, Sensors & Transparent Oceans

The Future of the Submarine - Emerging Threats, Sensors & Transparent Oceans

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On the modern battlefield the ability to move without detection is both incredibly valuable and often unattainable. No matter how pixelated your camo or how much foliage you stick in your cope cage, there's probably a sensor out there with your name on it. But even in a modern transparent battle space, submarines have long been something of an exception. In its most advanced iterations, the modern attack submarine is arguably horrendously overpowered, combining very dangerous weapon systems with a degree of stealth that can make them incredibly difficult to find and track. Because as good as some technology has got, the vastness of the world's oceans have also provided some of its last reliable hiding spots. That ability to move unseen has made submarines incredibly valuable for navies around the world, and submarine technology often a closely guarded national secret.

But now some sources are predicting that by the middle of the century new developments of technologies ranging from sensors to drones might turn the oceans transparent. And potentially rob some of the world's very expensive submarine fleets of their valued ability to hide. And so today we are going to look at submarines, some of the future threats they might face, and what it might mean if depth ever ceases to be a defence.

To do that I'll start with some history around submarine development and how they came to enjoy their current position. I'll look at some of the broad types and characteristics of submarines in service today, the missions they fill, and the economics around their construction and fielding. Then I'll ask what sort of technologies might be arriving in the coming years and decades to help nations more easily find and hunt these underwater vessels. Before closing out by asking whether or not those new threats herald the potential end of the submarine, or just a new driver for submarines and the way they are used to evolve.

Just a note that in the interest of time, I'm not going to be giving a run through of all the world submarine fleets today, instead the focus is going to be on technology and trends. But if we come back for a look at next generation submarine programs in the future, I'll be sure to include a bit of a discussion around who currently has what. So before we look at threats to the submarine's dominant position, we probably need to cover a bit of history as to how they became apex predators in the first place. Now humanity has been building warships that submerge for basically as long as we have been building warships. The trick to building a successful submarine though was to design something that would come up again afterwards. It turns out that second bit was much, much harder than the first, and so the first practical military submarines only really started to "surface" in the 19th century.

Compared to what would come later, the submarines of World War One were extremely primitive. A German Type 19 U-boat only displaced about 840 tons submerged, it had a crew of 35 men and could dive to maybe 50 metres. The electric motors they used while submerged put out less horsepower than a modern Abrams battle tank, meaning that while submerged the ship could manage maybe 150 kilometres, moving at a glacial 5 knots, about 9 kilometres an hour. Submarines also, at least initially, had to adhere to the prize rules when going after merchant shipping.

That meant a submarine would have to stop a merchant ship, board it, determine if it was carrying contraband cargo, and only then (after making proper provision for the survival of the crew on board) sink it or capture it. Perhaps unsurprisingly in a world where escort ships or armed merchantmen were a thing, dinky little submarines going and boarding merchant ships wasn't particularly practical. The Germans would then eventually move over to a system of unrestricted submarine warfare, where merchant ships could be sunk without warning. Enabling a submarine to use its greatest advantages, surprise and stealth, in order to make torpedo attacks with a relative degree of safety.

The diplomatic implications of that decision, particularly in nominally neutral America, were massive. And Germany would eventually back off the policy before re-embracing it in 1917. As far as a lot of the world was concerned, sinking merchant ships without warning was piracy, plain and simple. But in purely military terms the results were fairly dramatic.

In early 1917 the Germans would have roughly 30 submarines at sea at any given time. Taking a baseline of 35 crew per submarine meant roughly 1,000 German naval personnel at sea in submarines at any given time. In February 1917 those boats sank 520,000 tons of shipping.

In March they sank 564,000 tons and in April 860,000 tons. To put that in perspective, the entire modern Royal Navy displaces about 830,000 tons. And those 3 months combined total the displacement of the entire US Navy supercarrier fleet, as well as a significant number of escorting vessels. The exchange ratio was extreme, and while the Entente would come up with tactics and technologies to counter submarine attacks, even at this point statistically there was some truth to the modern submariner maxim that there are only really two types of ships: submarines and targets. With submarines being such a disruptive technology, there was a push for things that might counter them. By the end of World War One some development efforts for acoustic methods of detection for anti-submarine warfare were relatively well advanced.

And by the Second World War sonar and sonar-type systems were in fairly widespread service. These meant that warships, as well as just passively listening for the sounds of a submarine, could also send out sonic pings to bounce off a submarine hull, and use those active pings to more accurately determine its bearing, distance and depth. Such was the excitement around some of these developments that there were some theoreticians that suggested the age of the submarine was now already over. After all, now that the surface warships had a way to see the submarines, surely the latter had lost their advantage? While anti-submarine sensors were evolving however, so too were submarines.

Different nations experimented with different concepts. The Japanese wanted long range submarines that could directly support fleet actions. The French military, always driven to be a bit different from everyone else, decided to experiment with the so-called "cruiser submarines". By, as you can see on the right there, taking a cruiser-level gun armament and sticking it on a submarine. No, this didn't turn out to be a good idea. But hey, at least they tried something a bit different. There would also be all sorts of outlying developments during the Second World War as well.

The famous Italian frogman for example would employ a sort of manned torpedo. Putting on scuba gear, piloting the design you see on the top right there underwater up to an opposing warship in port, unscrewing the warhead, attaching it to the underside of the opposing warship, setting a timer, and then exiting stage right. Despite the relatively limited resources involved, these frogmen would reportedly claim about 200,000 tons of Allied shipping during the Second World War, including two battleships. Although admittedly, both HMS Valiant and HMS Queen Elizabeth were World War One veterans. The Japanese by contrast experimented with dispensing with the whole unscrewing the warhead and allowing the crew to escape thing, with the Kaiten, which you see on the bottom right there.

And despite being far more horrific a concept than the Italian design, they were arguably markedly less effective. The Japanese would reportedly lose more personnel piloting Kaiten or on the submarines carrying them, than on the US ships targeted by them. But perhaps the most important, almost quintessential, type of submarine during the Second World War was the type exemplified by American fleet boats or the German Type VII U-boat. A medium-sized submarine, usually with a mixed gun/torpedo armament, intended to carry out fairly long distance patrols. And they would very much make their strategic impact felt.

Despite the enormous resources poured by the Allied powers into combating German U-boats, they would still inflict significant damage during the Battle of the Atlantic. But less often discussed was the immense success of the American submarine fleet against Japan in the Pacific. American submariners began the war with a pretty rough hand in several respects. A lot of submarines were being used for jobs that weren't attacking Japanese shipping. And the primary torpedo the US submarine force started the war with, the Mark 14, was so tremendously, hilariously, bad that not only would it fail to destroy many of the targets it was launched at, it also caused a number of US casualties, including the sinking of the USS Grunion.

The submarine is believed to have attacked a Japanese merchant ship with multiple torpedoes. One torpedo is believed to have run low and failed to detonate, two more bounced harmlessly off the ship without exploding, while the fourth torpedo is believed to have missed the target, run in a circle, struck the submarine that launched it, and despite not detonating (because, you know, that would represent at least some modicum of functionality) it is still believed to have caused enough damage to have contributed to the loss of the submarine. Eventually however, the problems would be solved and the results kind of speak for themselves. Roughly 260 American submarines would undertake war patrols in the Pacific.

By various estimates, those submarines were responsible for sinking about half a million tons of Imperial Japanese navy warships, and about 4.8 million tons of merchant shipping. To put that in perspective, in the middle of 1941 the Japanese merchant fleet was about 6.4 million tons, by the end of 1944 it was down to 2.6. To achieve that, total US submarine losses during the Second World War came to 52 boats and 3,506 officers and men. And the breakneck pace of submarine development wouldn't stop as the world entered the Cold War era.

There was a brief window where every man and his dog it seemed was building a copy of the German Type XXI U-boat which had come out towards the end of World War Two. But that submarine's advances in conventional diesel-electric propulsion would soon be followed by the development of something else entirely. In both the Soviet Union and United States, the Cold War would see the birth of the nuclear navy.

US developments in this area were particularly rapid, driven by US Admiral Hyman Rickover. And with the addition of a nuclear reactor, arguably true submarines were finally born. Previously submarines had had a kind of love/hate relationship with the surface. The surface was where they were at their most vulnerable, but it was also where they could get oxygen to run their primary diesel power plants. Without running on the surface, or very near to it and using a snorkel, submarines would eventually exhaust their batteries fairly quickly. Submarines in the Second World War were generally much faster travelling on the surface than underwater, and their hull forms reflected that.

Submerging was a defence mechanism, a manoeuvre, not the submarine's default state. But with a nuclear power plant on board, submarine power plants didn't have to breathe any more. And with the nuclear reactor on hand to provide power for an electrolysis process that could rip oxygen from seawater, now the crew could (in a sense) breathe underwater as well. Their endurance would now be limited only by the number of weapons they could carry, and the frailties and limitations of the humans crewing them. Who obviously continued to require things like food and the occasional trip home to see their families. Nuclear submarines could be nearly permanently submerged submarines.

And they could afford to adopt hull forms optimised for underwater performance and stealth. The technology also facilitated the development of an entirely new type of submarine, the SSBN, the famous "boomers". The challenge of tracking nuke boats, especially as they became quieter, was one of the key features of the Cold War at sea. Another innovation was the development of detection systems on a truly strategic scale. NATO countries for example would build up a chain of underwater sensors covering the entirety of the Greenland/Iceland/United Kingdom gap. Meaning that even if Soviet submarines couldn't be tracked all the time, if they tried to make it into the North Atlantic there was a pretty good chance that the sensor network would ping them.

With the collapse of the Soviet Union though, the underwater arms race between the Soviets and various NATO states took a sudden and abrupt turn. Much of the Soviet fleet would fall into disrepair, while the US Navy was left trying to find a place for some of its Cold War monsters, like the 9,000 ton displacement Seawolf class. It turned out attack submarines didn't have a particularly large role to play in an era of counter-insurgency warfare. And at the start of the 21st century, realistically there was nothing out there that could come close to matching NATO submarine forces in either quality or even quantity. But in the 21st century the balance has been slowly shifting. The Russian submarine force is being recapitalised, the Chinese one rebuilt from almost the ground up, India has become a nuclear submarine power, and countries like Brazil are looking to follow.

And even as countries are dedicating immense resources to building or rebuilding their submarine arsenals, there's the spectre of new technologies and new potential threats emerging on the horizon. OK, so if that's a brief summary of how we got here, let's next ask: what are some of the roles and key features of modern submarines? This is particularly important with submarines as compared to some of the other platforms we've looked at. Because while there tend to be some common features, (they are all for example, going to be pressurised metal containers capable of travelling underwater, usually with at least some torpedo armament) depending on the choices you make during the requirements and design process, you can end up with some very, very different looking products. So let's look at some of those choices. First up: pick the mission. The two most significant categories when it comes to submarines are the attack submarines on one hand and the missile boats on the other.

If the goal of your system is to go kill things on or under the water, you probably have an attack or a hunter/killer submarine. Your primary armament is probably going to be the torpedoes. And depending on your propulsion system, your designation is going to be either SSN for a nuclear-powered attack sub or SSK for a conventionally-powered one.

We'll get to propulsion systems in a moment. If instead the role of your system is to help deter war by taking lots and lots of nuclear missiles and then going and hiding in the ocean somewhere, you have a ballistic missile submarine. Here your submarine probably still carries some torpedoes for self-defence, but the primary armament is going to be those nuclear missiles, which imposes a lot of design constraints.

Carrying submarine-launched ballistic missiles means carrying the tubes to launch them from. And as you can see from that Chinese Jin-class submarine pictured on the right there, missile compartments aren't small, and that imposes size constraints on the submarine as well. In the American system, a nuclear-powered ballistic missile submarine carries the designation SSBN. Those are the two primary missions, but you can see more specialised platforms as well. A guided-missile submarine for example is another missile-carrying submarine design, but instead of carrying nuclear ballistic missiles, it carries lots and lots of conventional ones.

The USS Ohio for example, namesake of its class, and originally a ballistic missile submarine, eventually had its capacity to carry 24 Trident nuclear missiles replaced with 22 tubes each carrying 7 Tomahawk cruise missiles, 154 in total. Meaning that hypothetically an SSGN can pop up somewhere, unleash a small fleet's worth of cruise missile strikes and then just disappear. You might also find designs that hypothetically have been optimised for carrying and deploying Special Forces teams, or interacting with undersea cables and infrastructure. Indeed now submarine technology is so relatively common that you can also see [vessels] designed for private sector purposes. Whether that be carrying James Cameron down to look at shipwrecks, or semi-submersibles intended to ship cargoes of dubious origins from buyers to sellers. But to get back to a purely military context, deciding upfront whether or not you need to make room for a shit ton of missile tubes is a pretty big one.

Perhaps your other major genre-defining choice is to pick a propulsion system. Broadly here you have two options: conventional or nuclear. A nuclear propulsion plant gives you about as much range as your crew can handle, and the potential for some very impressive sustained underwater performance. You have a huge amount of power on tap, so something with one of these reactors is going to be able to go, and keep going, for patrols that might last several months. The downside is you need to build and fit a nuclear reactor (or several nuclear reactors) into your submarine.

That places a pretty harsh floor on how small and cheap you can make the system, and has its own industrial demands. A conventional power plant by contrast can be much smaller and cheaper, but the range, endurance and performance that you get are going to be much more limited. Conventional power plants have actually got a bit of a leg up in the last couple of decades with the emergence of more practical Air-Independent Propulsion systems, which can provide a sort of middle-ground option to the old diesel and battery combo. At the moment AIP systems in service generally fall into two main categories. There are Stirling engines, which you will generally see in Swedish submarines, or submarines belonging to nations that have partnered with Swedish companies.

Japan stands out as a good example here with the Sōryū class. And then you have fuel cells, which are a feature of some Chinese and Indian designs and concepts, but for the most part they are associated with German designs. Germany's Type 212, 214 and 218 U-boats are all good examples, along with Spain's S-80s. What makes AIP-equipped conventional submarines different from purely diesel-electric boats is generally that they have better sustained underwater performance, and that they can be very, very quiet when doing so.

A Type 212 for example reportedly can stay submerged for about 3 weeks. For the older Swedish Gotland class, the reported number is 14 days at about 5 knots. Which gives you a sort of hybrid capability between conventional diesel-electrics and the months that some nuclear designs can manage. The key point here is that because of the diversity of missions and roles submarines are meant to fill, coupled with the implications of picking one type of propulsion system or the other, submarines as a family of platforms are one of the most diverse out there. To give a bit of sense of perspective here, the largest aircraft carriers humanity has ever produced, the American Ford class, displace about 2.5 times a relatively small fleet carrier like the French Charles de Gaulle.

Meanwhile, the largest ballistic missile submarines ever fielded, the Soviet Type 941, NATO reporting name Typhoon, displaced about 30 times as much as a Swedish Gotland-class attack submarine. So if you're looking to fit submarines into some very broad unscientific categories, there are your nuclear attack subs, the blue water predators, like the US Virginia or the UK's Astute. Here you'd expect to see displacements in the high 4-digit or low 5-digit range, crews around 100 or more, and underwater endurance measured in months.

And they are generally intended to be able to go out and project naval power over very long distances. At the other end of the spectrum you might have much smaller, conventionally-powered attack submarines. Compared to nuke boats, these are going to be much more comfortable operating over relatively short distances. Note I say "relatively short", as these submarines will often have ranges in the many thousands of kilometres, especially if they're able to snorkel or occasionally travel on the surface.

But displacement-wise, if your SSNs are your orcas, these are more like your dolphins. Systems like these might genuinely be an order of magnitude cheaper than the SSNs we just looked at, and often you'll be looking at much smaller crews. The Type 212 has fewer than 30 people on board.

The SSBNs then tend to be the largest boats out there, with an American Ohio for example being 10 times the displacement of that Type 212 we just looked at. So if this were a game where the larger submarine could simply eat the smaller one, it would be no contest. In reality it all comes down to mission and context. But if you are not going to judge a submarine based on its raw size and expense, what metrics might you look at instead? What are some of the indicators that might differentiate a good submarine from a bad one? The first metric that absolutely matters is stealth. And for a submarine first and foremost that means being very, very quiet. Everything from the hull form to the materials, to the propeller and propulsion system, to the nature of the reactor, the piping, the pumps etc.

All this goes into determining just how stealthy and hard to detect a submarine is going to be. And no matter what the mission of the submarine, this is going to matter because if you can be found you can potentially be killed. As far as we can tell, there's a fairly wide gulf right now in detectability between the submarines of the various major powers. I've seen translations of Chinese sources that describe the stealth of the American Seawolf and Virginia class in somewhat awed terms. Russian submarines aren't that far behind reportedly, with US sources describing the improved Akula II class as being about as quiet (or slightly quieter) than an improved Los Angeles-class submarine.

And for the moment the majority of the Chinese fleet lags behind somewhat. With the US Office of Naval Intelligence for example assessing that China's Jin-class SSBN, a type which first entered service in 2007 and which currently makes up a majority of China's boomer fleet, are actually easier to detect than the old Soviet Delta IIIs. The first of which entered service in September 1978. If quietening and stealth features enable a submarine to not be seen, the power and quality of its sensors determine its ability to see and if necessary to shoot. This is potentially the most significant for attack submarines that have to locate hard-to-find stealthy targets, namely other submarines.

Next would be performance factors like your speed, range and maximum depth. Here obviously there's a pretty clear cause and effect relationship from the decision you made around propulsion earlier. In terms of factors like range and sustained underwater speed, there really is no comparison between conventional and nuclear-powered boats. Half-jokingly, when fully submerged, conventional boats measure how far they can crawl. Meanwhile the nuke boats are trying to figure out how many times they could circumnavigate the globe before the cooks have to start getting a bit creative in the galley.

Even within those two propulsion sets though you can see massive variations. Some Soviet SSNs for example were much louder than their American equivalents, but their on-paper top speeds were sometimes considerably higher. So even if you could hear them, you might not be able to catch them. Provided you optimise your design sufficiently, have some very talented designers, and potentially lock all the accounts in the basement until you are done, you can obtain some pretty insane performance characteristics. During the Cold War for example the Soviets built a number of submarines not out of steel, but out of titanium. And while the Soviet military industrial complex certainly wasn't great at everything, it was good generally at material science, nuclear propulsion, and throwing away budget limitations.

Giving us these two extreme examples here. On the bottom right there you have the Soviet submarine K-222, NATO reporting name Papa class. This was the world's first all-titanium boat, entering service in 1970.

And its combination of two nuclear reactors with a lightweight high-strength hull enabled an insane underwater maximum speed reportedly of 44 knots, 81 kilometres an hour, or 51 miles an hour. Now the Soviets didn't really regard the boat as successful. It was very noisy and very expensive. But when it entered service it was so fast that if NATO fired a torpedo at it, it could probably outrun it.

Remembering that this was an era before the likes of the Mark 48 ADCAP or the British Spearfish. The Soviets would then field a succession of more reasonable attack submarine designs until we got K-278 in the early 1980s. Pictured on the top right there and with the NATO reporting name Mike class, this wasn't as fast as the Papa.

Instead its claim to fame with a double titanium hull was its design operating depth. The official test depth for a US Virginia-class submarine (so probably a hilarious underestimate) is 240 metres. The relevant depth figures for the Mike, whether you are talking about what's perfectly safe or the nominal crush depth, is somewhere between 1 and 1.5 kilometres.

What that meant was that hypothetically, as long as the ocean was deep enough to actually dive that deep, the Mike class may not have been able to outrun NATO torpedoes, but it could hypothetically dive beyond their maximum operating depth. Hypothetically the submarine could dive to a depth where the US Navy couldn't torpedo it from the surface. And it couldn't torpedo them in turn. Leaving the submarine with few offensive options other than perhaps blasting the Soviet anthem on repeat. I bring this up to build up to a point we'll come back to in a moment, which is that when it comes to submarines extremes are very much possible. Finally, you have the question of lethality and your on-board weapon load. This can have a major impact not just on the nature of the submarine's mission, but also the nature of the submarine's design.

Torpedo tubes, torpedo storage, conventional and nuclear missile tubes, all of these take up space. And so there can be feedback between the sacrifices you are willing or not willing to make here and all of your other design decisions. For example, the Virginia payload module is a missile module the US added to later versions of the Virginia-class nuclear attack submarine that gave the boats the ability to carry an extra 28 Tomahawk cruise missiles. There are entire submarines currently in service that displace less and cost less than that module. The kicker here though is that when you start to add those various capabilities together, they can begin to compound.

A platform that is stealthy is valuable, one that is heavily armed might be valuable, one that can move quickly and over long distances might be valuable. But when you start combining those capabilities into a single platform, you can arguably get something that is so hilariously overpowered that it's about as balanced as a machine gun in a boxing match. A top-tier nuclear attack submarine might represent a multi-billion dollar investment. But tactically it represents a tremendous challenge in terms of detecting and killing the thing.

And at the operational or even strategic level, its mere existence might impose some serious dilemmas for your opponent. To illustrate, let's consider an example for a moment. The age-old foes of Emutopia and Kiwiland are at it again.

Emutopia is the much larger more powerful nation, but its previous attempts to forcefully establish its hegemony over its smaller neighbour have so far fallen flat. The latest plan however, rather than invade Kiwiland directly is to spend hundreds of billions of dollarydoos building up a mighty surface warfare fleet that can instead blockade the Kiwi islands, cutting off its maritime lines of communication and trade. The only complication in this scenario is as well as some pretty impressive anti-ship missile batteries for their coastline, the Kiwis have also commissioned three nuclear attack submarines. Three is a magic number, because it means you can pretty much be guaranteed that one submarine will be on patrol at all times, and during a wartime emergency you are probably going to see two. Now Emutopia probably has anti-submarine warfare aircraft and ships.

And maybe 2 billion dollarydoos worth of ASW units can probably deal with 8 billion dollarydoos worth of submarine. The challenge is where do you put those ASW assets? As soon as one of those submarines leaves its port and submerges, the level of uncertainty starts to grow. After a day or two it could be anywhere in an expanding circle hundreds of kilometres wide. Give it a week or two and you have to assume it might be effectively anywhere.

The problem the Emus now have is they have to defend far too much. Every warship trying to enforce the blockade now has to have anti-submarine protection, otherwise the submarine might just go and sink them. And some consideration may even have to be given to protecting installations or supply lines to Emutopia itself, just in case the Kiwis decide to go cause some long-range havoc of their own. The combination of speed, stealth and range turns the entire situation into a sort of absurd shell game, where the entire ocean makes up the shell field. The situation can get even worse if you start factoring multiple submarines or different degrees of transparency into the equation. If you assume that both sides have access to satellites and intelligence that allow them to track each other's surface warships, then if there are any juicy task forces out there that don't have proper ASW protection the Kiwis might know about it and send their submarine after it.

And if they manage to sortie two submarines out at the same time rather than one, then perhaps having a single anti-submarine warfare frigate isn't going to be enough anymore. Maybe now every unit out there needs the protection of multiple ASW assets in case the Kiwis decide to attack as the world's first wolf pack made up entirely of aquatic flightless birds. And while, yes, the Emus will probably notice once some of their ships start getting sunk, trying to just rush other ships to the site of the attack may not be enough as the speed of those nuclear submarines potentially allows them to rapidly displace back into the vastness of the wider ocean.

Now, yes, this is a highly idealised, simplified scenario where among other things, the Emutopians don't have any SSNs of their own. But my point here is to demonstrate how even a relatively small submarine force might be able to impose an asymmetric threat on an opponent. And why we have more than a handful of publicly released wargame or military exercise results showing submarines having out-sized impacts.

In 2020 for example, the CSIS held a series of wargames modelling an escalation in the Taiwan Strait. Those games did make some potentially divisive assumptions (as many wargames do) including, among other things, giving the US Navy an effectively infinite supply of torpedoes. And making some potentially contentious decisions around modelled missile-defence success rates. And the ability of submarines to operate in very shallow waters like the Taiwan Strait.

But debate on assumptions aside, those war games showed US submarines going on an absolute rampage. With the average US submarine being modelled as sinking two large amphibious warfare ships plus two decoys or escorts every 3.5 days. In exchange for a roughly 20% chance of being sunk while doing so. It's also worth noting that a number of NATO countries can claim that one or more of their submarines have successfully sunk even heavily defended targets like aircraft carriers during allied exercises. And while stories like this one probably don't tell us too much unless you understand the full context that led to them, it's still worth noting that, in the words of one former naval officer, "Photographing aircraft carriers is a submarine pastime."

But while submarines might be potentially very valuable assets for national navies, the deep defence economics challenges involved in their design and production means that there's only a few nations out there that can claim to really produce top-tier products. Especially when you are talking about the nuke boats. Keeping submarines quiet is an immense and compounding technological challenge, with vast differences between different builders. Even something as seemingly simple as getting the design, construction, and maintenance of your screw correct can make a massive difference. And not every nation's ship builders are operating at the same level here.

Although the difference probably isn't what it used to be. Designing submarine propulsion systems is also something countries can't exactly just pick up overnight. A relatively small number of firms still dominate the market for modern air-independent propulsion systems for example. And while Russia is generally regarded as a very advanced submarine power, the country doesn't have any SSKs in service yet with AIP systems.

When it comes to submarine propulsion, and especially nuclear submarine propulsion, countries tend to very closely guard their secrets. Even to the point where photos of submarine nuclear reactor rooms, while they do exist, aren't exactly a dime a dozen on the internet. Fortunately for us, the 1990s weren't exactly a time of stringent security standards in the Russian Navy, so I can include this image (reportedly from 1998) of a crew posing over the top of a nuclear reactor. Personally, I can't decide if it's the moustaches or the sunglasses worn inside a submarine that really makes the shot what it is.

But jokes and questionable safety practices aside, I think this photo does bring home one thing, namely just how compact the Soviets were able to get their nuclear submarine propulsion systems. For many countries even now decades on, simply replicating where the Soviets and Americans were up to in the 1980s would require building up an entire nuclear defence industrial ecosystem. Although countries with an existing civilian nuclear sector might find that transition somewhat easier. But then even if you can bring all the technological pieces together, there is still the matter of having the shipyards and the workforces capable of building these things.

Such are the demands involved, that even relatively wealthy countries often won't have that many shipyards capable of producing submarines. And those they do have may tend to specialise over time. The US is generally assessed to be the leader in the field with the largest force of nuclear-powered submarines and some of the most advanced designs. The country's nuclear submarine producers however are currently in the process of recapitalisation. And currently a number of nuclear submarine construction projects are significantly behind schedule and below the levels the US Navy is ultimately going to need if it is going to hit its future force targets.

Despite the disruption caused by the 1990s, the Russians still have the largest and most advanced nuclear submarine force outside NATO. They have active production facilities capable of producing SSNs, SSBNs and SSGNs. And a number of NATO sources assess their most recent designs as being extremely challenging for allied nations to track. The French and British maintain active nuclear submarine production capacity. And while neither operate at the same scale as for example the Americans in terms of industrial capacity, the French have one of the most recent SSN designs currently on the market and are commissioning them at a decent rate. The People's Republic of China is actively producing nuclear submarines, but are still in a process of scaling up compared to some of the other powers.

A lot of the nuclear submarines it does have in service are of slightly older designs with less impressive performance characteristics. But there's evidence that construction capacity is scaling significantly. And the coming generation of Chinese nuclear submarines are expected to be a significant leap over what we've seen before. Finally, India is the country that most recently joined the nuclear submarine builders club. At the moment that's limited to indigenously-built SSBNs, but who knows what the future might hold? The conventional submarine builders market by contrast is a little more crowded. Russia and France, as well as being major nuclear submarine producers, are also major conventional submarine exporters.

And there they are joined by a number of countries including notably Germany, who continue to be masters of U-boat construction. Although hopefully this time for the purpose of making export dollars, rather than a third attempt to blockade the British Isles. Sweden, Japan, Italy, Spain, Iran and both Koreas are all other countries that should be mentioned here, and even then it is not exactly an exhaustive list. But the important point here is that for each of these countries the ability to produce submarines represents a significant industrial investment. Something that requires years of combined infrastructure and workforce investments in order to build up.

From infrastructure and design, through building and commissioning, submarines are incredibly long lead-time items. And once they are in service, most countries tend to keep them in service usually for several decades. And that's why, unlike a system that can be relatively quickly replaced (think for example a primary small arm) submarine investments and developments now have to be extremely mindful of what the future value of the platform might be.

And in that respect you can find some long-range predictions out there that might be worrisome for major submarine builders. Back in 2020 a group of researchers, primarily at the Australian National University, undertook a first principles assessment looking at the future of detection and counter-detection technology. They looked at broad areas of science and technology development which might affect detection, things like artificial intelligence, sensor technology and underwater communications, fused all of those predictions together using a software tool called Intelfuse, which some of you might be familiar with, and used it to spit out a probabilistic assessment. To quote the authors, "Our key result was that the oceans are in most circumstances at least likely (probability 75%) and from some perspectives very likely (probability 90%) to become transparent by the 2050s. Our certainty of these estimates, which the software evaluated independently, was high, above 70%. This suggests that regardless of progress in stealth technologies, submarines (including nuclear powered submarines) will be able to be detected in the world's ocean as a result of progress in science and technology."

That was only one assessment by one group of researchers, but it suggested the most probable outcome was that by the middle of the century the tide of technology might turn against submarine stealth. And if you in the 2020s, are investing in submarine programs that you hope to leverage out until the 2080s, hearing that the jig might potentially be up by 2050 could be a little bit worrying. So with that understanding in place, let's dig a little deeper into potential future sources of submarine vulnerability. And before we go through some of the technologies that countries might be leaning on to do so, I want to start with a bit of a caveat.

We are not just talking about predicting the future in general here, we are talking about predicting the future of technological development out till 2040 or 2050. That's a pretty difficult, contentious and imprecise exercise. So this is an area where you can find experts and reports running the entire spectrum.

From reports like this one that say, yes, it's probable the world's oceans will be substantially transparent by the year 2050, and on the other end those who argue the entire threat is a bit overblown and that submarines aren't just the weapons of the past, they are also the system of choice for the future. And so while I'm about to track through some of the potentially relevant technological developments, be aware there's a huge amount of uncertainty over how quickly this stuff will improve, how good it will get, and indeed in some cases, whether it'll work at all. Caveats in place, let's talk about some ways anti-submarine threats might get that bit more dangerous. Firstly, with the development of unmanned platforms it might become cheaper and more practical for countries to just put a lot more sensor platforms out there. At present, as we discussed, there are a couple of elements that tend to work in the submarine's favour.

It's a massive ocean out there that's very hard to cover. And that while submarines might often be big expensive monsters, often the only way to hunt them is with a big expensive monster of some kind or other of your own. Anti-submarine warfare ships are expensive, anti-submarine aircraft are expensive, and of course submarines to hunt other submarines are likewise expensive.

But if you start introducing unmanned systems to support your manned ones, you might be able to cover a lot more ground for relatively little additional investment. The US has already reportedly tested anti-submarine equipment on a surface drone and plans to integrate it into the MDUSV program, the Medium Displacement Unmanned Surface Vehicle. According to one report, which I will link in the description, these MDUSVs have already demonstrated "Autonomous SSK detection and tracking from the ocean surface from 3.2 km away."

And as that report notes, given that SSKs using air-independent propulsion or running on batteries are virtually silent, hunting nuclear submarines should be possible at greater distances, all else being equal. It's also been reported that, at least under favourable conditions, the Chinese estimate that ASW detection from a drone platform might be possible out to 18 kilometres. Now that might not sound particularly impressive given that in all cases those detection ranges are significantly shorter than the maximum range of torpedoes carried by modern submarines. But the two obvious notes here are that 1) that's the detection technology as it exists today. And 2) even if these things may not be able to see particularly far, there may be an awful lot of them. Having potentially increased the number of things out there that can detect a submarine, countries are also looking for ways to change how they detect them.

Historically, as we said earlier, acoustic detection has been the primary name of the game. But there are a variety of other detection methods that have been theorised, tested or even fielded. In the interest of time I'm going to skip over some of the more theoretical ideas, like trying to track submarines' nuclear reactors, and instead focus on two primary areas of development: magnetic detection and LiDAR. Magnetic detection exploits the fact that no matter how quiet a submarine is, it is still a pressurised metal tube somewhere a pressurised metal tube should not be. While very small in the grand scheme of things, any submarine-sized blob of ferro-magnetic material is going to create at least some tiny variation in the earth's magnetic field. That variation can then be detected by a specific sort of magnetometer called a Magnetic Anomaly Detector, or MAD.

MADs are already a part of established military arsenals. And if you look at the image of the ASW aircraft on the right there, that pointy tail section at the back is the MAD. Even if you silence a submarine to the point where the crew aren't allowed to breathe and hearts aren't allowed to beat, a MAD will still detect it. The problem is that current MADs have incredibly short ranges.

Aircraft-based detectors are really only useful, for example, if the aircraft can fly very low pretty much directly over a submarine's position. We are talking ranges measured in the hundreds of metres, or maybe low single-digit kilometres. If you already basically suspect where a submarine is, a MAD might allow you to get a fix and potentially engage it. But otherwise it can be a bit like trying to find a needle in a haystack using nothing but a microscope.

This potentially is where the SQUIDs come in. SQUIDs are Superconducting Quantum Interference Devices. They are an extremely sensitive type of magnetometer that might offer increased submarine detection ranges.

As one report put it, MAD-type magnetometers might detect a submarine's ferro-magnetic hull at a range of several hundred metres. A SQUID might be able to do it an order of magnitude further away. It's worth noting that in 2017 there was reportedly an announcement by the Chinese Academy of Sciences (later taken down) saying that a Chinese team had produced a SQUID with potential ASW applications. One expert theorised that an array of the sort of systems described might have a detection range of 6 kilometres or further.

Historically, SQUIDs have often been limited by "Their over-sensitivity to background noise and their need for super-cooling." And as we all know, battlefield conditions are famous for providing perfectly quiet environments that are super-forgiving of extremely fragile equipment. But with some additional development, countries might see potential here for a slightly less short-range detection option. For a country that wants to detect at a slightly longer distance however, lasers might be an attractive option. Conceptually you can think of Laser Imaging Detection and Ranging (or LiDAR) as kind of like a bat's echo-location system, only instead of using sound you are using light pulses. You shine a laser at something, measure the time for that light to reflect back and use that to create a 3D image of the surface in question.

This is not exactly new technology, and it's been used to map the earth's surface or shallow areas for ages. So the idea might go, "How about we just grab some of these sensors and put them on an aircraft (or even potentially a satellite) point it at the ocean, map the surface, and find out if among all those interesting rock formations we can find something that looks just a bit like a submarine." It's also been noted that, hypothetically, you might choose to fit LiDAR sensors to submarines themselves.

That could massively increase the ability of submarines to detect one another at certain ranges and under certain conditions. Although it would probably ruin those scenes that are an absolute stalwart of a whole bunch of submarine films where two opposing submarines are within knife fight distance of each other but don't know it, and are desperately listening for one another, building dramatic tension, because they can't exactly just look out a window. With LiDAR sensors, hypothetically, you kind of could. And for a variety of reasons, not just anti-submarine warfare usage, the technology has been evolving rapidly in recent years. We've seen the development of LiDAR systems that all else being equal will work better deeper because they rely on wavelengths that are less susceptible to being absorbed by seawater.

Sensors have also got considerably smaller and adjusted for inflation also are cheaper. There have been reports out of China of systems being tested that can penetrate 200 metres of water when mounted on an aircraft. And while it's not an anti-submarine warfare role, systems like this are actually already in service. What you are looking at on the right there, specifically the pod being carried by that helicopter, is the Airborne Laser Mine Detection System.

As the helicopter flies, that pod scans the ocean underneath it with a blue-green laser to try and identify sea mines. And while it may not operate to the depth you'd want for a dedicated ASW solution, mines tend to be a lot smaller than submarines. The challenges here from an ASW perspective are getting it to work at a sufficient depth with sufficient accuracy and sufficient reliability. The US also already has space lasers specifically for surface mapping.

NASA's ICESat-2 has been operating for a number of years at this point, cost about $1.1 billion to get going, and using its so-called Advanced Topographic Laser Altimeter System, or ATLAS, is capable of detecting land ice elevation with sub 2.5 cm accuracy. From a detection standpoint that's very exciting as a space-based system. But it's also obviously very expensive, and a long, long, long way from being suitable for an ASW mission. So again, as with magnetic detection, not a perfect technology, not a fully developed technology, but for submarines a potentially dangerous technology.

It also seems likely that even as new detection methods are developed and fielded, older styles of detection will iterate and improve. Modern acoustic sensors have got better and are likely to continue doing so. Back in 2020 for example, it was reported that a passive American underwater 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 vehicles over an area spanning roughly 200 kilometres in diameter." So 30,000 square kilometres.

Now there is obviously a massive difference between finding a singing whale and a submarine that is trying to hide. Most of the time submarines won't exactly be belting out the tunes for all to hear, although there was that one time involving HMAS Rankin, but we try and let the Americans forget about that one. That said, for a passive search area, a 200 kilometre diameter isn't nothing. The more aggressive active version of the system could reportedly localise man-made objects as short as 10 metres long over areas 100 kilometres in diameter, about 8,000 square kilometres. The system could also reportedly use multi-frequency measurements to help it distinguish between fish and seafloor clutter and man-made targets. So ideally it would be an opposing submarine getting torpedo, not Nemo and his mates.

Notably, most submarines tend to be more than 10 metres in length. At the same time, most 10 metre long man-made objects aren't designed to mitigate detection the same way a submarine hull is. But the key point here is that it's not just that new types of sensors are being developed. Magnetic, laser and acoustic detection are all fairly old concepts at this point, as are some other relevant options like synthetic aperture radar. But what is changing and is likely to continue changing, is that the resolution of those sensors and the data transmission and processing capabilities that support them are all improving.

One way to think about this is that you need sensors which are capable enough to find whatever it is you are trying to detect, but then you also need to be able to transmit that data to where it needs to be, and then the ability to process it into useful information. If you were a sonar operator in World War Two it was your job to look at a screen like this and try and determine what it meant. If you wanted to tell another ship in your force what you saw so that you could share notes so to speak, you'd have to get them up on the radio and tell them. But in the 21st century it is increasingly possible to have different sensors and different platforms talk to each other to share their data picture. And then potentially take that confusing mass of data, hand it to a machine, and ask it to essentially play Where's Wally with all the clues and fragments you can feed it. If you want an example of what might be possible with sufficiently accurate sensors and the ability to process data that would be utterly meaningless to a human operator without assistance, consider the concept of trying to detect a submarine based on its interactions with the environment.

Even a submerged submarine might create very subtle evidence of its passing on the surface. Subtle signs that synthetic aperture radar might be able to see, and that a sufficiently advanced computer system would then be able to identify as evidence of a submarine's passing. But note here that when I say subtle, I mean very, very subtle.

According to one source I found, even when you had a relatively large, relatively old submarine, a higher-class SSBN, moving at a relatively high speed of almost 20 knots at a relatively shallow depth of only 100 metres, the resulting elevation on the water surface would only be 1.6 centimetres. Come up with a slightly less generous scenario and suddenly you need synthetic aperture radars on aircraft or satellites to be able to detect abnormal projections on the surface that are measured in millimetres. I know that probably sounds like the sort of thing that would be very advanced top secret technology, so here's a public US defence offer from 2019 asking companies to come forward to help develop one.

This solicitation describes its goal as designing and developing a non-traditional airborne anti-submarine warfare system capable of detecting modern quiet submarine targets from high altitude aircraft. The goal was to do so using a non-disposable system that could fit on the P-8 Poseidon anti-submarine warfare aircraft, be capable of functioning at altitudes greater than 3,000 feet, preferably leverage existing equipment, and would do that by detecting targets through, "Exploitation of novel target/environment interactions." So as sci-fi as it sounds, the development efforts are probably there. And what I'm trying to get at here is that the future threat picture for submarines may not be the product of just one new sensor type or one new sensor platform, it might be a product of various technologies compounding together and then being enabled by sensor fusion. This is why if you go and look at the detail of that report I mentioned earlier that suggested that by 2050 the oceans would probably be transparent, you'll find that they base that assessment not on the development of a single technology, but a range of different developments coming together. These included improvements in battery technology, computer science, underwater communications etc. to the point where it would be practical to develop

what the report described as a "dense adaptive sensing mesh." A sensory network if you will, at least partially made up of unmanned systems. Maybe next generation LiDAR and acoustic systems alone aren't enough to detect submarines.

But if you can massively increase the number and type of sensors that you have out there, have the transmission capacity to bring all that data together, and the processing power to make sense of it, then just like the fusion engine on something like the F-35 can piece together different inputs and clues from different sensor systems and platforms in order to produce a high confidence track, then maybe the submarines give away just enough clues that by basically doing the digital equivalent of that conspiracy guy at the pinboard thing, a sufficiently advanced ASW system can start stripping away stealth from opposing submarines. Were that to happen, with oceans becoming fully transparent and submarines not that much harder to find than surface warships, then the impact on the balance of power at sea but also global strategic stability, might be pretty extreme. Countries which had invested heavily in their submarines and submarine industrial bases might find those investments devalued. But perhaps more importantly, countries that currently rely on sea-based missiles for their survivable second-strike capability might find that no longer so survivable.

In a world where ballistic missile submarines are out there and very difficult to hunt, a nuclear first strike against another nuclear power just doesn't make sense. You could probably never be confident that you do enough damage to your opponent's nuclear forces with a bolt-from-the-blue nuclear attack to reliably avoid the prospect of one of those submarines surviving, coming up to launch depth, and making the entire exercise very much not worth it. Because nuclear first strikes conceptually don't work against a country with a survivable second strike, countries have less reason to fear being hit by one. That means less of an impetus to be on hair-trigger nuclear alert, or to launch every time you see something that looks like it might be an opposing nuclear launch. In a strategic sense you can afford to take a moment, assess the situation, knowing that if you do decide to glass your opponent's country that capability will still be there no matter what happens.

And so ironically, arguably the immense, almost obscene, destructive power of ballistic missile submarines makes nuclear war less likely and encourages strategic stability. This is why India is spending so many resources to get SSBNs fielded. It's why the United Kingdom seems content to build basically its entire nuclear deterrent around the submarine force. And it's why across the board investment in next generation boomers is happening on a prodigious scale.

But if all of that survivability advantage, a

2024-05-22 08:08

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