New designs, new technologies and new weapons are shaping the submarines of the future, which are being manufactured right now, in response to global demand for more potent and flexible designs.
Old Cold War fleets are being replaced and conventional subs – smaller but still useful – that can remain underwater for weeks are being built.
Non-nuclear submarines use combustion engines that need oxygen to work. These are fine on the surface but, submerged, they must rely on battery power to operate. Depending on the battery type, submarines cannot submerge for long and need to resurface to recharge their batteries, putting them in a vulnerable position and open to detection by the enemy.
Air Independent Propulsion (AIP) is a technology which solves that problem and allows a submarine to remain submerged and relatively safe for extended periods – weeks instead of days.
First invented in Sweden in the 1990s, AIP is now used in most non-nuclear submarines by 20 navies.
Only a few countries can afford to run nuclear-powered submarines. Extremely expensive to produce, the reactors of these submarines allow them to stay submerged almost indefinitely.
They can desalinate water for the crew to drink and produce oxygen from seawater for the crew to breathe. Their range is virtually unlimited, allowing them to travel anywhere in the world’s oceans, loaded with their apocalyptic cargo of nuclear missiles. They remain hidden, a guarantee that if an enemy were to strike the home country in a surprise attack, the sub would be able to deliver a retaliatory blow, a nuclear second strike.
With that in mind, attack subs also prowl the oceans, acting as a line of defence. Fast and sleek, they are designed to sink other subs, especially high-value enemy missile submarines. This endless, deadly game of cat and mouse is played out daily under the surface of the world’s oceans as each side hones the skills needed to destroy the other in the event of war.
Submarines have unique features that make them deadly, the chief one being their stealth. Able to travel undetected underwater, they can strike without warning, the most powerful among them containing missile arsenals that could single-handedly destroy a continent.
The quieter a sub, the stealthier it is. Sound is everything under the sea and billions have been invested into acoustic properties that will muffle a submarine’s engine, as well as in better hull designs which allow water to flow more quietly over the sub’s surface. These hulls are made of materials designed to absorb sonar waves – a sonic version of underwater radar – rather than reflect them back, making them more readily detectable.
Such technological advances allow subs to remain undetected but constant developments in anti-submarine technology are keeping pace – with new, improved ways to detect submarines, making them vulnerable to destruction.
I can hear you
It is getting harder and harder to hide under the ocean. Underwater sensors can now pick up a submarine’s acoustic trail with greater ease. These sensors can be released from helicopters or planes over an area where a sub is suspected of lurking. The sensors pick up the sub’s sound profile and send the information back to the waiting aircraft. Torpedoes are then dropped into the sea with the intention of homing in on the submarine – now stripped of the one thing keeping it safe – and destroying it.
Anti-submarine warfare is as old as submarines themselves, with designers continually inventing new ways to destroy these potent weapons. Sensors are not just dropped from aircraft; surface ships are also equipped with ever more powerful and sensitive sonar suites that can pick the minute sounds that subs, despite their best efforts, end up making. Some countries have strung whole chains of sensors together across likely approach ways.
During the Cold War, for instance, the United States installed one called SOSUS, or Sound Surveillance System, across what is known as the GIUK gap; the area of the Atlantic Ocean between Greenland, Iceland and the United Kingdom. This was and still is the likely approach route for Russian submarines heading from their bases in the Kola Peninsula near Murmansk into the North Atlantic. This impressive system, covering hundreds of kilometres, was able to detect even the best Soviet submarines at the time, providing the US with vital information about their location and direction of travel. The SOSUS nets were extremely effective during the Cold War at picking up submarines moving in and out of the Atlantic.
Russia still uses this route. Last year, it sent 10 submarines through this gap which, while 1,500km wide, is still considered a choke point for naval vessels. In one of the biggest Russian deployments since the end of the Cold War, the exercise was designed to test whether they could be detected by NATO. The resulting detection by Western navies showed Russia that they were still vulnerable to potential destruction.
Russia has spent billions upgrading its antiquated fleet with new designs that make already quiet submarines even quieter. The new Borei-class subs are faster, more manoeuvrable, with their new pump jet propulsor systems which have replaced traditional propellers, making them even quieter. There are now better missiles which carry multiple warheads, with greater ranges, allowing the subs to hit targets thousands of kilometres away. The Russian Navy plans to build 12 of them, with half going to the Northern Fleet and the other half to the Pacific.
The developments do not stop there. A new class of Russian submarine, the Khabarovsk, will be fitted to carry the giant superfast autonomous nuclear torpedo, Poseidon, in effect an underwater nuclear-powered drone, capable of speeds of up to 180km/h (112mph) and armed with a huge, multi-megaton nuclear warhead. The torpedo’s range is virtually unlimited and is designed to destroy ports, coastal cities and large fleet concentrations.
Russia is not the only country upgrading its submarines. France, the UK and the US are all developing and building the next class of missile and attack sub. They can dive deeper to avoid detection and advances in engine design mean they are even quieter and therefore stealthier than previous generations. Many of these designs have already been fielded, while others are near completion.
China and India are also working on their own improved nuclear sub designs in an effort to dominate their own seas and keep up with regional competitors. There can be setbacks. India’s first nuclear-powered missile sub, the INS Arihant, was damaged when a hatch was left open, allowing water to partially flood the sub. The design has since been finalised and a second missile sub, or SSBN, INS Arighat is undergoing trials.
It is not all about nuclear propulsion. Improvements in Air Independent Propulsion (AIP) now allow non-nuclear submarines some of the advantages of their nuclear cousins.
Able to stay submerged for weeks at a time, these cheaper submarines give middle-ranking naval powers an affordable way to enhance their naval firepower, while also using their stealthy abilities to gather intelligence and land special forces teams ashore, their mission flexibility giving their commanders more options.
Unmanned Underwater Vehicles (UUVs), are also starting to make their presence felt. These robot subs can gather intelligence, lay mines and sweep the seas around them for enemy vessels. The US navy is planning a whole range of them, such as Boeing’s Orca, with other navies following suit. Able to operate autonomously, they can stay at sea for months at a time, sending valuable data back to their headquarters while remaining hidden. At least that is the idea. No country has publicly claimed a robotic submersible that was found a few years ago by a Chinese fishing vessel in the South China Sea. It was capable of satellite communications and recording images, and was suspected by the Chinese authorities of being used to spy on Chinese naval activity in the area.
China itself is developing its own fleet of unmanned AI-controlled submarines that, once completed, will be capable of a wide variety of missions. Without having to worry about keeping a human crew safe, these robot subs can be smaller, stay at sea almost indefinitely and operate at greater depths as they can be built differently to withstand the incredible pressures of the very deep sea.
Even minor nuclear power North Korea is researching how to turn small, yet quiet diesel-electric subs into missile carriers for its fledgeling nuclear weapons arsenal. Pyongyang is keen to develop its own invulnerable second strike retaliatory capability, ensuring the survival of the country.
The advantages of staying undetected are not lost on crime syndicates and a new class of drug-smuggling submarine, or “narco-sub”, is being discovered by the Peruvian and Colombian authorities.
Often built on the banks of remote jungle rivers in South America, narco-subs have increased in size and sophistication allowing larger and larger payloads of drugs to be smuggled undetected.
Initially towed underwater by a surface vessel, they now have their own propulsion systems and can travel further and further, smuggling tonnes of drugs at a time up the coast and also, on occasion, rendezvous with merchant vessels far out to sea, transferring their cargo away from prying eyes. These are not true submarines in the sense that they can dive deep underwater as they stay just below the surface, avoiding the attention of coastguard vessels and naval patrols.
For submarines generally, the future is looking increasingly automated. Submarines will be able to do more with smaller crews or, in many cases, no crews at all.
As detection technology develops, so, too, will the stealthy abilities of subs as opposing navies try to outwit each other. These silent killers are able to watch and report on enemy activity and, in some cases, destroy their targets without anyone detecting their presence.
With enhanced weapons like hypersonic missiles being developed, submarines are growing deadlier with each new generation. While major powers are sticking with nuclear propulsion, other countries are investing in cheaper, yet capable alternatives.
New advances in fuel cells mean that these new, non-nuclear subs can stay underwater for weeks if not months. Developments in sensor technology and design allow them to run with far smaller crews while still increasing the range of missions they can undertake. In short, subs are here to stay and underwater warfare is about to enter a new and important phase.