Underwater Predators

Submarine and anti-submarine warfare remain areas of concern; needs prioritisation

Cmde Anil Jai SinghCmde Anil Jai Singh (retd)

There is perhaps no other military platform that has had as profound an impact on maritime warfare in the last century as the submarine. From the time the Holland 1, the precursor to the modern submarine as we know it today, was commissioned into the Royal Navy in 1901 and ushered in a ‘Revolution in Military Affairs,’ submarines have played  a pivotal role in influencing the maritime history of the 20th century and will continue shaping  the maritime contours of the 21st century.

The effectiveness of submarines in disrupting global trade and commerce and inflicting devastating damage on surface shipping in World War I led to a paradigm shift in the concept of naval operations as this hitherto unknown element had to be factored into naval strategy and future force structuring. A little over two decades later, in World War II, it was again submarines which dealt the decisive blows that influenced the outcome of the war. In the first half (1939-42) it was the German U-boats in the Atlantic which would perhaps have won the war for Germany had the US not entered and in the second half (1943-45) it was the US submarines that humbled the mighty Imperial Japanese Navy in the Pacific theatre and  hastened the end of the war.

The Cold War that followed further highlighted the importance of submarines. Nuclear submarines of the two main protagonists operating in the depths of the Atlantic with enough firepower to annihilate the world several times over ensured that the Cold war remained ‘cold’ for over four decades. In the period immediately following the Cold war, as the world passed through a transitory state of flux, there was a perception that the relevance of submarines may diminish since the threat was perceived to have disappeared; defence budgets were slashed but events  thereafter have proved otherwise and the importance of the submarine as the ultimate deterrent still remains as relevant as ever.

What has changed in the last two decades though, is the shift in the global geopolitical centre of gravity from the depths of the Atlantic to the littorals of the Indo-Pacific.  The changing balance of power equation, the aggressive hegemonistic posture of an emerging regional giant with superpower ambitions and a likely ‘Cold War’ in the Indo-Pacific by the second half of this decade is going to create a host of bilateral and multilateral tensions in the region. This has led to nations in the region realigning their maritime security strategies to cope with this evolving dynamic. While the Big Powers, the US and China are competing for maritime dominance with power projection and sea control-centric force structures and the  larger medium powers like Japan, India, South Korea and Australia are seeking to secure their maritime interest in the region with limited sea-control capable blue water force development, it is the smaller nations, particularly those in South East Asia, the Western Pacific and now increasingly in the Indian Ocean which are adopting sea denial as their underlying strategic option and are, therefore, focussing on their submarine capability to secure their maritime frontiers.

Submarines are the most aspirational platforms for a navy and only those countries with a security imperative necessitating their presence are willing to make the sizeable investment necessary to develop a submarine force. While nuclear powered submarines (SSBNs and SSNs) are presently the preserve of just six nations (the five Permanent members of the Security Council and India), it is conventional submarines (SSKs) which remain the preferred choice of most navies operating in a littoral environment with limited maritime security objectives. Their inherent advantages of lethal firepower, stealth and mobility in restricted and shallow waters enables them to punch far above their weight against heavyweight adversaries. SSKs are ideally suited for a sea denial strategy which is the ability of a navy to deny a larger adversary the use of the sea and is usually the preferred strategy of smaller powers.

Union defence minister Rajnath Singh during commissioning of INS Khanderi in Mumbai

There are presently 15 navies in the Indo-Pacific region operating submarines and at least three more likely to acquire them soon which underscores their importance in the emerging regional security calculus. Of these, the US operates only nuclear submarines; China and India operate nuclear and conventional submarines whereas the rest operate only conventional submarines. An occasional extra regional presence of French and Russian nuclear submarines adds to the mix and further livens up the region.

Diesel electric submarines, or SSKs as they are generically termed, have become increasingly capable over the years. They have benefitted from modern technologies and have, to a large extent overcome their inherent limitation of having to expose their ‘snorkel’ often to recharge their batteries. They are now much better armed with missiles and torpedoes that can be fired from stand-off ranges and they are getting increasingly integrated into a network centric architecture. Various noise damping techniques have made them extremely silent and increasingly lethal. Some of these enhancements are highlighted.

Air Independent Propulsion (AIP)

Sweden was the first country to develop an AIP system. Its Stirling engine AIP was successfully demonstrated in 1989 and has been successfully operating in its Gotland class submarines with reported dived endurance of up to 14 days.  Since then various other technologies have been developed in AIP including fuel cell systems, closed cycle systems etc. AIP is now more or less a standard feature in most modern submarines.

In the Indo-Pacific, Japan and Singapore are using the Stirling AIP, South Korea the German fuel cell system, the Chinese have developed an indigenous fuel cell system and Pakistan is using the French Naval Group designed MESMA system. In fact, Pakistan is the only country in the world using this system. India is yet to adopt AIP technology. The delay in the P75 and P75(I) programmes has led to this serious shortcoming in our submarine capability. Defence Research and Development Organisation (DRDO) is developing an indigenous fuel cell system which, hopefully, will be installed on the Kalvari class (Project 75) submarines in the second half of this decade. Till then, Indian submarines will have to operate with this vulnerability while its two main adversaries have AIP on board their submarines.


Lithium-Ion Batteries

Lead acid batteries have been used to power submarines from the very beginning though these have improved greatly over the years. All SSKs presently are fitted with lead acid batteries. However, lithium-ion (Li-ion) batteries are now being developed which are likely to replace these in the next few years. Japan is the first navy to deploy Li-ion batteries on board an operational submarine and has recently launched a second submarine with this capability.

It is understood that the South Korean Navy has also decided to fit Li-ion batteries on their forthcoming KSS-III Batch 2 submarines. Hanwha Defense, the South Korean battery manufacturer claims that its Li-ion batteries provide 160 per cent more endurance (longer output) at economic speed and 300 per cent more endurance at maximum speed. Li-ion batteries also provide double the amount of charge cycles (up to 4,000 or about 10 years of operational life) compared to lead-acid batteries. Li-ion batteries were so far considered risky for fitment on submarines but once proved safe will be the battery of choice on future designs because of the power advantage they offer over the AIP-lead acid battery combination.

An AIP system provides longer dived endurance only at slow speeds; it enhances stealth but not speed and still needs a large bank of lead-acid batteries. Li-ion batteries, on the other hand, offer greater endurance at high speeds and occupy less space in a submarine. While presently Li-ion batteries may dispense with the need for AIP as the Japanese have chosen to do, future designs may be able to combine the benefits of both and offer a far more versatile operating envelope for SSKs. It is hoped that the Indian Navy will equip its future submarines with Li-ion batteries since the next submarine programme is still in its initial stages of discussion.


Non Hull Penetrating Masts

The conventional periscope with its monocular/binocular sight on board submarines is gradually being replaced with a non-hull penetrating optronic periscope system. The optronic mast is located in the fin of the submarine and instead of a periscope tube and mast, (as is the conventional practice) is connected to the inside of the submarine by an electronic cable. This not only reduces the need for a large hull opening thus enhancing the submarine’s watertight integrity but also liberates space inside the cramped confines of a submarine where the retractable periscope used to be housed when lowered.

The electronic digital camera array provides a wider picture remotely on a console with a large screen thus providing a better appreciation of the surface picture and consequently better situational awareness. Multiple sensors like ESM, communication etc mounted on a single mast also reduces the submarine’s vulnerability to detection. The periscope picture can be integrated with the Combat Management System on board to develop an attack picture and launch weapons.

From an ergonomic perspective, which is a critical feature in submarine design to mitigate crew fatigue, an optronic periscope obviates the requirement of having the Combat Information Centre (CIC) directly below the fin thus providing a designer with more flexibility to optimise the utilisation of the available space.

However, these very obvious advantages notwithstanding, there was initially a resistance to replacing the traditional periscope and in some submarines the traditional attack periscope was retained while the search periscope was replaced with an optronic system. However, in more contemporary designs, the traditional periscope has been totally done away with and optronic periscopes are now in use in most modern submarines. IN submarines too are now using optronic systems on board.


Communications and Networking

Conventional submarine operations have always been constrained by the restriction on transmission for fear of compromising their position. The requirement to expose its communication antenna above water even for reception further risks detection. Hence, SSK deployment is largely in pre-decided patrol areas with restricted flexibility or options for redeployment.

However, with the advent of VLF and now ELF this has changed, as submarines can now receive messages while dived. However, not all navies have yet invested in this and, therefore, continue with the traditional restrictions. However, in the near future this will change. With the improvement in technology and navies developing network-centric architectures, submarines operating in isolation with little or no communication will soon be a thing of the past. Modern submarines are becoming integral to network-centric warfare.

The SSK is a valuable intelligence, surveillance and reconnaissance (ISR) source and its advantages of stealth and concealment can offer enhanced situational awareness in a dense operational environment thus enabling a better operational appreciation and a coherent and effective response to a developing situation. Even in peacetime, the submarine is a valuable asset for enhancing one’s Maritime Domain Awareness (MDA) capability.


Tube Launched Missiles

Submarine launched missiles are generally associated with nuclear powered submarines – ICBMs and IRBMs on the SSBNs and conventional cruise missiles like the Tomahawk on the SSNs. It was only in the Seventies that SSKs began to be armed with anti-ship missiles that could be fired from their torpedo tubes.

The Tube Launched missile (TLM), now a common feature on SSKs, is a powerful force multiplier as it provides the capability to launch a weapon at stand-off ranges and ‘engage’ the enemy without having to close to the weapon and sensor range of the enemy. This greatly mitigates its vulnerability to detection and provides more time and room for the submarine to manoeuvre itself away from a possible counter-attack, thus offsetting its inherent limitation of speed and dived endurance.

The range at which a submarine can fire its weapon was earlier restricted to the detection range of its own sensors. However, in a contemporary networked environment a TLM capable submarine can carry out an attack at far greater ranges in tandem with a satellite, reconnaissance aircraft or even a ship by exchanging real time information of the target. This has enabled an enhancement in the range and lethality of TLMs which now also include a land attack capability. In a limited operational battlespace, this has made submarines a valuable asset to launch attacks from a concealed position at sea on land targets deep inside enemy territory and thereby influencing the outcome of the land battle.

Work is now in progress on developing a tube launched anti-aircraft missile that can attack a helicopter hovering near a submarine. The presence of an ASW helicopter can greatly inhibit a submarine’s tactical manoeuvrability and detection by a helicopter’s dipping sonar can be used to vector a concentrated attack on the submarine. The presence of a dipping sonar in passive detection mode would not be known to a dived submarine. With the improvement in submarine sonar technologies, it is possible to detect and track a hovering helicopter’s rotor wash on the sea surface and home on a missile attack.

The advent of missiles and their obvious advantages in no way detracts from the effectiveness of the Heavyweight Torpedo (HWT) as the SSK’s principal weapon. As mentioned earlier, the missile is a force multiplier but it is the HWT that will deliver the coup de grace to a high value surface target. A single HWT can break a ship in half. HWTs have also become increasingly ‘smart’ with various homing techniques to which effective counter-measures are yet to be developed.



Submarines make small navies credible. The proliferation of conventional submarines in the Indo-Pacific by large and small powers is a testimony to their effectiveness in the emerging maritime security contours taking shape in the region. Technological advancements, not just restricted to those highlighted in the preceding paragraphs, have greatly enhanced their versatility and effectiveness and, as in 1901, they continue to drive a ‘Revolution in Military Affairs’ more than a hundred years later.

(The author is a submarine veteran and vice president, Indian Maritime Foundation)


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