INS Chakra, India’s sole nuclear attack submarine, seen during TROPEX 2014
One of the first Asian navies to operate a credible submarine arm, the Indian Navy (IN) currently operates nine Russian-built Kilo-class (Project 877EKM ‘Paltus’) and four German-built Class 209 Type 1500 Shishumar-class diesel-electric submarines. However, the IN has remained strongly focussed on a possible nuclear submarine fleet for long because of the inherent rapid speed and “unlimited” range and endurance achieved by a nuclear powered fleet to encompass the Indian Ocean Region (IOR) with dominance.
Efforts of the IN to secure a nuclear powered hunter-killer submarine (SSN) in its fleet may be traced back to 1984 with reports of discussions with erstwhile Soviet Union on the supply of more advanced, possibly nuclear-powered submarines and the training of IN crews in the Soviet Union. Vice Admiral Tahiliani, then Vice Chief of Naval Staff, took a leading role in talks in Moscow in September 1984, after which official sources stated that the defence relationship had taken on “a new dimension” indicative of possible access to nuclear-powered submarines.
Meanwhile, a design of the Rubin Central Maritime Design Bureau at St Petersburg, the first Russian Type 877EKM Kilo-class diesel-electric hunter-killer (SSK) submarine INS Sindhughosh, entered Indian Navy service in 1985. The submarine is a robust single-shaft vessel with an albacore/ teardrop shaped double hull (a prominent feature of SSN types) with a seven-blade fixed-pitch propeller. The Type 877EKM has a displacement of 2,300 t surfaced and 3,950 t submerged and a maximum diving depth of 300 metres. Top speed is 17 knots when submerged. Reputed to be a ‘black hole’ for excellent stealth capabilities, the bow planes are positioned close to the midship to improve the performance of the MGK-400 sonar. To reduce the submarine’s acoustic signature, the flooding ports have been removed from the fore body and the hull is covered with rubber ‘cluster guard’ anechoic antisonar protection tiles to reduce the risk of detection. The combat information system consists of a multipurpose MVU-110EM computer which allows for five targets to be tracked simultaneously, two automatically and three manually. In 2015, at the naval exercise Malabar between the navies of India and the United States, Type 877EKM INS Sindhudhvaj reportedly managed to track USN Los Angeles-class SSN USS Corpus Christi and score a simulated kill without being detected.
The Type 877EKM has six 533 mm torpedo tubes and carries 18 heavyweight torpedoes (six in the tubes and 12 on the racks), with an automatic rapid loader. Two targets can be engaged simultaneously. Two of the launch tubes can fire the TEST- 71MKE TV electric homing torpedo, which has an active sonar homing system with TV guidance which allows the operator to manually switch to an alternative target, and can manoeuvre in two axes. It weighs 1,820 kg with a 205 kg explosive charge.
The submarine is also fitted with UGST wake-homing torpedoes, weighing 2,200 kg with a 200 kg explosive charge. It has a range of up to 40 km, and a depth of search of up to 500 m. The tubes are also capable of deploying 24 mines.
The Indian vessels are fitted with the 220 km-ranged Novator 3M-54E1 Anti-Ship Missile (AShM) with a 450 kg High Explosive (HE) warhead as part of the Klub-S missile system. Sub strategic reach is provided by the Novator 3M-14 Land Attack Cruise Missile (LACM), with a 499 kg warhead. While surfaced a launcher with eight Strela-3 or Igla Surface-to-Air Missiles (SAM) can be deployed. As apparent, Type 877EKM features multiple SSN features albeit with diesel-electric propulsion.
INS Kalvari, the first of six Scorpene-class boats, seen at sea during her delivery trials
Beyond conventional submarines, a formal agreement was signed to lease a Charlie-II-class customised for export (Project 670M/06709) nuclear-powered cruise missile armed submarine (SSGN) from the Soviet Union sometime in 1985. In January 1988, All-India Radio announced that the Soviet Union had leased a nuclear powered submarine to India with IN taking delivery of INS Chakra in the Soviet port of Vladivostok. Initially reported to be of Victor I Class SSN, published photographs clearly identify INS Chakra as a Charlie Class SSGN designed to carry eight P-80 Zubr/Ametist (SS-N-7 Starbright) Anti-Ship Cruise Missiles (ASCM), capable of being launched even while the SSGN remained submerged. Leased for a period of three years from January 1988, the SSGN was based at Visakhapatnam Naval Base and was returned in January 1991. In the aforesaid period, the submarine travelled 133,000 km with the reactor active for 430 days and fired five Ametist ASCM and forty-two torpedoes. Thirty Soviet instructors maintained key posts on the SSGN and forty Soviet industrial specialists were involved in servicing it.
On 23 January 2012, Russia handed over the much-awaited Russian Project 971A Schucka-B (NATO: Akula II) Class nuclear-powered attack submarine (SSN) K-152 ‘Nerpa’ to the Indian Navy on a ten year lease worth $920 million, with the signing ceremony undertaken at the Bolshoi Kamen ship building facility in the (Far East) Primorye region. Although back in 2008 then IN Chief of Naval Staff (CNS) Admiral Sureesh Mehta laid stress on to training of IN personnel on how to operate nuclear reactors and platforms and other systems, an India Today report stated that “the impending acquisition of the Akula (christened INS Chakra in Indian Navy service) gives India the long-awaited third leg of the nuclear triad…widely regarded as the most survivable mode of launching nuclear weapons.” The India Today report further asserted that the Chakra would be armed with “indigenously built nuclear tipped cruise missiles with a range of over 1,000-km.” At least another Akula-class SSN is likely to enter IN service in due course.
In the process, an international training centre was “expanded” in Sosnovy Bor, situated 70-km west of St. Petersburg, with the initial aim of imparting training to 300 Indian Naval officers selected for operations aboard the Akula SSN. The training reportedly started sometime in 2001. The centre incidentally trains Russian naval officers and houses working marine nuclear reactors and is used to test nuclear fuel and other technologies applicable to nuclear submarine reactors. Thus the accommodation of Indian naval officers at the Centre does indicate far-reaching consequences beyond leasing of the Akula-II SSNs and possibly aimed at imparting sufficient training and expertise to enable the Indians to develop nuclear-powered submarines that includes the Arihant-II Class ‘Ship Submersible Ballistic missile armed Nuclear-powered’ (SSBN) that appears to share technology of Akula-class SSN. Although initially and decades ago, the IN requirement for SSNs were to acquire the only credible counter to United States Navy (USN) presence in the Indian Ocean, in recent times, its value as multipurpose “stealthy and mobile thus invulnerable” strategic platform have taken predominance in response to rapidly shifting geo-political scenario with new equations. INS Arihant SSBN incidentally initiated deterrent patrol in August 2016. Powered by a 83 MW pressurised light-water reactor, the submarine has four vertical launch tubes to accommodate Submarine Launched Ballistic Missies (SLBM).
Led by Akula I K-284 Akula (Shark), the Russian-origin steel hulled third-generation Project 971 Shuka-B Bars Class SSNs are known in the West as the Akula Class. The design was initiated in 1976 and developed by St. Petersburg-based Malakhit Marine Engineering Bureau under their outstanding Chief Designer Georgy Chernyshev. A traditional follow-on to Victor III SSN design, the Akula-Class SSNs along with Project 945 Sierra-Class SSNs for the first time posed a serious challenge to western navies in terms of overall submarine technology. From the outset, acoustic silence was top priority among Russian naval designers (the noise level of Akula SSN is considerably lower than 110-decibels as widely believed) in which the western navies traditionally enjoyed a decent lead. At 110-metres long (Akula II), the Akula SSN is double-hulled with considerable distance between the outer and inner hulls, in the process reducing possible damage to the inner hull. To further complicate the problems of their adversaries, the Akula II with a dived displacement of 13,800-tons nevertheless sports a maximum submerged speed of at least 35 knots, owing to the main machinery that consists of a VM-5 pressure water reactor with a model OK-650B high-density reactor core rated at 190 to 200 MW with a GT3A turbine developing 35 MW driving a seven-bladed fixed-pitch propeller. The operational diving depth is reported to be 520 metres that extends to the maximum diving depth of 600 metres. Thus if deployed in a more offensive role, the high underwater speed along with a deep diving capability enables the Akula SSN to evade a considerable spectrum of enemy ASW defences by passing beneath them. Surface-launched ASW weapons such as homing torpedoes would take a long time to reach the operating depth of the Akula SSN that the later by then would have passed out of range of their acoustic homing device.
INS Kalvari underway in the ocean
Significantly, the Akula retains capability to approach the permanent thermo cline layers in the oceans, and in case of Akula II to exploit its formidable MGK-540 Skat-3 (Shark Gill) sonar suite with additional flank array extending for about one-third of the hull. The sonar suite provides automatic target detection in broad and narrow band modes in active mode while in passive, listening mode hostile enemy sonar faces risk of detection. The sonar signal processor is flexible enough to detect and automatically classify targets as well as reject spurious acoustic noise sources and compensate for variable acoustic conditions. The ‘thermo cline’ thermal layer in oceans has a major influence on ASW operations as it affects the velocity of sound and in permanent ‘thermo cline’, (found at depths of 300 to 400 metres in equatorial areas and 500 to 1,000 metres in sub-tropical areas) the velocity reaches the minimum. This layer of minimum velocity, known as the deep sound channel, has a variety of effects, and it is theoretically possible that a submarine can operate in this deep sound channel, exploiting this effect to achieve very long-range detection. In addition, in later Akula submarines a number of prominent non-acoustic sensors appear on the fin leading edge and in the forward casing capable of carrying out wake tracking of the enemy surface units under surveillance. To complement the formidable sensors, Molniya-M/Pert Spring Satellite Communications (SATCOM) provides greater situational awareness, critical in pursuit and interception missions of hostile fleet.
The MGK-540 Skat-3 sonar suite enables Akula II SSNs to enjoy considerable standoff distance as against enemy submarines and such a capability is duly complemented by their plunge-fly-plunge ASW missiles consisting of Novator Tsakra (SS-N-15 ‘Starfish’) and the Novator Vodopad (SSN-16 ‘Stallion’). The Starfish, fired from the six 533-mm tubes, has a target range (inertial flight) of 45-km while the Stallion, fired from the four 650-mm tubes, has a longer range of up to 100-km. Both the Stallion and the Starfish enjoy the choice of a 200-kt warhead or a Type 40/45 torpedo in response to tactical circumstances. Wake homing torpedoes if deployed, will inherently be less dependent upon accurate targeting solutions as they need to be fired at target’s wake rather than at the target itself.
Known countermeasures are the standard gas-producing decoy units, a holdover from the German Pillenwaffer, sonar jamming, and an ingenious acoustic decoy commonly referred to as the nixie cunningly emulating the sound signature of the parent sub while veering from the submarine’s track at three knots effectively obscuring the actual noise generated by the parent submarine. While the tracking submarine is deceived into tracking and launching on a decoy, the Akula may silently alter course and counterattack as also, a nixie will force opposing submarines to track multiple targets, uncertain which is the Akula.
MBDA’s tube-launched SM39 Exocet AShM arms the new Kalvari-class (Scorpene) submarines
The key weapon of INS Chakra is likely to be the sub strategic variant of the RK-55 Granat (SS-N-21 Sampson), the 3M-14E (SS-N-30) which is already in Indian Navy service. The 3M14E LACM has been designed to destroy ground-based targets and consists of a booster stage and a subsonic low-flying sustainer stage. The 3M14E is intended for use against stationary ground targets such as administrative and economic centres, weapon and petrochemical storage areas, command posts, seaports, and airports. Once the mission data needed by the midcourse navigation system has been prepared, it is loaded into the missile›s onboard computer prior to launch. The missiles are launched under the power of a tandem solid-propellant rocket booster fitted with four small lattice stabilisers. Once the missile has reached flying speed, it is powered by a small turbojet engine. Launched from a depth of 30 to 40 metres below the sea surface, the onboard control system includes a barometric altimeter used to maintain altitude in terrain-following mode (making the weapon stealthier than designs which rely on radar altimeters), plus a receiver for the GLONASS Satellite navigation system now jointly developed by Russia and India and used alongside a Global Positioning System (GPS) to provide a backup and extra security in case of interferences such as deliberate jamming. The missile has a low flight altitude, 20 metres above sea and 50 to 150 metres over land.
For most of the flight to the target area, the missile flies autonomously, following the pre-programmed route and turning points. Once over land, it uses a terrain-following flight path that will make it a difficult target for enemy air defences. This low-level flight mode poses a higher load on the wings and missile structure than flight over the sea surface, so the land-attack missile variant has slightly redesigned wings of shorter span and deeper chord, plus a stronger structure.
At the terminal stage of the flight, the guidance is effected by the ‘Korrelatsionaya’ system. This guidance system employs a Scene Matching Area Correlator package, which guides the missile to a set of coordinates within a pre-programmed image surrounding the target and is similar technology to the Digital Scene Matching Area Correlator (DSMAC) in the BGM-109 Tomahawk. European sources claim this guidance package can hit completely hidden targets with 400-kg high explosive providing their location is well known relative to visually prominent features surrounding the aim point.
The Naval Group Scorpene-class SSK INS Kalvari also prominently features characteristics of SSN including the albacore shaped hull and associated noise reduction measures. The submarines are likely to be fitted with a fuel cell Air Independent Propulsion (AIP) system in due course to extend their endurance over pure dieselelectric types. A shroud of secrecy cover the IN operated four German HDW Class 209 Type 1500 submarines, ideal for clandestine coastal operations. With a submerged displacement of 1,850 tonnes, the types are armed with AEG SUT torpedoes and encapsulated UGM-84 Harpoon AShM, and were equipped from outset with United States supplied fire control systems.
With more nuclear powered submarines likely to enter IN service, both from foreign lease and collaborated domestic production, it is likely that IN may operate a predominantly nuclear submarine fleet by 2040 if marine nuclear propulsion technology can be acquired through ‘package’ deals involving other prominent weapon systems.
Sayan Majumdar