The Scorpene: Enhancing India’s Underwater Capability

The Scorpene: Enhancing India’s Underwater Capability

The Third Scorpene-Class Submarine ‘Karanj’ was launched at Mazagon Dock on January 31, 2018. The ‘Karanj’ is the third of the six Scorpene-class submarines being built by shipbuilder Mazagon Dock Limited (MDL) under the P-75I project. Admiral Sunil Lanba, Chief of the Naval Staff, who    was the chief guest, said, “It is one of the most advanced submarines and better than those that the enemy country has. As of now, four to five companies have responded to the Request For Information (RFI) issued  by the Indian Navy. A meeting has also been conducted with the Indian Navy and finalisation of the firm will soon be decided.”

INS Kalvari, the first Scorpene class submarine was commissioned into the Indian Navy by Prime Minister Narendra Modi on December 14, 2016. The second submarine of this class, ‘Khanderi’ was launched at MDL in January last year, which is currently undergoing the rigorous phase of sea trials. It is scheduled to be delivered shortly to the Navy. ‘Karanj’ is expected to be handed over to the Navy after two years.

 

Weapon Systems

The Scorpene attack submarine can carry 18 torpedoes and missiles or 30 mines. It is equipped with six bow-located, 21-inch torpedo tubes providing salvo launch capability. Positive discharge launching is by an air turbine pump. Handling and loading of weapons is automated. The submarine’s weapons include anti-ship and anti-submarine torpedoes and anti-surface missiles. The handling and loading of weapons is automated.

 

SUBTICS Combat Management System

The SUBTICS combat management system, with up to six multifunction common consoles and a centrally situated tactical table, is collocated with the platform-control facilities. The combat management system is composed of a command and tactical data handling system, a weapon control system and an integrated suite of acoustic sensors with an interface to a set of air surface detection sensors and to the integrated navigation systemThe system can also download data from external sources. The integrated navigation system combines data from global positioning systems, the log, depth measurement and the ship’s trim/ list monitoring system. The Scorpene monitors the environment including seawater density and temperature as also the submarine’s own noise signature.

 

Sonar Suite

The vessel’s sonar suite includes a long-range passive cylindrical array, an intercept sonar, active sonar, distributed array, flank array, a high-resolution sonar for mine and obstacle avoidance and a towed array.

 

Control and Monitoring

All submarine handling operations are carried out from the control room. The vessel features a high level of automation and surveillance, with automatic control mode of rudders and propulsion, continuous monitoring of the propulsion systems and platform installations, centralised and continuous surveillance of all potential hazards (leaks, fires, presence of gases) and the status of the installations that affect the safety while submerged.

 

Construction

The submarine incorporates a high level of system redundancy to achieve an average 240 days at sea in a year for each submarine. The maximum diving depth is 300m, giving the commander more tactical freedom than previously available on conventional submarines. There is no limit to the duration of dives at a maximum depth, other than the power systems and crew limitations. The structure of the submarine uses high-yield stress-specific steel enabling dive to maximum depths when necessary.

Incorporating high-tensile steels has reduced the weight of the pressure hull, allowing a larger load of fuel and ammunition. The reduced complement minimises training costs and increases combat efficiency by making more space, while a larger payload enhances the ship’s autonomy. When dived, the Scorpene has low radiated noise that permits improved detection ranges of its own sensors and reduced risk of detection by hostile sensors. The low radiated noise is achieved through the use of advanced hydrodynamics with an albacore bow shape, with fewer appendages and an optimised propeller.

Between the suspended decks, the equipment is mounted on elastic mountings wherever possible, and the noisiest systems have a double-elastic mounting to reduce the risk of their noise profiles being radiated outside the submarine. The shock-resistant systems have been developed from systems incorporated in advanced nuclear-powered submarine designs. The low-acoustic signature and hydro-dynamic shock-resistance, give the Scorpene class the capability to carry out anti-submarine and anti-surface ship warfare operations in closed or open sea conditions, as well as the capability of working with special forces in coastal waters.

 

Crew Facilities

The ship can hold a total company of 31 men with a standard watch team of nine. The control room and the living quarters are mounted on an elastically supported and acoustically isolated floating platform. All living and operational areas are air-conditioned. The submarine also has space for six additional fold-down bunks for Special Operations crew. The vessel is equipped with all the necessary systems to provide vital supplies, water, provisions and regeneration of the atmosphere, to ensure the survival of all crew for seven days. The ship is equipped with full rescue and safety systems. A connection point for a diving bell or Deep Submergence Rescue Vehicle (DSRV) allows collective rescue operations.

 

Stealth Design

The planning and design of the Scorpene was directed towards achieving an extremely quiet vessel with a great detection capability and offensive power. The forms of the hull, the sail and the appendages have been specifically designed to produce minimum hydrodynamic noise. The various items of equipment are mounted on elastic supports, which in turn, are mounted on uncoupled blocks and suspended platforms. The isolation also provides better shock protection to the equipment.

 

Propulsion System

The Scorpene has two diesel generation sets providing 1,250kW of power. At the top of the hull immediately above the diesel generator sets is a Dutch Breach machinery shipping hatch. The submarine has an elastically supported 2,900kW electronic engine. There are two variants of the Scorpene, the CM-2000 with the conventional propulsion system and the AM-2000 equipped with air independent propulsion. The AM-2000 is capable of remaining submerged on underwater patrol for a period that is three times longer than that of the CM-2000.

 

Air Independent Propulsion

A conventional diesel-electrical submarine sailing underwater is difficult to detect. However, the need to come repeatedly to periscope depth to recharge the batteries using the diesel engine greatly increases vulnerability by:

  • Its aerial detectability, since the snorkel projecting from the water is detectable by radar.
  • Its underwater detectability due to increase in radiated noise from the working diesel engines.

The ratio between this time of greater vulnerability and the total operating time is known as the ‘indiscretion rate’ and for all conventional modern submarines the indiscretion ratio ranges typically from seven to ten per cent on patrol at 4kt, and 20 to 30 per cent in transit at 8kt. To reduce the submarine’s vulnerability, the vessel can be equipped with an air independent propulsion system such as the Stirling engine, the fuel cell, the closed-circuit diesel and the Module d’Energie Sous-Marine Autonome (MESMA) system. The MESMA anaerobic system, in which heat in the primary circuit is produced by burning ethanol with oxygen, can be easily installed either at the start of the submarine’s construction or in a later modernisation to convert the CM-2000 to an AM-2000 standard.  With the MESMA system, the AM-2000 submarine can stay down on underwater patrol three times longer than the CM-2000.

Its performance features remain the same in all other respects, except that the length increases to 70m and its submerged displacement to 1.870 tonnes (against the 61.7m and the 1,565 tonnes of the CM2000). The MESMA system is being offered by the French shipyard DCN for the Scorpène class submarines. It is essentially a modified version of their nuclear propulsion system with heat being generated by ethanol and oxygen. A conventional steam turbine engine is powered by steam generated from the combustion of ethanol (grain alcohol) and stored oxygen at a pressure of 60 atmospheres. This pressure-firing allows exhaust carbon dioxide to be expelled overboard at any depth without an exhaust compressor.

Each MESMA system costs around $50 to $60 million. In order to be installed on the Scorpène, it requires adding a new 8.3-metre (27-foot), 305-tonne hull section to the submarine and increases the capability of the submarine to operate for more than 21 days underwater, depending on variables such as speed.

 

Conclusion

The Indian Navy currently operates 14 diesel-powered submarines and one nuclear-powered submarine. The nuclear-powered Akula-class sub is operated on a ten-year lease from the Russian Federation. The backbone of the fleet is formed by ten Kilo-class Type 877EM – or Sindhugosh-class – units that are being progressively retrofitted to accommodate the Klub/3M-54E Alfa cruise missile system. India also operates four Shishumar-class Type 209/1500 vessels designed by Howaldtswerke-DeutscheWerft (HDW) in Germany. All four of the Shishumars have undergone refit since they were commissioned and together they form the 10th submarine squadron based at Mumbai.

In addition to the 14 active submarines, however, India is in the process of constructing six Scorpène-class boats that are being indigenously built at the Mazagon Dock in Mumbai, under the supervision of French technicians.  India’s defence planners have also begun development of the long anticipated indigenously built Arihant-class nuclear powered submarine fleet.     (IDR)

By Danvir Singh

 

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