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Volume 29 - Issue 05 :: Mar. 10-23, 2012
INDIA'S NATIONAL MAGAZINE
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FOUCS: DRDO

Underwater might

T.S. SUBRAMANIAN

The DRDO's triad of laboratories supply the Indian Navy with high-potential weapons systems.

BY SPECIAL ARRANGEMENT

S.V. Rangarajan, Director, NSTL.

THE 52 laboratories of the Defence Research and Development Organisation (DRDO) spread across India have a high-potential but low-profile trimurti, specialising in naval systems, among them – the Naval Science and Technological Laboratory (NSTL) in Visakhapatnam, the Naval Physical and Oceanographic Laboratory (NPOL) in Kochi, and the Naval Materials Research Laboratory (NMRL) at Ambernath, 60 km from Mumbai. “I describe them as Brahma, Vishnu and Siva [the triad of Hindu gods],” said S.V. Rangarajan, Director, NSTL.

The NSTL, situated in the foothills of the Eastern Ghats, is the only laboratory in the country to develop underwater weapons such as torpedoes and mines, their associated fire control systems, and decoys to “seduce” enemy torpedoes. It also develops stealth technology, produces autonomous underwater vehicles (AUVs) and conducts research in hydro-dynamics. The NPOL develops sonars, surveillance and underwater communication systems and counter-measures. The NMRL has come up with non-skid, anti-corrosion and fire-retardant paints, smart coating and fuel cells. It pursues research in protective technologies, marine materials, energy science, polymers and ceramics. “While the NPOL is Brahma, the perceiver, and the NMRL the protector, we are Siva, the destroyer,” declared Rangarajan, filling the room with his gentle humour. He predicted that future wars would be fought at sea and under water. But while most of the underwater technology was not available in the marketplace, he said India had made “significant progress, with an indigenous grip” in the field. “Our base is strong,” he said.

Scientists of the NSTL work in a harsh atmosphere as they work under water, which is about 850 times heavier than air. The technology of developing torpedoes is much more complex than building missiles because torpedoes have to speed under water where the resistance is far higher than in air. Besides, Rangarajan said, torpedoes are an amalgam of difficult disciplines: they include electro-chemistry, structural engineering, mechatronics, signal processing, real-time software, embedded systems, transduction and sensing, acoustics, gyroscopes, inertial navigation and guidance systems, and warheads.

The NSTL has developed both light-water torpedoes (LWTs), named TAL, and heavy-weight torpedoes (HWTs), named Takshak and Varunastra. Takshak has two versions, a submarine-launched variant with wire guidance and a ship-launched one with autonomous guidance. Varunastra is an advanced version of the ship-launched HWT. Under development is a torpedo called Shakti with thermal propulsion, which can generate 500 kilowatt of power and rev up the engine within a second. “Thermal propulsion is a challenging technology,” said Rangarajan. “It is a totally indigenous effort. We have already consolidated several technologies in its development. Only the United States, the United Kingdom and Russia had torpedoes with thermal propulsion when we took up the challenge.”

The LWT is 2-3 metres long, weighs 200 kg to 300 kg and packs 50 kg of explosives. It can be launched from ships and helicopters. When a helicopter releases the LWT, the latter drops down with the help of a parachute, which gets detached when the torpedo hits the water. TAL has a speed of 33 knots an hour and can operate at a maximum depth of 540 m. It is under production by Bharat Dynamics Limited, Hyderabad, for the Navy.

The Advanced LWT (ALWT) is currently under design and will be in production in 2015-16. In Takshak, which is an anti-submarine system, the wire is the medium of communication between the torpedo and the firing ship. If the wire breaks, Takshak would become an autonomous torpedo like its ship-launched variant. It can travel up to a distance of 40 km for taking out submarines and can operate up to a depth of 400 m.

Varunastra, which is ready for trials by the Navy, weighs more than one tonne and contains 250 kg of explosives. It travels at a speed of 40 knots an hour, going in circles and bobbing up and down to attack targets. K. Sudhakar, Principal Associate Director, NSTL, called the torpedo's homing device, located in its front portion, “its eyes and ears” as it detects and tracks the target. Its guidance system enables it to take the optimum path towards the target, and its onboard computer guides its rudder's navigation towards the target. The warhead has a proximity fuse, with the blast occurring about 8 m from the target. “The torpedo should have its own intelligence to reject the decoy and go towards the target,” Sudhakar said. Besides, torpedoes should be water-tight. “Development of a torpedo takes 10 to 15 years. It has to go through several sea trials. We started out in this field 25 years ago. No torpedo technology is available in the open market,” he added.

C.V. SUBRAHMANYAM

A TORPEDO DEVELOPED by the NSTL, being tested in mid-sea.

Decoys are mini-torpedoes that “seduce” and mislead torpedoes coming from enemy craft so that naval vessels can get away, explained N. Raghavarao, senior scientist. The NSTL has developed a submarine-launched decoy. The Navy has inducted this decoy into service. The NSTL and the NPOL are working on another decoy called Mareech. The NSTL is developing Mohini, a rocket-launched anti-sonar decoy.

Mines in underwater warfare are lethal and cost-effective weapons. Capable of detecting targets, they can be launched from ships, submarines and air. They can stay under water in “sleep” mode for several months and, on sensing magnetic, acoustic and pressure signatures, wake up to detonate. The NSTL has delivered processor-based ground (that is, seabed) mine to the Navy, says S.M. Bhave, a senior scientist. It has developed moored mines, which will hang at certain depths in the sea.

A big programme under way at the NSTL is the building of an AUV. Manu Korulla, scientist, called the AUVs “a new class of intelligent underwater vehicles, which will operate without human supervision to carry out survey, surveillance and reconnaissance missions.” The AUV can be configured to drop and hunt for mines, lift underwater bodies, do counter-communication measures and change course on sensing obstacles. It will have cameras, sonars and image processors. “We know the technology to develop various sizes of AUVs for various applications,” Korulla said.

C.D. Malleswar, a senior scientist, said the laboratory had developed Panchendriya, a submarine-based fire-control system (FCS), which has been inducted into the Navy's Vela class of submarines. The FCS receives information from the boat's sonar on the target's bearing and presets the torpedoes for destroying the enemy craft. The NSTL has supplied three helicopter-based FCSs for torpedoes to Hindustan Aeronautics Limited. “We have received production orders for seven FCSs for the integrated anti-submarine war complex,” Malleswar said. The NSTL has gargantuan facilities. There is a big hall with several state-of-the-art CNC [Computer Numerical Control] machines. R.V.S. Subrahmanyam, scientist, said the components used in torpedoes, mines and decoys were machined in CNC machines. “This is elite class work,” he said, showing a component where the clearance between a rotor and its cowl was just 0.5 mm.

The NSTL's High Speed Towing Tank is a huge building enclosing a water channel that is 500 m long, 8 m wide and 8 m deep. It holds 32,000 tonnes of water. NSTL scientists tow models of ships and submarines at high speed in the channel to study the resistance offered to them by water, the resultant drag, and the power required to overcome the resistance. “We study the resistance offered by water so that we can design the hull of these bodies more efficiently,” said P.K. Panigrahi, a senior scientist.

Another big facility is a cavitation tunnel. Here water is pumped on to a propeller to create flow conditions for the blades to study the phenomenon of bubbles formation. Amazing is the sea-keeping and manoeuvring basin, an artificial lake with a roof, which is under construction. Four giant borewells will pump 240 lakh litres of water over three months to form the lake, which will be 135 m long, 37 m broad and 5 m deep. Here, waves will be generated to study their impact on the seaworthiness and agility of vessels.



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