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On board the INS Chennai stealth destroyer

26th Jan 2018 6:00 am

We spend a day with the Indian Navy’s new stealth destroyer that can creep up enemies and take them out with a salvo of supersonic cruise missiles.

It’s not every day we feature a machine that’s manufactured just around the corner from our Mumbai office. But with the 163m-long, 7,500-tonne INS Chennai, that’s just what we did. Easily the largest and heaviest machine ever to be on our pages, the ship is made by our neighbours, Mazagon Dock Limited (MDL); no stranger to warship production. Started by the East India Company to refit and service its warships way back when the Mughals were still around in 1774, the yard later became famous for the Wadia shipbuilders, who are said to have made many of the best wooden ships ever possessed by the Royal Navy. So it’s no surprise that MDL today is a huge part of the ‘Make in India’ success story.

JET THRUST

My jaw hits the floor when I see the ship for the first time in the flesh; its flat panels and raked angles bathed in the early morning light. And it impresses immediately too. The seas around the harbour are calm, but INS Chennai is cutting through the water like a hot knife through butter, its sharp prow raised gently as if to proffer the correct angle of attack. There’s very little crashing and pounding where the hull of the ship meets the water, and there’s no impression of a battering ram punching through the waves. Also, there’s no thumping or crunching below. Later, even as the throttles are moved up and the speed increases, there’s hardly any increase in the wake. Neat.

We then turn right, towards the mouth of the harbour, now heading south – with the landmass of India on our left and the island of Mumbai on our right – and, as we clear of the harbour, our speed increases again. The sensation is unlike anything I’ve felt before. There’s no loud engine rumble, no black smoke, and almost no vibration; just a smooth, sustained push, with the sea rushing past on either side. This is because there are no noisy diesels onboard (at least none used for propulsion). What this ship has for motive power are four huge Ukrainian turbine engines that put out a combined 65,000hp. The Boeing 747-like quad-turbine setup delivers its thrust via two single-speed reduction gearboxes and two fixed pitch propellers. So outside, instead of the regular diesel drone, all you hear is a loud whine, overlaid by a distant roar.

As I climb up to a higher deck near the bridge, the noise gets even louder. There’s a mini whirlwind here, created by the intakes sucking in massive quantities of air. The exhaust from the square chimneys delivers quite a roar too. Noise emission norms clearly don’t come into play here.

Since we are now well clear of any marine traffic and well out to sea, the throttles are pushed forward again. “Notice the change in the sound,” says one of the engineers onboard, “that’s the second set of engines kicking in.” Turbines are only efficient at higher speeds, so when the boat is cruising, only one set of engines are switched on.

With its combined gas and gas (COGAG) Zorya M36E system, and all four turbines turning at around 14,000 or 15,000rpm, the 7,500-tonne INS Chennai can do in excess of 30 knots or around 60kph (its massive propellers churning the sea at 270rpm). And that, for a vessel as large as this, is pretty impressive.

INS Chennai (D65) Dimensions, propulsion and price
Length163.95m
Beam17.714m
Draft5.577m
Displacement7500 tonne
EnginesTwin Zorya M36E gas turbine plants (with 4 DT-59 reversible gas turbines) Combined Gas and Gas system Bergen/GRSE KVM diesel (2)
Total combined power65000hp
GearboxRG-54 (2)
Maximum speed30 knots (56kph)
Range8000 nautical miles (15000km) at 18 knots (33kph est.)
PriceRs 4000 crore (est)

DRAG REDUCTION, RIDE AND HANDLING

What also affects speed here, much more than on a car, is drag. This is because water is considerably denser than air. In the car industry, we call it drag coefficient, but marine engineers know it as the ‘block coefficient’. To calculate drag under water, an imaginary block is built around the hull. The block coefficient then is the ratio of the area occupied by the hull versus the area of the block.

Needless to say, the INS Chennai has a very good block coefficient. It doesn’t need to carry a lot of cargo or passengers, so having a figure like a ramp model is perfectly acceptable. And that’s where a lot of the speed comes from as well.

“We’re going to show you how manoeuvrable it is now, so hold on,” comes the warning. It sounds like a bit of an exaggeration, so while I grab onto the guard rail, I’m not really holding on. Big mistake. The Chennai begins to turn in a manner I totally expect. But then, it turns tighter and tighter, and tighter. Before I know it, my balance is gone and I’m stumbling, grabbing on to the railing like a drunk. The deck is now tilting at a serious angle. This is some evasive manoeuvre. “Rolls like a ship,” I yell back . . . but I think the joke is lost.

INS Chennai (D65) Complement and systems
Complement40 officers and 350 sailors
Sensors and processing systemsMF-STAR S-band AESA multi-function radar
BEL HUMSA-NG bow sonar
BEL Nagin active towed array sonar
BEL Combat management system
Electronic warfare and decoysEllora MK1 electronic counter measure and support
NSTL Maareech advanced torpedo defense system
Kavach chaff decoy system
Aircraft carried2 x Sea King helicopters
Flight deckDual enclosed hangar

HOW NOT TO GET NOTICED

So much for mobility, so much for performance, so much for ride and handling. But what of firepower and protection? This is a war wagon after all. Turns out, the best way to stay out of trouble is to be invisible. This in military terms is known as stealth. Now invisible doesn’t mean to the naked eye, but to radar at a distance of around 200km or so – the distance at which all sea battles take place today.

And no, this ship isn’t totally invisible to radar and other means of detection. What stealth does is delay detection, and that, in a war scenario, often makes all the difference.

Making a ship stealthy is primarily done by reducing the Radar Cross Section or RCS. Look at a low angle shot of the ship and you’ll see a single crease running across its length. Everything above and below slopes away or has diamond-cut surfaces. And this is done to make radar waves bounce away rather than back.

Stealth also isn’t just about RCS. Real stealth is actually a summation of five or six kinds of ‘signature’ reductions. Reduction of underwater noise, magnetic signature, and infrared signature are vital. The last one involves the reduction of ‘hotspots’ that an infrared camera can see – things like smoke stacks, hot exhausts, a warm engine room. The chimneys, interestingly, are staggered and spread out, and are built square rather than round to reduce their RCS. And the stacks themselves are huge – 10 to 20 times larger than they need to be – so as to help insulate the hot exhaust better. Even air intakes are placed on the exhaust, so the cool air rushing into the turbines also helps mask the hot exhaust gasses going out.

SEEK AND DESTROY

Every battleship, however, is only as good as its weapon systems and the Chennai does a stellar job here. To begin with, every modern warship has to be aware of its surroundings. And that’s where the main feature of the ship, the tall radar mast, comes in. Made by Israel Aircraft Industries or IAI, and known as MF-Star, it is literally the eyes of the ship, with every major weapon launched off the back of information gathered by it. The world-class MF-STAR antenna includes four fixed arrays that throw an over 600km wide dome of protection around the ship. The system employs both phased array and pulse Doppler tech to help extract targets that have a very low radar cross-section, up to 300km away. With its high sampling rate and sophisticated software, it can track hundreds of targets at the same time; all the while providing guidance to munitions fired off by the ship. And because levels of integration with the Indian-made fire control system are very high, things like target threat classification and even mid-course guidance of weapons are possible.

The other world-class system on board is the Indo-Russian BrahMos supersonic cruise missile. Named after the Brahmaputra and Moskva rivers, the BrahMos system is widely acknowledged as one of the fastest and most accurate ones around. Chennai carries 16 vertically launched BrahMos missiles that, if needed to take out a large important target, say an enemy aircraft carrier, can be fired in a single salvo. The almost three-tonne missile explodes out of its canister vertically, powered by rocket fuel, jettisons its first stage, turns at a very acute angle and then carries on horizontally, now powered by a ramjet. Operating at around three times the speed of sound (Mach 3.0), it can skim the water or execute a high-low flight, making it very difficult to spot.

When it hits, the destructive power is massive. Imagine the kinetic energy of a Hummer-sized SUV doing 3,600kph, concentrated down to the size of a coin. And that’s without the 300kg warhead. BrahMos missiles can currently hit targets up to 300km out, but India has already tested a new one with an even greater range. So, with MF-Star and BrahMos, this ship is truly a force to be reckoned with.

All aerial threats are dealt with by the Israeli-made Barak-8 surface-to-air (SAM) missile. It has an effective range of almost 90km. So, in theory, with MF-Star, the ship could take out an enemy aircraft coming in from, say Pune, while sitting in the Mumbai harbour. The threat would be picked up by the MF-Star radar way earlier, at around 180 or 200km (as the crow flies), the information would be passed on to the missile intercept system, and as the Barak covers around 40km a minute at Mach 2, the intercept could be made nice and early, say somewhere near the hill station of Lonavala. The scale of battle these days is huge.

In the medium range, the ship uses its main water-cooled 76mm Super Rapid Gun and then closer up there are four Russian AK-630 (six barrels, 30mm) fully automatic, radar-controlled guns. These form the last line of defense and can fire at a target from 5km out. They fire at a rate of over 5,000 rounds a minute. The Indian-made Kavach chaff (metallic) system can also be used up-close as a decoy.

And in addition, the Barak-8 SAM system also takes care of the anti-ship missiles. Submarines are another issue entirely. The Chennai has space at the rear for two submarine-hunting helicopters that can drop their own sonar buoys and torpedoes. And the ship even has a HUMSA-NG hull-mounted sonar and will get an active towed array sonar in the future. Also, there are the guided torpedoes and anti-submarine rocket launchers.

INS Chennai (D65) Armament
Anti-air missiles32 Barak-8 missiles (4 x 8 cells) (range 0.5-90km)
Anti-ship/land-attack missiles16 BrahMos missiles (2 x 8 cells)
Guns1 x 76mm gun OTO Melara SRGM
4 x AK-630 CIWS
Anti-submarine warfare4 x 533mm torpedo tubes
2 x RBU-6000 anti-submarine rocket launchers

SHOULD WE BUY MORE?

At around Rs 4,000 crore, it is expensive; imagine how many Ferrari 488s you can get. And yes, there are areas where the Project 15 A stealth destroyers need to be improved. But the easy answer to the ‘should we buy more?’ question is a resounding yes. Many more, and here’s why. With a couple of stealth destroyers, attack submarines and stealth frigates, India’s carrier task force looks ready to take on anything. But the real story is the ‘Make in India’ advantage. With two more indigenously made aircraft carriers on the way and more stealth ships in the pipeline, India is well on its way to having a builder’s navy instead of a buyer’s one. And that’s exactly what we need.

This article originally appeared in the September 2017 issue of Autocar India.

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