India's future main battle tank now grapples with a weight issue

As the Defence Research and Development Organisation (DRDO) begins designing the Future Main Battle Tank (FMBT), the army is sending out typically mixed messages on the vital question of how big and heavy India wants its tanks. While insisting that the DRDO’s 60-tonne Arjun tank weighs too much to move around the riverine terrain of Punjab and J&K, the army has demanded features in the next Arjun model (Arjun Mark II) that will raise its weight to 65 tonnes.
 Planning for the FMBT —the Gen-Next tank that will follow the Arjun Mark II by 2020 — is even more contradictory. The army wants the FMBT to weigh just 50 tonnes while bettering all the Arjun’s features.
 Officials at the Combat Vehicles R&D Establishment (CVRDE), Avadi, who will develop the FMBT, say it is impossible to build the FMBT 15 tonnes lighter while also improving crew protection; fitting a more powerful gun that can slam projectiles through improved enemy tanks; and making the FMBT faster and more powerful.

FEATURES OF THE FMBT
Weight	50-tonnes
Engine	1800 Horse Power
Transmission	CVRDE-developed
Armour	Active Protection System (APS)
Gun	120 mm smoothbore
Suspension	Hydro-pneumatic

CVRDE director P Sivakumar told Business Standard during an exclusive briefing on the FMBT, that it would meet weight targets only if the army identified its inescapable needs rather than demanding every feature available. One example is crew protection. The FMBT will have a cutting-edge Active Protection System that detects incoming enemy projectiles (which travel faster than rifle bullets); and then fires a projectile to hit and degrade the incoming warhead. But the army also insists on the conventional armour plate that has traditionally protected tank crews.
“If you want a 50-tonne FMBT you must choose wisely. If your Active Protection System can reliably defeat enemy projectiles, why do you also want the heavy armour plating of passive systems? Whatever you use — composites, lightweight materials, etc. — the weight of the tank will rise. Similarly, how can you increase your tank gun’s ability to penetrate enemy tanks without a weight increase?” asks Sivakumar.
Difficult choices like these are delaying the finalisation of the FMBT’s Preliminary Staff Qualitative Requirements (PSQR), the document that will specify its capabilities and major systems. With nothing settled, the DRDO is readying for a heavier-than-planned FMBT. Business Standard reported yesterday that CVRDE is developing an 1800 Horse Power engine, rather than the 1500 HP needed for a 50-tonne FMBT.
While foreign consultancy will drive the engine design, CVRDE will play the central role in building a transmission system, which transfers engine power to the FMBT’s tracks. Sivakumar, himself an accomplished transmission designer, says that the CVRDE’s home-grown design will be vetted by a consultant, who will be chosen from three candidates: Ricardo; AVL; or US-based South West Research Institute.
“CVRDE has a tradition in transmission design. We built a 1500 HP transmission for the Arjun, which was not used because the engine design was changed. We have also built the “aircraft mounted accessory gearbox” that is standard fitment in the Tejas Light Combat Aircraft. It is 35 kg of magnesium alloy, spinning at 16,800 rpm. This gearbox has successfully completed some 3000 flights,” says Sivakumar.
The FMBT will be armed with India’s first smoothbore 120-millimetre tank gun. While the rest of the world has long used smoothbore guns — which fire anti-tank missiles and high-explosive anti-tank (HEAT) rounds — the DRDO alone has stuck with rifled guns. There is confidence that the changeover will be smooth: the DRDO developed a smoothbore gun for the T-90 tank after Russia illegally blocked gun technologies. The DRDO is also working with Israel Military Industries (IMI), which developed the smoothbore gun for the Merkava tank.
Cushioning the FMBT’s ride will be one of the Arjun’s unique successes, its hydro-pneumatic suspension unit (HSU), which smoothens the jerks from driving fast over uneven cross-country terrain. The Arjun’s smooth ride allows its gun to accurately hit a suitcase two kilometres away while driving at 30 kmph. The initial FMBTs will have improved Arjun HSUs, while CVRDE proposes to develop an “active suspension” by 2030. This has sensors scrutinising the terrain just ahead of the tank and making anticipatory adjustments before the tank’s tracks roll over that area.
“The future is active suspension. The FMBT will initially roll out with hydro-pneumatic suspensions but we are commencing R&D for active suspension. It takes some time to develop a reliable active suspension. No tank has managed it so far,” says Sivakumar.

-Business Standard(Ajai Shukla)