Advanced Agni-6 missile with multiple warheads likely by 2017

DRDO technicians in Hyderabad assemble the payload stage of an Agni missile

Ending worldwide speculation about the futuristic Agni-6 missile, the Defence R&D Organisation (DRDO) has briefed Business Standard about the direction of India's ballistic missile development programme after the Agni-5 enters service, probably in 2015.

DRDO chief Dr VK Saraswat, and missile programme chief Dr Avinash Chander, say the Agni-6 project has not been formally sanctioned. However, the missile's specifications and capabilities have been decided and development is proceeding apace. Once the ongoing Agni-5 programme concludes flight-testing, the defence ministry (MoD) will formally okay the Agni-6 programme and allocate funding.

Chander says the Agni-6 will carry a massive three-tonne warhead, thrice the weight of the one-tonne warhead that Agni missiles have carried so far. This will allow each Agni-6 missile to launch several nuclear warheads -Multiple Independently Targetable Re-entry Warheads (MIRVs) - with each warhead striking a different target. Each warhead - called Maneuverable Reentry Vehicle (MARV) - performs evasive maneuvers while hurtling down towards its target, confusing enemy air defence missiles that are trying to destroy them mid-air.

The DRDO is at an advanced stage of developing these warhead technologies. But the difficult challenge is building a booster rocket that can propel a three-tonne payload to targets 5000 kilometres away. This weighs almost as much as the satellite payload carried by the Indian Space Research Organisation's much larger and heavier Global Satellite Launch Vehicle (GSLV).

"Our ballistic missiles must be compact and road mobile, even the Agni-6 with its heavy payload. We will do this by building the first stage with composites, fitting the Agni-6 with India's first composite 40-tonne rocket motor. This is a technical challenge but we have good capability in lightweight composites," says Chander.

The road mobile Agni-6 would also have stringent limits on its length. "It must be carried on a standard size trailer that can move from one part of the country to another, turn on our roads, cross our bridges and climb our heights. As the payload weight increases, we will require more advanced technologies to keep the missile's length constant," explains Chander.

Coaxing higher performance from smaller rockets becomes especially important in submarine launched ballistic missiles (SLBMs), which can be no longer than 13 metres so that they can fit into the cramped confines of a submarine. Even long-range SLBMs that can fly 14,000 kilometres, like the Chinese JL-2, are built no longer than 13 metres. The DRDO faces this challenge as it develops the K-4 SLBM for the country's Arihant-class nuclear-propelled ballistic missile submarines (SSBNs).

Eventually the Agni-6 will be no taller than the Agni-5, i.e. about 17 metres, says Chander. It will, however, be heavier and thicker - slightly over two metres - which will cater for the different shape of the MIRV payload.

"The timeframe for developing a new missile system is about five years and the DRDO has mostly achieved this in the Agni programme," says Chander. Calculating five years from April 2012, when the Agni-5 had its debut launch, the first test of the Agni-6 could happen in 2017.

The DRDO says the Agni-6 will have a longer range than the 5,000-kilometre Agni-5, but is not mentioning figures. "The MARVs and MIRVs will give us extended range. I will not be able to tell you how much because that is secret," Saraswat told Business Standard.

Ballistic calculations, however, suggest that at least some of the MIRV warheads on the Agni-6 would reach at least 6,000 kilometres. In a missile that travels 5,000 kilometres, the last MIRV warhead released flies an extra 1,000 kilometres.

Currently, the DRDO is readying for the second test next month of the Agni-5 Intermediate Range Ballistic Missile. This will be fired in the same configuration as its debut test a year ago, in order to establish the missile's reliability. A third test by end-2013 will see the missile fired from a canister.

"We will conduct at least five-six more Agni-5 tests before the missile enters operational service. After the repeat test this month or the next, we will conduct two test firings from a canister. Then the military units that will operate the Agni-5 will conduct two-three test firings as part of the induction process. Even after induction, the users conduct test firings as part of the Strategic Forces Command training plan," says Avinash Chander.

The Agni-5 is a three-stage, solid-fuel missile but its first stage consists of a metallic rocket motor, while the second and third stages have composite motors.