K-4 (SLBM)

K-4 is an intermediate-range nuclear-capable submarine-launched ballistic missile under development by DRDO of India to arm the Arihant class submarine and to complement K-15 Sagarika. The missile has an effective range of 3500 km.

Development
Difficulties with compacting the Agni-III to fit the 10 metre diameter INS Arihant hull led to the development of K-4. K-4 features range comparable to Agni-III while being significantly smaller in size (12m vs 17m). INS Arihant will carry 4 K-4s or 12 K-15s. The K-4 gas-booster were successfully tested from a submerged pontoon in 2010. There will be at least six tests before induction of K-4 which is likely to take place in 2017. The short development time of the missile is attributed to the fact that major systems of the missile were developed and perfected during the development of K-15 Sagarika missile.

Description
The K-4 is one of the most ambitious projects of the Defence Research Development Organisation (DRDO) and it was kept secret for many years. The missile is 12 metres long, has diameter of 1.3 metres and weighs 17 tonnes. It can carry a warhead up to 2 tonnes and uses solid propellant. This missile could be best characterised as a hypersonic cruise missile as it remains within the earth’s atmosphere during its entire flight duration. To make it even more survivable, it follows a zig-zag path in three dimensions. Defence scientists involved in the missile's development stated that the aim of the missile was to achieve a high accuracy, with a close to zero Circular error probable (CEP).

Once inducted, the missile will not only complete India’s third leg of the nuclear deterrent, but also be the second strike weapon system. It can target major Chinese cities even remaining away from the Chinese water. The next missile in this series is the K-5, which will have a strike range of nearly 5,000 km.

Testing
The missile was scheduled to be tested in September 2013, but the test was delayed due to unspecified technological development. It is now expected to be test fired in January 2014, from a pontoon (replica of a submarine) nearly 50 feet under the sea surface.