Measuring 10m (32 feet) long with a range of 3,500 km, the SLBM is destined for the indigenous nuclear submarine INS Arihant

The Defence Research and Development Organisation (DRDO) successfully test-fired India’s first submarine-launched ballistic missile, the K4 SLBM, from underwater on 19 January.

Having been trialled many times in the past seven years, this landmark test was carried out off the coast of Visakhapatnam from a submerged platform. It is expected to be the mainstay for the Indian Navy’s (IN's) submarine-based missiles. Titled the ‘Black Project’, the program remained classified for a long time.

‘The K-4 SLBM, with its very low circular error probability [CEP] and the ability to carry a variety of strategic warheads, adds strength to India’s projection of power in the Indian Ocean area,’ Rahul Gangal, a partner at consulting firm Roland Berger, told Shephard. The K-4 is believed to have a CEP of less than 40m.

‘The test augments India’s focus on creating a powerful deterrent on the front with China. It also underlines how the IN is making sustained progress, with a larger number of programmes achieving operational maturity as compared to the other two wings of the Indian military establishment,’ added Gangal.

Commissioned in 2016, Arihant is capable of accommodating four K-4 missiles or 12 K-15s. The submarine displaces 6,000t and is powered by an 80+MW light water reactor.

Then defence minister Nirmala Sitharaman said after one milestone was achieved in 2018: ‘India has achieved completion of her nuclear triad with the first successful deterrence patrol by INS Arihant. This places India in the league of the few countries that can design, construct and operate strategic-strike nuclear submarines.’

The K-4 is one of four K-series SLBMs named after former President A.P.J Abdul Kalam. The Sagarika/K-15, with a shorter range of between 700-1,500 km, is the SLBM version of the land-based Shaurya missile. To be integrated with Arihant-class submarines, it will have access to the Indian Regional Navigation Satellite System.

The K-5 missile is reportedly being developed by the DRDO for Indian strategic underwater platforms. The K-6 missile, with a 6,000 km range, is also reportedly under development by the DRDO’s Advanced Naval Systems Laboratory in Hyderabad.