NEW DELHI: India tested its nuclear capable K-4 submarine-launched ballistic missile (SLBM), designed to have a strike range of 3,500 km, for the second time in six days on Friday. The missile test, as the one conducted on January 19, was undertaken from an undersea platform in the shape of a submersible pontoon off the coast of Andhra Pradesh.

The solid-fuelled K-4 missile is being developed by DRDO to arm the country’s nuclear-powered submarines in the shape of INS Arihant and its under-development sister vessels. INS Arihant, which became fully operational in November 2018 to complete India’s nuclear triad, is currently armed with the much shorter K-15 missiles with a 750 km range.

“The K-4 is now virtually ready for its serial production to kick-off. The two tests have demonstrated its capability to emerge straight from underwater and undertake its parabolic trajectory,” said a source.

India has the land-based Agni missiles, with the over 5,000-km Agni-V inter-continental ballistic missile now in the process of being inducted, and fighter jets jury-rigged to deliver nuclear weapons. But INS Arihant gives the country’s deterrence posture much more credibility because nuclear-powered submarines armed with nuclear-tipped missiles are considered the most secure, survivable and potent platforms for retaliatory strikes.

Once the K-4 missiles are inducted, they will help India narrow the gap with countries like the US, Russia and China, which have over 5,000-km range SLBMs. The K-4 missiles are to be followed by the K-5 and K-6 missiles in the 5,000-6,000 km range class.

The 6,000-ton INS Arihant, which is propelled by an 83 MW pressurised light-water reactor at its core, in turn, is to be followed by INS Arighat, which was launched in 2017. The next generation of nuclear submarines, currently called S-4, will be much larger in size.