NEW DELHI: India is taking a crucial step for its Rs 1.2 lakh crore project to produce future nuclear-powered submarines, with top levels of the government processing clearances for the detailed design phase.The plan to build six advanced attack submarines — to be nuclear powered but armed with conventional missiles and torpedoes — is being monitored closely and the first of the boats could roll out in a decade if things go as per plan.Sources told ET that the initial design phase for the new boats has progressed successfully and more resources will now be deployed to move to the more complex detailed design and construction — to be undertaken by the Directorate of Naval Design Submarine Design Group) with assistance from the Defence Research and Development Organisation ( DRDO ).The timing of the critical clearances coincides with the pace of current work at the Ship Building Centre (SBC) in Visakhapatnam, where the Arihant class of nucleararmed submarines are being built. Major structural work on the fourth of the class is nearing completion and the centre would be able to take on work for the next generation of vessels as early as next year, if need be. Though this is unlikely as the developmental phase will take longer.Sources said the second of the Arihant class — the slightly bigger and better-armed INS Arighat — is expected to be commissioned this year, adding teeth to India’s nuclear deterrence. Two follow-on boats after that are likely to enter service before 2024.This would leave SBC with adequate space and resources to commence building the next generation of nuclear-attack submarines. While the Arihant project took over two decades to fructify, the next generation submarines are likely to progress at half the given time as adequate experience is now available, both in terms of design and construction of nuclear submarines.As reported by ET, work on the submarine project gained pace last year with a defence public sector unit working on a special metal alloy for the hull and testing of a scale model as part of the design process. The plan to build six nuclear-powered attack submarines (SSNs) kicked off in 2015 when the NDA government gave a go ahead to a long-pending project for the Indian Navy India and Russia have also signed a $3 billion deal to lease an advanced nuclear attack submarine that will be fitted with indigenous communication systems and sensors. This submarine will fill in the gap and will be used for crew training before the indigenous boats are pressed into service.Nuclear attack submarines — powered by a nuclear reactor but armed with conventional weapons — will give India a significant strike and area denial capability in the region. These vessels can remain underwater for months, making them almost impossible to detect and are a big deterrence for enemy vessels. The US Navy operates over 55 nuclear attack submarines. China has at least 10 in service and is rapidly expanding the fleet, including deployments in the Indian Ocean and several port calls to neighbouring nations.The project will enter India to a select league of five nations that have such a capability. The last country to enter this club was China in 1974 with its Han class boats. Details are not known but a new, more powerful nuclear reactor is being designed for the programme as well by the Bhabha Atomic Research Centre. The INS Arihant and Chakra (on lease from Russia) are the two nuclear-powered submarines currently in service with the navy.