S5-class submarine

S5 is the code name for a planned class of Indian nuclear-powered ballistic missile submarines currently being developed for the Indian Navy. S5 will weigh around twice as much as the preceding. It is reported that
four boats of the class are expected to enter Indian service by the late 2030s.

Design

The S5-class of submarines are planned to weigh around. The submarines are planned to be armed with up to twelve K6 Submarine-launched ballistic missiles, each armed with multiple independently targetable reentry vehicles.

In 2006, a high-level committee led by R. Chidambaram, the then principal scientific advisor to the Government of India, had assessed India's ability to construct three S5 series of SSBNs. The project with a budget of divided among DRDO, BARC and the ATV headquarters. The construction would tentatively begin in 2015 followed with the first submarine to be deployed in 2021. The has limitations with its reactor and payload capacity.
Around 2012, with the S5 project remaining in developmental stage, another Arihant-class submarine was cleared for production to avoid idling of the production line. The new unit was designated as S4*. The boat would also feature the Arihant Stretch design.
As of December 2017, the final design work for the submarine was underway. The submarine would be equipped with 12 ballistic missiles.
the S5-class submarine was to enter production by 2027.
As of September 2024, the design phase of the submarine was nearing completion and project sanction was expected soon.
In September 2025, the Times of India reported that the Bhabha Atomic Research Centre is developing a 200 MWe-rated nuclear reactor for the Indian Navy's next-generation nuclear submarines, including Project 77 and S5-class submarines.
In December 2025, it was reported that construction of the first two S5 SSBNs had commmenced with four of the submarines expected to be commissioned by late 2030s.''''''