New Delhi: India’s naval forces are undertaking one of the country’s most ambitious underwater defence modernisation programmes, aimed at creating a highly integrated and standardised submarine fleet for the future.
The initiative focuses on developing the upcoming Project-77 nuclear-powered attack submarines (SSNs) and the Project-76 conventional submarines (SSKs) around a shared ecosystem of sensors, combat systems, weapons, and operational technologies. Defence planners believe the move will strengthen indigenous manufacturing capabilities, simplify crew training, and reduce long-term dependence on foreign defence suppliers.
At the heart of the programme is the concept of a unified “National Submarine” architecture that could eventually become the foundation for all future Indian underwater combat platforms.
A major component of this strategy is the development of a common indigenous Combat Management System (CMS), which will serve as the digital nerve centre for both submarine classes. Designed with a modular architecture, the CMS will integrate sensor fusion, weapon targeting, navigation, and battlefield management functions into a single operational framework.
The Navy also plans to standardise operator consoles and multi-function displays across both conventional and nuclear submarine fleets. This is expected to make maintenance and software upgrades easier while enabling smoother transition and training for submarine crews across different platforms.
The approach marks a major shift from India’s earlier procurement model, under which multiple imported submarine classes operated with different foreign-built combat systems and support ecosystems, often creating logistical and maintenance challenges.
Situational awareness technologies are also being unified. Both submarine classes are expected to replace traditional optical periscopes with advanced non-penetrating optronic masts being developed by Instruments Research and Development Establishment. These next-generation masts will provide high-definition optical, thermal, and infrared imagery directly to the CMS through secure fibre-optic networks.
In addition, both submarine fleets are likely to share common electronic warfare systems, communication masts, and Electronic Support Measures (ESM), ensuring standardised intelligence-gathering and surveillance capabilities.
India’s underwater strike capabilities are also moving toward convergence. Both submarine classes are expected to deploy the indigenous Varunastra heavyweight torpedo along with the under-development Takshak torpedo system.
According to defence assessments, the larger Project-77 nuclear submarines may feature a 24-cell Vertical Launch System (VLS) capable of deploying land-attack and hypersonic missiles. Despite the differences in size and propulsion, the launch interfaces for systems such as the Nirbhay cruise missile and future BrahMos hypersonic variants are expected to remain largely standardised across platforms.
This shared architecture could potentially allow Project-76 diesel-electric submarines to launch similar advanced missiles through torpedo tubes or modular launch systems, improving tactical flexibility while simplifying logistics and ammunition management.
Underwater detection systems for both submarine classes are being developed around a common Integrated Sonar System (ISS) by the Naval Physical and Oceanographic Laboratory. The sonar suite is expected to include bow-mounted, flank-array, and towed-array sonar systems along with passive interception capabilities for tracking hostile underwater threats.
To improve stealth performance, both classes are likely to use indigenous anechoic tiles — specialised rubber coatings that absorb enemy sonar waves and reduce internal machinery noise signatures.
One of the most significant technological overlaps under consideration is the possible adoption of shared pump-jet propulsion concepts. While the Project-77 SSNs will rely on nuclear propulsion and the Project-76 submarines will use diesel-electric systems with Air Independent Propulsion (AIP), pump-jet systems could substantially reduce underwater acoustic signatures compared to conventional propellers.
The two submarine classes will nevertheless differ considerably in size and mission profile. Open-source estimates suggest that the Project-77 SSNs could displace nearly 10,000 tonnes and operate using a compact 190 MW light-water nuclear reactor. In contrast, the Project-76 conventional submarines are expected to displace around 3,000 tonnes and rely on advanced lithium-ion batteries and AIP technologies.
Despite these operational differences, the Indian Navy is pushing for maximum commonality across acoustic systems, sonar technologies, battery management, combat interfaces, and weapons integration.
Both submarine programmes are also expected to use advanced high-tensile steel grades, including HY-130 class materials developed by Mishra Dhatu Nigam Limited, providing a significant boost to India’s domestic defence manufacturing ecosystem.
Defence officials believe the long-term standardisation plan is intended to help India avoid excessive dependence on imported technologies and maintenance ecosystems — a vulnerability often associated with earlier foreign-origin submarine acquisitions. By prioritising indigenous systems and shared architectures, India aims to create a more self-reliant, scalable, and future-ready underwater combat force.
