OPINION | INS Nistar: Elevating the Indian Navy’s Submarine Rescue Power

In the vast expanse of the Indian Ocean, where strategic maritime operations unfold, the Indian Navy has taken a significant stride forward with the commissioning of INS Nistar. This indigenously designed and constructed diving support vessel, inducted on 18 July 2025 in Visakhapatnam, marks a milestone in enhancing the Navy’s underwater rescue capabilities.

Built by Hindustan Shipyard Limited at a cost of Rs 2,393 crore, INS Nistar embodies India’s push towards self-reliance in defence technology, with over 80 percent indigenous content involving more than 120 micro, small, and medium enterprises. As the first of two such vessels, it serves as a vital asset for deep-sea operations, highlighting the Navy’s commitment to safeguarding its submariners.

The Role of INS Nistar in Submarine Support

INS Nistar, measuring 118 metres in length and displacing over 10,000 tonnes, is equipped with state-of-the-art facilities that position it as a cornerstone of the Indian Navy’s submarine rescue framework. It acts as the ‘mother ship’ for Deep Submergence Rescue Vehicles (DSRVs), providing logistical and operational support during emergencies. The vessel’s advanced equipment includes remotely operated vehicles (ROVs), self-propelled hyperbaric lifeboats, and diving compression chambers, enabling it to conduct saturation diving and salvage operations up to depths of 300 metres.

This capability is crucial for a navy that operates a diverse fleet, including conventional submarines like the Sindhughosh, Shishumar, and Kalvari classes, as well as nuclear-powered ones. By serving as a mobile base, INS Nistar ensures rapid deployment and sustained support in the Indo-Pacific region, where India emerges as a preferred partner for submarine rescue. Its induction not only boosts operational readiness but also highlights the Navy’s proactive approach to maritime security.

Understanding Deep Submergence Rescue Vehicles (DSRVs)

At the heart of modern submarine rescue lies the Deep Submergence Rescue Vehicle, a sophisticated mini-submarine designed to locate and evacuate personnel from distressed submarines. The Indian Navy acquired its first flyaway DSRV system in 2018, supplied by James Fisher and Sons from the UK, making India one of a select few nations with this advanced technology.

A DSRV operates without a tether, allowing it to manoeuvre freely at depths of up to 650 meters. Crewed by three operators, it can rescue up to 14 personnel per trip by ‘mating’ with the submarine’s escape hatch, a process in which it seals onto the hull to create a pressurised transfer chamber. This third-generation system is engineered for extreme sea conditions, up to Sea State 6, ensuring reliability in challenging environments.

The vehicles are air-transportable, enabling swift mobilisation from bases in Mumbai or Visakhapatnam to any global location via air, land, or sea. Once deployed, the DSRV uses sonar and ROVs to locate the disabled submarine, assess its condition, and initiate rescue. This capability was demonstrated when the Indian Navy assisted Indonesia during the 2021 Nanggala submarine incident, showcasing its regional leadership.

Diving Support: Enabling Safe Underwater Operations

Diving support forms a critical pillar of submarine rescue, and INS Nistar excels in this domain with its multi-deck saturation diving complex. Saturation diving enables divers to live and work at high pressures for extended periods, thereby minimising decompression risks. Onboard compression chambers maintain a controlled environment, while ROVs extend their reach to 1,000 metres for monitoring and salvage, eliminating human risk.

These systems support tasks like clearing debris around a submarine’s hatch or inspecting hull integrity. By integrating such technology, INS Nistar ensures divers can operate efficiently, enhancing the overall rescue timeline and safety.

The Submarine Rescue Process: Step by Step

Submarine rescue is a meticulously orchestrated process that combines technology and expertise to save lives under immense pressure. It begins with detection: upon receiving a distress signal, rescue teams deploy assets to locate the submarine using sonar and EPIRBs.

Once located, an initial assessment is conducted. A diver in an Atmospheric Dive System or an ROV inspects the site, confirming survivor presence and clearing obstacles. The DSRV then descends, mates with the hatch, and transfers personnel in groups, maintaining pressure to prevent decompression sickness.

Evacuees are brought to the surface via the DSRV and transferred to decompression chambers on the support vessel, such as INS Nistar, for gradual pressure normalisation. This cycle repeats until all are rescued, with the process capable of continuous operation thanks to the DSRV’s power tether.

In simulations and real scenarios, such as thermal stress management inside a disabled submarine, these steps ensure crew survival. The Indian Navy’s proficiency was evident in international exercises like Pacific Reach and MILAN, reinforcing its global standing.

The commissioning of INS Nistar marks a new era of underwater prowess for the Indian Navy. By integrating DSRVs, advanced diving support, and streamlined rescue processes, it not only safeguards national assets but also extends a helping hand to regional partners. This development reflects India’s growing maritime confidence and dedication to innovation, ensuring that in the depths of the ocean, hope and rescue are always within reach.

About Author

Cmde. Ranjit Rai is an Indian Naval Veteran who has served as the Director Naval Intelligence and Director Naval Operations, and is the author of the book ‘Indian Navy @75: Reminiscing the Voyage’