The Indian Navy marked a milestone in its undersea operations with the successful deployment of its Deep Submergence Rescue Vehicle (DSRV) Tiger X during a multinational submarine rescue exercise called XPR-25, hosted by the Singapore Navy.
For the first time, India’s submarine rescue system operated outside the Indian Ocean Region, executing a full-spectrum rescue drill in the South China Sea that saw the Indian DSRV dock with allied submarines under simulated conditions.
The Exercise: XPR-25
XPR-25, conducted between September 15-25, brought together more than 40 countries and their naval contingents. Structured in two phases — a shore phase (September 15-20) and a sea phase (September 21-25).
The DSRV Tiger X deployed.
Three submarine rescue units participated in the sea phase. Each was embarked on a dedicated mother ship: Singapore’s MV Swift Rescue, Japan’s JS Chiyoda, and India’s recently commissioned INS Nistar. These operated alongside submarines from the South Korean Navy, the Japan Maritime Self-Defence Force, and the Singapore Navy, which simulated as “disabled submarines” (DISSUBs).
Maiden Dive In South China Sea
The defining moment came on September 23, when India’s DSRV Tiger X carried out its maiden dive outside home waters. The mini-submersible first achieved mating with South Korea’s submarine Shin Dol-Seok (S-082). Shortly after, it docked with Singapore’s submarine RSS Invincible, completing two successful matings.
India’s DSRV Tiger X achieved mating with South Korea’s submarine Shin Dol-Seok (S-082)
India currently operates two DSRVs procured from the UK-based company James Fisher Defence (JFD Global) under a 193 million pounds contract signed in 2016. Each system includes the rescue vehicle, launch and recovery equipment, TUP systems, and comprehensive logistics support, with maintenance guaranteed for 25 years.
In deep-sea missions, the TUP system (Transfer Under Pressure) is a special setup that helps safely move people from one pressurised space, like a submarine or DSRV, to another without suddenly changing the pressure. For example, it can transfer crew from a rescue submarine or a diving bell into a bigger hyperbaric chamber or even a lifeboat, while keeping the same pressure so they don’t suffer from decompression sickness.
INS Nistar: A New Mothership
The exercise also marked the first operational deployment of INS Nistar, India’s indigenously designed Diving Support Vessel (DSV). Commissioned on July 18, the 118-metre-long vessel was built by Hindustan Shipyard Limited (HSL).
The INS Nistar was commissioned this year.
The order for two DSVs was placed in 2018, with delays arising from the COVID-19 pandemic. Both vessels were launched in 2022, and Nistar was formally delivered to the Navy on July 8. The ship has since been assigned to the Eastern Naval Command, headquartered in Visakhapatnam, which also operates India’s nuclear-powered submarines.
With a displacement exceeding 10,000 tons, a beam of 23 metres, and an endurance of over 60 days, Nistar has been purpose-built to act as a mothership for DSRVs. It carries a 15-tonne subsea crane, a diving bell, ROVs, side-scan sonar, compression chambers, and a Self-Propelled Hyperbaric Life Boat. A front flight deck allows for helicopter operations.