The unseen depths: A look at the general characteristics, history, and accidents of the K-152 Nerpa Submarine

The fearsome Russian attack submarine K-152 Nerpa, propelled by nuclear power, had a turbulent past, involving delayed development and an awful disaster in 2008. The difficulties involved in the submarine’s operations are highlighted by two incidents: a damaging incident in 2017 and a death accident in 2008.

In 1993, Russia began development on the Nerpa, an 8,140-tonne nuclear-powered attack submarine that was formerly known as Project 971 (or Project 518; NATO: Akula-class). However, progress was suspended due to a lack of funds. India then became the sponsor, helping the completion of the submarine’s construction and performing sea trials. K-152 Nerpa, which was launched in October 2008, formally joined the Russian Navy’s fleet in late 2009.

General Characteristics:

The Russian submarine Nerpa (K-152) is a powerful nuclear-powered attack submarine known for its capabilities. When surfaced, the submarine has a displacement of 8,140 tonnes (8,010 long tonnes), which adds to its operational prowess. The vessel’s length ranges from 108.0 to 111.7 metres (354.3 to 366.5 feet), though precise dimensions may vary depending on the source. Its beam is 13.5 metres (44 feet 3 inches), and the draught is 9.6 metres (31 feet 6 inches).

The Nerpa, equipped with advanced nuclear propulsion technology, is an imposing opponent in the undersea domain. Its significant displacement, combined with precision engineering in length, beam, and draught, demonstrates its effectiveness as a nuclear-powered attack submarine. The vessel’s strong design and proportions contribute to its adaptability, allowing it to negotiate a wide range of marine settings with efficiency and stealth. 


In 2008, Russia and India were negotiating a $2 billion leasing agreement for the K-152 Nerpa and another Project 971 Shchuka-B-class submarine. The planned lease, at an estimated $670 million, stated that the K-152 Nerpa would be in India’s control for ten years. This submarine, known as INS Chakra after being commissioned on December 30, 2011, was critical to India’s Arihant-class nuclear submarine programme.

Before its delivery, Indian naval sailors trained in St Petersburg, with more groups scheduled to participate in sea trials at Vladivostok in late 2008. The crew’s training was regarded as critical for India’s independent nuclear submarine projects. Despite a mishap in 2008 and conflicting reports on the status of the lease, Russian officials eventually verified the submarine’s handover to India by the end of 2009, with Russian President Vladimir Putin providing a financial release of 1.2 billion roubles.

Nerpa was commissioned into the Russian Navy on December 28, 2009, and underwent additional modifications in February 2010. Russia resumed preparing an Indian Navy crew for the submarine’s passage to India, to commission the INS Chakra by October 2011. Russian Navy Chief Admiral Vladimir Vysotsky verified the Indian crew’s readiness for the 10-year lease on July 1, 2011. On January 23, 2012, INS Chakra was officially commissioned at Bolshoy Kamen, and it set sail from Vladivostok to its Indian base in Visakhapatnam. On April 4, 2012, the sub was officially inducted into the Indian Navy.

However, Nerpa’s service with the Indian Navy was cut short, and it was returned to Russia in June 2021, before the 10-year lease expired. The decision was made due to reliability and maintenance concerns with the power plant, as well as the vessel’s overall condition. The vessel is heavily utilised by the Indian Navy for crew training on sophisticated nuclear submarines. Other reports stated that in spring 2020, a high-pressure air cylinder positioned between the two hulls exploded, resulting in the regrettable loss of a crew member and damage to electronic weapons, hydro-acoustic equipment, and hulls.


A fatal incident occurred aboard the Russian submarine K-152 Nerpa on November 8, 2008, at 8:30 p.m. local time, during an underwater test run in the Pacific Ocean. The submarine, which was carrying 208 people (81 military personnel and 127 civilians), suffered an unprecedented disaster killing at least 20 people due to asphyxiation and injuring another 21. This was the worst Russian submarine accident since the Kursk sank in 2000.

The accident was caused by the accidental activation of a fire extinguishing system, which locked two forward compartments and released Halon 2402 (Freon R-114B2), and dibromotetrafluoroethane gas into them. Survivors described being caught off guard by the gas discharge, with warning sirens ringing only after the gas had begun to fill the compartments. Unfortunately, several victims were unable to activate breathing kits before succumbing to suffocation. Initial investigations led to an “unsanctioned operation” of the fire suppression system, which had triggered automatically without human participation. Subsequent investigations indicated that a crewman had activated the system “without permission or any particular grounds.”

In early October 2017, Indian media reported that the INS Chakra had been damaged when it entered Visakhapatnam harbour. The submarine, built in collaboration with India and Russia, sustained a big hole in its bow sonar dome. A joint investigation with a Russian team was launched, which eventually led to the dry docking of INS Chakra for repairs. The damage repairs were ₹125 crore ($20 million). This incident highlighted the difficulties and complexities associated with submarine operations, emphasising the significance of severe safety precautions and joint efforts to mitigate hazards.