The Indian Navy’s Russian-made Sindhughosh-class submarine INS Sindhukirti is set to undergo final trials on 26 June, after completing almost a decade-long retrofit at Hindustan Shipyard (HSL) in Visakhapatnam, Andhra Pradesh, India.

Commissioned in January 1990, the upgraded diesel-electric submarine is expected to be delivered to the navy in July. The final ‘full-power trials’ will be performed after the successful completion of ongoing sea-trials.

During the modernisation programme, the submarine received new weapons, sonars, and fire control systems.In addition, it will now be able to fire the 300km range Klub-S land-attack missiles.

HSL chairman and managing director rear admiral NK Mishra said: "Today is a red-letter day in our history as retrofitting involved a complex process, a more difficult process than building a new submarine.

"Our workforce deserved credit for completing the Herculean task adhering to stringent quality standards stipulated by the navy."

The retrofitting of INS Sindhukirti began in 2006 and was scheduled to be completed within three years.

"Retrofitting involved a complex process, a more difficult process than building a new submarine."

However, the programme faced delays after Russian authorities reportedly insisted on the use of electrodes and several parts manufactured in their country.

The total cost of the modernisation project is estimated at approximately Rs7bn ($110m) to Rs8bn ($125.6m).

India is currently planning to construct six new stealth submarines under Project-75India initiative.

Scheduled to be built on the lines of the predecessor P75 Scorpene production line, the new submarines will feature advanced detection range and combat management systems, as well as better sensors for optimum performance and a weapon system that includes torpedoes and missiles.

Image: An Indian Navy’s Sindhughosh-class submarine INS Sindhukirti. Photo: courtesy of