New Delhi: In a major leap forward for India's Deep Ocean Mission, the Indian Space Research Organisation (ISRO) has successfully completed a critical welding process for MATSYA-6000, the country's first human-rated deep-sea submersible capable of diving up to 6,000 metres beneath the ocean surface.

The breakthrough marks a significant engineering feat, achieved after more than 700 weld trials on the titanium personnel sphere at ISRO’s Liquid Propulsion Systems Centre (LPSC) in Bengaluru, reports TOI.

The titanium sphere, the core of the submersible, has been jointly developed by ISRO’s Vikram Sarabhai Space Centre (VSSC) and the National Institute of Ocean Technology (NIOT), under the Ministry of Earth Sciences (MoES). The 2.26-metre-diameter crew compartment, with 80mm-thick walls, is built to withstand extreme deep-sea pressures up to 600 bar and temperatures as low as -3°C.

Achieving the high-precision weld required for the sphere was among the most challenging aspects of the mission. ISRO had to upgrade its electron beam welding (EBW) capability from 15kW to 40kW and conduct extensive trials to develop a robust, high-penetration weld process. The final 80mm-thick weld, covering a length of 7,100mm, was executed in a single, continuous 32-minute operation, a national first in both scale and precision.

Earlier, MATSYA-6000 has also completed a round of integrated wet tests at the L&T Shipbuilding facility at Kattupalli Port, near Chennai. Conducted from January 27 to February 12, 2025, the tests evaluated the submersible’s functionality across critical parameters, including power systems, stability, manoeuvrability, life-support, navigation, and communication.

The harbour trials involved eight dives, five unmanned and three manned, validating the integration of all subsystems, including the human support system, underwater navigation devices, thrusters, ballast systems, and scientific payloads. Due to limited harbour depth, underwater voice communication faced challenges, prompting the need for further deep-water trials.

Officials now plan a 500-metre depth demonstration by the end of 2025, setting the stage for full ocean-depth missions in the years ahead.

What is MATSYA-6000?

MATSYA-6000 is a 4th-generation deep-ocean human submersible developed under Samudrayaan, part of India’s Deep Ocean Mission. Designed to carry three occupants, the vehicle features a titanium crew sphere, syntactic foam for buoyancy, electric thrusters for multi-directional movement, and advanced control and life-support systems. All major components and software have been indigenously developed.

The mission, targeted for completion by 2026, aims to boost India’s capabilities in deep-sea exploration, resource mapping, and marine biodiversity studies. It will allow scientists to access mineral-rich zones in the Indian Ocean, including rare earth elements, cobalt, and nickel.