The Indian Space Research Organisation (ISRO) and the National Institute of Ocean Technology (NIOT) have successfully completed a critical welding process on the personnel sphere of the deep-sea submersible Matsya-6000 for the Samudrayaan mission, marking a major milestone in India's Deep Ocean Mission.

This titanium sphere, which will serve as the crew capsule for this manned submersible, has a diameter of 2,260 mm and walls 80 mm thick, designed to withstand pressures up to 600 bar and temperatures down to -3°C at depths of 6,000 meters under the sea.

The weld involved joining thick titanium alloy plates—a difficult metal to weld—using advanced electron beam welding (EBW) technology, typically reserved for spacecraft and nuclear energy components. This was India's first-ever high-penetration weld on such thick titanium material, covering a length of 7,100 mm executed continuously over 32 minutes.

Achieving this weld was particularly challenging due to titanium's high reactivity with oxygen and nitrogen, which can cause porosity and embrittlement in the weld. To meet these challenges, ISRO's Liquid Propulsion Systems Centre (LPSC) in Bangalore enhanced its welding infrastructure, upgrading the EBW machine capacity from 15 kW to 40 kW and adapting chemical cleaning and handling equipment.

For quality assurance, they developed a high-energy 7.5 MeV X-ray radiography facility for non-destructive evaluation (NDE) to certify the weld's integrity without damaging it. Multiple NDE techniques—including Time of Flight Diffraction (TOFD) and Dual Linear Array (DLA) Phased Array Ultrasonic Testing (PAUT)—were used to detect microscopic defects and ensure safety and reliability.

The completion of this weld came after nearly 700 trial welds, some including artificial defects to rigorously test the process, making this a pioneering achievement for India in human-rated deep-sea submersible technology.

This critical step brings the Matsya-6000 closer to underwater trials and eventual deployment. Once operational, it will place India among a select group of nations capable of sending humans to depths of 6,000 meters for deep ocean exploration, mineral resource assessment, marine biodiversity studies, and advanced underwater technology development.

This welding accomplishment is not only a technical breakthrough in materials engineering but also a foundational achievement that advances the Samudrayaan mission’s goal of human-crewed deep-sea exploration, expected to realize full operational capacity by around 2026.

Agencies