BENGALURU: In a step towards India’s first human mission into the deep ocean, the National Institute of Ocean Technology (NIOT) and Isro’s Vikram Sarabhai Space Centre (VSSC) have successfully completed a critical welding process for Matsya-6000 — a crewed submersible being developed under the Ministry of Earth Sciences’ “Samudrayaan” project.Samudrayaan is part of the Deep Ocean Mission and aims to send a three-member crew into the ocean up to a depth of 6km. Central to this effort is the creation of a Human Occupied Vehicle (HOV) that can withstand extreme pressure and temperature conditions on the seafloor.“At the heart of the HOV is a titanium personnel sphere, a 2,260 mm diameter enclosure with 80 mm thick walls, made from a high-strength Ti6Al4V (ELI grade) alloy. Designed by VSSC, the sphere is built to endure pressure up to 600 bar and temperatures as low as -3°C,” Isro said Wednesday.ChallengesIt added that the critical challenge in realising this human-rated vessel lay in developing a reliable high-penetration Electron Beam Welding (EBW) process to join the thick titanium components. “This required welding depths between 80mm and 102mm, a first for the country. The Liquid Propulsion Systems Centre (LPSC) led this effort, establishing the necessary welding infrastructure and non-destructive evaluation (NDE) facilities,” Isro said.LPSC’s Bengaluru facility, which previously handled EBW up to 20mm, was significantly upgraded, Isro said, adding that the EBW machine was enhanced from 15kW to 40kW capacity, and additional systems were installed for chemical cleaning and handling the high mass components. “The existing X-ray testing system, which operated in the kilovolt range, was similarly upgraded to a 7.5 MeV facility to enable deeper inspection. To ensure safety and certification, multiple NDE methods were employed to verify weld quality — including Time of Flight Diffraction (TOFD) and Dual Linear Array Phased Array Ultrasonic Testing (DLA PAUT). 700 trialsNearly 700 welding trials were carried out to fine-tune process parameters. Artificial defects were introduced in test samples to validate and calibrate the inspection techniques. Third-party agencies are reviewing and certifying the welding specifications, qualification protocols and NDE processes.The breakthrough came with the successful completion of the first high-penetration weld on the actual sphere hardware. This involved 80 mm thick welds over a 7,100 mm length, achieved in a continuous 32-minute operation, “a national first in scale and precision” as per Isro.The milestone marks a significant leap for India’s underwater exploration ambitions and brings Matsya-6000 closer to sea trials. Once complete, the vehicle will be among the very few human submersibles in the world capable of reaching such depths, opening new frontiers for deep sea science, resource exploration and technology development.
