A quietly interesting thing about this is that the same group that helped India get to the moon is now working to send people to the bottom of the ocean. India’s first deep-sea submersible that can carry people is being built at the Vikram Sarabhai Space Centre (VSSC), which is an ISRO facility better known for making rocket parts and spacecraft structures. It’s called Samudrayaan. The name of the car is Matsya-6000. And by 2027, three Indian aquanauts will go down six kilometers into the ocean if everything goes as planned.
That depth is not a small thing. The water pressure at 6,000 meters is about 600 bar, which is 600 times the pressure in the air at sea level. The temperature stays around -3°C. There is no light, no room for mistakes in the structure, and no quick way to get back to the surface. In terms of engineering, only a few countries have ever been able to make something that can safely carry people into that environment, keep them alive for 12 hours under normal conditions and up to 96 hours in an emergency, and then get them back. On that list are the US, Russia, China, Japan, and France. India wants to join them.
The crew compartment is a sphere that is 2,260 millimeters across and 80 millimeters thick. It is made from a titanium alloy called Ti6Al4V, which is ELI grade. In this case, titanium was the only real choice. It’s strong enough to withstand crushing pressure, light enough that it won’t sink the vehicle, and doesn’t rust in the way that saltwater at very low levels would speed up the rusting of almost any other metal. VSSC handled the design and material development. The bigger project is being run by the National Institute of Ocean Technology, which is part of the Ministry of Earth Sciences. They made a formal deal to work together to bring the sphere to life.
The welding is something that isn’t talked about enough. Electron Beam Welding is the process used to join two hemispheres of titanium together to make a single, perfect pressure vessel with walls that are 80 to 102 millimeters thick. With EBW, a focused beam of electrons in a vacuum is used to join metals together very precisely and with very little heat distortion. India’s Liquid Propulsion Systems Centre in Bengaluru had EBW capability, but only up to about 20 millimeters thick. To handle the Matsya-6000 sphere, they had to upgrade their machine from 15 kilowatts to 40 kilowatts. After almost 700 weld tests, the team decided on the final process parameters. That number — 700 — says more about the difficulty of the problem than any press release could.
Verifying the welds was hard in and of itself. The kilovolt range is where most X-ray systems used in manufacturing work. To look at titanium that is more than 80 millimeters thick, you need a 7.5 MeV X-ray system that can go through metal like a hospital scanner can go through bone. LPSC built that facility too, complementing it with ultrasonic testing techniques, including Time of Flight Diffraction and Dual Linear Array Phased Array methods. Artificially created defects were used to calibrate the systems and confirm that the inspections could actually catch real flaws. All of this will be reviewed by a third party, which is the right thing to do for anything that involves people’s lives.
It’s time to take a step back from the specifics of the problem. As part of their training, India’s two aquanauts did a dive in the Atlantic on France’s Nautile submersible. This is a small but important detail that makes the whole thing feel more real. It seems like the people in charge of this program know what’s at stake and aren’t skimping on quality to meet a deadline. The goal for 2027 is ambitious, maybe even very ambitious. But the methodical approach — hundreds of trials, multiple NDE techniques, third-party certification — suggests a team that has internalized the consequences of getting it wrong.
There is a strategic logic to this that goes beyond the engineering. Polymetallic nodules are found on the deep ocean floor. They are full of manganese, cobalt, nickel, iron, and rare earth elements. It has already used self-driving underwater vehicles to explore parts of the Central Indian Ocean Basin and found mineral-rich areas more than 5,000 meters below the surface. A human-rated submersible gives us options that robots can’t: the ability to see more clearly, make decisions in real time, and have the scientific presence that proves a country’s claim to a resource frontier that will become more important in the years to come.
Samudrayaan is not a project for its own sake. As with most serious engineering, it is slow, careful, and not very exciting. Seven hundred weld trials for a sphere that might never make the news outside of a small group of readers. That’s what it looks like to build something real.
