Earlier this month, two Indian “aquanauts” travelled thousands of metres into the Atlantic Ocean aboard the French vessel, Nautile, in preparation for deep sea exploration under the Samudrayaan mission. India plans to send three humans to the depths of 6,000 metres as part of the mission by 2027.Cdr (Retd) Jatinder Pal Singh and R Ramesh travelled 5,002 metres and 4,025 metres respectively in dives that took place on August 4 and 5. Just as learnings from the Axiom-4 mission will enhance the Gaganyaan programme, the experience gained during the dives will inform the country’s deep sea exploration mission.First, what does the Samudrayaan mission entail?The Samudrayaan Mission is one of the six components of the Deep Ocean Mission approved by the cabinet in 2021 to explore and sustainably utilise the resources of the deep ocean. At the cost of Rs. 4,077 crores over five years, the Deep Ocean Mission will:Develop technologies for deep sea mining, underwater vehicles and robotics, as well as a crewed submersible for activities that require human intervention.Develop an ocean climate change advisory service by developing a suite of observations and models for future projections of important climate variablesLook for technological innovations for the exploration and conservation of deep sea biodiversity.Conduct deep ocean surveys, mainly to look for mineral depositsDevelop technologies to derive energy and freshwater from the oceanEstablish an advanced marine station for developing capacity in ocean biology and engineering in the country, helping translate research to industrial application to support the blue economy (economic growth based on ocean resources)Under the Samudrayaan mission, the coordinating agency, the National Institute of Ocean Technology, is developing a submersible capable of carrying three humans to the depths of 6000 metres.What is Matsya-6000? Matsya-6000 successfully underwent wet testing in February 2025 (PIB)Matsya-6000 is the vehicle that will carry the aquanauts to the deep sea under the Samudrayaan mission. Designed somewhat like a big fish, it will contain a personal sphere with a diameter of 2.1 metres that will house the humans. The vehicle will be capable of sustaining three humans for 12-hour missions, as well as systems to support them for up to 96 hours in case of an emergency.For the initial test involving carrying humans to a 500-metre depth, a personal sphere made of steel would be used. This, however, is not strong enough to bear the pressures at 6,000 metres under the sea — pressures up to 600 times what is felt at sea level. For the vehicle carrying humans to the deep sea, the personal sphere would be made of titanium alloy with 80mm thickness.When humans travel to the extreme depths of the ocean, they face several challenges, the biggest of which include keeping the vessel intact and all equipment functional even under extreme pressure. Communicating from the depths of the ocean is also a big challenge that the Indian scientists had to overcome in planning for the mission.DEVELOPING THE VESSELStory continues below this adThe first challenge is developing a vehicle capable of sustaining life in the deep sea. Titanium alloy was chosen as the preferred material for manufacturing the personal sphere. However, it is not commonly found, and not many countries are willing to share their reserves.Even after acquiring the material, the sphere must be fabricated through a precise technique called electron beam welding, where a focused beam of high-velocity electrons melts and joins the materials. The method is very precise and does not create any areas of structural weakness. Dr M Ravichandran, Secretary of the Ministry of Earth Sciences, said: “When we say 80mm thickness, it has to be precisely the same across the sphere. Even a 0.2mm deviation could lead to the collapse of the structure under such intense pressures.”Also Read | ISRO conducts air drop test for Gaganyaan: why is it crucial to the mission?The titanium alloy sphere is being fabricated by the Indian Space Research Organisation.MAINTAINING THE ENVIRONMENTGiven that the aquanauts will be restricted to the personal sphere deep underwater, there is a requirement for life-support systems to maintain the environment within. These systems must ensure that the oxygen levels remain precisely at 20% and the carbon dioxide levels are managed with scrubbers absorbing it.Story continues below this adThe personal spheres will also be equipped with packed re-breather oxygen systems, which will be deployed during emergencies. These systems can recirculate the user’s exhaled air after removing carbon dioxide and adding oxygen, similar to systems used for diving.AQUANAUT HEALTHThe aquanauts must be physically fit to ensure they can conduct the missions properly and handle any emergencies safely. They also tend not to eat or drink too much before and during their mission as they are restricted to the sphere and cannot access washrooms. During the nine-hour-long dive undertaken by Cdr Singh, he limited his diet to some dry fruits he had carried with him.ACOUSTIC COMMUNICATIONCommunication is another major challenge for deep sea missions. Since the radio waves, on which our day-to-day communications are based, cannot penetrate the water, deep sea missions need to use acoustic telephones, where sound waves carry information through the sea to a receiver placed just underneath the surface of the water.Given that most countries are unwilling to share the technology, India has developed an acoustic telephone on its own. When it was tested initially at a harbour, however, it did not work. This is because factors such as the temperature and salinity of the water play a role in the effectiveness of such communication. It did work later in the open ocean.Why is India investing in deep sea missions?Story continues below this adWith its 7,517 km long coastline, the Indian government has long pushed for a Blue Economy policy to support future growth. The deep ocean is home to several minerals, fuels, and biodiversity resources, several of which remain unexplored. Union Science Minister Dr Jitendra Singh says that the unexplored and under-explored domains of deep sea and space will contribute significantly to the government’s vision of Viksit Bharat.There are presently only a few countries with deep sea exploration capabilities, including the United States, Russia, China, Japan, and France. India will join this select group of nations with the Samudrayaan mission.