CHENNAI: A 27-member scientific crew from Chennai-based National Institute of Ocean Technology (NIOT), an autonomous body under the Union Ministry of Earth Sciences, created history in April this year conducting world's deepest underwater locomotion trials of an indigenously developed seabed crawler based mining machine at Central Indian Ocean Basin.
Even as the deadly second wave of coronavirus engulfed the country and brought life to standstill, the NIOT crew undertook a gruelling voyage onboard research vessel ORV Sagar Nidhi traversing 1,700 nautical miles (3,000 km approx) to execute a complex mission of field testing the 8-tonne crawler sending it to 5,270 metres deep down into the Indian ocean.
The crawler is a key component of Varaha deep sea mining technology, which is underdevelopment for harvesting polymetallic nodules from the depths of 6 km in the area allocated to India by the International Seabed Authority (ISA) in the Central Indian Oceanfor survey and exploration. It is part of Indian government's ambitious Deep Ocean Mission, which was formally launched last month with a purse of Rs 4,077 crore.
NIOT director GA Ramadass told The New Indian Express that the locomotion trails were successful and met all the intended objectives, paving way for the next level of development and trials at sea. "Entire underwater operation was transmitted live to NIOT and the Ministry of Earth Sciences headquarters via satellite link."
He said this test subsea mining machine forms the first level of the Integrated Mining System called Varaha. "This machine will be used for collecting polymetallic nodules, lying on the surface and just below the surface of the seabed, in the nodule bearing parts of the ocean. The subsequent stages of the development, viz. pumping the slurry of crushed nodules and seawater from these depths to the mother ship using a high pressure positive displacement pump and a riser hose, are in progress. An integrated demonstration is expected by 2024," Ramadass said.
The current trials conducted is a first for India at these enormous depths of over 5 km. This is also the first locomotion demonstration anywhere in the world for a seabed crawler, tethered to the ship through an umbilical cable, intended for deep sea mining.
The successful deep sea mining trials for collecting polymetallic nodules in the 1970s conducted in the Pacific Ocean were at depths just over 4 km. Presently, there are many countries and industrial consortia working in developing deep sea mining technology to sustainably collect these nodules lying on the seabed, as potential mineral resources for the future. Polymetallic nodules, the potato-like clumps, contain a variety of metals such as copper, nickel, cobalt and manganese.
How NIOT team pulled-off the Mission in hostile conditions
At 6 km depth, the pressure is over 500 times the surface atmospheric pressure and the ambient temperature is 3-4 degrees Celsius. The ocean conditions were rough making the mission even more complex, but still the team from National Institute of Ocean Technology (NIOT) did it with great precision.
Chief Scientist of the cruise K Gopakumar and the team shared their experience with The New Indian Express. The expedition started on March 20, meeting all the Covid-19 related safety and health protocols, by 27 of them signing-on onboard the ship ORV Sagar Nidhi at Chennai Port. The ship was an infection-free bubble and all the team members coming onboard had to be proved to be free of being infected or being carriers. The ship had her dedicated crew for running and operating the ship. The project team of deep sea mining were the designers, developers and also the operators, for deploying and testing the mining systems.
After necessary statutory clearances and preparations, the ship sailed out in the early hours of March 24 from Chennai Port. A few hours out of the harbour, we did our check dive in the Bay of Bengal at depths of 3,206 m. This was to test the mining system for functionality at these high depths, test the ship systems for integrated operations and to work-up the trial team, before proceeding to the trial site, far away to the southern latitudes of the Central Indian Ocean.
The distance from Chennai to the trial site at the CIO is about 1,700 nautical miles (i.e. over 3,000 km). The team reached the mining trial site at 13.5 degrees South latitudes on April 4, about 11 days after the departure from Chennai.
The southern latitudes for prolonged periods have rough weather and high swells and one has to wait patiently for a crack of fair weather, when such deep sea operations over nearly a day can be carried out. The team had to move little northwards within the allocated mining area, in lookout for improved ocean state conditions.
Moment of truth
Finally, on April 16, the trial commenced at 1115 hr with lifting off the mining system from the deck using a custom-built umbilical cable and deep sea winch and ship's stern mounted A-frame, and lowered into the water. It takes more than 4 hours to reach 5,000 m depth and these are anxious moments, with the ship in dynamic positioning (DP) heaving with the seas and the trial team monitoring and recording every aspect and parameter carefully. The systems were periodically switched on and tested during the deployment down, to ensure that the system is working and integrity maintained.
The crawler touched the seabed at 5,270 m depth by 1538 hr. The entire operation was observed through live video at the control station on the ship, heralded the successful landing of our mining system on the seabed. This was transmitted live from the ship to NIOT through the internet, from where it was transmitted live to the Ministry of Earth Sciences.
Crawler moved for 120 m for 2 hours
Robotic system was driven remotely from the ship over the 6500 m long umbilical cable connection. While the seabed locomotion continued at various speeds within planned mining speed range, driving over 120 m on the seabed for over 2 hours. All the systems worked as expected and all related data were collected as per our trial targets.
The lift off from the seabed was smooth and by 2110 hr the system was on deck from over 5000 m depth, bringing to completion the deepest dive to the seafloor, successfully undertaken by a mining system. Few more tests of the systems were conducted at the site before starting the journey back to Chennai.
Team shares anxious moments
Operations at sea, especially at these depths on the seafloor at over 5000 m depth, are always anxious. The ship on DP in a heaving sea, with the weather conditions so fickle. In addition, such deployments and trials involve a large set of specialized equipment, controlled remotely, manned and managed by a large team of engineers and marine crew, working in tandem. Our mission was planned and executed well, the systems worked as expected and prepared for and the sea and the weather held, wanting us to successfully complete our operations.