First Blue Nodules field test successfully accomplished
On 20 August 2018 a Blue Nodules research team onboard the Spanish research vessel Sarmiento de Gamboa returned to the port of Cádiz, after a successful two weeks of trials at sea with Apollo II, the scaled mining vehicle prototype built by IHC Mining. The accomplishment of the first field test represents an important milestone in the Blue Nodules project. After extensive testing of individual components in the lab, the field test was the first occasion on which the technical and environmental performance of the integrated propulsion and nodule collector system could be assessed at open sea in an environment approximating seabed conditions in the deep eastern equatorial Pacific Ocean where future mining of polymetallic nodules is likely to take place.
Preparations for the field test had been intense, especially during the last four months preceding the test when the Apollo II test vehicle was assembled at IHC Hytech in Zaltbommel, The Netherlands. After an immersion test in the coastal North Sea off Rotterdam in late July had demonstrated that the vehicle was sea-water proof, Apollo II was loaded on a truck and, in a convoy of three more trucks carrying equipment, driven to Cádiz in southern Spain. Five days of hard work in port were needed, concluded with a harbor acceptance test of Apollo II on 7 August 2018, before all lights were green for RV Sarmiento de Gamboa to leave port and set course to the test area.
In the blue waters 10 miles offshore from Málaga, with the city and its mountainous hinterland in full view from the ship, Apollo II was hoisted overboard and lowered to the seabed 300 m below the ship and subjected to a sequence of technical tests. This was not done, however, before team members from NIOZ and University of Aarhus had made a first inventory of the local current regime, hydrographic characteristics of the water column, and consistence of the seabed sediment, and participants from Flanders Marine Institute (VLIZ) had surveyed the seabed by means of remotely operated vehicle (ROV) and confirmed that it was free of potential obstacles.
During test runs of Apollo II, the performance of the vehicle was closely monitored by the IHC members of the research team, who received a continuous stream of data and live video images from the vehicle via the umbilical cable by which it remained connected with the ship. After gaining confidence with simple exercises – driving straight ahead, driving at different speed, turning, and switching the hydraulic collector on and off – more complex exercises were performed. While driving Apollo II over the seabed, the CTD water column profiler and ROV were deployed from the ship to monitor and sample the plume of suspended sediment drifting in the wake of the vehicle.
Nearing the end of the field test, a final experiment was set up, in which Apollo II was driven along a path parallel to an array of moored current profilers and turbidity sensors. In a first try this experiment nearly caused the premature end of the field test, when the umbilical of Apollo II crossed one of the mooring lines anchored to the seabed, pulling the mooring line down and jamming the steering system of the vehicle. A second try two days later worked out better, and whilst Apollo II covered a total distance over the seabed of 3.5 km, the moored sensors clearly recorded the passage of the sediment plume as it drifted away with the bottom current.
Even though this fourth and final test run ended a few hundred meters before the planned finish line due to a jammed steering mechanism, this could not spoil the cheerful mood of the entire field test team about the overall success of the trials. On its first full test at sea, Apollo II had been immersed for a total of 128 hours, during which the electronical control system remained fully functional, except for for a failure of the collector pump motor just before the end of the test. In this time the vehicle drove a total distance of 5 km while performing a sequence of technical tests. Excellent weather and sea-state conditions contributed to the success of the field test, as did the technical qualities of RV Sarmiento de Gamboa and the professionality of its captain and crew, and CSIC-UTM staff providing support both on board and on land.
The test team gained a great deal of experience in overall operation of the system, which will be of great use during the second field test scheduled for the summer of 2019. Until then, there is a lot of technical and environmental data analysis to be done, to provide feedback to the IHC engineering team to design an efficient nodule collecting system with optimal environmental performance.