VESSEL REVIEW | DriX – Unmanned vehicle to support NOAA’s ocean exploration programs

The University of New Hampshire's Center for Coastal and Ocean Mapping (UNH CCOM), as a member of the Ocean Exploration Cooperative Institute (OECI) and funded by NOAA Ocean Exploration, has taken delivery of an uncrewed surface vehicle (USV) developed by French unmanned systems company iXblue.

The Drix USV and its dedicated launch and recovery system (LARS) have been fully integrated into Nautilus, the exploration vessel owned by the Ocean Exploration Trust. The USV is a versatile and efficient craft that can host a wide range of payloads and that offers optimum conditions for high-quality data acquisition in both shallow and deep waters.

The USV has a length of 7.7 metres, a beam of 0.824 metres, a draught of two metres, and a displacement of 1.4 tonnes. A 28kW diesel engine drives a fixed-pitch propeller via a straight shaft to deliver a maximum speed of 14 knots and an endurance of 24 hours. At a speed of four knots, the USV can stay out at sea for 10 days.

The hull is made out of composite material, making the USV lighter than vessels made from steel or aluminium. It also means the craft is not susceptible to corrosion. The use of a lightweight hull also enables the USV to be powered by smaller engines for the same level of performance, resulting in lower fuel consumption, reduced GHG emissions, and less radiated noise in the water.

iXblue said the highly hydrodynamic monohull and drop keel provide stability and balance to the platform and that the USV will pierce waves and cannot capsize, even in high sea states. Keeping movements to a minimum, the USV ensures high stability, thus widening the operation window of the onboard sensors.

DriX's shape and stability allow for very high-speed capabilities, reducing transit downtime and providing high survey speeds with improved data quality harvested in significantly less time. All sensors are embedded within a gondola located two metres below the surface, in a highly reduced-noise and bubble-free environment to offer optimum conditions for high-quality data acquisition.

DriX has the flexibility to work in both shallow and deep waters. With a draught of two metres, it is able to conduct missions in coastal shallow waters down to four-metre depths with all types of shallow water multibeam echosounders. The USV can also operate in deeper offshore waters thanks to iXBlue's proprietary tracking and communication systems.

The manufacturer added that the acquisition conditions are further induced by the craft's outstanding line keeping, including in high sea states (up to sea state five) and cross current situations. The post-processing phase can also be significantly shortened due to the high quality of the collected data.

An advanced collision avoidance system uses data fusion, gathering data from a variety of onboard sensors such as radar, LIDAR, and cameras. When combined with the USV's relatively small turning radius, collision avoidance is possible even in more restrictive waters. A follow me mode (FMM) enables the USV to transit over a large expanse of sea at high speed while staying in the wake of its mothership.

Deployment and recovery of the craft in conditions up to sea state three are done with the aid of a Bureau Veritas-certified LARS.

NOAA Ocean Exploration Director Jeremy Weirich said the USV can be operated over-the-horizon and away from a ship, thus increasing the rate at which the US Exclusive Economic Zone (EEZ) can be explored in support of the National Strategy for Ocean Mapping, Exploration, and Characterization. Supervised autonomous operation is also possible.

Drix was selected by OECI for its mission endurance, its ability to operate at high-speed, and its significantly enhanced offshore seakeeping ability. The craft will support NOAA Ocean Exploration's mission by providing mapping and characterisation capabilities and supporting other autonomous vehicles that are independent of the activities of the mother ship, greatly expanding the efficiency and effectiveness of ocean exploration operations.

Click here for more news stories, feature articles, and vessel reviews as part of this month's focus on unmanned craft.