VESSEL REVIEW | Princeton University acquires unmanned vehicle for earthquake research

Massachusetts-based unmanned technology company SeaTrac Systems has supplied one of its unmanned surface vehicles (USVs) to Princeton University for use by geosciences experts.

A team led by Princeton’s Dr Frederik Simons will use the craft for activities related to seafloor geodesy, which is the science of understanding the depth, shape, and movement of the seafloor, and how seafloor bathymetry relates to its gravitational and magnetic fields. By combining acoustic data with GPS/GNSS data (GPS-A), the team’s specific interest is persistently monitoring deep seafloor tectonic plate movement to better measure its change and shape before and after earthquakes.

Using an innovative system and method for seafloor geodesy developed by underwater acoustic research and design company DBV Technology, the craft employs either Temporary or Continuous Deep Ocean Geodetic Sensors (T-DOGS and C-DOGS), which measure seafloor tectonic plate movement at any ocean depth, using very low power, and for very long-term deployments more accurately and economically than present methods. To this end, the SeaTrac USV will transit desired acoustic survey data paths for up to 12 hours at a time, loiter over the DOGS to receive their telemetered data, and regularly send the data to shore via satellite.

The USV selected for the studies is designed to  efficiently, safely, and cost-effectively perform real-time data collection and communications in all marine environments. Powered by solar energy with a large payload capacity and power, the platform enables the use of various combinations of payloads including high-powered sensors during any one mission.

The craft boasts self-righting ability and can autonomously operate continuously over long durations, reducing the risk and costs for marine data collection over conventional methods. Deployment and recovery can be done without specialised equipment, ensuring fast mobilisation and demobilisation with a smaller logistical footprint.

The SeaTrac USV has a length of 15.9 feet (4.8 metres), a beam of 4.6 feet (1.39 metres), a draught of only 1.4 feet (0.42 metre), an empty displacement of 606 pounds (275 kilograms), and a payload capacity of 154 pounds (70 kilograms). A 1kW brushless motor powered by a 6.75kWh lithium battery propels the craft to speeds of up to five knots while the solar panels with a total capacity of 750 W allow it to stay out at sea for months at a time, ensuring comprehensive data collection. Navigation is possible even under Beaufort Force Seven conditions, though the hull is designed to withstand up to Beaufort Force 11.

For full or supervised autonomous navigation, the craft relies on a collision avoidance system consisting of AIS, running lights, and cameras providing a full 360-degree field of view. A waterproof handheld remote provides operators with direct control of the USV using a line-of-sight RF link for up to roughly 0.25 mile (0.4 kilometre) with a standard whip antenna or up to two miles (3.2 kilometres) with a directional antenna. It is intended for launch and recovery operations or for any other time when local manual control is needed. For storing collected data, the USV has a local server, though data may also be uploaded directly to the cloud while the craft is deployed.

The Princeton University team conducted test missions using the SeaTrac USV in Puerto Rico in the autumn of 2022 and in Bermuda the following spring.

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