In A Historic First, Underwater Drones Collect Real-time Acoustic Data Off Hawaii

The Naval Postgraduate School of U.S. and Seatrec, manufacturer of energy harvesting systems that generate electricity from ocean temperatures, have together developed an autonomous underwater drone, the Persistent Smart Acoustic Profiler (PSAP) Voyager, capable of collecting and transmitting oceanographic and acoustic data in real-time and nearly indefinitely.

The PSAP Voyager was deployed off the coast of Kona, Hawaii, in November 2024. It operates using ocean thermal energy conversion, allowing it to power its onboard instruments without requiring battery swaps, external power sources, or data retrieval.

This marks the first-ever acoustic data collection by hydrophone-equipped underwater drones powered by energy harvested from the ocean’s temperature differences. The system is expected to benefit naval operations, research and marine science.

Naval forces rely on stealth and quiet operations at sea, making underwater acoustic sensing essential.

Traditional hydrophones used for listening to underwater sounds are either deployed from ships, costing around $50,000 per day, or placed on the seafloor with power cables connected to land, a method only available in a few locations.

The PSAP Voyager eliminates these limitations by self-generating power and operating independently in any part of the ocean.

Reports reveal that PSAP Voyager is designed to remain deployed indefinitely, transmitting data in real time without needing retrieval for maintenance or data transfer.

It uses energy-harvesting technology that converts temperature differences in the ocean into electricity, making it a cost-effective and sustainable solution for ocean monitoring.

Passive acoustic sensing plays a major role in undersea warfare, marine research and environmental monitoring. Experts report that the ability to listen to and analyse ocean soundscapes helps with detecting objects, monitoring marine life, improving marine life, and improving sonar system performance.

A lead researcher on the project explained that PSAP Voyager provides a major advantage by allowing continuous acoustic monitoring for extended periods without the high costs associated with ships and cables.

The collected data will be used to enhance naval oceanographic models, improve sonar capabilities, and support maritime domain awareness. Reports indicate that this data will be used in student thesis research to analyse ambient ocean noise, marine mammal monitoring, and underwater soundscapes.

This project originated through NPS’ Consortium for Unmanned Systems Education and Research (CRUSER) and is funded by the Office of Naval Research (ONR). The idea emerged after Yi Chao, Seatrec’s CEO and a well-known oceanographer, introduced the company’s energy harvesting system at NPS.

Recognising its potential, NPS researchers collaborated with Seatrec to integrate undersea acoustics expertise with innovative power-generation technology.

Seatrec has been recognised for its exemplary work in defence technology. In 2023, the company was selected for the National Security Innovation Network (NSIN) Propel Hawai’i Accelerator, a program supporting early-stage companies developing cutting-edge technology for the U.S. Navy and Department of Defense (DoD).

The company was chosen from over 200 companies to join this elite program, which operates in partnership with the U.S. Navy’s Pacific Fleet, covering 100 million sq mi.

Traditional hydrophones are positioned at depth, often in the SOFAR (SOund Fixing And Ranging) channel, where sound waves can travel long distances. These hydrophones require either expensive ship operations or land-based fibre optic cables to function.

Reports explain that PSAP Voyager eliminates these restrictions by providing unlimited acoustic data collection in remote areas without needing external power sources.

An expert on the project said that sound is crucial for understanding the ocean and monitoring natural and man-made movements underwater.

Previously, hydrophones needed to be tethered to ships or shore stations, but PSAP Voyager now enables real-time ocean listening at a fraction of the cost. The PASP Voyager provides unmatched capabilities for continuous underwater observation while greatly reducing operational costs.

Reference: US Navy

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