Manta ray submersible capable of reaching 2,000-meter depths

Northwestern Polytechnical University in Xi'an, Shaanxi province, has developed a manta ray-inspired submersible capable of operating at depths of up to two kilometers beneath the water surface.

The remotely operated electric-powered craft is designed to generate minimal disturbance to marine life, offering a quieter alternative to traditional propeller-driven vehicles for ecological monitoring and deep-sea exploration.

Traditional propeller-driven submersibles generate high levels of noise and strong water flow, often stirring up seabed sediment, producing blurry images and disturbing marine organisms, making them unsuitable for high-precision near-seabed detection and environmentally friendly monitoring missions.

"We have translated the swimming mechanics of manta rays into engineering technologies to make deep-sea exploration more efficient, quieter and better adapted to the marine environment," said Cao Yong, a researcher at the university's School of Marine Science and Technology.

Cao said the submersible utilizes a manta ray-inspired undulating flapping fin propulsion system.

The research team overcame a long-standing limitation in conventional marine equipment by applying the same variable buoyancy technology that is used in underwater gliders, Cao said.

Traditional systems typically achieve either long-range cruising at the expense of maneuverability or high maneuverability at the cost of endurance.

In glide mode, the submersible uses its variable buoyancy system to perform periodic diving and ascending motions with ultralow power consumption, enabling wide-area ocean surveys spanning thousands of kilometers.

In flapping mode, its pectoral fins move at low frequencies to execute highly agile maneuvers, including in-place turning, rapid pitching and precise hovering.

Seamless switching between the two modes enables both long endurance and operational flexibility.

Without high-speed rotating components, it generates low operational noise and minimal water disturbance. It also avoids stirring up sediment during near-seabed operations and offers excellent biocompatibility, Cao said.

Its flat fuselage provides superior stability when landing on the seabed. Designed for long-term deployment, the vehicle can remain in dormant mode before being reactivated, and carry payloads for integrated detection and operational tasks.

"To improve target recognition in complex seabed environments, the submersible adopts hierarchical recognition technology to accurately distinguish between interference from reefs, sunken vessels and other underwater objects," Cao said. "It can withstand pressure of up to 200 atmospheres, enabling operations at depths of up to 2,000 meters."

To achieve this, the university team studied manta ray movement by analyzing tens of thousands of video clips and raising cownose rays — which have similar biological characteristics to manta rays — in laboratory facilities.

The team also collaborated with Ningbo University in Zhejiang province on 3D scanning and CT imaging to analyze the rays' muscle and skeletal structures.

"During ecological monitoring missions, this submersible can conduct long-term silent observation of ecosystems such as coral reefs and submarine hydrothermal vents, providing important data support for biodiversity conservation," Cao said.

"For the operation and maintenance of marine ranches, it can enable early warning of fish diseases, precision feeding and escape monitoring, supporting the development of the 'blue granary'," he added.

The submersible can also serve as a safe and efficient platform for underwater archaeology and marine science education.

Cao highlighted that the team plans to integrate artificial intelligence and swarm algorithms for autonomous underwater navigation under low-bandwidth communication conditions.

"The research fills China's technological gap in bionic underwater submersibles capable of integrating wide-area detection with high precision operations," said Pan Guang, president of the School of Marine Science and Technology. "It advances autonomous unmanned underwater technologies from single-function systems to multifunctional integrated platforms."

chenmeiling@chinadaily.com.cn