Unveiling the "Heart" of Deep Sea Propulsion

The deep sea, this unknown realm covering over sixty percent of the Earth's surface, is humanity's final frontier. Conquering this vast, dark world relies on a crucial piece of equipment—the deep sea thruster. It is the "heart" that allows submersibles and underwater robots to navigate effortlessly through the abyssal depths of ten-thousand-meter trenches, and the power source enabling scientists to reach the secrets of the ocean floor. From the biomimetic swaying of a "fish tail" to the efficient surge of a "water jet," the types and evolution of deep sea thrusters themselves represent a condensed history of our technological quest to explore the deep ocean.

The most classic and widely used is undoubtedly the propeller thruster. Acting like the "traditional wheel" of the ocean, its principle is consistent with that of ship propellers, generating thrust by rotating blades that cut through the water. To adapt to the high pressure and complex environment of the deep sea, its materials have evolved from special alloys to titanium alloys, and its designs have become more sophisticated. Whether it's the "Jiaolong" manned submersible or the "Deep Sea Warrior," the quietly spinning propeller at their stern is the core force enabling them to resist ocean currents and achieve precise positioning. Its advantages lie in mature technology and powerful thrust, though it has some limitations in flexibility.

When missions shift to scenarios requiring higher demands for silence and agility, the pump-jet thruster comes to the fore. It is akin to the "jet engine" of the ocean, generating thrust by accelerating water flow inside a duct. This design not only effectively reduces cavitation (the formation of bubble noise), making its operation much quieter—crucial for military applications or marine life observation missions where stealth is important—but its compact structure also allows for multi-directional placement on submersibles, enabling more flexible vector thrust.

The pace of technology never stops. The rim-driven thruster (RDT), as a rising star, brings structural innovation. It integrates the motor rotor with the propeller blades directly into the surrounding duct (the rim). This highly integrated "hub motor" style design eliminates the traditional drive shaft and sealing structures, significantly reducing hydrodynamic resistance, vibration, and noise, while also simplifying maintenance. It represents an important trend towards higher efficiency, compactness, and quietness in thruster development.

Looking to the future, biomimetic and special thrusters open up limitless possibilities for imagination. Researchers draw inspiration from creatures like squid and jellyfish to develop biomimetic undulating fin thrusters and jet propulsion systems. By simulating the soft-body movements of these animals, they can propel through water with extremely low noise and high efficiency, making them particularly suited for delicate tasks in sensitive areas like complex and fragile coral reefs or archaeological sites. Furthermore, the magnetohydrodynamic (MHD) thruster, a "propeller-less" propulsion concept that uses magnetic fields to ionize and expel seawater rearward, theoretically operates with almost no noise or vibration, representing the ultimate dream for future ultra-quiet deep-sea submersibles.

From the primitive concept of imitating a fish's tail fin to today's sophisticated systems where multiple principles coexist, the evolution of the deep sea thruster is a microcosm of the ongoing contest between human ingenuity and the challenges of nature. Behind each type of thruster lies a deeper understanding of the deep-sea environment and the pursuit of极致 engineering. As we venture deeper and farther into the ocean, this underwater "heart" will undoubtedly beat more powerfully and intelligently, continuing to propel the course of human exploration towards the abyssal secrets where even light cannot reach.