What are the key technical challenges in designing and manufacturing a high-performance underwater robot?

Building a robot that can operate well and last long underwater presents a myriad of challenges, vastly different from those encountered on land or in the air. Let me give you a few examples to illustrate.

1. Immense Water Pressure – Like Dressing a Robot in "Iron Armor"

You might have seen scenes in movies where deep-sea submersibles are crushed; this isn't fiction. At a depth of one hundred meters, the pressure is equivalent to over ten atmospheres, roughly like an adult standing on your thumbnail. In extreme depths like the Mariana Trench, the pressure is so immense it can flatten steel plates like paper. Therefore, the robot's shell must be made of lightweight yet super-hard materials like titanium alloy, and all structures must be meticulously designed to avoid any weak points. This "iron armor" needs to be impenetrable yet not too heavy, otherwise the robot would be too "fat" to move. This is the first major hurdle.

2. Watertightness and Corrosion Resistance – "Germaphobe" Level Sealing

Electronic devices are extremely vulnerable to water, especially corrosive saltwater. A robot has countless wires, sensors, and motor interfaces, and every single point must be absolutely sealed. This is like dressing an incredibly complex device in a seamless wetsuit; any pinhole-sized leak, under high deep-sea pressure, would become a fatal weakness. Water would instantly "sizzle" in, and the entire system would be ruined. Thus, the design and testing of seals and waterproof connectors alone require tremendous effort.

3. Communication and Remote Control – "Loss of Contact" is Commonplace

On land, we have Wi-Fi, Bluetooth, 4G/5G, but underwater, these electromagnetic waves are largely ineffective and cannot travel far. There are mainly two ways to communicate with an underwater robot:

• Tethered (Fiber Optic/Cable): This is the most reliable method, offering fast and stable signals, and it can also supply power. However, its drawbacks are obvious: the robot is always dragging a "tail," limiting its range of motion. It can easily get entangled, preventing it from traveling far or reaching complex areas.
• Acoustic Communication (Sonar): Like dolphins communicating with sound, information is encoded into sound waves and transmitted through water. The advantage is wireless freedom. The disadvantage is extremely slow speed, comparable to dial-up internet; transmitting a single photo could take half a day, and the signal is prone to interference and instability. Real-time high-definition video is virtually impossible.

Therefore, enabling robots to autonomously complete tasks even when "out of contact" becomes critically important.

4. Navigation and Positioning – Underwater "Blindness"

GPS is completely useless underwater. This means that once submerged, a robot can constantly be asking, "Who am I? Where am I?" To prevent it from getting lost, engineers have devised many solutions:

• Inertial Navigation: Relies on internal gyroscopes and accelerometers to estimate how far it has traveled and what turns it has made. However, this method accumulates errors, much like walking with your eyes closed; it works initially, but you'll inevitably drift off course over time.
• Acoustic Positioning: Involves placing several sonar beacons at known locations on the surface or seabed, then triangulating the robot's position by measuring the sound propagation time between the robot and these beacons. This system is expensive and cumbersome to deploy.
• Terrain Matching: As the robot moves, it uses sonar to scan the seabed topography and then compares it with pre-stored nautical charts to determine its location.

Typically, a combination of these methods is used to barely allow the robot to know its approximate position.

5. Energy Issues – "Range Anxiety"

Unless tethered, robots must carry their own batteries. Underwater movement faces significant resistance, and various equipment consumes power, so battery requirements are extremely high. You need to pack as much power as possible into a limited space and weight. This is similar to our smartphone battery anxiety, but far more challenging. If the battery is too large and heavy, the robot becomes an immobile "fatty"; if it's too small, it will have to "go home to recharge" after a short operation, unable to perform long-duration missions.

6. Control and Maneuverability – Swimming in "Jelly"

Water is over 800 times denser than air, making movement in it extremely resistant, compounded by various ocean currents and undercurrents. Enabling a robot to move stably and precisely in such an environment, or even hover in a specific position for delicate operations (like turning a valve or cutting something), is incredibly difficult. This requires very powerful thrusters (propellers) and extremely intelligent flight control algorithms to constantly adjust its posture in real-time to counteract water flow interference.

In summary, building a high-performance underwater robot is like creating a "deep-sea special forces soldier" capable of withstanding immense pressure, carrying its own ultra-long-lasting power source, autonomously navigating a dark maze without GPS or network signals, and performing complex tasks. Every single aspect is a tough nut to crack.