How do submarines work?

They are essential for various purposes, including military defense, research, exploration, and even leisure activities like tourism. But how do they manage to dive beneath the surface, navigate the depths, and resurface? Let’s break down the science and engineering behind how submarines work.

The Basics of Submarine Design

Submarines are specially designed to operate in the harsh underwater environment. The structure of a submarine is built to withstand the immense pressure of deep water and the challenges of moving in three dimensions. A submarine consists of several key components that allow it to function effectively:

Hull (Pressure Hull): The hull of the submarine is its core structure, made of high-strength materials like steel or titanium. It is designed to resist the pressure exerted by the water at different depths. The pressure increases with depth, so the hull must be able to withstand pressures that could crush an ordinary vessel. Submarines are generally built with a double hull, which provides added protection.

Ballast Tanks: One of the most important parts of a submarine is its ballast tanks. These are large, sealed tanks that can be filled with water or air. By adjusting the amount of water in the ballast tanks, the submarine can control its buoyancy and whether it rises or sinks.

Propulsion System: Submarines are powered by either nuclear or diesel-electric engines. Nuclear-powered submarines use nuclear reactors to generate heat, which drives turbines that produce electricity. Diesel-electric submarines use diesel engines to charge batteries, which in turn power electric motors. The propulsion system enables the submarine to move through water, either on the surface or beneath it.

Sails and Rudders: Submarines have a sail-like structure that houses the control systems, periscopes, and other necessary equipment. This sail helps in maneuvering the submarine and assists in the balancing of the vessel. The rudders control the submarine’s direction, allowing it to turn and adjust its angle of ascent or descent.

Buoyancy and Submersion

A submarine’s ability to float or sink is based on the principle of buoyancy, which states that an object will float in a fluid if it displaces its weight in that fluid. To dive or surface, submarines use their ballast tanks, which are located inside the hull. These tanks play a key role in controlling the submarine's density compared to the surrounding water.

Submersion: To dive, the submarine fills its ballast tanks with water. This increases the overall weight and density of the submarine, causing it to sink. The amount of water filled in the ballast tanks determines how deep the submarine can go. When the submarine needs to submerge quickly, it can use high-pressure air to push water out of the tanks and replace it with air, which helps it rise back to the surface.

Surfacing: When the submarine needs to surface, the ballast tanks are flooded with compressed air, forcing the water out of the tanks and causing the submarine to become less dense than the water around it. As a result, it rises to the surface, where it can breathe in fresh air, recharge batteries, or re-enter its operational position.

Propulsion and Navigation

For movement, submarines rely on a combination of propulsion and control mechanisms:

Propellers (Screws): Submarines use propellers, or “screws,” to generate thrust and push the submarine forward or backward. These are powered by the propulsion system, whether diesel-electric or nuclear. The propeller is usually mounted at the stern (rear) of the submarine and is carefully designed to minimize noise and vibration, which is critical for stealth in military submarines.

Hydrodynamics: The design of the submarine’s body is sleek and streamlined to reduce drag while moving through water. The shape is also optimized to allow for maximum maneuverability. The hull is usually cylindrical, tapering at both ends to minimize resistance, while control surfaces such as rudders and stern planes help steer the submarine and control its depth.

Control Surfaces: Just like aircraft, submarines have control surfaces like rudders, planes, and dive planes to help guide them through the water. These surfaces are used to control the pitch (up and down movement) and yaw (left and right movement) of the vessel. The dive planes are typically positioned near the bow and stern and are used to help the submarine adjust its angle of descent or ascent.

Life Support Systems

A crucial aspect of submarine operation is maintaining a safe and livable environment for the crew, especially when they are submerged for long periods. Submarines are equipped with advanced life support systems, including:

Air Purification: Submarines carry a limited supply of air, so they rely on systems that remove carbon dioxide and replenish oxygen. This is done through chemical scrubbers or high-tech machines that convert carbon dioxide back into oxygen.

Freshwater Production: Since submarines are at sea for extended periods, they need a source of fresh water. They use desalination systems to turn seawater into potable water, which is essential for drinking, cooking, and hygiene.

Waste Management: Sanitation is also a critical issue. Submarines have onboard systems that manage human waste, which is collected and processed to ensure hygiene and prevent any contamination.

Stealth and Detection

Submarines are designed to operate stealthily, especially military ones. To achieve this, submarines use a range of techniques to minimize the noise and detectability of their operations. For instance, nuclear submarines are particularly quiet because they don’t need to surface frequently, unlike diesel-powered ones that require surfacing for air. Additionally, submarines use sonar systems to detect objects around them and avoid collisions, but they are also equipped with technology to make their own sonar signature harder to detect.

Conclusion

In conclusion, submarines are marvels of engineering that combine principles of buoyancy, propulsion, and advanced technology to navigate the depths of the oceans. They are carefully designed to withstand the harsh conditions underwater, maintain a safe environment for the crew, and operate stealthily when required. Whether it's for scientific research, military defense, or exploration, submarines have proven to be invaluable tools in our exploration of the underwater world.