Submarines, dubbed as the “wonders of engineering,” operate at depths of thousands of meters in the ocean.
Humans have been exploring and navigating underwater since around 300 BC. Various methods have been employed to move beneath the waves for research purposes throughout history.
According to legend, the first attempt to create a submarine prototype was made by Alexander the Great. It is said that submarines might have existed as early as 332 BC, with historical accounts mentioning Alexander descending into the sea in a glass barrel to study fish. If true, the concept of a submarine has been around for about 1,800 years, as reported by Worldwideboat.
However, venturing deep underwater in a glass barrel does not seem like an effective method for exploring the underwater world.
In AD 1578, William Bourne, a British naval officer, built a wooden vessel covered with waterproof leather that could be rowed underwater.
The first officially recorded submarine, named “Turtle,” was created during the American Revolutionary War in 1776.
By the late 19th century, submarines had developed into practical vessels with advanced propulsion systems and technology.
Entering the 20th century, the US Navy launched the world’s first nuclear-powered submarine, the USS Nautilus.
How Deep Can Military Submarines Dive?
Submarines may have existed as early as 332 BC. (Illustrative image).
Marineinsight states that because the specifications of any defense asset are classified military secrets, there is no absolute confirmation regarding the designed diving depths of military submarines. All available information about their capabilities is based on speculation, data leaks, limited government reports, or high-level press releases, along with technical estimates based on available design data, operational environments, and observed test depth performance.
Depending on their capabilities, defense submarines can dive to various depths, with most values or figures available pertaining to their design depth. Military submarines have been recorded diving to depths of up to 1,500 meters.
Marineinsight has listed several military submarines with varying diving capabilities from Russia, the US, China, and India.
- Russian Akula-class submarines (formerly of the Soviet Union), the largest submarines ever built, are believed to be capable of reaching a maximum depth of 1,200-1,300 meters below sea level. The last of this class was decommissioned in early 2023.
- Yasen-class attack submarines are estimated to dive to approximately 600 meters. In contrast, ballistic missile nuclear submarines like Russia’s Borei class can reach depths of around 500 meters.
- The US Navy also has an impressive fleet of deep-diving submarines, with Los Angeles-class submarines capable of operating at depths of up to 600-700 meters. Their unclassified test depth remains around 250 meters.
- Ohio-class submarines, which are nuclear-powered, are also believed to dive deeper than 500 meters, although their operational depth is around 300 meters.
- Virginia-class submarines are considered the successor generation to Los Angeles-class submarines and boast advanced technical capabilities. With a test depth of about 500 meters, they are designed to dive deeper, ranging from 800 to 900 meters.
- Nuclear-powered submarines, such as China’s Jin-class submarines and Germany’s Type 212 diesel-electric submarines, are also powerful military vessels capable of reaching depths of up to 400 meters.
- India’s Arihant-class submarines are also capable of a test depth of 300 meters and are believed to be able to dive deeper under harsh conditions.
How Do Submarines Maintain Atmospheric Pressure While Diving Deep?
Submarines are designed in a way that allows them to maintain internal pressure similar to atmospheric pressure at sea level.
This raises the question, why is it so important to maintain appropriate pressure? If the internal pressure significantly differs from the external pressure, it can cause unnatural stress (strain) on the hull, leading to structural failure, leaks, or even explosions.
Submarines are equipped with “pressure spheres” to prevent internal air pressure from becoming too high. (Illustrative image).
When the submarine is on the surface, the ballast tanks are filled with air, making the vessel lighter than water, allowing it to float. However, when the submarine needs to dive, it releases air from the ballast tanks and replaces it with water, which increases the vessel’s density compared to water, enabling it to sink easily.
As the submarine dives deeper, water pressure increases, compressing the air pressure inside the vessel. Therefore, to balance the internal pressure during ascent or descent, the ballast tanks will be flooded or pumped out accordingly.
All submarines also have an internal system called “pressure spheres” to prevent the internal air pressure from becoming excessively high.
What is a Pressure Hull and Why is it So Important?
Submarine engine with pressure gauge. (Source: Charles-Edouard Cote/Shutterstock)
The pressure hull is a critical structure inside a submarine, but what exactly is its function?
The primary load-bearing structure in military submarines is the pressure hull, designed to withstand the hydrostatic pressure (pressure exerted by a stationary liquid) associated with diving.
It is constructed to endure external pressure from the ocean’s depths to protect the crew and internal systems.
One of the most crucial tasks engineers must be vigilant about when designing a submarine is ensuring that the pressure hull is leak-proof.
It must withstand external hydrostatic pressure without collapsing or deforming while maintaining the overall integrity of the pressure hull.
What Causes a Submarine to Explode?
Submarines are pressure vessels capable of operating at submerged depths. They are mechanically balanced by evenly distributing the hydrostatic pressure exerted on their surfaces.
Any submarine design must always consider the theory of hydrostatic pressure and the linearly increasing depths. Therefore, when selecting a specific submarine design, its survivability is limited to a certain depth; exceeding that depth will cause it to collapse due to pressure load exceeding the limit state.
In other words, a submarine explosion occurs when the external pressure on the submarine exceeds the structural integrity of the pressure hull.
When operating at great depths, the surrounding water can exert immense pressure on the pressure hull. When that pressure exceeds the threshold, the pressure hull may fail. This leads to the vessel collapsing inward.
Several factors can contribute to this catastrophic failure, including structural integrity weaknesses, design flaws, or even excessive depth limits.
The sudden collapse of the hull results in immediate loss of life aboard the submarine, loss of the vessel, and numerous other environmental hazards.
The sudden collapse of the hull leads to immediate loss of life aboard the submarine. (Illustrative image).
Therefore, submarines often undergo rigorous training and testing to ensure that such tragic events do not occur.
Maintaining pressure akin to the surrounding atmosphere is crucial for the safe operation of submarines. Adjusting internal pressure is necessary to make the vessel robust enough to withstand the strong external water pressure, thereby protecting the crew and internal systems.
Although submarine explosions are rare, they remain an unavoidable concern that must be considered before deciding to explore the secrets of the deep ocean waters.
