Types of Underwater Vehicles and Submarines
Different types and sizes of underwater vessels are used for various purposes, from defence to research and exploration. They can venture into the abysmal depths of the ocean and can stay put for hours to days. They are suitable for sustaining life inside or being unmanned. Moreover, they can be self-powered or operated by secondary modes of power.
A submarine is the most prominent type of underwater vehicle. It is a self-propelled large underwater craft of single or multiple large pressure vessels with a dedicated propulsion and supply system. However, apart from submarines, there are other underwater vehicles as well.
Types of Underwater Vehicles
Based on occupancy, underwater vehicles are classified into the following types.
- Submarines
- Submersibles
- Autonomous Underwater Vehicles (AUVs)
Submersibles are smaller underwater crafts used for various underwater operations. Most are ‘not self-propelled’ and fully or partially dependent on an external operator, facility, support vessel, or submarine. However, several submersibles are also self-propelled. They are mainly used for research and exploration, sometimes adventure and commercial purposes. As surprising as it may sound, these submersibles were the precursors to submarines as humans have explored the world under the oceans and seas for centuries.
Now, let us look at the phrase manned or unmanned. As explanatory, crewed vehicles are the ones that are capable of carrying one or many people on board. On the other hand, unmanned ones operate without human occupancy. This brings us to another declassification of submersibles as manned or unmanned.
The first manned submersible was built 400 years ago by a Dutch scientist in 1620. Since then, humankind has been experimenting with these vessels. The famous “Bushnell’s Turtle” in 1775 was the first revolutionary manned submersible design recorded in history. The hull was simply an oval-shaped pressure vessel carved out of wood and brass.
The ballasting operations for sinkage and flotation were carried out through small tanks operated by a primitive hand pump. Two simple hand-operated cranks propelled the vessel. Small windows provided a good view, while many instruments had radium luminescence coating for seeing them in the dark.
It was constructed to fit explosives in enemy ship hulls and is still considered a pioneer in the domain of underwater vehicles. Even modern, colossal, heavily armed nuclear-powered naval assault submarines are indebted to this breakthrough invention.
Modern manned submersibles are called Human Occupied Vehicles or HOVs. However, they have some unique sub-types like:
Deep-Submergence Vehicles (DSVs): They are intended for critical deep-sea operations, military, and research, carrying crew, and are self-propelled. They are designed to withstand titanic pressures and conditions at extreme depths. Moreover, they have very high endurance and range. The oldest and the most famous DSV to date is the Alvin, owned by the US Navy and operated by the Woods Hole Oceanographic Institution, and active for almost 60 years! Other than being involved in a plethora of research and exploration expeditions, it was most notably used in scouring the sunken wreckage of the Titanic. It also has three sister prototypes that feature robust titanium hulls.
Bathyscaphes: These are free-diving, deep-sea manned submersibles. Their distinguishing feature is a sizeable top hull or float. Below it is a dome-like pressurized chamber for crew members. During diving, this hull or float is filled with extra ballast water, which allows the entire vessel to sink. There are dedicated tanks in the float, which are also filled with gasoline, helping in the sinkage, but this has a more significant role at higher depths.
At greater depths, the incompressibility of gasoline enables it to withstand a large modulus of external pressures. This gasoline is entirely removed at the surface, and the ballast water is adjusted accordingly for the desired flotation. Sometimes, the float may also have spaces for using iron pellets or shots as ballast which are released during ascent.
Though they can venture to a great depth, they have a limited capability for lateral movement. A small propeller or a fan is placed atop the float. The inherent tendency of lateral movement due to underwater currents helps move up to a few meters within the site of interest. They are often towed to the launch point at the surface using guide ropes or towing lines.
They are considered advanced improvements over Bathyspheres, unpowered and primitive vessels used for deep-sea explorations in earlier days.
Unmanned Submersibles are smaller as they do not carry a crew. Remotely Operated Underwater Vehicles ROVs are the most common types of unmanned submersibles. They operate from the surface or shore using tether lines or cables. Power cables or chords connected to the control point supply electricity to the vessel. Depending on the configuration, they can operate at various depths and move at all degrees without any problem, accounting for their flexibility.
Autonomous Underwater Vehicles or AUVs are essentially the same as ROVs with one significant difference, control. As the name suggests, they can move independently without cables or tethering along with a time-to-time direct user control mode. They run on systems pre-programmed by the operator.
So, instead of conventional submersibles, they are more like unmanned, autonomous, underwater robots that can propel themselves. They are considered a massive breakthrough for research and military applications over the last few years. Sizes are highly variable, ranging from the size of a portable gas cylinder to larger ones measuring 10 to 20 meters. The equipment-carrying capabilities of an AUV are proportional to its size and are calculated as the payload capacity of the submarine.
Based on the designs, submersibles can be of the following types:
Single atmosphere submersibles: They have a strictly watertight and airtight singular pressurized hull that can sustain the crew inside under atmospheric conditions. So, the hull must withstand high external hydrostatic pressure without compromising on the lower internal pressure. They are complicated and more expensive to design and construct.
Equal pressure submersibles: They maintain equivalent pressure both internally and externally. Thus, the net pressure on the hull is low. They have a relatively more uncomplicated design.
Wet Sub: In this configuration, the vessel is more or less exposed to the water with only specific equipment and systems enclosed or encased. Here the occupants (if any) are exposed to the marine environment. Thus, as expected, they require proper SCUBA equipment and all breathing apparatus akin to deep-sea divers, the only difference being that they are not required to swim!
They can be best visualized as riding a motorbike, an open kayak, or a roofless sportscar underwater! The depths at which these vessels can ply are limited to a certain extent as the occupants can endure only a certain amount of underwater pressure. These vessels offer a firsthand marine environment experience.
Types of Submarines
Submarines are the largest and the most advanced forms of underwater vehicles. Based on the design, some submarine types are:
U-Boats: Brainchild of the two World Wars, U-boats are considered one of the pioneering developments in naval warfare. During the wars, they were indispensable and intimidating components of Germany’s and Britain’s maritime fleet. The typicality in their design was very different from modern, simple, symmetrical, and cylindrical structures. They were shaped more or less like ships with features that allowed them to operate both at the surface and underwater.
Midget Submarines: They are small submarines generally within 150 tons in weight. They are usually for a maximum of five to six crew members. They are self-propelled and can carry and launch torpedoes, bombs, and mines to attack enemy vessels. These vessels generally require the support of another support vessel or giant submarine. One important point to note is that midgets are only used for military purposes and not for civilian research, unlike submersibles.
Human Torpedoes: Smallest submarines that carry a diver or operator for launching torpedoes to assault enemy fronts. They are manned and underwater torpedo head launchers. Human torpedoes were very popular during the world wars as formidable lethal weapons. They were phased out as large submarines began to be used for launching multiple missiles, torpedoes, and a variety of armaments.
Conventional Submarines: Symmetrical, cylindrical, self-propelled vehicles of varying sizes used for various purposes, from military to commercial.
Based on Propulsion, modern submarines can be categorized as:
- Conventional diesel propulsion
- Diesel-electric or hybrid Propulsion (using electrical or diesel power combination)
- Nuclear or hybrid Propulsion (using nuclear or nuclear-diesel-electric combination)
- Air-independent Propulsion
- Steam or mechanical-powered submarines (phased out)
Based on the utilities or purpose of the application, submarines can be classified as:
- Naval or defence
- Commercial
- Civilian
- Research
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About Author
Subhodeep is a Naval Architecture and Ocean Engineering graduate. Interested in the intricacies of marine structures and goal-based design aspects, he is dedicated to sharing and propagation of common technical knowledge within this sector, which, at this very moment, requires a turnabout to flourish back to its old glory.
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Disclaimer :
The information contained in this website is for general information purposes only. While we endeavour to keep the information up to date and correct, we make no representations or warranties of any kind, express or implied, about the completeness, accuracy, reliability, suitability or availability with respect to the website or the information, products, services, or related graphics contained on the website for any purpose. Any reliance you place on such information is therefore strictly at your own risk.
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