Submersibles work primarily by controlling their buoyancy to descend, maneuver underwater, and ascend.
Mastering Buoyancy for Underwater Operation
A fundamental aspect of how submersibles operate is the precise management of their buoyancy. Buoyancy is the upward force exerted by the water that opposes the weight of the submersible. By adjusting their overall weight relative to the weight of the water they displace, submersibles can achieve different states to perform various tasks.
According to the reference:
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Neutral Buoyancy: During underwater operation a submersible will generally be neutrally buoyant. This means the submersible's weight is equal to the weight of the water it displaces, allowing it to remain suspended at a specific depth without sinking or rising. This state is ideal for horizontal movement and maneuvering.
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Negative Buoyancy: To descend, a submersible increases its weight, becoming heavier than the water it displaces. This can be achieved by taking on water into specialized tanks called ballast tanks. Negative buoyancy may also be useful at times to settle the vessel on the bottom, allowing it to rest stably on the seabed for research or exploration.
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Positive Buoyancy: To ascend, a submersible decreases its weight, becoming lighter than the water it displaces. This is typically done by expelling water from the ballast tanks, often using compressed air to push the water out. Positive buoyancy is necessary to float the vessel at the surface once the mission is complete.
How Buoyancy is Controlled
Submersibles use systems, primarily ballast systems, to manage their buoyancy:
- Ballast Tanks: These are tanks that can be flooded with seawater to increase weight (creating negative buoyancy for descent) or emptied (often by forcing water out with compressed air) to decrease weight (creating positive buoyancy for ascent).
- Trim Tanks: Smaller tanks used to adjust the submersible's pitch and roll, maintaining stability.
- Droppable Weights: Some submersibles have weights that can be quickly released in an emergency to rapidly achieve positive buoyancy and surface.
Here's a summary of buoyancy states and their uses based on the reference:
| Buoyancy State | Action | Purpose |
|---|---|---|
| Neutral | Suspended | General underwater operation |
| Negative | Sinks | Vertical motion (descent) |
| Negative | Settles | Rest on the bottom |
| Positive | Rises | Vertical motion (ascension) |
| Positive | Floats | Stay on the surface of the water |
Beyond Buoyancy
While buoyancy control is key for vertical movement and depth, submersibles also require other systems to function:
- Propulsion: Thrusters or propellers are used for horizontal movement and precise maneuvering.
- Power Systems: Batteries or other sources power the propulsion, lights, life support, and scientific equipment.
- Life Support: Systems provide breathable air for the crew and remove carbon dioxide.
- Navigation and Communication: Systems like sonar, cameras, and inertial navigation are used for orientation and maneuvering underwater.
- Scientific or Manipulator Systems: Depending on their purpose, submersibles may have cameras, sensors, robotic arms (manipulators), or collection tools.
In summary, submersibles navigate the ocean depths by expertly controlling their buoyancy to move vertically, resting neutrally buoyant during operation, and using propulsion for horizontal movement and positioning.
