Search and extraction operations in deep waters, unlike operations in near-surface waters, require special underwater vehicles, precise positioning systems and detailed planning.
As the technical complexity of manned diving increases with depth and the decompression load on divers increases, remotely operated underwater vehicles (ROVs) are becoming essential tools in many deep-sea operations.
At depths where manned diving is not possible, ROVs and other underwater systems specially designed to withstand this pressure undertake the task.
During the operation, the movement of the ship on the surface, the current, the thrust power of the robot, the position of hundreds of meters of cable, visibility conditions, underwater navigation, the operation of the manipulators and the loads on the lifting system are managed simultaneously.
9 ships under the command of the Southern Sea Area Command of the Naval Forces Command from Türkiye continue their activities with high sensitivity to the factors in question in search operations.
Precise calculations for location
In deep sea exploration, it is not only necessary to see a target, but also to determine its location with sufficient precision. Advanced sensors are used for this purpose.
The possible search area is created by evaluating the point where the incident occurred, the last known location of the ship or target, the distance it may have moved during the sinking, currents, the structure of the seabed and available witness or sensor information.
The ship or towed sensor is then moved along parallel routes at regular intervals to systematically scan the seabed.
After the wreck is found, the position of the wreck must be determined, the surrounding parts and obstacles must be mapped, entry points must be determined, and the person or object sought must be displayed.
Lowering the underwater vehicle
The stages of launching the ROV from the surface ship and reboarding it are considered to be one of the stages where the vehicle is most vulnerable to damage.
While waves and currents can drag the ROV towards the ship, the ship's own motion can also cause the vehicle to strike the hull or equipment.
As the ROV goes deeper, the length of the cable in the water increases, and current and drift effects may increase. Leaving the cable too loose may increase the risk of snagging, while excessive tension may limit the vehicle's mobility.
Therefore, maintaining the surface ship's position and orientation precisely is considered one of the basic requirements for safe ROV operation.
Vehicles defy the pressure at 554 meters
For this reason, locating the wreckage in a shipwreck at a depth of 554 meters, identifying missing persons and bringing them to the surface are not a single operation, but a series of deep-sea operations that follow each other, each with different technical difficulties.
The bodies, electronic systems, cameras, cables, connection points and manipulators of the ROVs on the ship have a design that can withstand the pressure at that depth.
Electronic systems such as cameras, lights and computers in such vehicles are placed in pressure casings that will not collapse.
ROVs can be connected to the control center on the surface with a connecting cable that provides power, control and data transfer. Since this cable is in water for hundreds of meters, it is exposed to the current, creating drag and can limit the robot's movement.
The hundreds of meters of connection between the surface ship and the robot at a depth of 554 meters means that the current affects not only the ROV but also the cable.
Fragments of metal in debris, broken cables, or other obstructions also pose a risk of the ROV or connecting cable getting stuck.
Movement of a few meters on the surface can affect a vehicle 554 meters below
The success of a deep-sea operation depends not only on the conditions on the seabed but also on the location of the support ship on the surface.
Since the ROV is connected to the ship on the surface by a cable hundreds of meters long, the movements of the ship can affect the position of the cable and the robot's mobility. Getting the cable caught in debris, the ship's hull or other equipment also poses a risk to the operation.
For this reason, the Dynamic Positioning System on ships such as TCG Işın and TCG Alemdar plays an important role in the precise execution of robotic operations by ensuring that the ship remains as stable as possible at the specified point despite wind, waves and current.
Special lifting systems are used in the deep sea
When the missing person, black box or another target is detected with ROV cameras, the second important phase of the operation begins.
Just having a strong enough crane is not enough to lift a target from the deep sea.
With increasing depth, the own weight of the hundreds of meters long lifting line, the drag effect of the water on the line, the movements of the surface ship and the condition of the target on the seabed increase the forces that the lifting system has to calculate.
For this purpose, special winch systems, steel or high-strength synthetic ropes and modular lifting systems for deep ocean rescue operations are used.
Performing the removal process without damaging it
In deep sea operations, when the target is the body of a missing person rather than a piece of debris or technical equipment, the extraction process must be carried out as controlled and without causing damage as possible.
ROVs with mechanical arms can directly grasp their target with the ability to grasp and extract. ROVs use manipulator arms, debris cutting tools, hooks, locking mechanisms and special attachment equipment for this purpose.
In these systems, not only the weight of the extracted object, but also the weight of the rope hundreds of meters long, the force of separation from the seabed and the dynamic loads resulting from the movements of the ship are taken into account.
When lifting from underwater, not only the weight of the target but also the underwater weight of the lifting line used puts a load on the system.
If the wreck is buried in the seabed, the force required to save the target can be one of the largest loads that the lifting system must meet.
During this time, it is important that the surface ship does not move up and down due to waves.
If a relaxed line is suddenly tightened, shock loads called "snap loads" occur.
Therefore, ship movement, lifting speed and line tension need to be constantly controlled.
In deep sea operations, environmental conditions such as wind, wave height, currents and visibility determine not only the comfort of the operation, but also whether it can be carried out technically safely.
