What do most people think of when they hear the word ‘drone’? Most people probably imagine a drone flying in the sky. With the development of the drone industry and drones being commonly used to take pictures and people taking up drones as a hobby, it is quite common to see drones here and there every once in a while.
But drones aren’t just for flying. There are drones that move on the ground, drones that work like a boomerang, drones that glide across the ocean like a boat and many other types of drones. The type of drone we will be discussing today is a drone that goes under water.
An underwater drone is a drone that is capable of being controlled underwater to take pictures or perform other functions. In short, it is a small submarine that is controlled remotely.
An underwater drone operates very similarly to a submarine. The reason that submarines are able to both float on top of the water and submerge into the water is the Archimedes’ Principle. For an object to submerge in water, it must use the power of gravity and for an object to float, it must use the power of buoyancy.
For example, if we put an inner tube and a stone on top of the water of a swimming pool, we can see that the tube will float and the stone will sink to the bottom. Because the mass of the air in the tube is less than that of the water, the tube floats (gravity<buoyancy). Since the mass of the stone is greater than that of the water, the stone sinks (gravity>buoyancy).
Underwater drones use the same type of ballast tanks used in submarines that control the amount of water in them and make it possible for them to submerge underwater. When the tanks fill with water, the gravity of the drone increases and it can go underwater. When the tanks empty the water out of them, the buoyancy of the drone increases and it can float on top of the water.
The 2 most well known underwater drones to be released are the Loon Copter developed by the research center at Oakland University in the US and the OpenROV Trident, which is registered on KickStarter and developed by the US IT firm, OpenROV.
① Oakland University Research Team’s Loon Copter
Loon Copter is a 4 propeller quad-copter that uses the propellers to navigate underwater. Loon Copter also has the advantage of being able to fly in the air and also operate under the water. When flying, it can submerge one end into the water and move underwater at an angle. Loon Copter uses a ballast system to go underwater and is capable of transmitting videos and data via a cable that can be attached to the device.
② Open ROV’s OpenROV Trident
OpenROV Trident uses 3 propulsion devices, 1 in the front and 2 in the back, to move freely underwater. The drone’s aerodynamic design allows it to smoothly traverse the water and it is capable of depths of 100m, speeds up to 2m/s and it can run for up to 3 hours.
The drone can also be attached to a Wi-Fi capable buoy via a cable that allows it to be controlled at long distances and transmit HD video.
③ O-Robotics’ Sea Drone
SeaDrone has a ballast system within its frame that allows it to navigate underwater. It can reach speeds up to 1.5m/s and run for up to 3 hours. SeaDrone can take full HD video at a 130 degree field of view and the camera and body can rotate, which makes it capable of shooting various types of video. SeaDrone was developed to for the aquaculture industry and may be very helpful to small and medium sized fisheries and similar businesses.
If we look at the history of submarines, the majority of them have been used in military operations. But underwater drones are capable of many more diverse functions.
Cyclops is a drone developed by the Korean company POSTECH’s R&D team. In April of this year, Cyclops successfully produced Korea’s first 3D submarine topography model.
Because underwater drones can overcome the limits of the human body that restrict us from exploring deep underwater for long periods of time, they could play a big role in oceanographic research.
② Search & Rescue
Drones are capable of staying underwater for long periods of time. After a disaster occurs on the ocean, drones can perform functions that humans cannot in order to find missing persons.
Another example of a underwater drone is the SeaDrone made by O-Robotics that was mentioned above. Drones like SeaDrone could have a significant impact on the fishing industry. Traditionally, fishermen had to physically swim into the ocean to clean or perform maintenance on fishing farm equipment. Underwater drones can now perform these tasks.
Underwater drones can be used in many various fields but there are obstacles keeping them from coming into common use.
There is one common problem with the Loon Copter, OpenROV Trident and SeaDrone drones mentioned above. The problem is that they are all only able to be controlled with cabled connected. They are not controllable wirelessly. The reason for this is because radio waves cannot be properly transmitted underwater.
Currently, drones are limited to depth of just a few meters. Drones cannot send video data wirelessly and all images and data must be collected only after the drone is retrieved.
In order to overcome the limits of cable connectivity, ultrasonic wireless transmission methods are being developed. Since ultrasonic waves can travel well through water, this technology could be used to transmit data wirelessly underwater.
Underwater drones also have issues with security just as flying drones. Drones could be misused in restricted territory or for illegal purposes. So, proper regulations must be instated to ensure our safety.
We have now taken a look into the world of underwater drones. As the drone industry continues to develop and a diverse range of drone types emerge, it is fascinating to imagine what the future of drones has in store!
Written by Donggu Kang, LG CNS Student Reporter
 Archimedes’ principle: The upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces and it acts in the upward direction at the centre of mass of the displaced fluid. [Wikipedia] [back to the article]
 Buoyancy: an upward force exerted by a fluid that opposes the weight of an immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. [Wikipedia] [back to the article]
 Ballast Tank: A compartment within a boat, ship or other floating structure that holds water, which is used as ballast to provide stability for a vessel. Using water in a tank allows for easier adjustment of weight than stone or iron ballast as was used in older vessels. [Wikipedia] [back to the article]
 KickStarter: an American public-benefit corporation based in Brooklyn, New York which has built a global crowdfunding platform focused on creativity. [Wikipedia] [back to the article]