Technology | Submersibles | Remotely Operated Vehicles (ROV)

Remotely Operated Vehicles (ROV)

Remotely operated underwater vehicles (ROVs) are unoccupied, highly maneuverable underwater robots operated by a person aboard a surface vessel. They are linked to the ship by a group of cables that carry electrical signals back and forth between the operator and the vehicle. Most are equipped with at least a video camera and lights. Additional equipment is commonly added to expand the vehicle’s capabilities. These may include a still camera, a manipulator or cutting arm, water samplers, and instruments that measure water clarity, light penetration, and temperature. First developed for industrial purposes, such as internal and external inspections of pipelines and the structural testing of offshore platforms, ROVs are now used for many applications, many of them scientific. They have proven extremely valuable in ocean exploration, and are also used for educational programs at aquaria and to link to scientific expeditions live via the internet.

Deployment and Maneuverability

ROVs range in size from that of a bread box to a small truck. Deployment and recovery operations range from simply dropping the ROV over the side of a small boat to complex deck operations involving large winches for lifting and A-frames to swing the ROV back onto the deck. Some even have “garages” that are lowered to the bottom. The cabled ROV then leaves the garage to explore, returning when the mission is completed. In most cases, however, ROV operations are simpler and safer to conduct than any type of occupied-submersible or diving operation.

The disadvantages of using an ROV include the fact that the human presence is lost, making visual surveys and evaluations more difficult, and the lack of freedom from the surface due to the ROV’s cabled connection to the ship. The S2 Phantom ROV highlighted here has been rated to an operating depth of 2,400 ft. The vehicle has four thrusters that each provide one-half horsepower of thrust for horizontal, lateral, or vertical movement. Two of the thrusters are mounted horizontally. They allow the vehicle to move forward and backward, and to turn left and right. The other two thrusters are mounted at an angle, slanted in opposite directions. They provide vertical thrust (when both spin in the same direction) and lateral thrust (when they spin in opposing directions, one pushing water up, the other pushing it down).

An ROV operator controls the vehicle from a system on board the ship. Using a joystick, a camera control, and a video monitor, the operator moves the vehicle and the camera to desired locations; the operator’s eyes essentially “become” the camera lens. The vehicle’s depth, heading, and geographic position (latitude and longitude) are also recorded.

Multiple Uses

ROVs are often kept aboard vessels mounting submersible operations for several reasons; the first is safety. In the event that a submersible becomes entangled or otherwise incapacitated, an ROV can investigate the scene to help the operators decide how to respond. If appropriate, cutter blades can be attached to the manipulator arm and used to free the sub. If a sub loses power and cannot surface, the ROV’s manipulator arm can grab onto the sub. The deck crew can then bring the sub to the surface.

ROVs also support exploration and science objectives. When the submersible cannot be used because of weather or maintenance problems, the ROV often can take its place. It can also be used to investigate questionable dive sites before a sub is deployed, limiting risk to the expensive subs and their pilots.

The Web team gratefully acknowledges this contribution by Steve Gittings, the research coordinator of NOAA's National Marine Sanctuary System

 

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