A remotely operated underwater vehicle (ROUV) or remotely operated vehicle (ROV) is a free-swimming submersible craft. ROVs are underwater machines that are often used to explore the ocean depth while being operated by people at the surface, usually from a control room. ROVs are used to perform underwater observation, inspection, and physical tasks such as valve operations, hydraulic functions, and other general tasks within the subsea oil and gas industry, military, scientific and other applications. ROVs can also carry tooling packages for undertaking specific tasks such as pull-in and connection of flexible flowlines and umbilicals, and component replacement. They are often used to do research and commercial work at great depths beyond the capacities of most submersibles and divers. Most users of the machines use the term "remotely operated vehicle" (ROV).
Description This meaning is different from remote control vehicles operating on land or in the air because ROVs are designed specifically to function in underwater environments, where conditions such as high pressure, limited visibility, and the effects of buoyancy and water currents pose unique challenges. While land and aerial vehicles use wireless communication for control, ROVs typically rely on a physical connection, such as a tether or umbilical cable, to transmit power, video, and data signals, ensuring reliable operation even at great depths. The tether also provides a stable means of communication, which is crucial in underwater conditions where radio waves are absorbed quickly by water, making wireless signals ineffective for long-range underwater use.
ROVs are unoccupied, usually highly maneuverable, and operated by a crew either aboard a vessel/floating platform or on proximate land. They are common in deepwater industries such as offshore hydrocarbon extraction. They are generally, but not necessarily, linked to a host ship by a neutrally buoyant tether or, often when working in rough conditions or in deeper water, a load-carrying umbilical cable is used along with a tether management system (TMS). The TMS is either a garage-like device which contains the ROV during lowering through the splash zone or, on larger work-class ROVs, a separate assembly mounted on top of the ROV. The purpose of the TMS is to lengthen and shorten the tether so the effect of cable drag where there are underwater currents is minimized. The umbilical cable is an armored cable that contains a group of electrical conductors and fiber optics that carry electric power, video, and data signals between the operator and the TMS. Where used, the TMS then relays the signals and power for the ROV down the tether cable. Once at the ROV, the electric power is distributed between the components of the ROV. However, in high-power applications, most of the electric power drives a high-power electric motor which drives a hydraulic pump. The pump is then used for propulsion and to power equipment such as torque tools and manipulator arms where electric motors would be too difficult to implement subsea. Most ROVs are equipped with at least a video camera and lights. Additional equipment is commonly added to expand the vehicle's capabilities. These may include sonars, magnetometers, a still camera, a manipulator or cutting arm, water samplers, and instruments that measure water clarity, water temperature, water density, sound velocity, light penetration, and temperature.
Classification Submersible ROVs are normally classified into categories based on their size, weight, ability or power. Some common ratings are: Micro - typically Micro-class ROVs are very small in size and weight. Today's Micro-Class ROVs can weigh less than 3 kg. These ROVs are used as an alternative to a diver, specifically in places where a diver might not be able to physically enter such as a sewer, pipeline or small cavity. Mini - typically Mini-Class ROVs weigh in around 15 kg. Mini-Class ROVs are also used as a diver alternative. One person may be able to transport the complete ROV system out with them on a small boat, deploy it, and complete the job without diver intervention. Some Micro and Mini classes are referred to as "eyeball"-class to differentiate them from ROVs that may be able to perform intervention tasks. General - typically less than 5 HP (propulsion); occasionally small three finger manipulators grippers have been installed, such as on the very early RCV 225. These ROVs may be able to carry an imaging sonar unit and are usually used on light survey applications. Typically the maximum working depth is less than 1,000 meters though one has been developed to go as deep as 7,000 meters. Inspection Class - these are typically rugged commercial or industrial use observation and data gathering ROVs - typically equipped with live-feed video, still photography, imaging sonar, ultra-short baseline acoustic positioning system (USBL), cathodic protection (CP) probe, ultra-sonic thickness (UT) gauge, and other data collection sensors. Inspection Class ROVs can also have manipulator arms for light work and object manipulation. Light Workclass - typically less than 50 hp (propulsion). These ROVs may be able to carry some manipulators. Their chassis may be made from polymers such as polyethylene rather than the conventional stainless steel or aluminium alloys. They typically have a maximum working depth less than 2000 m. Heavy Workclass - typically less than 220 hp (propulsion) with an ability to carry at least two manipulators. They have a working depth up to 3500 m and are capable of performing more technical tasks that involve great strength and dexterity. Trenching & Burial - typically more than 200 hp (propulsion) and not usually greater than 500 hp (while some do exceed that) with an ability to carry a cable laying sled and work at depths up to 6000 m in some cases.
Underwater ROVs may be "free swimming" where they operate neutrally buoyant on a tether directly from the launch ship or platform, or they may be "garaged" where they operate from a heavy submersible "garage" or "tophat" on a tether deployed from the garage which is lowered from the ship or platform. Both techniques have their pros and cons; however very deep work is normally done with a garage.
History
The first ROV, named POODLE, was developed in 1953 by the French engineer and underwater photographer Dimitri Rebikoff. It was initially designed as an underwater camera platform and was later developed further because of naval interest in remotely operated underwater vehicles. The U.S. Navy funded most of the early ROV technology development in the 1960s into what was then named a "Cable-Controlled Underwater Recovery Vehicle" (CURV). This created the capability to perform deep-sea rescue operation and recover objects from the ocean floor, such as a nuclear bomb lost in the Mediterranean Sea after the 1966 Palomares B-52 crash. Building on this technology base; the offshore oil and gas industry created the work-class ROVs to assist in the development of offshore oil fields. In the 1970s and '80s the Royal Navy used "Cutlet", a remotely operated submersible, to recover practice torpedoes and mines. RCA (Noise) maintained the "Cutlet 02" System based at BUTEC ranges, whilst the "03" system was based at the submarine base on the Clyde and was operated and maintained by RN personnel. More than a couple of decades after they were first introduced, ROVs became essential in the 1980s when much of the new offshore development exceeded the reach of human divers. During the mid-1980s the marine ROV industry suffered from serious stagnation in technological development caused in part by a drop in the price of oil and a global economic recession. Since then, technological development in the ROV industry has accelerated and today ROVs perform numerous tasks in many fields. Their tasks range from simple inspection of subsea structures, pipelines, and platforms, to connecting pipelines and placing underwater manifolds. They are used extensively both in the initial construction of a sub-sea development and the subsequent repair and maintenance. The oil and gas industry has expanded beyond the use of work class ROVs to mini ROVs, which can be more useful in shallower environments. They are smaller in size, oftentimes allowing for lower costs and faster deployment times.
Submersible ROVs have been used to identify many historic shipwrecks, including the RMS Titanic, the Bismarck, , the SM U-111, and SS Central America. In some cases, such as the Titanic and the SS Central America, ROVs have been used to recover material from the sea floor and bring it to the surface, the most recent being in July 2024 during a Titanic expedition in recovering artefacts for the first time through a magnetometer.
While the oil and gas industry uses the majority of ROVs, other applications include science, military, and salvage. The military uses ROV for tasks such as mine clearing and inspection. Science usage is discussed below.
Construction Work-class ROVs are built with a large flotation pack on top of an aluminium chassis to provide the necessary buoyancy to perform a variety of tasks. The sophistication of construction of the aluminum frame varies depending on the manufacturer's design. Syntactic foam is often used for the flotation material. A tooling skid may be fitted at the bottom of the system to accommodate a variety of sensors or tooling packages. By placing the light components on the top and the heavy components on the bottom, the overall system has a large separation between the center of buoyancy and the center of gravity: this provides stability and the stiffness to do work underwater. Thrusters are placed between center of buoyancy and center of gravity to maintain the attitude stability of the robot in maneuvers. Various thruster configurations and control algorithms can be used to give appropriate positional and attitude control during the operations, particularly in high current waters. Thrusters are usually in a balanced vector configuration to provide the most precise control possible.
Electrical components can be in oil-filled water tight compartments or one-atmosphere compartments to protect them from corrosion in seawater and being crushed by the extreme pressure exerted on the ROV while working deep. The ROV will be fitted with thrusters, cameras, lights, tether, a frame, and pilot controls to perform basic work. Additional sensors, such as manipulators and sonar, can be fitted as needed for specific tasks. It is common to find ROVs with two robotic arms; each manipulator may have a different gripping jaw. The cameras may also be guarded for protection against collisions.
The majority of the work-class ROVs are built as described above; however, this is not the only style in ROV building method. Smaller ROVs can have very different designs, each appropriate to its intended task. Larger ROVs are commonly deployed and operated from vessels, so the ROV may have landing skids for retrieval to the deck.
Configurations Remotely operated vehicles have two basic configurations. Each of these brings specific limitations. Open or box frame ROVs - this is the most familiar of the ROV configurations - consisting of an open frame where all the operational sensors, thrusters, and mechanical components are enclosed. These are useful for free-swimming in light currents (less than 4 knots based upon manufacturer specifications). These are not suitable for towed applications due to their very poor hydrodynamic design. Most Work-Class and Heavy Work-Class ROVs are based upon this configuration.