Remotely operated underwater vehicle

A remotely operated underwater vehicle (ROUV) or remotely operated vehicle (ROV) is a free-swimming submersible craft. 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).

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.

Submersible ROVs are normally classified into categories based on their size, weight, ability or power. Some common ratings are:

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;^{[clarification needed]} however very deep work is normally done with a garage.

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.

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. More than a decade 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, USS Yorktown, 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.