Underwater vehicle

(oceanography) A submersible work platform designed to be operated either remotely or directly.

A submersible work platform designed to be operated either remotely or directly. Underwater vehicles are grouped into three categories: deep submersible vehicles (DSVs), remotely operated vehicles (ROVs), and autonomous underwater vehicles (AUVs). There are also hybrid vehicles which combine two or three categories on board a single platform. Within each category of submersible there are specially adaped vehicles for specific work tasks. These can be purpose-built or modifications of standard submersibles.

There are five types of DSVs: one-atmosphere untethered vehicles; one-atmosphere tethered vehicles, including observation/work bells; atmospheric diving suits; diver lockout vehicles; and wet submersibles. While they differ mainly in configuration, source of power, and number of crew members, all carry a crew at 1-atm (10²-kilopascal) pressure within a dry chamber. An exception is the wet submersible, where the crew is exposed to full depth pressure. The purpose of the DSV is to put the trained mind and eye to work inside the ocean. The earliest submersibles had very small viewing ports fitted into thick-walled steel hulls. In the mid-1960s, experimental work began on use of massive plastics (acrylics) as pressure hull materials. Today, submersibles with depth capabilities to 3300 ft (1000 m) are being manufactured with pressure hulls made entirely of acrylic. Essentially the hull is now one huge window.

The first ROVs were developed in the late 1950s for naval use. By the mid-1970s, they were used in the civil sector. The rapid acceptance of these submersibles is due to their relatively low cost and the fact that they do not put human life at risk when undertaking hazardous missions. However, their most important attribute is that they are less complex. By virtue of their surface-connecting umbilical cable, they can operate almost indefinitely since there is no human inside requiring life support and no batteries to be recharged. There are four types of ROV: tethered free-swimming vehicles, towed vehicles, bottom reliant vehicles, and structurally reliant vehicles.

AUVs are crewless and untethered submersibles which operate independent of direct human control. Their operations are controlled by a preprogrammed, on-board computer. They were first developed in the military where applications include such tasks as minefield location and mapping, minefield installation, submarine decoys, and covert intelligence collection. Civilian tasks include site monitoring, basic oceanographic data gathering, under-ice mapping, offshore structure and pipeline inspection, and bottom mapping. These submersibles are particularly useful where long-duration measurements and observations are to be made and where human presence is not required.

AUVs span a wide range of sizes and capabilities, related to their intended missions. Each is a mobile instrumentation platform with propulsion, sensors, and on-board intelligence designed to complete sampling tasks autonomously. At the large end of the scale, transport-class platforms in the order of 10 m (33 ft) length and 10 metric ton (11 tons) weight in air have been designed for missions requiring long endurance, high speed, large payloads, or high-power sensors. At the small end of the scale, network-class platforms in the order of 1 m (3.3 ft) length and 100 kg (220 lb) weight in air address missions requiring portability, multiple platforms, adaptive spatial sampling, and sustained presence in a specific region. Vehicles can also be categorized in terms of propulsion method (propeller-driven or buoyancy-driven) or in terms of their maximum operating depth.

Hybrid vehicles are those that combine crewed vehicles, remotely operated vehicles, and divers. For example, the hybrid DUPLUS II can operate either as a tethered free-swimming ROV or as a 1-atm tethered crewed vehicle. This evolved to provide capability for remotely conducting those tasks for which human skills are not needed, and then to put the human at the place where those skills are required. Other hybrid examples include ROVs that can be controlled remotely from the surface or at the work site by a diver performing maintenance and repair tasks.