ROVs and AUVs: two different machines
Unmanned underwater vehicles come in two broad types. A remotely operated vehicle, or ROV, is connected to a ship by a cable that supplies power and carries video and commands, so an operator controls it in real time. An autonomous underwater vehicle, or AUV, carries its own batteries and computer, follows a programmed mission, and works without a cable. Radio waves travel poorly through seawater, which means an AUV cannot be steered by remote control from the surface in the way that an aerial drone can. It must operate largely on its own, communicating by occasional acoustic signals or only after it surfaces. This difference explains much of the history.
The 1950s and 1960s: navy and laboratory origins
Interest in unmanned underwater machines grew during the Cold War, when navies wanted to find objects on the seabed, track submarines and recover items from deep water. The first vehicle generally described as an AUV is the Self-Propelled Underwater Research Vehicle, or SPURV, built at the University of Washington’s Applied Physics Laboratory in the late 1950s for the US Navy. It was used for studies of how sound travels through water and for other measurements, and it reportedly operated through the 1970s.
At the same time, tethered vehicles advanced faster. The US Navy’s Cable-controlled Underwater Recovery Vehicle, or CURV, was developed in the 1960s and used in recovering lost objects from the seabed. It became widely known after helping to find and recover a hydrogen bomb that fell into the Mediterranean off Spain in 1966. Experience with submarine history and deep submergence vehicles such as the crewed Alvin, which first dived in 1964, contributed to ocean engineering in this period.
Lessons from the 1970s and 1980s
Early AUVs were large, costly and limited by batteries and by computers that were slow and bulky. At the same time, the offshore oil and gas industry was growing, and it adopted ROVs in large numbers beginning in the 1970s and 1980s to inspect and maintain underwater structures. This commercial demand helped create a supplier industry that later served AUV makers.
Meanwhile, researchers worked on smaller, more reliable AUVs. Universities and institutions such as the Massachusetts Institute of Technology, the Woods Hole Oceanographic Institution and the University of Washington built experimental designs. Advances in microprocessors and in sonar made it possible for vehicles to navigate by inertial sensors, acoustic beacons and sensors detecting the seabed, rather than by pre-set courses alone.
The 1990s: AUVs become practical
By the 1990s, AUVs were shifting from prototypes to tools. The Woods Hole REMUS vehicle, a small, torpedo-shaped design, was developed in the 1990s and used for coastal surveys. The British Autosub, developed at the Southampton Oceanography Center, completed long under-ice and open-ocean missions. Navies adopted small AUVs for mine detection, a task suited to a machine that can search a hazardous area without risking a crew. Improvements in lithium-ion batteries, and in some cases fuel cell designs, extended mission length in later years.
A related line of development was the underwater glider. Oceanographer Henry Stommel proposed networks of gliders in a 1989 article, and various gliders were later built. A glider changes its buoyancy to sink and rise, with fixed wings turning vertical motion into forward motion, so it uses little energy and can stay out for weeks or months, measuring temperature, salinity and other properties. Gliders move slowly, but they offer a low-cost way to sample the ocean over long periods.
Commercial use
By the 2000s, the oil and gas industry began using AUVs for seabed mapping and for surveys along pipeline routes. An AUV can travel close to the seafloor with a multibeam sonar and a side-scan sonar, yielding higher-resolution images than a surface ship’s equipment can obtain in deep water, and it can run on its own while the ship does something else. Companies also use AUVs for surveying routes for submarine cables and for inspecting pipelines, often alongside ROVs, which are still better at tasks needing manipulation, such as turning a valve.
AUVs have become important for science. They map hydrothermal vents, survey coral reefs and measure conditions under ice shelves where ships cannot easily go. In 2011, AUVs were used in the search for the wreckage of Air France Flight 447 in the deep Atlantic, locating debris on the seafloor after earlier searches had failed. Several AUVs were also used in the search for Malaysia Airlines Flight 370 in 2014, though that aircraft was not found.
Limits and outlook
AUVs are still limited by battery life, by the difficulty of communicating and positioning underwater, and by cost. Navigation errors build up over time without a reference, so vehicles may rely on acoustic beacons or periodic surfacing to correct position. Research on artificial intelligence aims to allow vehicles to adapt missions on their own, detect features of interest and cooperate in groups.
The history of AUVs illustrates how a military and research technology can find commercial uses once costs drop and reliability rises. A technology that began as a navy test vehicle now helps inspect pipelines, map the seabed and collect data about the oceans.