Nereus (underwater Vehicle)
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''Nereus'' was a hybrid uncrewed autonomous underwater vehicle (HROV, a type of
remotely operated underwater vehicle A remotely operated underwater vehicle (ROUV) or remotely operated vehicle (ROV) is a free-swimming submersible craft used to perform underwater observation, inspection and physical tasks such as valve operations, hydraulic functions and other g ...
) built by the
Woods Hole Oceanographic Institution The Woods Hole Oceanographic Institution (WHOI, acronym pronounced ) is a private, nonprofit research and higher education facility dedicated to the study of marine science and engineering. Established in 1930 in Woods Hole, Massachusetts, it i ...
(WHOI). Constructed as a research vehicle to operate at depths of up to , it was designed to explore
Challenger Deep The Challenger Deep is the List of submarine topographical features#List of oceanic trenches, deepest known point of the seabed of Earth, located in the western Pacific Ocean at the southern end of the Mariana Trench, in the ocean territory o ...
, the deepest surveyed point in the global ocean. ''Nereus'', named for Greek sea titan
Nereus In Greek mythology, Nereus ( ; ) was the eldest son of Pontus (the Sea) and Gaia ( the Earth), with Pontus himself being a son of Gaia. Nereus and Doris became the parents of 50 daughters (the Nereids) and a son ( Nerites), with whom Nereus ...
(who has a man's torso and a fish-tail) through a nationwide contest of high school and college students, began its deep sea voyage to Challenger Deep in May 2009 and reached the bottom on May 31, 2009. On this dive the ''Nereus'' reached a depth of , making the ''Nereus'' the world's deepest-diving vehicle in operation at the time, and the first since 1998 to explore the
Mariana Trench The Mariana Trench is an oceanic trench located in the western Pacific Ocean, about east of the Mariana Islands; it is the deep sea, deepest oceanic trench on Earth. It is crescent-shaped and measures about in length and in width. The maxi ...
, the deepest known part of the ocean. On 10 May 2014, ''Nereus'' was lost while exploring the Kermadec Trench at a depth of . Communications were cut off at around 2 p.m. local time, and debris retrieved later revealed that it imploded due to high pressure.


Hybrid design

Being a hybrid ROV means that the vehicle could operate untethered or tethered with a thin
optical fiber An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can transmit light from one end to the other. Such fibers find wide usage in fiber-optic communications, where they permit transmission over longer distances and at ...
cable and operated by pilots aboard the ship. The latter enabled it to make deep dives while being highly maneuverable. The optical fiber tether has the approximate diameter of a human hair, and can bear only . It is made up of a thin layer of plastic surrounding a slender glass fiber core. The vehicle carried approximately of cable wound in two small canisters that pay out the fiber as the vehicle descends. This slim tether is smaller, lighter, and more cost-effective than cable. ''Nereus'' weighed approximately 3 tons and was about 4.25 meters (14 feet) long and 2.3 meters (8 feet) wide. Approximately 2,000
lithium-ion batteries A lithium-ion or Li-ion battery is a type of rechargeable battery that uses the reversible intercalation of Li+ ions into electronically conducting solids to store energy. Li-ion batteries are characterized by higher specific energy, energy ...
provided its power. The vehicle made use of precisely designed ceramic spheres rather than the much heavier syntactic foam that is typically used for submersible vehicles. Each hull contained between 700 and 800 9-cm (3.5-inch) hollow spheres that were specifically designed to handle intense pressure. ''Nereus'' had a lightweight robotic manipulator arm to conduct the sample collecting that operates hydraulically and was able to perform under intense pressure. As an alternative to the tether, the ''Nereus'' could be switched to a free-swimming mode and operated as an autonomous vehicle to survey the ocean floor. In designing the vehicle, the design team led by Andy Bowen at the Woods Hole Oceanographic Institution relied on previous experience in developing autonomous underwater vehicles (AUVs) and tethered robots to build a hybrid ROV that could both fly like an aircraft to explore large areas of the ocean floor, but would be easily converted to able to hover over the small areas to conduct experiments or collect samples of rocks and sea life.


Deepest dive

The
Challenger Deep The Challenger Deep is the List of submarine topographical features#List of oceanic trenches, deepest known point of the seabed of Earth, located in the western Pacific Ocean at the southern end of the Mariana Trench, in the ocean territory o ...
is located in the
Western Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the contine ...
near the island of
Guam Guam ( ; ) is an island that is an Territories of the United States, organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. Guam's capital is Hagåtña, Guam, Hagåtña, and the most ...
in the
Mariana Trench The Mariana Trench is an oceanic trench located in the western Pacific Ocean, about east of the Mariana Islands; it is the deep sea, deepest oceanic trench on Earth. It is crescent-shaped and measures about in length and in width. The maxi ...
, the deepest known part of an
ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...
on Earth, and the deepest known location on Earth. The May 2009 dive by the ''Nereus'' achieved a depth of , making it the world's deepest-diving vehicle then in operation, and the first since 1998 to explore the Mariana Trench. To accomplish this dive, the vehicle had to sustain pressures over 1,000 times the atmospheric pressure at the Earth's surface. It hovered over the trench for more than 10 hours and sent back live video to the mother ship. ''Nereus'' is the third vehicle in the world to reach the bottom of the Pacific Ocean's Challenger Deep. The first was the crewed Bathyscaphe Trieste, which carried U.S. Navy Lieutenant Don Walsh and Swiss engineer Jacques Piccard and made the voyage on 23 January 1960. The ''Nereus'' dive aimed for the same spot. On 24 March 1995 a Japanese robotic deep-sea probe called '' Kaikō'' made the first uncrewed trip to the Challenger Deep. Once at the bottom, ''Nereus'' collected liquid and rock specimens. Patricia Fryer, co-chief scientist of the expedition, said the following about the samples.
"We want to know how all of this relates to subduction around the globe, changes in the chemistry of the ocean in general and, therefore, potential effects those changes may have on ocean-atmosphere interactions and things like global climate change."


Loss

On 10 May 2014, at around 2 p.m. local time, ''Nereus'' was lost while conducting a dive at in depth in the Kermadec Trench, believed to be caused by extreme pressure at up to . ''Nereus'' was sent to complete the first systematic study of a deep-ocean trench as part of the NSF-sponsored Hadal Ecosystems Study (HADES) project under chief scientist Timothy Shank, a WHOI biologist who also helped conceive the vehicle. It was being controlled from the Research Vessel ''Thomas G. Thompson''. Thirty days into the forty-day mission, about seven hours into a nine-hour dive, communications with ''Nereus'' were lost. When standard emergency recovery protocols were unsuccessful, the team initiated a search near the dive site. They then spotted several pieces of debris on the surface nearby later identified to be parts of ''Nereus'', indicating a catastrophic implosion. The ship's crew recovered the debris to confirm its identity and to discover more information about the nature of the failure. Despite this, WHOI Director of Research Larry Madin stated that WHOI will continue to develop, build, and operate more underwater research craft for oceanographic exploration.


References


External links


New Hybrid Deep-sea Vehicle Is Christened ''Nereus''

BBC featured report on the ''Nereus''
{{2014 shipwrecks Autonomous underwater vehicles Maritime incidents in 2014 Woods Hole Oceanographic Institution