Nereus (underwater vehicle) facts for kids

Nereus
Quick facts for kids History
United States
Name	Nereus
Owner	Woods Hole Oceanographic Institution (WHOI)
Operator	WHOI
Builder	WHOI
Acquired	1995
Commissioned	2009
In service	2009~2014
Home port	Woods Hole, Massachusetts, United States
Fate	Imploded due to high pressure in Kermadec Trench 10 May 2014
__1B0X_5H1P__	career
General characteristics
Type	remotely operated underwater vehicle
Displacement	2,800 kilograms (6,200 lb)
Length	3 metres (9.8 ft)
Installed power	electrical (rechargeable Lithium-ion batteries)
Speed	3 knots
Test depth	10,902 metres (35,768 ft)
Complement	unmanned
Sensors & processing systems	side-scan sonar & LED search lights
__1B0X_5H1P__	characteristics

Nereus was a groundbreaking uncrewed robotic underwater exploration craft built in the United States. Engineers at the Woods Hole Oceanographic Institution (WHOI) designed this vehicle to explore the deepest trenches on Earth. It was named after the ancient Greek sea titan Nereus, who had the torso of a man and the tail of a fish. The name was selected through a nationwide naming competition for students.

This advanced machine was a hybrid remotely operated vehicle, or HROV. That means it had the special ability to work in two different modes: either controlled by human pilots using a slender cable or swimming freely as an autonomous robot. Nereus traveled to the deepest surveyed point in the world ocean, known as Challenger Deep, in May 2009. It reached depths of nearly 11,000 meters (36,000 feet) and helped scientists gather essential data about extreme marine environments.

What Made the Hybrid Underwater Vehicle Special?

Exploring the deep sea is one of the most difficult engineering challenges in human history. To explore these regions, scientists previously had to choose between two main types of robotic systems. The first type is a remotely operated vehicle (ROV), which stays tethered to a ship with a thick, heavy cable. The second type is an autonomous underwater vehicle (AUV), which swims on its own without any cable attached.

Nereus was designed to combine the advantages of both systems into a single craft. This dual design allowed marine scientists to save money and expand their scientific research capabilities.

Operating as a Tethered Robot

When configured as an ROV, Nereus was linked to a research ship on the ocean surface. A team of human pilots and scientists steered the robot using joysticks and computer controls.

• The vehicle sent real-time, high-definition video directly back up to the ship's control room.
• Scientists used its robotic arm to collect rock specimens, sediment samples, and strange living creatures.
• It could hover motionless over specific targets to conduct delicate ocean experiments.
• Pilots could steer the robot around underwater obstacles with extreme precision.

Operating as a Free-Swimming Drone

When engineers switched Nereus into AUV mode, they removed the control cable entirely. In this configuration, the vehicle operated as a free-swimming robotic explorer.

• The vehicle followed pre-programmed computer instructions to map wide areas of the ocean bottom.
• It utilized side-scan sonar systems to build detailed, three-dimensional acoustic maps of the sea floor.
• It could fly through the water like an underwater airplane, covering vast distances efficiently.
• Sensors on board measured water temperature, salinity, and chemical signatures across broad regions.

Engineering Challenges and Innovative Design

Water pressure increases dramatically as an object goes deeper into the ocean. At the surface of the Earth, normal atmospheric pressure is about 14.7 pounds per square inch (psi). At the bottom of an ocean trench, the pressure can exceed 16,000 psi (110 megapascals). This intense pressure is more than 1,000 times greater than the pressure at sea level. It is equal to having the weight of three heavy transport trucks pressing down on every single square inch of the robot's surface.

Solving the Pressure Problem with High-Tech Ceramics

Traditional deep-sea submarines rely on thick steel spheres or dense synthetic foam to stay buoyant and resist pressure. However, these materials become far too heavy when designed for trenches deeper than 8,000 meters.

To overcome this issue, lead engineer Andy Bowen and his team used advanced ceramic technology:

• Engineers filled the twin hulls of Nereus with between 700 and 800 hollow ceramic spheres.
• Each ceramic sphere measured roughly 9 centimeters (3.5 inches) in diameter.
• These spheres were custom-manufactured from high-strength aluminum oxide material.
• The ceramic spheres provided excellent buoyancy while withstanding crushing deep-sea pressure.
• This lightweight design kept the total weight of Nereus at approximately 2,800 kilograms (around 3 tons).

Micro-Thin Optical Fiber Tether System

Traditional deep-diving tethered vehicles use massive, steel-reinforced cables. These heavy cables require giant mechanical winches and heavy research ships to deploy them safely.

Nereus solved this problem with a revolutionary micro-thin optical fiber tether:

• The fiber optic strand was roughly as thin as a single human hair.
• It contained a core of ultra-pure glass surrounded by a protective plastic outer coat.
• The fragile tether was designed to break under a pull force of just 4 kilograms (about 8.8 pounds).
• Because it was so light, it did not create heavy drag in ocean currents.
• The robot carried about 40 kilometers (25 miles) of this glass fiber wound inside small canisters.
• As the robot descended, the fiber simply paid out smoothly from the canisters on the vehicle.
• This hair-thin link transmitted crisp digital signals and live video across miles of open ocean.

Electric Power and Mechanical Systems

Running a robotic vehicle in the deep ocean requires dependable electrical power. Nereus carried an internal energy storage system that powered all its thrusters, cameras, and computers:

• Power was supplied by approximately 2,000 rechargeable lithium-ion battery cells.
• These batteries were sealed inside protective, pressure-resistant enclosures.
• The vehicle carried powerful LED searchlights to cut through the total darkness of the deep ocean.
• A specialized hydraulic arm was mounted on the front to grab delicate geological and biological samples.

Historic Mission to Challenger Deep

Location of the Challenger Deep in the Mariana Trench

In May 2009, Nereus embarked on an ambitious journey to the Mariana Trench in the Western Pacific Ocean near Guam. Its goal was to reach Challenger Deep, the deepest known point on planet Earth.

Reaching the Ocean Floor

On May 31, 2009, Nereus completed its historic descent:

• The vehicle dove to a recorded depth of 10,902 meters (35,768 feet).
• It became the deepest-diving operational underwater vehicle in the world at that time.
• It was the first robotic craft to explore the Mariana Trench since the Japanese robot Kaikō visited in 1998.
• The robot remained at the bottom for more than 10 hours, sending live video back to the surface ship.

Important Scientific Discoveries

During its hours on the ocean floor, Nereus performed essential scientific research:

• It gathered samples of sea floor mud, mineral liquids, and deep-sea rock formations.
• The robotic arm placed these specimens safely inside on-board storage containers.
• Scientists analyzed how tectonic plates push against one another in subduction zones.
• The expedition gathered clues about how ocean chemistry interacts with global climate cycles.

Deep Exploration History

Nereus became only the third exploration craft in history to touch the bottom of Challenger Deep:

• 1960: The crewed submarine Bathyscaphe Trieste, piloted by Jacques Piccard and Don Walsh, became the first vessel to reach the bottom.
• 1995: The Japanese uncrewed robotic vehicle Kaikō became the second vehicle to reach the trench floor.
• 2009: Nereus became the third craft to reach the bottom, proving the effectiveness of its hybrid lightweight design.

Deep Sea Exploration in the Hadal Zone

The extreme parts of the ocean located below 6,000 meters (20,000 feet) are called the hadal zone. This zone was named after Hades, the ancient Greek god of the underworld. The hadal zone consists mostly of steep ocean trenches formed by colliding tectonic plates.

Life in Extreme Ocean Trenches

For many decades, scientists believed that the crushing pressure and freezing temperatures of deep trenches made life impossible. However, vehicles like Nereus proved that these extreme habitats are full of life:

• Specialized organisms thrive around volcanic vents and cold methane seeps.
• Deep-sea sea cucumbers, amphipods (small shrimplike crustaceans), and snailfish live in complete darkness.
• These organisms have unique cell membranes and proteins that stop them from being crushed by water pressure.
• Many trench species feed on organic material, called marine snow, that drifts down from the upper ocean.

The Final Mission in the Kermadec Trench

In 2014, Nereus joined the Hadal Ecosystems Study (HADES), an ambitious project funded by the National Science Foundation (NSF). The mission was led by chief scientist Timothy Shank from WHOI aboard the research vessel Thomas G. Thompson.

The Kermadec Expedition

The goal of this expedition was to conduct the world's first systematic biological study of the Kermadec Trench, located north of New Zealand in the southwestern Pacific Ocean:

• The expedition was planned as a comprehensive 40-day scientific research journey.
• Scientists sought to compare trench wildlife with species found in other deep ocean regions.
• Nereus performed several successful dives during the first four weeks of the expedition.
• The vehicle captured extraordinary video footage of rare deep-sea creatures and geological formations.

Loss of the Vehicle

On May 10, 2014, Nereus began a planned nine-hour dive down to a depth of 9,900 meters (32,480 feet):

• Approximately seven hours into the dive, all communications with the vehicle stopped suddenly at 2:00 p.m. local time.
• Emergency protocols were activated, but the craft did not return to the surface.
• The crew aboard the research ship launched an immediate search of the area.
• Searchers soon discovered pieces of floating ceramic and composite materials on the sea surface.
• Careful examination confirmed that the parts belonged to Nereus, proving the vehicle had suffered a sudden structural implosion under the immense pressure.

The Legacy of Nereus

Although Nereus was lost in 2014, the engineering lessons learned from its construction helped change modern deep-sea robotics.

• It demonstrated that micro-thin fiber optic cables could replace heavy, expensive steel-armored cables.
• It proved that ceramic spheres are a practical, lightweight alternative to standard syntactic foam.
• The discoveries made during its dives expanded our knowledge of marine geology and extreme biology.
• Engineers at research institutions around the world continue to build new hybrid submersibles based on the technology pioneered by Nereus.

Related Pages

• Autonomous underwater vehicle
• Bathyscaphe Trieste
• Mariana Trench
• Remotely operated underwater vehicle
• Woods Hole Oceanographic Institution