A bathyscaphe is a self-propelled vehicle used for deep-sea dives


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Earth Science, Oceanography, Geography, Geographic Information Systems (GIS), Physical Geography, Social Studies, World History

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A bathyscaphe is a self-propelled vehicle used for deep-sea dives. Bathyscaphes can dive deeper than a person with scuba gear, and even deeper than submarines.

Design features reveal that the bathyscaphe was engineered with one goal in mind: to reach the deepest depths of the ocean. In fact, the word "bathyscaphe" takes the first part of its name from the ancient Greek word for "deep": bathys. ("Scaphe" indicates a light, bowl-shaped boat.)

The bathyscaphe is made of two main components: a crew cabin and a float. The heavy steel cabin is designed to resist pressure, which increases the deeper you go. The pressure at the bottom of the ocean can be 1,130 kilograms per square centimeter (16,000 pounds per square inch). Thats enough to crush submarines, so the cabins ability to withstand pressure is important for the crew inside!

A bathyscaphes float has air tanks and gasoline tanks. These tanks allow the vehicle to propel and maneuver itself, as well as dive and ascend.

The vehicles gasoline tanks are lighter than water. This allows the bathyscaphe to float on the oceans surface rather than sink immediately. Gasoline is also incompressible, meaning it does not shrink, or compress, under pressure. This enables the bathyscaphe to maintain equal pressure between its interior and the sea, even at extreme depths where water is highly pressurized. A bathyscaphe relies on its gas tanks to maneuver and perform important navigational functions.

The bathyscaphe begins to descend when the floats air tanks are slowly filled with water. The more water in the tanks, the deeper the bathyscaphe can travel. The air tanks are located to the side of the gasoline tanks, which help maintain equal pressure inside and outside the float structure.

In order to descend to great depths, a bathyscaphe is also equipped with cone-shaped containers, called hoppers, filled with heavy iron pellets. The pellets are ballast, used to control a ship's weight. The weight of the ballast, reaching up to 16 tons, allows the vehicle to sink. To ascend, the bathyscaphe releases the heavy iron ballast, held in place by magnets. This magnetic system allows the bathyscaphe to ascend even in the event of a power failure.


The bathyscaphe can descend farther and faster into the ocean than its predecessor, the bathysphere. The bathyspheres cabin was suspended from a cable and could not move with as much freedom as the self-propelled bathyscaphe. This makes the bathyscaphe an important innovation in oceanic exploration.

Swiss oceanographer Auguste Piccard designed the bathyscaphe. His most successful vehicle, the Trieste, was launched in 1953 and dived to 3,150 meters (10,300 feet).

In 1958, the United States Navy purchased the Trieste and designed a new cabin that would enable it to reach the floor of deep ocean trenches. Equipped with this new cabin, the Trieste reached the deepest known point on Earth, the Challenger Deep in the Mariana Trench, on January 23, 1960. Located 10,916 meters (35,813 feet) below the oceans surface, the Challenger Deep is deeper than the height of Mount Everest!

An amazing feat of oceanic navigation, the Trieste expedition remained the only manned dive to reach the Challenger Deep until the DEEPSEA CHALLENGE expedition in March 2012. In that expedition, Canadian inventor and filmmaker James Cameron became the first person to dive solo to the bottom of the Mariana Trench. Cameron and the DEEPSEA CHALLENGE team relied on research and challenges presented by the Trieste in developing their sophisticated submersible, the DEEPSEA CHALLENGER. In particular, they relied on the experience of Don Walsh, an American oceanographer who descended to the Mariana Trench in the Trieste and became an integral part of the DEEPSEA CHALLENGE mission.

The Trieste is now housed at the U.S. Navy Museum in Washington, D.C., although other nations continue to pursue deep-sea exploration using bathyscaphes.

The so-called "Sea Pole" class of bathyscaphe, for instance, was developed in China in the early 2000s. Little is known about this vehicle, except it is constructed of titanium and has a more streamlined, teardrop shape than earlier bathyscaphes.

Fast Fact

Up in the Air,
Down in the Sea
The Trieste bathyscaphe was considered the underwater equivalent of a hot air balloon. With its small gondola-like cabin attached under a massive float, the Trieste looked the part. In fact, the 12 gas-filled tanks on the Trieste provided as much lift as the hydrogen gas on an airship. These similarities in design were no coincidence. August Piccard, the designer of the Trieste, was a pioneer in high-altitude ballooning as well. His expertise in traveling high up in the air helped him engineer a vehicle that could dive deep under the sea.

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Jeannie Evers, Emdash Editing, Emdash Editing
National Geographic Society
Last Updated

October 19, 2023

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