Bathyscaphe facts for kids

Bathyscaphe Trieste before its historic dive into the Mariana Trench.

The Trieste in 1958.

A bathyscaphe is a special kind of free-diving, crewed deep-sea submersible. It was designed to reach the deepest parts of the world's oceans. Unlike standard military submarines or older diving spheres, a bathyscaphe operates independently without any cables attached to a surface ship.

The vehicle consists of two main parts: a heavy steel crew cabin and a massive float. The crew sphere provides a safe, pressurized space for scientists. The float above it gives the vessel the buoyancy needed to float back up to the surface.

The name comes from two Ancient Greek words: bathys, meaning "deep", and skaphos, meaning "vessel" or "ship". Swiss scientist Auguste Piccard invented this groundbreaking craft in the 1940s to explore uncharted marine depths.

How a Bathyscaphe Works

Internal arrangement of the Trieste bathyscaphe.

To understand how a bathyscaphe works, it helps to think of an underwater hot air balloon. Instead of using hot air to float in the sky, a bathyscaphe uses lightweight liquids to float in dense ocean water.

The Float and Gasoline Buoyancy

Standard submarines use air-filled ballast tanks to rise and sink. However, at extreme depths, water pressure is so intense that standard tanks would be crushed instantly. Air gets squeezed into a tiny volume under high pressure, losing its lifting power.

To solve this problem, Auguste Piccard filled the large hull float with gasoline (petrol):

• Gasoline is lighter than water, which provides positive buoyancy.
• Like most liquids, gasoline is almost completely incompressible.
• Extreme water pressure does not compress the gasoline inside the tanks.
• Pressure stays equalized between the inside and outside of the float.
• The outer float walls can be built out of thin, lightweight metal.

The Strong Crew Sphere

Beneath the buoyant float hangs a thick, sphere-shaped cabin called the gondola:

• The sphere shape distributes external crushing force evenly over the entire surface.
• The walls are made of high-strength steel several inches thick.
• The interior remains at normal sea-level air pressure (1 atmosphere).
• Scientists inside breathe safely without special diving suits.
• Tiny cone-shaped windows made of thick acrylic glass allow direct visual observation.

Diving and Returning to the Surface

A bathyscaphe controls its vertical journey using water and heavy iron weights:

Starting the Dive

• The crew opens valves to let seawater into small ballast tanks.
• The added weight of the water overcomes positive buoyancy.
• The bathyscaphe slowly sinks downward toward the ocean floor.

Staying Balanced

• As the craft goes deeper, colder water makes the gasoline contract slightly.
• Small amounts of iron shot can be dropped to slow down descent speed.

Surfacing Safely

• The vessel carries tons of tiny iron pellets in funnel-shaped hoppers.
• Strong electromagnets hold the iron shot inside the hoppers.
• To rise, the pilot turns off the magnets, releasing iron pellets onto the sea floor.
• As weight drops away, the gasoline float carries the craft back to the surface.
• If power fails completely, the magnets switch off automatically, causing an emergency ascent.

History of Deep-Sea Bathyscaphes

Before the invention of the bathyscaphe, scientists used tethered metal chambers called bathyspheres. These round chambers hung from long steel cables lowered by surface ships. Deep diving with cables was risky because cables could snap or tangle easily.

Auguste Piccard and the FNRS-2

Auguste Piccard was an adventurous physicist who originally designed pressurized balloons to explore the Earth's stratosphere. In the 1930s, he realized the same physical principles could work underwater:

• In 1948, Piccard built the first working bathyscaphe, named FNRS-2, in Belgium.
• It was funded by the Belgian scientific foundation FNRS.
• The float held 37,850 liters (about 10,000 gallons) of aviation gasoline.
• In unmanned test dives, the heavy cabin withstood high pressure over 1,400 meters deep.
• The outer float was damaged by rough ocean waves, leading to redesigns.

The Improved FNRS-3

The French Navy took over the sphere from FNRS-2 to build an improved model:

• Named FNRS-3, it featured a larger float holding 75,700 liters of gasoline.
• It included a better walkway and a protective fin structure.
• In 1954, it carried French explorers down to a depth of 4,050 meters (13,290 feet).
• This dive proved that free-diving submersibles were dependable exploration tools.

The Famous Bathyscaphe Trieste

Piccard built another submersible in Italy called the Trieste:

• Launched in 1953, it featured an upgraded crew sphere made by the Krupp company.
• The float carried 120,000 liters (32,000 gallons) of gasoline.
• The United States Navy purchased Trieste in 1958 for deep ocean research.
• Engineers fitted it with stronger instruments, searchlights, and navigation gear.

The Historic Mariana Trench Dive

The most famous achievement of any bathyscaphe took place on January 23, 1960.

Journey to the Challenger Deep

Swiss oceanographer Jacques Piccard (Auguste's son) and US Navy Lieutenant Don Walsh boarded the Trieste:

• Their target was the Challenger Deep in the Mariana Trench, the deepest place on Earth.
• The descent through total darkness took nearly five hours.
• The crew cabin withstood immense water pressure exceeding 1,000 times standard sea-level pressure.
• At the bottom, the depth gauge read approximately 10,916 meters (35,813 feet).

Discoveries on the Ocean Floor

When the pilots turned on the external floodlights:

• They saw the ocean floor covered in soft, light-colored diatomaceous sediment.
• They reported seeing a flatfish resembling a sole resting on the seabed.
• This sighting provided early evidence that complex animal life could survive at extreme ocean depths.
• After spending twenty minutes on the seafloor, they dropped iron ballast and returned safely to the surface.

Legacy and Modern Submersibles

The success of the bathyscaphe opened up a new era of underwater scientific discovery.

Later Bathyscaphes

• The French craft Archimède explored deep trenches across the Atlantic and Pacific in the 1960s.
• The US Navy built Trieste II, which helped recover lost equipment from deep sea floors.

Transition to Modern Submersibles

While bathyscaphes were great at deep vertical dives, they were large and difficult to steer horizontally. In later decades, engineers created new, nimble submersibles:

• Synthetic materials called syntactic foam replaced volatile gasoline for buoyancy.
• Vehicles like Alvin, MIR, and DSV Limiting Factor explored shipwrecks and hydrothermal vents.
• Unmanned robotic rovers now carry cameras and sensors to deep trenches without risking human life.

Comparison of Deep-Sea Diving Vehicles

See also

• 1948 FNRS-2
• 1953 FNRS-3
• 1953 Trieste
• 1961 Archimède
• 1964 Trieste II
• 1964 Alvin
• 1964 Aluminaut
• 1970 DSV Shinkai
• 1987 MIR
• 2012 Deepsea Challenger
• 2018 DSV Limiting Factor
• Deep-sea exploration
• Diving chamber
• Sea Pole-class bathyscaphe
• Submersible
• Timeline of diving technology