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On January 23, 1960, the deep-diving self-powered submersible, bathyscaphe TRIESTE, made history when it descended to the ocean floor in the Mariana Trench’s Challenger Deep, the deepest known point in the world’s oceans and the deepest spot on the Earth’s crust. Navigated by Swiss oceanographer Jacques Piccard and American Lieutenant Don Walsh, the bathyscaphe Trieste reached a record depth of approximately 10,916 metres to complete the goal of the US Navy’s Project Nekton.
Designed by Swiss physicist, inventor, and explorer Auguste Piccard — father of the aforementioned Jacques Piccard — the bathyscaphe TRIESTE allowed for free diving, as opposed to previous bathysphere designs where a vessel was lowered and raised to surface by a cable attached to a ship. This pioneering self-powered design meant that man could go deeper than ever before to push the frontier of deep-sea exploration.
Swiss-designed, but Italian-built — part of the submersible was constructed by a company from the Free Territory of Trieste, hence the bathyscaphe’s name — the TRIESTE was comprised of two spheres: one consisting of a float chamber and the other a pressure sphere to act as a cabin for the crew. Offering just enough space for two people, the cabin was built to withstand the enormous pressure of 1.25 metric tonnes per centimetre-squared at the bottom of Challenger Deep. This translated into the sphere weighing an incredible 14.25 metric tonnes in air and 8 metric tonnes in water, thus the need for the second sphere to provide buoyancy. Filled with gasoline as it is less dense than water thus acts as a float fluid, the float chamber’s design mirrored the components used to ensure lift on airships — the mechanics of which were particularly familiar to Auguste Piccard who was also an accomplished hot-air balloonist.
In addition to two electric motors equipped on the bathyscaphe TRIESTE, this unique design involving gasoline tanks is what enabled the bathyscaphe to manoeuver on its own at depth. To descend to such deepness while still controlling the bathyscaphe’s weight, the TRIESTE was also equipped with hoppers, cylindrical-shaped containers filled with heavy iron pellets held in place by magnets. Coming in at 9 metric tonnes, this ballast allowed the submersible to sink, while the release of the iron is what enables the bathyscaphe to ascend even in the case of an electrical failure.
During the dive to the ocean floor, which took a total of 4 hours 47 minutes, one of the outer Plexiglas windowpanes cracked, shaking the entire vessel and alarming the crew. Fortunately, Piccard and Walsh were still able to reach the ocean floor unharmed, where they spent barely 20 minutes at maximum depth. Surprisingly, however, using a sonar/hydrophone voice communications system, the pair regained communication with their support ship, the USS Wandank, while at the bottom. With temperatures in the cabin dropping to 7 °C and eating chocolate to keep their strength up, the navigators witnessed a number of small sole and flounder swimming around proving that some vertebrate life can withstand the extreme pressure in the deepest part of the ocean. Thankfully, the bathyscaphe’s ascent went smoothly and took only 3 hours and 15 minutes.
An unparalleled achievement in oceanic navigation, the TRIESTE’s dive remained the only manned submersible to reach the bottom of the Challenger Deep until March 2012, when — piloted by film director James Cameron — the Deepsea Challenger descended to 10,908 metres, still a maximum depth slightly less than that of TRIESTE’s 1960 descent.
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.