The Trieste would be tweaked over the following year to reach deeper locations, but it inevitably had to be tested. On October 5, 1959, the Trieste was hoisted aboard the Santa Mariana freighter, and the two ships set sail towards Guam, where the Mariana Trench is located (per "To the Ocean Deep” by Valerie Bodden, posted at the Internet Archive).
Over the following weeks, the Trieste made many daring attempts to reach the ocean's deepest point, yet always fell a little short. Each failure provided invaluable insights. On November 15, the Trieste broke the world's previous record, reaching an astounding depth of 18,150 feet (via Naval History and Heritage Command). However, the crew reported a heart-stopping bang from the Trieste when it expanded and strained to cope with the pressure of these unprecedented depths. The crew, presumably horrified, discovered that minor volumes of water had leaked into the ship after docking, although it was nothing that a little glue and mechanical rings couldn't fix (via U.S. Naval Institute).
Continuing the crew's success, the seventh attempt saw the Trieste reach an incredible 23,950 feet before the crew's safety became jeopardized. The Trieste was just 50 feet from the Nero Deep when it was forced to return owing to further booms, lights shattering, and a pipe's collapse. The crew later discovered that the gasoline valves had also been damaged in the attempt (per U.S. Naval Institute). The Trieste needed apertures that could actively relieve part of the pressure, the crew discovered. With this in mind, the stage for the eventual record-breaking dive was set.
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