In Depth Knowledge: Designing, Testing, and Building the World’s Most Extreme Ocean Exploration Tool

Craig Barnett
Triton Submarines, Barcelona, Spain

On 24 August 2019, Victor Vescovo touched down at a depth of 5,560 m in the frigid dark waters of the Arctic Ocean’s Molloy Trench, piloting the Triton 36000/2 submersible. The last in a long line of “firsts”set over a 10-month-long expedition, this was the final dive of the Five Deeps Expedition (Figure 1) and represented far more than another record collected; it demonstrated conclusively that, for the first time in history, a submersible exists that can provide safe, reliable, and repeatable human access to the entirety of the world’s oceans.

After successful dives to the deepest point of the Atlantic Ocean (8,376 m) in December 2018, Southern Ocean (7,433 m) in February 2019, and Indian Ocean (7,192 m) in April, the Five Deeps Expedition headed to Guam and the Mariana Trench for the ultimate test of their system. Following extensive surveying and mapping of the entire trench, the team analyzed the data and determined the deepest location. On April 28th, Vescovo climbed inside the Triton 36000/2, opened the ballast tanks, and began his record breaking solo 3.5-h descent.

Based on all available data including a depth range provided by the ship’s EM124 sonar, during over 4 h spent on the bottom, the deepest point achieved was 10,928 m (±10.5 m) in Challenger Deep’s relatively flat“Eastern Pool.” The data will be further analyzed and possibly revised in the future, as occurred with both prior dives to the bottom of the Challenger Deep by Trieste (1960) and Deepsea Challenger (2012). On May 1st, during the Dive 2 and Vescovo’s second solo into Challenger Deep, DNV GL certified a depth reference datum of 10,927 ± 8 m (with a 6.5-m standard deviation and 95% confidence interval) at a lander location visited by the Triton 36000/2 submersible.

Two further dives into Challenger Deep piloted by Patrick Lahey, accompanied by Jonathon Struwe (DNV GL Surveyor) and John Ramsay (Triton Principal Designer), were followed by the last dive in the Mariana Trench at the Sirena Deep by Vescovo and Dr. Alan Jamieson (Chief Scientist), where geological and biological studies were conducted and samples were collected. Due to embargoes currently in place pending the broadcast in 2020 of “Deep Planet,”a Discovery Channel five-part documentary series covering the Five Deeps Expedition, the full extent of important scientific findings made during the expedition remain unreported at this time. Eventually though, all data, samples, and documented findings will be made open-source. However, the scientific team have communicated that new species were discovered in each of the Deeps visited. In the Mariana Trench, the scientific team identified at least three new species of marine animal, including a type of long appendage amphipod.

Following five dives to Full Ocean Depth (FOD), the Triton 36000/2 was awarded an “Unlimited Depth”certification by DNV GL, a first for a third-party classification society-approved and human-occupied submersible. The enormity of the task involved in designing, engineering, testing, certifying, manufacturing, and then operating such a craft over the course of an ambitious and completely unprecedented expedition is perhaps best viewed against the backdrop of space exploration.

Reliably launching a rocket into orbit is a challenging task. Having it return and available for repeat missions increases complexity by multiple degrees, as Elon Musk will no doubt attest. When one considers that just 12 people have reportedly walked on the moon, and Don Walsh, Jacques Piccard, and James Cameron alone had previously descended to the bottom of Challenger Deep, the spacecraft comparison is no stretch. The gauntlet Victor Vescovo threw down at the Florida headquarters of Triton Submarines, to “build a submersible capable of carrying me to the deepest point of all five oceans, bears comparison with JFK’s 1962 exhortation to NASA and the world. Implicit in the request for repeatability are the requirements for durability and reliability. Triton persuaded Vescovo the additional expense, time, and complexity required to build the Triton 36000/2 with accreditation by a third-party classification society would be an intelligent investment, especially when it came to the ongoing commercial viability and potential for the onward sale of the entire Hadal Exploration System (HES) at the end of the Five Deeps Expedition.

The HES comprises the FOD submersible, which accommodates two people and is outfitted with a manipulator arm; an assortment of navigation aids, sensors, and an array of cameras; and a 68-m (223-foot) diesel electric former U.S. Navy “ultra-quiet” surveillance vessel converted by NOAA in 2004 into an effective scientific exploration vessel (DSSV Pressure Drop or PD; Figure 2). PD is outfitted with wet and dry laboratory spaces, a media area, a retractable and fully climate-controlled submersible hangar, plus accommodation for up to 49 people, enabling extended expeditions for ocean exploration and marine science research at reasonable cost.

Another component of the HES is the three FOD capable and autonomous hadal landers, which feature an array of scientific instruments, sophisticated sampling systems, and multiple HD cameras with powerful LED lighting for documentation purposes. The hadal landers are a critical component for submersible naviga- tion and provide a mechanism for the recovery of samples retreived by the submersible.

The Triton 36000/2 submersible consists of a spherical titanium pressure hull that sits inside a titanium framework, which holds the external batteries, junction boxes, motor con- trollers, lights, and thruster nodes. Everything is housed within a perfectly shaped and contoured syntactic foam chassis, which accounts for nearly 80% of the submersible’s displacement. Four inverted main ballast tanks sit on top with a space in the center for passengers to access the interior through a free-flooding trunk. The submersible is elliptically shaped to optimize hydrodynamic efficiency, which allows the craft to slip through the water column at vertical speeds more than 3 knots.

The main pressure boundary’s two hemispheres were machined to within 99.9% of perfect sphericity and then clamped and bolted rather than welded, ensuring a homogenous structure that avoids any materialistic variables or areas of high stress. Featuring six through-hull penetrations, unprecedented for an FOD capable submersible, the Triton 36000/2 features three wide-angle acrylic viewports in addition to the three penetrator plates through which interior control is conducted to exterior systems. For pressure testing, the sphere was flown to the Krylov Institute in St. Petersburg, Russia, where it slipped into the world’s largest hyperbaric chamber capable of 1,400 bar, with just millimeters to spare.

As with each element of the HES intended to achieve depth, DNV GL experts closely scrutinized and monitored every step of the process, from approval of the original design, through the metallurgic, ultrasonic, and materials testing of samples from every piece used on the craft. This scrutiny continued through production, pressure testing, final assembly, sea trials, and eventually conducting a final certification dive to FOD in the Mariana Trench with a surveyor onboard.

Every component not contained within the pressure hull is required to withstand the pressure at FOD, equivalent to 16,000 pounds per square inch or 1,100 bar for thousands of cycles, and many of the components are tested 20,000 PSI or 1,400 bar to validate their suitability for long-term use in the submersible. With almost no components commercially available off the shelf (COTS) able to withstand the extreme pressures at FOD, Triton had two hyperbaric chambers capable of cycling to 120% of FOD (20,000 PSI or 1,400 bar) manufactured for the project.

From the largest of the two chambers, which features an internal diameter of 550 mm (21.65 inches) by 1,000 mm (39.3 inches) in length, key components such as the acrylic view-ports, batteries, thrusters, motor controllers, and junction boxes were all slipped into the ice-filled water under the watchful eye of a DNV GL surveyor, before being subjected to multiple test cycles. A smaller but equally impressive testing chamber was used to exert electrical circuitry and individual components to the same 120% of FOD pressure as prescribed by the classification society.

The Triton test chambers in Barcelona are in continuous service because, for every two dives completed on the viewport test fixture in the chamber, the submersible is permitted to make a single dive in the ocean. Although Triton has already completed hundreds of cyclic tests on the viewport fixture, eventually thousands of cycles will be made to ensure the submersible will have a life expectancy measured in decades of service and thousands of dives to hadal depths. The potential for ongoing discoveries in the deepest and most remote parts of our world’s ocean is very exciting and completely unprecedented.

Triton is also making their pressure testing facilities available to client companies, with a recent project involving Omega’s Seamaster Planet Ocean Ultra Deep Pro timepieces, which not only underwent scrutiny in the chamber but also adorned the submersible manipulator arm and landers during the record-breaking dives in Challenger Deep. Just three of these timepieces exist.

Scientific Mission: The Landers

To achieve precise navigation in the hadal zone, the HES employs three autonomous landers. Each lander measures 1,000 × 1,500 × 1,800 mm, and they are named Skaff, Closp, and Flere. “The naming of the vessels is a tip of the hat to both author Iain Banks and his ‘Culture’ series of sci-fi novels, as well as to Mr. Musk, who is sending things up via his firm SpaceX, while we are sending things down. I decided to draw on the Culture series in naming the vessels of the Five Deeps Expedition,” says Vescovo. Acoustic modems on the landers allow the Triton 36000/2 to range between them, thus triangulating its own position.

The landers are also equipped with an array of scientific instruments that effectively document numerous measurements and collect samples for the scientific team’s analysis. Flere and Skaff both feature a rack of six push core samplers, while Closp has an autonomous motor-driven corer. They have all recovered valuable geological, sedimentary, and biological fauna samples from each of the Five Deeps. Autonomous science gear includes conductivity, temperature, and depth sensors and Niskin water sampling devices to record and sample the hydrographic conditions throughout the entire water column. Meanwhile, time-lapse cameras record the presence and behavior of large mobile fauna on a baited frame while crustacean and fish traps enable the capture of animals.

Critical to determining where to dive, the Five Deeps Expedition used a state-of-the-art Kongsberg EM124 Multi-Beam Echo Sounder (MBES) for precise mapping of the ocean floor, even to FOD. Arguably the most advanced MBES currently available on any civilian vessel, the EM124 produced digital 3D renderings of the sea floor that were used to identify and verify the deepest point in the trench by an international team of sonographers and oceanographic scientists. During the expedition, the EM124 clarified inaccuracies in documented depths and created the most accurate recorded charts of each of the dive sites visited. All data collected during the Five Deeps Expedition has been donated to the GEBCO Seabed 2030 initiative. Over 750,000 km2of ocean bottom were mapped during the Five Deeps Expedition at unprecedented levels of accuracy and in many cases for the first time ever in these remote hadal trenches.

In Profundo: Cognito

With the Five Deeps Expedition now successfully concluded, focus turns to the future of the HES, currently being marketed for $50.5 million (USD). As a proven reliable platform for adventure, discovery, exploration, and scientific research, the owner and builder’s preference would be that it remains within the international research community to continue advance our understanding of the deep ocean. As the Five Deeps Expedition slogan “In Profundo: Cognito” states, “In the deep: knowledge.” The HES undoubtedly has potential in other disciplines, however, as Dive 3 into Challenger Deep proved.

Following the conclusion of Dive 2, the submersible and two landers returned to the surface. After several nervous hours, it became clear the third lander, Scaff, with the priceless Omega watches strapped on, was trapped in the soft bottom sediment of the trench. During that evenings briefing, Expedition Leader Rob McCallum, suggested: “Well, we have the only vehicle in the world capable of retrieving it. Let’s go again.” The dive plan for Dive 3 was quickly reconfigured; the Triton 36000/2 dived again to 10,927 m, navigated to the spot, located the lander, and used the Kraft manipulator arm to dislodge Scaff for an unhindered returned to the surface. The world’s deepest salvage mission? Tick.

Following the completion of five dives to FOD in 10 days, Rob McCallum of EYOS Expeditions, whose company is managing the expedition, said: “It has been a monumental time for ocean exploration; we have broken world records and achieved a number of world firsts, but most importantly, we have opened the door to the final frontier—the exploration of the hadal zone and the workings of the deepest parts of the world’s oceans. The Triton submersible is effectively a reliable elevator that can transport us to any depth, in any ocean. At this point in the expedition, we have traversed over 110 vertical kilometers (68 miles) and proved the capabilities of a that will be a platform for science,filmmaking, and exploration of Earths hidden recesses.”

After 3 years in the making and a year in the undertaking, Victor Vescovo, the Five Deeps Expedition, and the Triton 36000/2 have successfully visited the deepest point of the world’s five oceans, precisely as the mission goal stated (Figure 3). The journey, though completed by one man, was made possible by the input of hundreds of others from around the planet. The advancements and progression in intellectual property and expertise was not limited to Triton Submarines alone; almost every partner that contributed to the project—through a supply chain that involved over 150 companies through 36 different countries—progressed their own capability in some way. The global village of deep ocean pro- fessionals is richer as a result of this groundbreaking project. This increased depth of knowledge and knowledge of the deep should benefit mankind for generations to come. In Profundo: Cognito.

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