If you thought that space travel was the “next frontier” of human discovery, you may not have considered deep-sea exploration. While 12 people in the world have been to the surface of the moon, only three have spent time at the deepest part of our oceans. Much of this has to do with the immense pressure at the bottom of the sea, as well as its frigid temperatures and total darkness.
Still, there are several companies who have braved the unknown including Triton Submarines who have managed to engineer a sub that can reach the deepest spot in the ocean. Then, there is the now infamous OceanGate Expeditions whose ill-fated dive this summer ended in a “catastrophic implosion.” What went wrong with OceanGate? And more importantly, what has to go right to make a submersible that can withstand deep-sea pressure?
The OceanGate Tragedy
A little over a month ago news outlets announced that the Titan, a submersible made by OceanGate inc., was missing en route to explore the Titanic wreckage. At the time, the vessel reportedly only had at most 48 hours of oxygen left. For the next few days, the world watched with horror as the minutes and hours dwindled on macabre countdown clocks all over the internet.
On board the doomed vessel were 5 men: Paul-Henri Nargeolet, a French deep sea explorer and Titanic expert; Hamish Harding, a British businessman and aviator; Shahzada Dawood, a Pakistani-British businessman; his 19 year old son Suleman Dawood; and Stockton Rush, the CEO of OceanGate himself.
As soon as authorities reported the sub missing, a massive search operation went underway. The U.S. and Canadian Air Forces and Coast Guards led the search along with aircrafts from both countries’ air forces. Other commercial and research vessels from around the world joined the effort by providing ROV’s (remotely operated vehicles) and other deep sea tech. About a week later the U.S. Coast guard announced that crews had found a debris field near the titanic wreckage. The Titan had suffered a “catastrophic implosion,” with no chance of survival for all 5 passengers.
Are All Submersibles Inherently Dangerous?
In the fog of such a terrifying and tragic event, it almost seemed like the Titan’s demise was a casualty of cutting edge technology braving the unknown. But soon, a twitterstorm resurfaced videos of Stockton Rush touting experimental and frankly alarming DIY features of his vessel including the use of a bluetooth Playstation 3 controller and an “elevator button” to turn on and maneuver the sub.
And it turns out, the Titan is certainly not the first submersible to carry out such a dive. Around the world there are a few other vessels capable of reaching the depths of the Titanic- some 12,500 feet below the surface.
One submersible, the DSV Limiting Factor, has gone much further. The vessel belongs to Florida based company, Triton Submarines. Triton’s subs have reached the so-called “Challenger Deep” within the Mariana Trench. The Challenger Deep is the deepest area of any ocean in the world with a staggering depth of 35,768–35,856 ft.
But not only that, The DSV Limiting factor has completed a mission known as the “Five Deeps Expedition,” where the sub became “the first manned descent to the bottom of each of the world’s five oceans.” So it’s safe to say that the DSV Limiting Factor has lived through a few deep dives.
So, it begs the question: how could passengers on the DSV Limiting Factor go down some 35,000 feet multiple times and return to tell the tale, but the Titan imploded at less than ⅓ of that depth?
High Pressure in the Depths of the Ocean
One of the biggest challenges to deep sea exploration is the extreme pressure. As you descend into the ocean, water pushes down on you. The further down you travel, the greater the amount of water and therefore pressure is placed on your vessel. In fact, every 10 meters (around 33 feet) you travel down, 14.25 lbs of additional pressure is exerted on your vessel at every square inch of its surface. Because the Titanic is 12,400 feet down, the pressure exerted on a vessel would be 5,500 lbs on every square inch of its surface. Pressure in the Mariana Trench can reach 15,500 PSI. Obviously, in order to be able to withstand such pressure, you would need to design a submersible with incredibly strong materials and perfect engineering.
Triton Submarines: Engineering a Sub that can Withstand Extreme Pressure
Other Safety & Tech
- Tracking- Throughout the entire dive, a vessel called the Pressure Drop hovers over the surface of the water tracking the sub via USBL tracking beacons. In the event of a power outage, “Externally mounted USBL tracking beacons can operate on independent internal rechargeable batteries.” And if all else fails, passengers have the ability to release a buoy to help rescuers pinpoint the subs location if necessary.
- Communications– Engineers equipped Triton Submarines Limiting Factor with an Underwater Telephone system (UWT) that uses acoustic transmission to communicate with the team above the water. This way, the Pressure Drop can maintain constant contact with the Limiting Factor.
- Complete Visual Awareness- In addition to three viewports, the sub is equipped with low-light cameras that offer a 360 view of the passenger’s surroundings. This greatly aids the pilot who has the vital job of navigating the sub in the darkest depths of the Hadal zone (the deepest zone in our oceans).
- Sonar and Ocean floor Mapping– Mounted on the bottom of the hull is the so-called “Kongsberg EM124 multi beam echo sounder,” a sonar device that uses echoes to completely and accurately map the ocean floor. This not only allows aids in planning future dives, it can also map uncharted areas or fix mistakes of previously mapped areas in the deep sea. This could help us with our deep sea mapping and may potentially “lead to the reclassification of some” recorded depths.
For more on Limiting Factor’s safety features click here.
Why the Titan Failed
Obviously, creating a submersible vessel that has the ability to dive to such depths takes time, money and resources. Was the Titan’s catastrophic implosion just a fluke? Or was it a preventable tragedy? Many experts in the submarine/submersible community seem to think the latter.
The Titan lost communication with its mothership when the sub was reportedly around 11,500 feet down. While nowhere close to the Mariana Trench, the immense pressure at that depth is akin to the weight of the Eiffel Tower. While the investigation into what caused the Titan to implode is still ongoing, we have seen many experts take some educated guesses.
Perhaps the most likely reason the Titan failed was because of its experimental hull. Unlike Triton Submarine’s Limiting Factor and most other submersibles, the Titan’s hull was not made of titanium or steel. Instead, OceanGate opted to use carbon fiber composite, a material that has never been used in deep-sea exploration. This is because “The ability of carbon fibers to withstand repeated cycles of stress, especially compressive stress, under deep-sea pressures is not well understood, making it difficult to design safe hulls based on carbon fibers.”
Essentially, Carbon fiber, unlike titanium or steel, will break down slowly under repeated pressure. I.E. repeated deep-sea dives: “Unlike homogenous, isotropic material, such as the titanium… carbon fiber hull suffers with each dive. The fibers can crack, bend, lose adhesion with the epoxy matrix… and other problems that are peculiar to composites.” Given that the Titan had reportedly traveled to the Titanic at least 10 times, it seems likely that the hull had begun to break down over time.
The Shape of the Vessel
The reason that OceanGate and CEO/Co-founder Stockton Rush probably wanted to use carbon fiber is because of its light-weight, yet strong properties. Rather than being spherical in shape like other submersibles, OceanGate designed their hull to be cylindrical, probably to be able to fit more high-paying customers. However, the shape required more material and became heavier, leaving OceanGate to try to lighten the load- hence the idea to use carbon fiber.
Carbon fiber is used in engineering for many purposes, including on aircrafts. The material is often used in airplane fuselages, like in the Boeing 787 Dreamliner. The main difference between airplanes and subs however, is that airplanes are subject to internal pressure, while submersibles are subject to external pressure. The material is great at resisting expansion, not so great at compression. Additionally, the hull’s cylindrical shape could have contributed to its implosion. According to experts, spherical shapes are much safer than cylindrical when it comes to submersible hulls because “water pressure can apply equally to the vessel’s surface.”
Lack of Certification
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