by Greig Beck
Deep Sea Vehicles (DSVs) were designed as a replacement for bathyscaphes, many of which were basically slow-moving diving bells. They were a more maneuverable design brought about through the use of a new type of inner construction padding called syntactic foam, which is buoyant and yet strong enough to serve as a structural material at great depths.
DSVs, like the Alvin design, were squat and ungainly looking and weighed in at seventeen tons and allowed for three submariners – two scientists and one pilot – to dive for up to nine hours at 4500 meters (14,800 feet). As a safeguard, if an Alvin ever became stuck on the sea bottom, its outer casing, or pod, could be released and then the titanium sphere would rise to the surface as a bubble.
The Deepsea Challenger – On 26 March 2012, Canadian film director James Cameron reached the bottom of the Challenger Deep, the deepest part of the Mariana Trench. The maximum depth recorded during this record-setting dive was 10,908 meters (35,787 feet). The specially constructed vessel he used was called the Deepsea Challenger, and was a 7.3-meter (twenty-four feet) purpose-built submersible designed to reach the deepest-known point on Earth.
However, Cameron was not the first – on 23 January 1960, Jacques Piccard and US Navy Lieutenant Don Walsh achieved the goal of Project Nekton, in the Trieste, a Swiss-designed, Italian-built deep-diving research bathyscaphe, to be the first manned vessel to have reached the bottom of the Challenger Deep. Their maximum depth was 10,911 meters (35,797 feet), in the deepest known part of the Mariana Trench near Guam in the Pacific, and deeper by ten feet than Cameron went.
WHAT COULD POSSIBLY GO WRONG?
I mentioned briefly in my story the case of Dr. William Beebe and his early bathysphere in the 1930s. It was the first physical example of what dangers pressure alone could present to humans in the depths.
Beebe was a pioneer in deep-sea exploration. With support from the National Geographic Society and the New York Zoological Society, Beebe constructed his bathysphere, basically a steel sphere where he would be lowered to depths of over 2500 feet. The thick-walled sphere was designed to withstand the great pressures of the ocean deep. The sphere had two thick quartz windows for viewing. To test the windows the bathysphere was lowered unoccupied to 3000 feet.
But when the great steel ball was hauled up, Beebe noticed that something was very wrong. For a start, the crane groaned under the enormous weight as the ball weighed much more than it should have – even much more than if it was full to the brim with water.
In addition, there were needles of water shooting out from places around the windows, and looking inside the bathysphere, he saw it was full of water, and there were strange ripples dancing across the water’s surface. But that small amount of air remaining inside at the top of the bathysphere was super compressed, and when the bolts over the heavy door were removed, at first there was a high pitched singing noise, and then came a mist that seemed like steam.
The singing noise then became a scream, and the workers and Beebe ran for cover as the door blew off. The bolts and frame flew across the deck, embedding themselves or shearing off some parts of the ship’s hardened steel panels. The water came out like a solid jet for several seconds, such was the pressure it was under.
Beebe knew then that the pressures of the deep were deadly, and any person who had been in that bathysphere would have been crushed to death.
SUPERCAVITATION
I know what you’re thinking: I made all that stuff up about the creation of a bubble under the water and then flying through it. Wrong! Sometimes fact is just as amazing as fiction:
Flying under water – supercavitation.
Everyone who has swum in the ocean or a pool knows that pulling yourself through water is damned hard. Basically, water is a lot thicker than air, so it takes a lot of energy, it’s a lot slower, and creates lots of drag. So, for something like a submarine you can imagine that the problem would be significantly magnified.
Supersonic flight has been achieved so the answer might just be that what’s needed is not just flight underwater through water, but flight through air, under the water. And the US Navy’s laboratories are on the verge of a solution – flying within a bubble!
Scientists at Penn State Applied Research Laboratory are creating a system based on an existing process called supercavitation. In fact, the technology is not new and is based on designs and developments from old Soviet technology developed during the Cold War.
It was termed supercavitation, and the process coats a submerged craft inside a bubble of air to shield it from problems caused by the drag of the dense water. As I mentioned in my story, the process was first trialed in a Soviet torpedo called the Shkval, which achieved a speed of 230 miles per hour – significantly faster than any other torpedo at the time.
On paper, a vessel in its supercavitating bubble could attain the speed of sound underwater, or about 767 miles per hour, which would make the travel time for a cross Pacific journey to a little over an hour and a half.
But speed brought chaos in the form of something called pulsation, object-shaking, that could literally tear a craft apart. However, the researchers now believe they’ve got this beat.
In simple terms, to create a coating of air, or bubble, around a vessel, the air is delivered to the front and then expands back to envelop the entire underwater entity. But the sporadic expansion and contraction of the air-coating created significant instability, so the scientists looked at the problem analytically, which on paper suggested there might be a solution, but then when it came to physically verifying their analysis it turned out to be not as simple as they thought.
Generating a supercavitation sleeve and then getting it to pulsate so they could observe the pulsation effect inside the water tunnel facility wasn’t easy, and took years. Eventually the scientists created a fluctuating airflow and generated the pulsation effect. Then through moderating the airflow, they were able to neutralize the pulsating. Designs have been improved and the next step is a working model.
However, a speed-of-sound underwater vessel could provide dominance in the field of ocean warfare, so other countries are now rapidly developing their own supercavitation vessels.
China is also developing a “supersonic” submarine developed by a team of scientists at Harbin Institute of Technology’s Complex Flow and Heat Transfer Lab. They have also begun work on the next phase of their supersonic underwater craft design by planning a new type of powerful submersible rocket engine.
The race is on – literally!
About Greig Beck
Greig Beck grew up across the road from Bondi Beach in Sydney, Australia. His early days were spent surfing, sunbaking and reading science fiction on the sand. He then went on to study computer science, immerse himself in the financial-software industry and later received an MBA. Today, Greig spends his days writing, but still finds time to surf at his beloved Bondi Beach. He lives in Sydney, with his wife, son and an enormous German shepherd.
First published 2018 in Momentum by Pan Macmillan Australia Pty Ltd
1 Market Street, Sydney, New South Wales, Australia 2000
Copyright © Greig Beck 2018
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