Last week, China's "Strivers" manned submersible twice "clocked in" the Mariana Trench, sitting at a depth of 10,909 meters, creating a new record for China's manned deep diving, marking a new stage in China's deep diving career. Yesterday, the Strivers once again conducted a 10,000-meter sea trial.
From shallow to deep, from divers to deep divers, how do humans step by step to the bottom of the sea? And how hard is it to build a submersible?
01 Great forerunners
The mysterious ocean has been a breeding ground for mysterious legends and great dreams of exploration since ancient times. Tens of meters long stout brachiopod sea monsters, Western Siren and Eastern Fishmen, lost Atlantis, inhabited by the Dragon King's underwater dragon palace... Countless mythological and sci-fi works have been inspired by that deep blue, and human exploration of it has never stopped.
Neptune Neptune, by Antoine Coysevox
Limited by technical conditions and wealth levels, ancient people's exploration of the depths of the sea was mostly superficial. For them who do not have diving equipment, the water at a depth of tens of meters is already dangerous. Even so, the ancients left valuable diving experience for future generations.
In the 4th century BC, the Persian Empire produced the world's first professional diver, responsible for salvaging cargo and jewelry from shipwrecks on the seabed. In addition, the Phoenicians who collect pearls on the eastern shore of the Mediterranean Sea, the sea women in Japan and South Korea, and the ancient people in China's Guangdong region have also explored the coastal waters around the world with their flesh. Although the diving tools they use are just simple hemp ropes, stones or inflatable animal bladders, and the original intention of going to the sea is also forced by life, objectively speaking, these ancestors are indeed the forerunners of human exploration of the world below sea level.
Korean Haenyeo (Image: Miss Cat Adult /lvmama.com)
In the 16th century, the British scientist William Bourne first proposed the idea of a submarine. In 1578 he designed a leather seal with wooden strips as a skeleton that could slide underwater.
William. Submarine by William Bourne, in Inventions or devices, 1578.)
William. It is unclear what Bourne's "barrel" looked like, but there is no doubt that the birth of this "submarine" opened the door to a new world for the engineers of that era. They began to think about a mode of transportation that had never been envisioned before. 40 years later, the Dutchman Cornelis With the support of King James I of England, Drebel built the world's first ship that could sail underwater with human power, which was the world's first human-powered submarine and the prototype of modern submarines.
Cornelis · Drebel submarine restoration (https://www.hisour.com/zh/cornelis-drebbel-13858/)
02 From submarines to deep submersibles
The appearance of submarines has greatly broadened the horizons of human beings, and since then, the thick sea water has begun to slowly become "thin", and the fog of the deep sea has gradually been unveiled by humans. However, the diving depth of submarines is very limited, the working limit depth of various submarines is only a few hundred meters, and if you want to dive deeper, ordinary submarines are far from enough, and specialized submersibles are needed.
The enormous water pressure of the deep sea places completely different demands on a submarine-like deep-sea submersible. In 1928, The American Barton made a spherical diving device out of steel. This "ball" has built-in simple lighting, breathing and communication facilities, and modern submersibles such as power systems and life support systems are not standard, but rely on a steel cable + cable connected to the mother ship to dive and float.
Schematic view of babe and Patton's diving ball (Image source: Chinese Ship Research)
In 1934, Barton and a naturalist named Bieber dived to a depth of 923 meters. Later, Bieber also wrote a book about the experience of diving, describing to the public in detail the underwater world they saw. However, due to the photographic technology of the time, they did not obtain reliable video data on the seabed, and could only rely on verbal descriptions to let the painters draw the appearance of the creatures they saw on the seabed. The strange creatures he told about the seabed made him a laughingstock in the scientific community for a while— and people at that time thought that such a deep seabed was a forbidden area for life.
Barton and Babe (left) (Credit: Chinese Ship Research)
03 Go deeper!
But the desire to go into the abyss and explore the unknown drives humanity to go deeper. In the decades since, the development of deep-sea exploration technology has been in full swing, and the two most noteworthy submersibles are:
The first is the Swiss explorer Picard's improved and built "Diriast" based on Barton's spherical submersible. It became famous in 1960 as the first manned submersible to dive deep into the bottom of the Mariana Trench.
Diriast (Image source: Wikipedia)
The other is the USS Alvin, which entered service in 1964. Although its diving depth of 4500 meters is less than half of that of the Diriast, it has divened more than 4000 times in nearly 40 years of service, and is a well-deserved "model worker" in the world of deep submersibles. In addition, the diving depth of 4500 is actually enough to explore most of the deep sea area of the world, so it has made great contributions in the field of deep sea exploration.
USS Alvin (Image: Wikipedia)
In addition, the United States "Deep Sea Challenger", Japan 'Deep Sea 6500 ', Russia's "Mir I", and france's "Nautilus" manned submersible are also well-known members of the deep submersible family. Of course, we will not forget China's Jiaolong and Deep Sea Warrior. Here is a little knowledge point about the "Jiaolong", the maximum diving depth of the Jiaolong is 7062 meters, which is enough for it to explore 99.8% of the global ocean, and the "Strivers" that dive this time, its goal is only 0.2%.
Nautilus manned deep submersible (Credit: Helmholtz Institute of Oceanography)
04 Deep submersibles, really not what you want to build
A closer look at the list of countries with deep submersibles above will find that although the deep submersible family looks thriving, and many countries are involved in deep-sea scientific research projects, it is still a few scientific and technological powers that can manufacture deep submersibles.
Some people may wonder, in 1960, human beings have built submersibles that can penetrate deep into the bottom of the Mariana Trench, why is it that 60 years later, the countries that can make deep submersibles are still only the United States, France, Russia, Japan, and a few other countries? Where is the technical threshold for building a submersible?
In fact, deep submersible manufacturing is like aerospace engineering, a "big project" that can only be achieved by the cooperation of various industrial sectors. Let's take a few examples:
1. Throw away the clumsy "braids" attached to the mother ship. To dive to depths of several kilometers, a simple "metal ball" like Barton's is not enough. Its volume is too small to hold more air, the diving time is very limited; it can only be pulled up and down by the steel cable, the range of motion is limited by the mother ship and the length of the steel cable, not to mention, as the steel cable continues to lengthen, the risk of steel cable break will also rise rapidly with the increase of depth.
The deep submersible must learn to float and dive, cruise and hover on its own at a depth of nearly 10,000 meters. In order to achieve floating and diving, the main tool of the current submariners is electromagnet, using electromagnets to absorb a piece of ballast iron or iron sand outside the deep submersible or special cabin, so that the overall density of the deep submersible is greater than that of seawater to achieve diving, and only need to throw away these things when floating.
Schematic diagram of the submarine process of Jiaolong (Source: CCTV video)
2. Keep the submersible in communication with the sea. The underwater situation is very complex, and the turbulent currents, curious marine life, and possible errors in the operation are all threats to the deep submersible, which must maintain communication with the mother ship at all times. However, electromagnetic waves decay very quickly underwater, and the distance of the farthest communication is less than a kilometer. Because the attenuation of sound waves as they propagate in water is much smaller than that of electromagnetic waves, it becomes the first choice. At present, the world's most reliable underwater communication technology is underwater acoustic communication, which is a continuous nesting doll technology that converts sound signals into electrical signals, and then converts electrical signals into acoustic signals with a sound wave frequency of about 4000 Hz.
Application Diagram of Underwater Acoustic Communication (https://kknews.cc/science/9x56kl5.html)
A simple description does not explain how difficult this technology really is, the ocean sound field is mixed with ship noise, water flow echoes and other sounds emitted by fish and other marine life, how to correctly identify and convert the sound waves coming from the seawater is a huge problem. So this technology alone can keep most of the countries on Earth with weak military research capabilities out.
3. The biggest test of the deep sea on the deep submersible is still the huge pressure. If we throw a tanker truck common in daily life into the sea, the water depth of about ten or twenty meters in the case of no load is enough to crush it into a twisted iron sheet. In the 10,000-meter deep sea, the other parts of the deep submersible are also filled with seawater, and the internal and external pressure is consistent and will not be crushed into scrap iron, but the spherical manned cabin equipped with the deep diver is not successful, and the pressure on each point of its surface is about 100.6MPa, which is converted into 10,000 tons of pressure per square meter, "just"one-sixth of the Liaoning ship ... Therefore, we need special materials to cope with the more extreme deep sea.
On the left is a thermos pot that withstands the high pressure of deep water (https://www.zhihu.com/question/47453175)
In general, titanium alloys with high strength, high toughness, very stable, corrosion resistance (and very expensive) are the most suitable materials for making diving warehouses, so this step has driven away a large number of countries with tight scientific research funds in the field of new materials. China's use of The Strivers is a new high-strength and high-toughness titanium alloy independently developed by China, and the theoretical yield stress reaches or exceeds 820MPa, which is enough to cope with the huge water pressure of the deep sea.
4. Processing technology. The parts manufacturing, cold bending, welding, precision machining, etc. of the deep submersible are not played by a weak manufacturing country. For example, the Jiaolong is processed with an accuracy of about one-50th the size of a human hair, and for fear of metal scratches that machining can cause, the work can only be done by skilled workers.
When installing, it should also be noted that there must be no scratches or a little foreign body falling between the gaps in the instrument, otherwise the huge pressure of the deep sea will tear this inconspicuous gap into a huge opening. In addition, control, oxygen supply, battery, lighting, imaging... All test the ability of a country in precision instrument manufacturing, electronic engineering technology and so on.
05 Conclusion
The Strivers 10,000-meter deep submersible launched this time is a real "big country heavy weapon", which not only means that China is moving towards the forefront of international deep diving facilities manufacturing, but also represents the improvement of China's international discourse power in the field of deep-sea geology, environmental pollution, and the origin of life in the future. Once again, let us congratulate the Strivers!
Finally, let's end it with the words of Fu Wentao, the first submariner of the "Jiaolong" and "hero of manned deep diving": "Deep-sea exploration is not only the need for marine resource exploration and scientific research, but also the need for environmental protection. As an important part of deep-sea exploration, the continuous development of China's manned deep diving undertaking has promoted the construction of a maritime power and greatly enhanced our national self-confidence and pride. "
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Source: Science Compound