Humans not only have a dream for Mars, but also a dream for the deep sea

The Hollywood science fiction adventure film "The Martian" was released nationwide in mainland China, and the human dream of Mars has once again set off a craze.

In fact, in the world we live in, there are many places that humans cannot reach alone, such as the moon, Mars, and even the center of the earth.

Some friends may say that these places are a bit too "extreme", so what about the deep sea?

70% of the Earth's surface is covered by oceans. Among the more than 7 billion people in the world, only a few have ever been to the depths of 10,000 meters. Some scientists have said that humans know less about the seafloor on Earth than they do about the moon. So what is it like under these oceans? Why is it so difficult to reach? What creatures are there? How do deep-sea submersibles dive to the bottom of the sea? Let's talk about these questions below.

1. The car dancing on the fingernail

People often say that something is harder than climbing to the sky. In fact, for humans, climbing to the sky is relatively easy, but "going into the deep sea" is harder than climbing to the sky.

The first problem you encounter in the ocean is the huge pressure of the endless sea water. For every 10 meters of sea water depth, the pressure increases by one atmosphere. For example, in 1,000 meters deep sea water, we have to face about 100 atmospheres of pressure. Under such pressure, an ordinary piece of wood will be compressed to half of its original volume. It is difficult for us to break a piece of wood with our bare hands, let alone compress it. If you reach the bottom of the sea at a depth of 10,000 meters, the pressure can reach 1,000 atmospheres, which is about the pressure of a car supported by your fingernail. What would it feel like if a car danced on your fingernail?

Humans cannot survive in seawater for a long time and require certain equipment, but such a high pressure places extremely high demands on the airtightness of the submersible.

2. Deep-sea “treasures”

When I was a kid, I watched the movie "The Goonies", which tells the story of a kid who bravely fights the bad guys and finally finds the pirate treasure. In fact, there are also huge "treasures" hidden in the deep sea. What are these treasures?

1. Huge reserves of manganese nodules.

Manganese nodules are minerals distributed on the ocean floor below 4,000 meters. They contain more than 70 elements such as cobalt, nickel, and copper. Scientists estimate that the total reserves of manganese nodules in the world's seabed are 3 trillion tons, which is enough for human beings to mine for tens of thousands of years.

2. Undersea oil and gas.

Scientists estimate that the proven offshore oil reserves are about 140 billion tons, accounting for 45% of the world's total recoverable oil, while offshore natural gas accounts for about half of the world's reserves.

3. Methane hydrate.

Another treasure on the seabed is natural gas hydrate, which is formed by the combination of formaldehyde gas molecules and water molecules in a low-temperature and high-pressure environment. It is also called "combustible ice". It is also one of the future energy sources for mankind.

How about these "deep-sea treasures"? They are tempting enough, but you can only look at them. It is not easy to hold them in your hands, because the "treasures" are all on the bottom of the deep sea and are not easy to mine. What should we do? Deep-sea manned submersibles are the first step for humans to mine the deep sea.

3. The stress-resistant expert cruising on the seabed

Layer cakes are delicious, but did you know that the ocean is also divided into layers? The water layer from the surface to 200 meters deep is called the upper layer, where the water is relatively clear. The layer from 200 meters to 1000 meters is the middle layer, where sunlight cannot penetrate all the seawater and the light is very weak. Below 1000 meters, there is almost no sunlight at all, it is pitch black and cold. Are there any creatures in such a harsh environment?

Yes, the picture above is a more distinctive type of marine creature.

Although they are ugly, they are good at resisting pressure. In order to adapt to the harsh environment, the physiological functions of some fish have undergone great changes. Due to the huge pressure in the deep sea, the bones of fish have become very thin and easy to bend, and the muscle tissue has become particularly flexible, the fiber tissue has become dense, and more importantly, the fish skin tissue has become just a very thin layer of membrane, which keeps the victory tissue in the fish body full of water and maintains the balance of internal and external pressure. Such a body structure allows these fish to live well in the deep sea.

4. Imitation or innovation?

The general structure of a deep-sea submersible (Note 1)

Without any pressure-resistant equipment, the world record for the deepest scuba diving is 330 meters. This is far from the deep sea standard of 1,000 meters. The human body cannot withstand such great pressure, so we can only use deep-sea detectors to help.

Can the structure of deep-water submersibles learn from deep-sea fish?

It is okay to borrow part of it, but the main core part cannot be borrowed from deep-sea fish.

The ultimate goal of a deep-sea submersible is to carry people to explore the deep sea. The Jiaolong, independently developed by my country, can already dive to a depth of 7,000 meters. So what is its structure like?

The most critical part of Jiaolong is the manned cabin, which creates a normal pressure environment for researchers and instruments to ensure the normal operation of the crew and instruments. This manned cabin is roughly a sphere with an inner diameter of 2.1 meters and is made of a 70 mm thick titanium alloy. In addition to the pressure-resistant structure, there is also a pressure tank, which can be used to supply air to the manned cabin and adjust the pressure of the water tank. In addition to the pressure-resistant structure, there is also an external structure, including the frame of the submersible. The frame of the submersible is used to install instruments and provide an installation environment for other external structures, such as buoyancy blocks, stabilizers, and other external equipment.

As we mentioned at the beginning, humans cannot survive in water for a long time, which requires the Jiaolong to provide a life support system. In addition to the titanium alloy spherical shell to protect the researchers, this life support system maintains the survival of personnel by controlling the air composition in the cabin. The life support time of the Jiaolong is that three people can work and survive in it for 84 hours.

Deep-water submersibles are generally not designed with special surfacing and diving power systems in order to save energy. For example, the Jiaolong submersible basically uses a disposable ballast device, which is calculated at the beginning of the dive and pressed on the iron to achieve diving and surfacing.

The Jiaolong is particularly equipped with two independent electromagnets and a hydraulic jettisoning system, which can provide multiple safeguards to prevent accidents during diving and maximize the safety of personnel and submersibles.

The Jiaolong's deep diving record was 7,062 meters in the Mariana Trench Experimental Area in July 2012. This is China's manned deep diving record and the world's largest diving record for similar submersibles. The Jiaolong has the world's leading stable automatic cruising capability close to the seabed and precise hovering positioning capability. Coupled with excellent underwater acoustic communication and excellent extravehicular operability, the Jiaolong is also a role that cannot be underestimated in the deep-sea diving community.

Most of the deep-sea submersibles in the world have been inspired by the body structure of deep-sea creatures, but most of them are innovations made by scientists to suit human deep-sea diving. With these powerful submersibles, we can swim in the deep sea. However, to conduct large-scale deep-sea research, we still need a deep-sea space station that provides large space and long-term deep diving.

The deep-sea space station that appeared in "Deep Sea Sphere"

In the science fiction movie "The Cube", the story takes place in such a deep-sea space station. Simply put, the space station is improved and sunk to the bottom of the sea, and it can be converted into a deep-sea version of the space station. The difference is that it must withstand the huge deep-sea pressure and provide the function of docking with deep-sea submersibles.

The deep-sea space station that appeared in the movie "The Cube" is our ideal. my country has been conducting research and planning in this area since 2006. Relevant units have exhibited related models at the Science and Technology Expo at the end of 2012.

In the future, China will build a deep-sea space station that can dive to a depth of 2,500 meters and can accommodate up to 50 personnel for two months underwater. The station will be about 22 meters long and 8 meters high, and can dock with deep-sea submersibles to transport personnel and materials. Such a deep-sea submersible can conduct research and operations in the deep sea for a long time and around the clock, which will play a huge role in deep-sea research and resource exploitation.

In the more distant future, perhaps humans can start building underwater cities and underwater factories, and living underwater will no longer be a distant dream.