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Shenhai Yongshi

Though the Chinese submersible Jiaolong is able to descend to a depth of 7,000 meters, China still needed to work on the 4,500-meter-level one as its a way to improve the countrys capability of independent innovation. After making breakthroughs in a series of key technologies for overall design and optimization, design and manufacturing of a thick titanium alloy manned cabin, buoyancy materials for deep submergence and a low-noise deep-sea thruster, the submersible was finally delivered after 8 years of development.

Supported by the National High Technology Research and Development Program (863 Program), the State Oceanic Administration, and the China Ocean Association as the owner's organization, the first self-designed and self-integrated Xiaolong manned submersible was developed in China and 2009. After successfully completing the 1000-meter and 3000-meter sea trials in the year, the 5,000-meter sea trial was carried out in the Polymetallic Nodules Exploration Area of the Northeast Pacific China Ocean Association from July 1 to August 15, 2011, and achieved great success.

In the 5,000-meter sea trial, the manned submersible completed a total of 5 dive, with a maximum dive depth of 5,188 meters, completing the bottom, cruising, underwater photography, marking, seawater and (micro) Sampling, seabed high-precision mapping and other submarine operations have verified the performance and functional indicators of the 5,000-meter water depth of the Jilong manned submersible.

The success of the 5000-meter sea trial has realized the historic leap of Chinas manned deep dive, making China the fifth country with the 5,000-meter dive ability after the United States, Japan, Russia and France, marking Chinas People have the ability to work in more than 70% of the world's oceans. This breakthrough in depth reflects China's major advances in the field of deep-sea technology. This is a feat of the Chinese scientific and technological community and the maritime community to fulfill their mission and realize the grand will of the Chinese nation to "capture the five oceans."

China's self-developed 4,500-meter-level manned submersible named Shenhai Yongshi, or Deepsea Warrior, was scheduled for test expeditions into the deep sea in 2018 for scientific researches. It successfully completed the deep-sea testing in South China Sea in October 2017. The Chinese manned submersible was expected to complete 50 missions in the South China Sea and southwestern Indian Ocean in 2018, six of which will be conducted in the South China Sea for archaeological purposes.

The Deepsea Warrior is among the most-advanced manned submersibles of the world due to its competitive performance. Statistically, 95 percent of the manned submersible Shenhai Yongshi is made in China, including all key devices such as buoyance materials, lithium batteries and mechanical arms. It is a showcase of Chinas growing capability of independent innovation in deep-sea equipment manufacturing.

When the manned submersible dives into the deep sea, the acoustic wave, which can penetrate the seawater, becomes the only communication medium between the submersible and its mothership. However, when the acoustic signal from the seabed reaches the surface, it becomes no longer clear due to the noise pollution caused by the mothership. The traditional solution is to keep the receiving transducer array on the surface away from the noise source, which is inconvenient and unsafe for the operation, especially under extreme sea conditions.

A research team led by Prof. ZHU Min from the Institute of Acoustics (IOA) of the Chinese Academy of Sciences proposed advanced signal processing schemes to overcome the deterioration of signal quality and developed a multi-service communication system between the submersible and the mothership in the shipborne mode. The study was published in China Ocean Engineering. When designing the communication system of 4500m-depth manned submersible Shenhai Yongshi, Prof. ZHU's team adopted the shipborne mode and found that the in-band noise power was increased by 100 times compared with previous non-shipborne data.

To achieve high-speed communication in the low signal-to-noise ratio condition, researchers employed advanced code modulation and receiving algorithms, with the sparse adaptive turbo equalization algorithm based on turbo code proposed for the coherent transmission. In the scheme, the sparse decision-directed soft equalizer automatically adjusted the tap pattern and the tap weights according to the varying channel, while the turbo code significantly suppressed the error floor and decreased the turbo equalizer's iteration times.

From the 4680 records of the coherent communication in the 28 dives up to the depth of 4534m in 2017, the failure rate of the coherent frames was 6.13%, where both synchronization errors and decoding errors were taken into account. The error-free transmissions of color images were achieved by the inter-frame error correcting code and the transmission duration of each image was less than 45 seconds. As the next step, Prof. ZHU's team further researched array signal processing and high spectral-efficiency acoustic communication technology to achieve the high-data-rate multi-service communication of the full ocean depth submersibles.

This research was supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, and the National High Technology Research and Development Program of China.



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Page last modified: 05-09-2019 18:50:16 ZULU