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The marvelous spacecraft power supply is made like this
Since 1957 when the world first man-made earth satellite was launched, several thousands of spacecrafts have been launched, and there have been more than two thousand in-orbit spacecrafts. These spacecrafts can realize continuous operation in the vast space because they have a power system. Today, let’s go to the production site of the efficient gallium arsenide solar cell pieces for space use of No. 811 Institute to see how these marvelous spacecraft power supplies are made.
Only the sound of machinery can be heard, not a person can be found.
After putting on the cap, dust-proof clothing and shoe covers, let’s go to the mysterious five-star product site to find out what we want. Here, the design, manufacturing, assembling, and inspection, and other technical processes of high accuracy photoetching, vacuum coating, and corrosion cleaning of the efficient gallium arsenide solar cell pieces for space use are finished.
At the production site, 90% processes have realized full-automatic operation. “We have more than 50 high accuracy process equipment and 10 test equipment. Now, we have had an annual mass production capability of more than 250,000 pieces, and the product quality can reach the international advanced level represented by the Germany AZUR and US Spectrolab.” said Guo Lili, Director of the single cell group.
During the process of transformation from manual operation to automatic operation, the Physical Power Source Division of No. 811 Institute developed 6 pieces of automation equipment. In 2017, the first automatic resistance welding equipment in China was put into use. During the half-a-year field debugging period, 26 technical problems were solved, and finally, the reliable full-automatic resistance welding of solar battery pieces was successful. “At present, the equipment has already run for about 2 years stably, and finished the welding of about 200,000 cell pieces. This is much better than the former welding level, and the production efficiency has been doubled.” said Li Xiaoran, a specialized technologist.
In the training room, we found the visualization documents of each process. In the past, in order to finish one process, many documents were needed. The visualization technique optimized the entire operating process. According to what Yang Guang, Director of Physical Power Source Division, said, in 2018, the department made special improvements to each key link of product development, sorted out all weak spots in the operation, detailed and quantified the operating requirements, and optimized 117 control points in all. In the meanwhile, according to the reworking process of production, the department integrated the former 80 technological documents, and broke the whole process down into 16 secondary processes and 28 tertiary processes. The department also prepared visualized process documents for each process, and applied all optimization measures in the new edition of technological documents and formed a systematic technological system. The improvements were significant. In 2018, the single-piece percent of pass of solar cells rose from the former 84% to 90%. In the same year, the final assembly percent of pass of solar cells also exceeded 90%.
Each cell has a unique ID card.
At the production site, you can see that all cells have their own QR Code. “In this way, each cell is given an ID card. This is helpful for our traceability of the product from its raw materials to its assembly. The QR Code can also make it reliable and convenient for information reading, and more effectively support the product data packet management.” said Zhou Jinning, director of lamination group.
These single solar cell pieces are assembled to form the core part of the power system of the aircraft.
The conversion efficiency of the solar cells produced here has reached the international advanced level. “Our third generation of triple-junction gallium arsenide solar cells and fourth generation of triple-junction gallium arsenide solar cells have been taken as the pedigree products of the group company. These two products have been successfully used in the lunar exploration program and Fengyun (Wind and Cloud) satellites. They have the advantages of high efficiency and radiation resistance, and are the mainstream product of domestic spacecraft solar flaps.” said Yang Guang.
The products produced here have reached the advanced level at home and internationally. At present, the efficiency of the third generation of triple-junction gallium arsenide solar cells has reached 30%, which is equivalent to that of overseas manufacturers in this industry. The efficiency of the fourth generation of gallium arsenide solar cells has reached 32%. In 2018, it was successfully used on Pakistan’s PakTES-1A satellite. “Calculation shows that the solar cell conversion efficiency only varies by 0.26% compared with that under the same operating conditions on the ground. Currently, these solar cells have the highest efficiency in in-orbit application in the world. The efficiency of the fifth generation of gallium arsenide solar cells has exceeded 34%.” said Zhang Wen, the product deputy chief designer.
From 32% to 34%, the rise of conversion efficiency by 2% can’t be achieved without the hard work of technologists day and night. The special technical team of solar cells has made improvements one by one from the product structure principle, technological process, and detection means, and solved many critical technological difficulties in the process of research and development. “Our efficient gallium arsenide solar cells have been imported to many countries. We hope that in the very near future, our products can be used all over the world.” said Yang Hongdong, the product deputy chief designer.
Source：Shanghai Academy of Spaceflight Technology
Author: Miao Xinpei