A number of high-tech blessings flying over Tiananmen’s huge party flag is really beautiful
Zhang Yajing, Li Shaoteng, Li Li, reporter Fu Yifei
On July 1, over Tiananmen Square, a bright party flag flew high in the wind, blooming with majestic beauty; slogans on all sides followed closely, adding more mighty momentum.
At the celebration meeting for the 100th anniversary of the founding of the Communist Party of China held on the same day, the five helicopters of the aerial display echelon flew over Tiananmen Square with a party flag and four slogans respectively, demonstrating to the Chinese people and the world that they are under the leadership of the brilliant Chinese Communist Party , The vigorous new era China has achieved the heroic spirit of the great rejuvenation of the Chinese nation. The huge party flag is 9 meters long and 6 meters wide, and the huge slogan is 14 meters long and 2.5 meters wide. At a flying speed of 160 kilometers to 180 kilometers per hour, it is majestic and tidy, rolling magnificently, and flying hot.
Under the aerodynamic impact of such high-speed flight, the tail of the ordinary huge flag will shake violently, causing partial damage to the edge of the flag, which will cause the entire flag to be torn. In this regard, the scientific research personnel of the 508 Institute of China Aerospace Science and Technology Group Co., Ltd. gathered their wisdom to tackle key problems, applied spacecraft aerodynamic deceleration technology and parachute development experience, and gave the huge party flag a number of high-tech.
The flag surface strength is higher than the Shenzhou spacecraft parachute
Based on many years of experience in the development of spacecraft parachute products, the choice of materials is the basis for precise design.
When flying in airflow, the inertial force received by the tail of the flag surface is proportional to the mass distribution rate of the material. Therefore, under the premise of ensuring strength, the lighter the flag surface material, the smaller the destructive force loaded on the flag surface.
After comparing various types of materials, the 508 research team finally chose a high-strength brocade silk material used in the spacecraft parachute canopy as the flag surface material to adapt to the erosion of the high-speed airflow. The material has high strength and light weight. Even if a small area is damaged, there will be no serious wire loss, and the jitter sound is small. The linear density of its silk filament can reach 20 deniers or less, and its thickness is only one-third of the diameter of ordinary hair, but its strength is twice that of ordinary civilian silk, which is stronger than the material of Shenzhou spacecraft parachute canopy. It is also 17% higher, while the weight is reduced by 15%.
However, considering that the light transmittance of this material is too strong, the display effect of flying at high altitude is not perfect. The 508 Institute and the material manufacturer worked together to tackle the problem, and used a special coating process on the original fabric, which not only improved the appearance, and made the flag pattern from the ground. It can be clearly seen from the past, and it also makes the party flag have good rain resistance. Even if raindrops fall on the flag, it will quickly fall off. It does not affect the party flag flying high in the sky, but makes it bright and picturesque.
Design a “careful machine” to make the flag stretched and flat
In view of the environment of use, the rigidity of this thin and soft brocade silk material is not enough to meet the requirements of a huge party flag. When it encounters high-speed airflow in the air, it is not only prone to breakage and tearing, but also large deformation at the tail of the flag surface. Greatly affect the hanging flight display effect.
To this end, the development team has conducted several explorations and verifications, combined with parachute fluid-structure coupling simulation analysis and real flight test data, and optimized the design of the flag surface by adding a “wind pocket” structure at the tail of the flag surface to improve the overall rigidity of the flag.
The cross section of the “wind pocket” is trapezoidal, located on both sides of the tail of the flag surface. The size of the trapezoid is tailored to the size of the flag surface. When the flag surface is flying at high altitude, the “wind pocket” is fully inflated to increase the aerodynamic stability of the flag surface. This design greatly improves the force-resisting ability of the tail of the flag surface, reduces the pressure on the tail of the flag surface by the wind, and can not only ensure the perfect flat deployment of the flag surface, but also protect the flag surface from damage.
“Seven Steps into a Flag” process to ensure that the product is foolproof
After receiving the development and processing tasks of party flags and slogans, the development team analyzed, summarized and summarized various flags used in major celebration flight activities, and formed a unique “seven-step flag” technical processing technology, that is, “picking and cutting”. , Point, sew, test, record, and complete”.
Each flag surface material is carefully selected, and the surface quality is stained, damaged, or broken. The fabric with obvious color difference is decisively replaced. Because it is a huge party flag and slogan, the splicing and stitching of fabrics are required during the processing. Each piece of fabric should be naturally placed for more than 12 hours before cutting to release material stress and avoid shrinkage of the material due to stress after cutting, resulting in dimensional deviation. Each cut flag surface is marked with sewing positioning points to ensure the perfect presentation of the flag pattern after stitching. Each stitching position adopts the sewing process of the spacecraft parachute to ensure that the number of stitches in the fixed sewing size meets the range requirements. After the production of each party flag and slogan is completed, the raw materials, apparent quality, sewing quality, installation location, product size are inspected and accepted in accordance with the development standards of the aerospace parachute, and there is an independent and complete quality process record that can be traced layer by layer. From the selection of materials to the finished product, every step of the process is strictly controlled to ensure that there is nothing wrong.