Environmental Disaster Reduction No. 2 E star is in the sky, and no one may pay much attention to it. There is actually a particularly remarkable technological achievement behind this satellite . This technology was previously monopolized by the United States and Russia. It can be said that there is no place to teach or learn, but this situation did not stump us.
my country successfully launched the Environmental Disaster Reduction 2 E satellite. Everyone may not pay much attention to this news. After all, with China's current space capabilities, people in manned space flight are accustomed to it. What should I pay attention to when launching some satellites? Indeed, my country's launch of satellites is as common as eating, but the satellite we are going to talk about is different from what everyone generally thinks of. Compared to the satellite itself, it carries a huge and complex antenna that is inconsistent with itself, even a circle larger than the satellite along with the unfolded Sunwing .
This kind of antenna is called a truss antenna. The huge truss antenna is equivalent to a giant eye and ear, and can bring excellent performance. So why is such a good antenna not common? It is just because of this technology, it is a black technology in the aerospace field. How did such a huge antenna be sent to space? Why is it difficult to make such an antenna? Which countries have this technology?
[Environmental Disaster Reduction No. 2 E-Star, the antenna appears particularly large after it is unfolded, and the large is even a little inconsistent]
[Trust Antenna] is also called [Mesh Expandable Antenna]. Among the solutions of several spatial expansion mechanisms, its advantages are that it is very light in weight and has a large volume shrinkage ratio. Its innate advantages may be compared with only [inflatable structure]. But it has higher shape accuracy after being expanded and is more suitable for antennas. In addition, truss antennas have a great advantage, that is, the weight of the antenna will not increase significantly with the increase in size, which is suitable for aerospace scenarios. After all, the cost of aerospace launch is very high. The diameter of the truss antenna can be from a few meters to more than one hundred meters. It is very risky to make such a huge antenna unfold smoothly under extremely cold and extremely hot conditions in the universe. Most domestic and foreign countries use cable method. Its principle is discussed in primary school mathematics textbooks, using the unstable characteristics of parallelogram and the stable characteristics of triangles. Truss basic structure is a parallelogram. Setting a telescopic oblique rod on the diagonal line is like the telescopic clothes rod we often use. The principle or operation process is actually very simple.
[The truss antenna can be very huge. Without this clever design, it is almost impossible to send such a large antenna into space]
Before launching, you must first flatten it, and then use a rope to penetrate into truss structure , pulling several key nodes. After entering the rail, first unlock the mechanism that tied the trusses, then start the motor and roll up the rope. During this process, the parallelogram gradually spreads, and after reaching the predetermined position, the telescopic oblique rod locks, turning the truss structure into many stable triangles.
[The closed antenna is light and small, and the space is fully utilized, which is very suitable as a space payload]
The risk of this process is that when faced with so many node components, sometimes there are as many as hundreds. Once a node or slash rod is stuck, the antenna cannot continue to expand and the satellite will be scrapped. Therefore, how to wear cables, how to apply force, and how to lubricate nodes and oblique rods all require high-difficulty design and simulation for mechanical professionals.
Today's truss antenna generally adopts the so-called articulation rod expansion mechanism. The truss rods are connected together by hinges. The hinges here are also divided into folded and spherical shapes. The simplest folding is to connect the two rods with a cylindrical shaft, which can rotate within a plane. The spherical shape is like the human shoulder joint. It can achieve the highest unfolding stiffness and highest accuracy, but the structural complexity is not the highest, and it is the best choice.However, the dynamic characteristics of spherical hinges are very complex and must be fully simulated and analyzed on the ground before they can be used on satellites. After all, the environment where the antenna is unfolded is harsh space, with hundreds of temperature differences between parts with or without light. It is not so easy to ensure that all components work smoothly in such extreme environments.
[The simpler the principle, the more difficult it is to do a good job of fine work. These institutions must ensure smooth development in harsh space]
The largest antenna currently has the largest size, and is the antenna used by the US electronic reconnaissance satellite . For example, the "Advanced Vortex" satellite, which can reach 100 meters in diameter after entering the geostationary orbit. The size of the "Big Wine Bottle" antenna can reach 152 meters. This abnormal large antenna is used to detect weak radio models on the earth, such as the telemetry signal in the missile flight test.
[Advanced Vortex satellite (Advanced Vortex satellite) antenna, diameter up to 100 meters, the larger the antenna, the sharper it is]
solved the expansion problem, but in fact it was just the first step. The truss itself cannot be used as an antenna. To reflect electromagnetic waves , a high-precision reflective surface is also required to arrange a high-precision reflective surface on the truss. Of course, the reflective surface also needs to meet the same conditions, fold it into the sky, and carry out the task. However, both as a communication antenna or an radar antenna have high requirements for shape accuracy. Currently, the materials that can meet the requirements include mesh reflector antennas and membrane reflectors. The mesh reflectors have high molding accuracy and stable performance. Therefore, most of them use mesh antennas in orbit satellite models or spacecraft under development. This kind of mesh and window screen are not the same thing. The special metal wire mesh cloth used is very expensive, and during the processing process, 90% of the mesh cloth becomes scrap material.
[The structure of a yarn mesh is a special metal wire mesh cloth]
When the antenna unfolds, what is formed is not a real parabolic surface, but a plane of a triangle or parallelogram. The mesh is tightened under the traction of the truss. Use a large number of such planes to approach a parabola. In fact, it is the mesh that determines the design of the truss. For example, the thicker the pipe material and the higher the node strength requirements, the thinner the mesh and less elastic, the lighter the truss can be. The ideal mesh cloth feels similar to the touch of women's stockings.
[Details of ultra-light alloy reflective mesh, using soft metal wire, producing such fine and accurate fabrics, you can imagine how difficult it is. This is a material that uses tungsten wire gold-plated]
Both the United States and Russia are capable of producing this kind of mesh cloth. But Americans are obviously much more tyrants. Russia is braided with alloy wire with a diameter of 0.05 mm on low-frequency antennas and nickel-plated surfaces. In the Ku band, use molybdenum wire with a thickness of 0.025 to 0.03 mm, and the surface is gold-plated; in the higher band, use tungsten wire 0.015 to 0.02 mm, and the surface is gold-plated. Americans use molybdenum wire and the surface is gold-plated.
truss antenna was once monopolized by aerospace powers such as the United States and Russia, and basically belongs to black technology without anyone to teach or learn. US companies once had more than 80% of the market for this type of antenna. Harris and Norg account for more than 90% of the market for super-large truss antennas above 10 meters.
When Chinese scientists were poor and blank, they could create two bombs and one satellite. Faced with the monopoly of individual aerospace technology in the United States and Russia for a while, it would not be difficult for us. The sky of E-Star of Environmental Disaster Reduction 2 is the best proof. China Aerospace researchers have mastered this technology through self-reliance and will no longer be controlled by others.
With this technology, it means that sending larger and more complex antennas to space is no longer an unrealized dream.
