The key point of the long “running fire” road and “brake derailment” is the difficulty of separating and landing

At 12:41 on July 23, China’s first Mars exploration mission, tianwen-1, was launched. The opening of the “Tianwen” journey marks the first step in China’s independent planetary exploration. After launching into the earth fire transfer orbit, the probe will fly for about 7 months to arrive near Mars, enter the ring fire orbit through “braking”, and select an aircraft to carry out landing, inspection and other missions to carry out scientific exploration of Mars. < / P > < p > the three-step exploration scheme of “encirclement, landing and inspection” has been completed in one time, and the feat of “tianwen-1” is the first in the world. If the mission is successful, China will become the first country in the world to explore Mars, that is, to complete a soft landing mission, and become the second country to complete a Mars cruise after the United States. < / P > < p > the pursuit of the universe and the exploration of planets repose the space dream of the Chinese nation. The “tianwen-1” three in one journey will acquire valuable Mars data and promote China’s deep space exploration into depth. < p > < p > < p > to Mars. Whether it’s a 7-month earth fire flight, a “brake maneuver” into Mars orbit, or a measurement and control communication with a maximum distance of 400 million kilometers Compared with the 380000 kilometers of the moon landing, the journey of tens of millions of kilometers from earth to Mars is full of challenges and dangers. One of the key points in the mission is how to capture the gravitational field of Mars successfully after a long-distance flight. With the help of rocket, the probe gets the energy to get rid of the gravity of the earth. With the carefully designed transfer orbit, the probe can finally reach the vicinity of Mars. According to experts, during the long journey after tianwen-1 takes off, scientific and technological personnel will constantly correct the flight direction of the probe according to the specific conditions of its orbit. In the process of flying to Mars, there is only one chance of being captured by Mars’ gravity. However, at the time of capture, the probe is only 400 km away from Mars, and the speed of the probe relative to Mars is as high as 4-5 km / s, so it is necessary to “brake” in time when reaching Mars. Liu Tongjie, spokesman for the first Mars exploration mission and deputy director of the lunar exploration and space engineering center of the National Space Administration, said that during the capture process, the Mars Orbiter needs accurate ignition and braking. If the braking ignition time is too long and the speed of the probe drops too much, the probe will hit Mars. If the braking ignition time is too short and the probe speed is too fast, it will fly It is impossible to enter the orbit due to the absence of Mars, which requires the autonomous navigation and control of the orbiter. < / P > < p > to achieve perfect capture, we mainly rely on “ourselves”. When captured by Mars, the Mars probe is 193 million kilometers away from the earth, and the one-way communication time is up to 10.7 minutes. The ground can not monitor the braking process in real time, so it can only rely on the spacecraft to implement the acquisition strategy independently. < / P > < p > in addition, during the braking process, the orbiter needs to complete the corresponding processing independently in case of its own sudden situation, so as to ensure the success of Mars capture. In order to solve the problem of ultra long distance communication, Mars Orbiter is also equipped with an integrated system of measurement, control and data transmission, which achieves the goals of light weight, high communication efficiency and reliable communication link. After successfully captured by Mars, the probe began to fly in the ring fire orbit, which lasted for several months. But “tianwen-1” is not just “running in circles”, but also busy and preparing for the next landing and parking. < / P > < p > how to choose landing site? According to experts, the rover weighs about 200 kg and is powered by solar panels. If it lands in the northern hemisphere of Mars, the power supply system may be affected by the lack of sunlight, so it is ideal to land near the equator. At present, the possible landing areas are two preliminary sites on the utopian plain, the largest plain on Mars. The high resolution camera on the ground control orbiter will conduct detailed survey of the preferred landing area and take photos for the landing Rover to land later. < p > < p > after the landing area is determined, “tianwen-1” will transfer its orbit descent into the separation stage of the two spacecraft, that is, the orbiter and the landing Rover are separated, and the Mars rover is off orbit and landing. Different from lunar landing, the dynamic descent process of Mars soft landing is very short, and the time delay of ground measurement and control is more than ten minutes, so the control system is required to have higher autonomy and real-time. Only by completing three attitude adjustments and two orbit changes in a short time can the orbiter be separated from the landing Rover accurately and timely. < / P > < p > although the landing process is only 7 minutes, the landing process called “terror 7 minutes” is the key point of the whole mission. Before that, no country in the world has been able to complete a soft landing mission during its first exploration of Mars. Many Aerospace experts pointed out that the landing process of the lander on the surface of Mars can be described as “breathtaking”, and it must meet a series of difficult actions and challenges. Bao Weimin, academician of the Chinese Academy of Sciences and director of the science and Technology Committee of the aerospace science and technology group, said that during landing, the Mars probe needs to reduce its speed from 20000 kilometers per hour to zero in seven minutes, which requires the integration of aerodynamic shape, parachute, engine, multi-stage deceleration and landing recoil and other technologies to implement soft landing, which requires high requirements for software and hardware. < p > < p > it is reported that the Mars probe has been flying at a high speed on the way to the fire, and it needs to slow down before landing. At present, there are mainly two deceleration modes in the world. Based on the technical experience in the lunar exploration project, China gradually decelerates through four stages, and finally makes the probe reach the surface of Mars smoothly. < / P > < p > the first stage is pneumatic deceleration, which can reduce the speed from 4.8 km / s to 460 M / s by means of “sudden braking”; the second stage is to open a parachute to reduce the speed to 95 M / S; the third stage is to reduce the speed to 3.6 m / s by firing the reverse thrust engine of the detector; the last 100 m of the fourth stage is hovering obstacle avoidance stage, and the detector will hover In the air, observe the surface of Mars, make final preparation for the selected landing site, and finally arrive at Mars stably. After the successful soft landing on the surface of Mars, the lander will release the rover to carry out patrol exploration and Research on the geomorphological characteristics of Mars. On July 22, before the launch of tianwen-1, China’s Mars exploration project officially released “tianwen-1 1 landing platform and rover for China’s first Mars exploration mission”, which opened the mystery of China’s Mars rover. < / P > < p > a mast is erected at the front end of the rover, and the square device at the top is like the head of a robot. The square box at the top is the rover’s “eyes,” with panoramic cameras to help the rover avoid obstacles and carry out real-time exploration, as well as multispectral cameras to identify mineral composition. At the same time, the rover also has four “wings” – solar panels. < / P > < p > in addition, the rover is equipped with a detection radar, a magnetic field detector and a weather meter, which can carry out all-round exploration of Mars. The subsurface detection radar installed on the Mars rover will “perspective” the internal structure of Mars at a depth of 10 meters or even 100 meters below the surface of Mars after arrival, detect the surface soil thickness and ice layer structure of the inspection area, and obtain the ultra wideband full polarization echo data of the surface and subsurface layer of Mars; it can also detect the subsurface structure of the inspection area and obtain the geological structure data of the subsurface layer. According to experts, the design life of the rover is 90 Mars days. Since a day on Mars is slightly longer than on earth, the rover will work on Mars for 92 Earth days. Bao Weimin said that due to the long-distance data transmission delay, the rover must have a high degree of autonomy. At the same time, the Mars light intensity is small, and the Mars atmosphere reduces the sunlight, so the energy supply of Mars rover is more difficult than that of lunar rover. These factors make the Mars exploration mission more difficult and complex. < / P > < p > while the Mars rover is carrying out exploration and inspection missions on the surface of Mars, the Mars Orbiter should also be busy. The orbiter carries seven kinds of payloads, which can carry out scientific exploration on the earth fire transfer space, Mars orbital space, Mars surface and secondary surface layer, and obtain the interplanetary radio spectrum data, Mars surface image, Mars geological structure and topography, Mars surface structure and water ice distribution, Martian mineral composition and distribution, Mars space magnetic field environment and near Mars space environment The characteristics of the energy particles in the transfer orbit of the earth fire and its variation law. < p > < p > among them, the medium resolution camera can carry out the global topographic survey of Mars, and the high-resolution camera can carry out the detailed survey of local high-resolution topography in key areas of Mars, and take clear photos of Mars. With the development of Aerospace Science and technology, human interest in planetary exploration is increasing. Among them, Mars has become the most popular planet “travel destination” in the world. Up to now, there have been 44 Mars exploration activities in the world, but the success rate is only 40%. As the farthest distance between Mars and the earth is hundreds of millions of kilometers, high requirements are put forward in the fields of launch, orbit, control, communication and power supply. < / P > < p > since it is so difficult to detect fire, why do humans still yearn for Mars? Because of its similarity to the earth’s environment and its relatively close distance, Mars has always been regarded as the next home for human beings, and also the first choice for human beings to go out of the Earth Moon system and carry out deep space exploration. < / P > < p > are there conditions for life on Mars? Will it become a home suitable for human habitation? During the launch window, China, the United States and the United Arab Emirates have launched or will launch their own Mars probes, and many countries are competing to explore Mars in order to find more definite answers. Experts believe that searching for extraterrestrial life and studying the formation and evolution of Mars are the two major scientific topics of Mars exploration. Mars exploration is not only helpful to explore the existence and evolution process of Mars life, but also to understand the evolution history of the earth and predict the future change trend of the earth, so as to open up new living space for human beings and find potential targets. Liu Tongjie said that the project goal of the Mars exploration mission is to realize Mars circumnavigation and patrol exploration, obtain scientific data of Mars exploration, and realize China’s technological leapfrogging in the field of deep space exploration; at the same time, establish an independent deep space exploration engineering system to promote the sustainable development of China’s deep space exploration activities. The scientific objectives of the exploration are to study the morphology and geological structure of Mars, the characteristics of soil and water ice distribution on the surface of Mars, the composition of Martian surface materials, the atmospheric ionosphere and surface climate and environmental characteristics, the physical field and internal structure of Mars. After the completion of the Mars exploration mission, China’s planetary exploration program will move into depth. It is understood that around 2030, China will carry out missions such as Mars sampling return and Jupiter system exploration, and is currently carrying out key technology research. Sun Zezhou, chief designer of the “tianwen-1” probe of the Fifth Academy of China Aerospace Science and technology group, said that Mars exploration will be the first step in China’s planetary exploration, a key link connecting the past and the future in the development of deep space exploration from the moon to the planet, and it is also necessary to move further into deep space in the future

Author: zmhuaxia