So many satellites are sent into space every year, and then?
2021-12-03
In the vast universe, three astronauts who were working out of the warehouse suddenly received a notice from the ground control center that a large amount of space debris was about to attack them. The astronauts responded quickly, but the debris was in front of them. They witnessed their spacecraft being hit into debris by the high-speed space junk! Finally, in this space disaster, two male astronauts died, and female astronaut Ryan fled to Tiangong space station and took Shenzhou to escape back to earth "Gravity" poster - Douban film The scene described above is the Hollywood space disaster film gravity in 2013. You know, such a plot is not entirely the fantasy of the film creation. It is a real situation that space debris impacts a spacecraft. Since the former Soviet Union launched the first man-made satellite Sputnik 1 on October 4, 1957, over the past 60 years, mankind has launched a large number of spacecraft into space, including satellites, rockets, detectors, manned spacecraft, etc. These spacecraft will produce a large amount of space waste during launch, use and after the completion of the mission. There is a lot of space junk in space | station kuhelo The professional name of space junk is space debris. The rocket shell falling off during launch, the parts falling off during use, and the machine debris after the scrapping of the whole spacecraft are all regarded as space garbage. In addition, there are also some space junk that was deliberately spread, such as the West Ford project of the United States in 1965. At that time, the United States planned to launch hundreds of millions of slender metal needles into space and spread them around the earth. The purpose was to form a natural radio network to facilitate the U.S. combat forces overseas to communicate with their own country through radio equipment. Later, although there were not so many metal needles actually launched, they still produced a lot of garbage. By the end of 2019, the number of man-made objects around the earth is about 20000, including 2218 spacecraft in operation. In other words, about 90% of the objects moving around the earth are space debris. The number of man-made objects and spacecraft in operation has doubled in the past five years, and this number will continue to increase with the development of space industry in all countries in the world. In addition to these overall spacecraft debris, there are more than 120 million debris with a size of less than 1 cm in space, including nearly 1 million space debris with a size of between 1 cm and 10 cm, and tens of thousands of space debris with a size of more than 10 cm. According to incomplete statistics, the total weight of these fragments exceeds several thousand tons. Space waste is increasing year by year | giphy Space junk moves in orbit around the earth at a speed of more than 7 kilometers per second, more than ten times faster than the speed of bullets. Such a high speed means that these fragments also carry huge kinetic energy, and colliding with other objects will create disaster. If a small piece of space debris collides with other spacecraft still in operation, it will cause damage to the spacecraft shell and create a big hole for the spacecraft. In serious cases, it will even threaten the personal safety of astronauts. What's more terrible is that if space junk hits a spacecraft, it will damage and smash the spacecraft, and more space junk will be created. More space junk continues to move, hitting the next target, causing a chain reaction. Such a disaster is a bit like the rear end collision of multiple vehicles on the highway, with huge losses. Such an accident is not alarmist. It happened once in 2009. On February 10, 2009, iridium 33, which was in operation in the United States, and satellite 2251, which had been abandoned by Russia for many years, collided at an altitude of 776 kilometers over the taimel Peninsula in Siberia. At the time of the collision, the relative speed of the satellite exceeded 11 kilometers per second. After the collision, NASA tracked more than 500 new space debris, and more small debris were not found. The collision occurred at the height of the orbit of the international space station. A small piece of debris flew towards the international space station. Fortunately, it passed the international space station without causing more damage. Schematic diagram of the collision between iridium 33 and 2251 | sina.com With so much garbage and debris moving at such a high speed, it is almost impossible to monitor them comprehensively and closely. The current solution can only be to "grasp the big and let go of the small", and monitor the larger, faster and more dangerous space debris as much as possible. At present, using ground-based radar, telescope and space monitoring equipment, thousands of large-scale space debris can be tracked and their trajectory can be determined to give early warning of possible impact. Tracking thousands of space debris is the best human technology can achieve. There are more garbage and debris in the blind area of mankind, threatening our environment at any time. According to the observation statistics of astronomers, some space debris will naturally fall to the ground. The falling speed is about one per day on average, and the largest batch of fragments will take more than ten years to fall, not counting the newly added fragments. Therefore, relying on the method of natural fall to remove space garbage has little effect. We must take the initiative to clean up space garbage. International tests are being carried out on the removal of space debris. There are three types of schemes that can be realized by the current technology. Launch spacecraft to push space waste to a "graveyard orbit" farther away from the earth In order to reduce the impact of space debris on areas near the earth, they can be pushed further away. However, to complete this work, we need to launch new spacecraft and use the thrust of the new spacecraft to push the space garbage to the super geosynchronous orbit 3600 kilometers away from the ground. The spacecraft that can do this work is bound to have amazing power and need huge rockets. In this way, Rockets will create new waste. Moreover, it only moved the space garbage to a temporarily unaffected location, and did not fundamentally clean up the garbage. In the future, the scope of human exploration of space will be larger, and new spacecraft may encounter these garbage again in higher orbit businesses. Pushing space garbage into the "graveyard track" is like stacking garbage on the outskirts of the city, treating the symptoms but not the root cause | pixabay Therefore, this plan is like transporting the domestic garbage to the suburbs for stacking. It seems that it is much cleaner around, but the garbage still exists. One day, it will be close to our life again with the expansion of the city. Bring space junk back to earth Pulling back to the earth for recycling is a conventional idea at present. In the process of entering the atmosphere, most materials will be burned and consumed in the atmosphere, and a small part of the remaining materials will fall to the ground for recycling, and some of them can be reused. If the mesh container is used to collect space debris, the efficient operation of recovering multiple debris at one time can also be realized. After five years of exploration, Kanagawa University and Japan space agency have made fishing nets with ultra-thin wires of stainless steel and aluminum. The space debris catcher launched in 2014 was originally planned to launch a fishing net, but it failed due to technical failure. In 2016, Japan failed again to catch space garbage with a robotic arm on the international space station. Let space junk burn and melt in space Just as incineration is used to treat urban garbage, using ground means to help space debris burn or melt in place in space can fundamentally remove these garbage, but the current technical requirements are high. The United States once launched a reconnaissance satellite called 193. In 2008, 193 gradually lost control and rapidly reduced its altitude. The satellite carries highly toxic fuel, so the U.S. government decided to focus on destroying the satellite to prevent the spread of toxic gases. On February 20, the United States launched an SM-3 missile from a cruiser and hit the satellite. After being hit, the satellite broke, and the debris fell and burned in the atmosphere. In this way, scheme III can be regarded as a relatively feasible way at present. Launch of missile SM-3 intercepting US satellite 193 | Wikimedia（ http://www.navy.mil/view_image.asp?id=55403 , Public Domain, https://commons.wikimedia.org/w/index.php?curid=3593822 ） According to current international agreements and practices, each country has the obligation to maintain a certain number of spacecraft in space. Countries adopt a "one up and one down" approach to limit space waste as much as possible. If new spacecraft are launched, old spacecraft must be recycled. This spirit is very much like the concept of separation in our home life. In the work of family sorting and storage, one idea is to dispose of an old dress when you want to buy an additional dress. The principle of "one up and one down" ensures that the space around the earth is not filled with garbage. Recycling spacecraft is like a "broken and abandoned" station in the process of family sorting and storage In addition, most countries agree that the launched spacecraft can not be used in space for more than 25 years. Before the expiration, it should crash and recover by itself, or temporarily send it to the graveyard orbit, waiting for further cleaning with better technology in the future. The reason why the time limit of 25 years is that if the service time is too long, the spacecraft is likely to lose effective control, prone to collision accidents in space and create more garbage debris. At present, we do not have a particularly general mature technology that can solve all space junk once and for all. However, the attention paid to the concept of space garbage makes us rethink human technology. While exploring space, it is possible to cast a wall around the earth, creating obstacles for future exploration. More importantly, in order to truly enter the space age, human beings need to learn to put down some values of the center of the earth and think on a larger scale of time and space. Space junk is an inspiration that gives us the opportunity to consider all this and find a balance between a large number of attempts to launch spacecraft and reducing unnecessary waste. Human exploration of space has greatly expanded the boundary of human cognition, such as the "new horizon" flying to the edge of the solar system. (Xinhua News Agency)
Edit：Li Ling Responsible editor：Chen Jie
Source：iScientist
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