What is space junk? What are the hazards?

What is space junk? To put it simply, it is all kinds of debris and waste that are abandoned in space intentionally or unintentionally in the process of exploring the universe. Recently, the National Aeronautics and Space Administration (NASA) of the United States announced with anxiety: On June 65438+1October 17, 2005, a seemingly unexpected "cosmic traffic accident" occurred-the relic propelled by the Raytheon rocket launched 31year ago, and the CZ-4 rocket launched by China six years ago. This is a typical space junk "cosmic traffic accident". The concept of "space junk" was first put forward by the air defense personnel on duty. The national space monitoring department monitors more than 50,000 celestial bodies every day, and space junk often confuses them. 16 years ago, a meteorological observatory in Canada announced that a star exploded near Perseus. Later, it was found that this was just the effect of an abandoned satellite being reflected by sunlight. According to "Russian newspaper", in 1987, there was a case that the quantum module could not be docked with Mir because the connector was not tightened. At that time, the experienced ground control center thought that something must have interfered with the docking outside the cabin, so it sent an investigation team to check and found a piece of metal there. Before the 1960s, no one had heard of objects falling in space, but since 1973, hundreds of pieces of space junk have fallen to the earth every year. Thankfully, no one has been injured so far. How much space junk is there? There are many names for space junk: the big ones are satellites, space stations and other spacecraft that are "dead" but still hovering in space orbit, and the abandoned ones carry rocket propulsion debris; Moderate, with debris from accidental explosion. For example, on June 3, 1996, an American Pegasus rocket exploded, producing about 300,000 dangerous fragments. There are also some small parts, such as explosive bolts, satellite straps, springs for separating stars and arrows, and garbage that astronauts "throw around". For example, in 1965, during the first spacewalk in the United States, astronaut Edward accidentally lost a glove (fortunately, a month later, this glove with a speed of nearly 28,000 kilometers per hour and the greatest lethality in human history fell into the atmosphere and burned); More are tiny space particles, such as paint particles falling from spacecraft. So how much space junk is there in low earth orbit? It is estimated that there are about 25,000 pieces of space junk since the beginning of the space age 50 years ago. Because many of these objects burned when they entered the atmosphere, there are about 9000 pieces that can be seen now. Moreover, if the spacecraft flies at an altitude of 600 kilometers, it will revolve around the earth for 25-30 years. If you are at an altitude of 1000 km, you can fly to 400 1 year. A little higher, it will almost become an eternal object. Now there are more and more such "longevity" garbage in space, and it will be extremely difficult to remove it. How much do you know about the harm of space junk? Since the 1950s, mankind has launched more than 4,000 space launch vehicles. According to incomplete statistics, there are more than 9,000 fragments with a diameter greater than 10 cm in space, hundreds of thousands of fragments with a diameter greater than 1.2 cm, and millions of tiny particles such as paint flakes and solid propellant dust particles. Don't underestimate these space junk. Because of their extremely fast flight speed (6-7 km/s), they all contain great lethality. A piece of space junk weighing10g hits a satellite, which is equivalent to two cars colliding head-on at the speed of 100km/h-the satellite will be punctured or destroyed in an instant! Imagine if it hits a manned spaceship ... and humans can't control the flight path of space junk, so they can only make a rough prediction. This garbage is just like those driverless cars on the highway, driving around at will. You never know when it will brake or change lanes. They are the biggest potential "perpetrators" of traffic accidents in the universe, and they are a great threat to astronauts and aircraft. At present, the space around the earth is still quite open, and the probability of space debris colliding in space is very small, but once it hits, it will be devastating. What bothers aerospace experts even more is the "avalanche effect"-each impact does not annihilate the debris, but produces more debris, and each new debris is a new collision danger. If one day, the earth is full of these space junk, where should humans explore the universe? Space junk is all kinds of objects and debris abandoned by human beings in space activities. They fly around the earth in a certain orbit like satellites, forming a dangerous garbage belt. Space junk can be divided into three categories: first, the relatively large objects that modern radar can monitor and track, mainly including various satellites, satellite protective covers and various components. At present, it has reached more than 8,000; Second, small objects, such as engines, are produced when space explodes, and the number is estimated to be at least several million; Third, nuclear-powered satellites and the radioactive debris they produce. By the year 2000, these satellites will send 3 tons of debris into Earth orbit. 1957 10 year 10 4 October, the former Soviet Union successfully launched the first artificial earth satellite, which opened the prelude to the human space age and sent the first batch of garbage into space. At that time, the astronauts completed the task, leaving the satellite's loading cabin, spare cabin, instruments and equipment in the satellite orbit. Since then, with the feat of human space history, space junk has increased day by day. Humans have launched more than 4000 satellites into space, and only 400 satellites are still in normal operation. The rest either crashed on the surface of the earth, or stayed in space and became space junk. According to statistics, there are currently about 3,000 tons of space junk flying around the earth, and the number is still increasing at the rate of 2%-5% every year. Scientists predict that the increase of space junk at this rate will lead to a catastrophic chain collision. If this situation continues, nothing will be able to enter space orbit by 2300. Space junk has brought hidden dangers to the development of space industry, become a potential killer of satellites and orbiting space stations, and seriously threaten the safety of astronauts. You know, space junk runs at the speed of the universe. An oncoming metal particle with a diameter of 0.5 mm is enough to pierce the sealed flight suit; Dust that people can't distinguish with the naked eye (such as paint chips and paint powder) can also kill astronauts; A fragment the size of an aspirin tablet can "paralyze" a satellite and send a spacecraft costing hundreds of millions of dollars into a dead end. In the history of human spaceflight, accidents and disasters caused by space junk are common. 1983, the American space shuttle Challenger collided with a paint tape with a diameter of 0.2 mm, which damaged the porthole and had to keep flying. The "Salute -7" orbital station of the former Soviet Union was also damaged by such "dust" many times. 1986, the Ariane rocket exploded shortly after it entered orbit, becoming 564 fragments with the size of 10 cm and 2300 small fragments. The wreckage of this rocket made two Japanese communication satellites "die"! 199 1 05 September 15, the space shuttle discovery launched by the United States almost collided with the rocket wreckage of the former Soviet Union. At that time, Discovery was only 2.74 kilometers away from the uninvited guest. Fortunately, the command system on the earth issued a warning signal in time to prevent it from dying. According to the calculation, the probability of catastrophic collision of each flying object in space orbit is 3.7%, and the probability of non-catastrophic collision is 20%. Based on this calculation, the collision between space junk and spacecraft may occur every 5- 10 years in the future, and it will reach once every two years by 2020. Space junk not only brings great hidden dangers to the space industry, but also pollutes space and brings disasters to mankind, especially when the nuclear-powered engine falls off, which will cause radioactive pollution. At present, the United States and the former Soviet Union have 1 ton of uranium -235 and other nuclear separations in nuclear reactors in space. The former Soviet Union launched 3/kloc-0 nuclear-powered reconnaissance satellites, two of which have polluted the ground: 1978, a large number of radioactive debris from Cosmos 954 fell into the Canadian Sea of Clafin; 1983, the reactor core of Cosmos 1402 fell into the South Atlantic.