To date, countries around the world have launched more than thousands of satellites so far. If a satellite still travels in orbit after "dying", there is a danger of colliding with the new satellite and is a space junk. If such an event happened, it would cause a catastrophe in outer space, and the Hollywood blockbuster "Gravity" once depicted the worst-case scenario that space junk could cause.
Therefore, international treaties stipulate that satellites with an orbital altitude of less than 2,000 kilometers must be destroyed within 25 years of the termination of the mission. Before the satellite ends its mission, it receives an order to lower its altitude and eventually crashes to Earth. Of course, there are not a few satellites that have to wait for a natural fall due to uncontrolled failure. From the 1970s to the 1980s, about 200 rockets and satellites fell each year, and recently there were about 50 a year. Most of them burn to ashes in the atmosphere, and only a few satellite parts fall to the ground each year.
Some useless satellites are still flying in orbit. Although they will eventually burn up with the atmosphere due to reduced flight speed and re-entry into the atmosphere, it is afraid that it will be decades to hundreds of years later. In near-Earth space, there are also many remnants of rockets floating, such as the discarded metal shell of the rocket, the last stage remnants of the launch vehicle, the scattered engines and various connecting parts.
There are several ways to effectively control the threat of a failed satellite falling to the ground: decommissioned satellites can be moved to orbits that do not impede the operation of other spacecraft, or they can be directed into designated sea areas; smaller satellites can be allowed to fall freely and burn completely in the atmosphere; and if satellites fall into space orbits close to Earth, they can be blown to pieces with anti-satellite weapons. This method is usually only used for classified satellites, because if this method is not implemented well, satellite debris will fly upwards, generating more space junk; another method is to use large manned spacecraft such as the space shuttle to capture decommissioned spacecraft and bring them back to the ground, but due to the decommissioning of the US space shuttle, this method is now impossible to implement.
There is more than one kind of garbage in space, it has a very wide range of sources, as well as scrapped rocket boosters; even spacesuits, tool shovels, vises, cameras, and toothbrushes left by astronauts during operations; peeling off of spacecraft surface materials, paint patches that have fallen off from the aging of surface coatings; solids and liquids leaked from spacecraft, and debris generated during spacecraft collisions, etc., and even domestic garbage abandoned by astronauts.
The most important small garbage in space is the wreckage of spacecraft produced by intentional or unintentional explosions, and the vast majority of this kind of space garbage comes from the "preview" of soviet and American space wars. Among them, the Soviet Union has conducted 19 satellite interception and explosion tests, bringing 500 to 1,000 pieces of debris of various sizes to space. Unintentional explosions, such as 1973, the United States had 7 rockets in orbit. In 1986, the "Ariane" rocket launched in Europe exploded as soon as it entered orbit, and 564 of its fragments were larger than 10 centimeters, and more than 2300 were smaller than 10 centimeters.
Then there is the astronaut's careless negligence. For example, in 1982, when astronaut Valentine Liebtev was on a routine spacewalk, he had just opened the decompression hatch of the "Salyut 7" space station, and due to the huge suction of the near-vacuum space, some bolts, gaskets and a pencil that the astronauts accidentally left in the decompression chamber were sucked into space and became space junk.
More regrettably, some Soviet astronauts also threw the household garbage generated in space into space. It was also found that a glove lost by an American astronaut had been floating in space for more than 20 years.
A newly released video from the Space Centre at the University of Surrey in the United Kingdom shows that its dominant "clean up the debris" satellite successfully completed the test of casting a net to catch space junk like fishing in the sea. In fact, as more and more garbage appears in space, scientists from all over the world are studying how to clean it up.
In order to save fuel, Texas A&M University proposed that the "Slingshot-Satellite Space Sweeper" can capture space junk, then throw space junk into the Earth's atmosphere to burn, and then use momentum to sail to the next space wreck target for removal.
British scientists have proposed the construction of a "cubic solar sail" that uses small artificial satellites to drive solar sails to capture space debris into low orbit. The project was originally scheduled to be implemented in 2011, but has not yet begun.
Daniel Gregory of Thor BBN Technologies in Virginia has also proposed a bold plan – to create an "explosion" in the atmosphere that would put the satellite debris into low orbit and burn. The research tests they conducted showed that this method was enough to disrupt the trajectory of space debris in low-Earth orbit.
When China's new generation carrier rocket, long march 7, first flew, it carried the "Aolong-1 space debris active clean-up vehicle", which is also exploring space debris removal related technologies.
Removing space junk is related to whether we can freely enter space in the future, we can't let them fly in the sky, scientists from all over the world are taking action, I believe that we will be able to restore a clean starry sky in space.