“Crazy” laying satellite networks, who will clean up the space junk?

1. The satellite “RemoveDebris” (RemoveDebris), which looks exactly like the “Cosmic Rubik’s Cube” in a science fiction movie, has a special purpose: it can collect debris floating in space and burn it in the earth’s atmosphere. The satellite is equipped with a 3D camera, which can locate floating garbage and micro-satellites in space, and can also measure the speed of floating objects. When collecting floating garbage, the satellite will release a built-in net to capture the target. 2. From the pictures synthesized by the European Space Control Center, it can be seen that there are astonishingly many objects in low-Earth orbit, geostationary orbit, and trackable objects between them. 3. In 2021, a Russian startup StartRocket launched a new project called “Fragment Bubble Catcher”. The small cylindrical foam satellite designed by the company will spread out its sticky tentacles to capture the debris, and then bring them into the atmosphere to burn.

The amount of space junk has been growing rapidly: According to a report by NASA, as of October 2019, the agency has tracked more than 22,000 orbiting objects (2,000 of which are satellites in operation). The trajectories of these tracked objects are known, and the collision probability can be clearly estimated. However, NASA estimates that there are more than 1 million floating debris that are difficult to observe, and even more than 100 million micro-garbage smaller than 1 cm!

Space junk becomes “Sword of Damocles”
Although the United States, Russia, etc. are already monitoring space junk larger than 10 cm, the existing surveillance systems for space junk below 10 cm are completely in a state of powerlessness.

In addition, according to the statistics of Japan Sky Perfect Sunstar, as of 2020, there are about 34,000 pieces of space junk above 10 cm, about 900,000 pieces of 1-10 cm, and about 130 million pieces of 0.1-1 cm. The power of a few millimeters of space junk is equivalent to being hit by a bowling ball at a speed of 100 kilometers per hour, and the power of 1 centimeter of space junk is equivalent to a car colliding at a speed of 70-80 kilometers per hour.

What’s more worrying is that these fragments will collide with each other, resulting in more fragments, which is the so-called “Kessler phenomenon” vicious circle: If there is no intervention, a large amount of space will orbit the earth. Garbage occupation, minor collisions from small debris are enough to cause a major accident, and humans will not be able to safely launch new spacecraft.

Dutch artist Dan Rosgaard also gave a very pessimistic prediction: one day the earth will be trapped in the cage of the debris nebula. This extreme prospect also requires human beings to be more sensitive to this issue.

In front of no matter how small it is, the space station is extremely weak
In 2009, NASA issued a research conclusion that in order to curb the growth of space debris, 5-10 of the largest debris must be removed every year-scrapped satellites ranging in size from refrigerators to urban buses.

In fact, the “resistance” of the International Space Station is limited to debris within 10 mm. It is equipped with a debris shield to block debris smaller than 1.5 mm. The ground control system is responsible for tracking larger debris (above 3 mm) and when necessary Use thrusters to implement emergency orbit changes to avoid accidents. Habits become natural, the International Space Station has to avoid 2-3 attacks from disordered debris from space every year.

NASA began to install the Space Debris Sensor outside the International Space Station in December 2017 to carry out micro-debris monitoring activities (0.05-0.5 mm) and provide relevant material information-size, density, speed, orbit, etc., And determine whether the impactor comes from space or is man-made space debris.

Joseph Hamilton, the main researcher of the sensor project, said: “Even fragments as small as 0.3 mm can damage exposed thermal protection systems, space suits, portholes, and unshielded sensitive equipment… On the space station, it may be Sharp edges were left on the handles in the astronaut’s path, which caused damage to the spacesuit.”

At present, European scientists have two main strategies to deal with space junk: one is to monitor large junk to avoid collisions; the other is to use technical means to clean up smaller space debris.

Big companies make the situation more chaotic?
Although commercial companies have strengthened their innovative capabilities to remove space junk, on the other hand, they are also entirely likely to increase the risk of space missions. For example, in 2019, the European Space Agency’s “Aeolus” and the US’s “Starlink” had a collision risk. The European Space Agency had to manually change the orbit of the “Aeolus” to avoid “traffic accidents” and generate more space junk. .

In fact, the “Starlink” satellite is an important part of Musk’s satellite Internet plan. Musk once explained in detail that as long as the number of Starlink satellites deployed reaches 800, it can initially provide network services for most parts of the world. In January 2021, another 143 satellites were launched aboard a SpaceX Falcon rocket into the scheduled orbit. Starlink has nearly 900 satellites, this number has surpassed all the satellites launched in Europe!

In addition, Amazon also recruited several former SpaceX executives, and made the “Starlink Project Reissue” in the same way: In 2019, it stated that it plans to deploy 3236 satellites in three different low-Earth orbits.

As these wealthy companies join the space club, the number of satellites in space will inevitably experience explosive growth, which will put greater pressure on space transportation and space junk cleaning: for example, the “Aeolus” insurance and “Starlink” satellites just mentioned. How did the collision happen? Luisa Inosanti, the head of the European Space Agency’s space junk clean-up program, explained that, generally speaking, when different space agencies manage their respective satellites in operation, they will contact and coordinate with other space agencies. However, SpaceX is a private operator, and when the European Space Agency engineers contacted it, they only searched for the company’s contact information on the Internet and sent a message (no response). Therefore, the European Space Agency decided to unilaterally adopt an avoidance plan. This means that national space agencies need to communicate more fully with new commercial operators in the space market.

Pandora’s box was opened?
According to Inosanti, according to regulations, satellites must be processed before the age of 25, but in fact only 20% of satellites are effectively recovered: satellites are of high value, and their operators often “squeeze” their value to the last minute. . But the consequence is that once it fails, it becomes garbage that can stay in space for up to 200 years. A dead satellite in low-Earth orbit will slowly descend under gravity and re-enter the atmosphere. Inosanti believes that SpaceX chose to lay satellites in low-Earth orbits with this in mind, but she is worried that SpaceX will choose a higher orbit that is more difficult to recover satellites in the future?

On this issue, Pierre O’Malli of the French National Center for Space Research gave a more detailed explanation: In the early days, SpaceX required the use of a higher orbit. However, because it submitted an authorization application involving as many as 12,000 satellites, the US regulatory agency made it lower the preset altitude to about 500 kilometers. O’Malley also specifically mentioned that these objects are clearly visible with the naked eye at the beginning and end of the night, imposing light pollution barriers on astronomers conducting observation activities!