China's space station was forced to avoid collision twice? Space is vast, but Starlink can't do whatever it wants

★ Although space is vast, the number of usable orbits is limited.

★ Too many satellites will pose significant hidden dangers.

In the past few days, a piece of news that made people feel scared and angry has been circulating on social media. The general idea is that Musk's Starlink satellite changed its orbit without notifying China, threatening the safety of the Chinese space station, and the Chinese space station was forced to adjust its orbit to avoid collision. What's even more infuriating is that this happened twice! On July 1 and October 21 respectively. So what is going on? Will the Chinese space station suffer any losses? Space station rendering concept map | TuChong Creative

01

Is there any loss to our space station?

Some people may think that since there was no real accident, there is actually no loss. It is not that simple. First of all, the space station needs to use thrusters to adjust its orbit, and once the thrusters work, fuel is consumed. Although the Chinese space station is equipped with Hall thrusters with higher working fluid utilization, it also has ordinary chemical propellant thrusters. Space is not like the earth. If the fuel is consumed too much, a cargo spacecraft must be launched to replenish it. Although adjusting the orbit once or twice does not consume much, considering the huge total number of satellites in the Starlink project, if there are more Starlink satellites in the future, making this avoidance a norm, the situation may not be optimistic. In addition, there were astronauts on the Chinese space station at the time, and the Starlink satellites changed their orbits without notification. Considering the relative speed between spacecraft, this is more or less like suddenly merging lanes without turning on the lights on the highway. Even if no accident occurs, it is an unethical behavior that disregards the safety of other people's lives.
Dangerous driving should be condemned | Tuchong Creative

02

Are space orbits infinite?

Some friends may wonder, there is a vast universe outside the earth, how can there be no space for a few spacecraft, and why do we need to give way to each other? The thing is, when we go to the stadium to watch a concert, the venue is large, but the good seats in the front row are few and expensive; similarly, although the space is large, the most valuable orbit is the low-Earth orbit, especially concentrated within the range of no more than 600km from the ground. At this distance, the satellite can "see" the ground more clearly and the signal transmission delay is lower, which is very suitable for satellite detection or the establishment of communication systems. Therefore, the Starlink project chose to deploy nearly 1,900 satellites at an orbital altitude of 550 kilometers, and plans to continue to launch tens of thousands of satellites. Tuchong Creative But according to experts' speculation, the total number of satellites that can be accommodated in the low-Earth orbit is about 60,000. From this perspective, orbital resources are actually limited, and the abuse of orbits is a waste of resources for all mankind.

03
What happens if you launch too many satellites?

Taking the largest number of Starlink satellites as an example, these satellites are shaped like door panels, weigh only 260 kilograms, and are roughly the size of two office desktops (about 2.8*1.4 meters). After entering orbit, they will also unfold 10-meter-long solar panels.
Although this size is not large in space, don't forget that the spacecraft in orbit are moving at high speed. When there are more of them, once a collision occurs, a large number of fragments moving at high speed in all directions will explode instantly. These fragments cover a wider range and may destroy other nearby spacecraft, generate more new fragments, and cause a chain reaction. If the density of spacecraft is too high and such an accident occurs, the number of debris in orbit will increase exponentially in a short period of time. In addition, many spacecraft, including Starlink satellites, can change their orbits to avoid collisions, but this may lead to a chain reaction. For example, we often see that all vehicles are driving normally in their respective lanes, and suddenly a car changes lanes. In order to avoid it, other cars have to change lanes as well. Many accidents are caused by this. In addition, spacecraft actually have a lifespan and are also likely to fail. When the density is high, once a failure is out of control, it is easy to cause a chain reaction.
Tuchong Creative

Moreover, it is difficult to accurately determine which orbit a satellite that is continuously changing its orbit will eventually enter. The second avoidance by the Chinese space station was because it could not determine where the nearby Starlink satellite was going, so it had to avoid it for safety. In fact, when the first batch of Starlink satellites were launched, the European Space Agency's "Wind God" Earth observation satellite was forced to avoid it because the Starlink satellite suddenly adjusted its orbit. Later, there were two more emergency avoidances by our Chinese space station.
04
Are Starlink satellites space junk?

Some netizens are outraged by these things, and even say that Starlink's satellites are "space junk." To be honest, this statement is not appropriate, because according to the general definition of space junk, they refer to all abandoned man-made objects in orbit. In other words, only those things that cannot be controlled, have lost contact, have lost their functions, and are floating in orbit are considered space junk. Most of Starlink's satellites are fully functional, and even have their own Hall thrusters that can change their orbits according to instructions. Obviously, they should not be counted as space junk. However, it is not very clean to make such a dangerous move when it is clearly fully functional...
Author | Ding Zong

Review | Liu Yong, Ambassador of China's Space Science Popularization, researcher and doctoral supervisor at the National Space Science Center of the Chinese Academy of Sciences, Doctor of Science from the University of New Hampshire, Director of the China Science Writers Association, Special Expert of the Space Science and Technology Education Alliance

Editor: Ding Zong This article is produced by the "Science Rumor Refuting Platform" (ID: Science_Facts). Please indicate the source for reprinting. This article is from the copyright gallery and is not authorized for reprinting.