Musk is going to launch 42,000 Starlink satellites, will it threaten the security of Tiangong Space Station?

On April 29, 2021, the "Tianhe" core module was successfully launched into orbit, officially starting the construction process of the Tiangong space station. On the same day, Musk’s SpaceX launched 60 satellites, and the number of Starlink satellites in low-Earth orbit has increased to 1,438; on May 4, Starlink plans to launch 26 batches of satellites, raising the total number of satellites in orbit to 1,498. particles.

Since the first artificial satellite was launched in 1957, humans have launched a total of 9,000 satellites and spacecraft, and about 6,000 have been in orbit so far, and SpaceX's Starlink accounts for nearly a quarter. And that's not all, because the total number Musk plans to launch is 42,000, far more than you can imagine!

Starlink has a total of 42,000 satellites

The sky looks wide open. Every time we talk about the risk of satellite collision, some friends always make this analogy: If 42,000 people are scattered on the surface of the earth, can they see each other?

The surface area of ​​the earth is about 510 million square kilometers. If 42,000 people are evenly distributed on the surface of the earth, each person can occupy 12,143 square kilometers, that is, one person can be divided into two Shanghai cities. So some people came to the conclusion: the sky is so big, and the satellites are distributed in orbits of different altitudes, it is unfounded to worry about the collision of satellites.

Sounds reasonable, doesn't it?

man and earth

What these friends overlooked is that unlike people on the ground, satellites in the sky are all moving at high speed. The speed of satellites in low-Earth orbit is roughly above 7.66 km/s, and they will crash below this speed. People walking on the street can easily keep a distance from each other. Cars on the highway need to maintain a distance of more than 100 meters, and satellites all fly at 23 times the speed of sound. superior. The price of communication satellites is often hundreds of millions, and the cost of the space station starts at 10 billion. There are astronauts in it, so they can't afford it!

Space collisions are devastating

A well-known satellite collision event in history dates back to February 10, 2009, when the US Iridium-33 hit the Russian scrapped communication satellite Kosmos-2251 sideways at an altitude of 789 kilometers, resulting in tens of thousands of collisions. There are still more than 1,500 fragments flying around in the sky.

In March 2021, the NOAA-17 satellite and our Yunhai-1 02 satellite disintegrated successively. The reason is unknown. Some analysts believe that these two events may be caused by space junk.

Musk's Starlink does not have the problem of collision? In August 2019, the European Aviation Agency found through telemetry that their "Aeolus" earth observation satellite intersected with the orbit of the Starlink 44 satellite and there was a possibility of a collision. SpaceX refused to adjust the orbit of starlink 44, and finally forced ESA to change the "Aeolus". Fly in orbit to avoid US satellites.

"Aeolus" dodges Starlink - 44 stars

Although the probability of two satellites colliding in the sky is not high, and it is more likely that they will pass each other, but no one is stupid enough to take their own satellites worth hundreds of millions to bet against other people's millions of small satellites. Therefore, it is better to consume fuel to shorten the life and avoid the one in 100,000 probability.

So, under normal circumstances, is it possible for the Starlink satellite to meet the Tiangong space station?

From the public information, the Tiangong Space Station officially operates at an orbital height of about 400 kilometers and an orbital inclination of 45.1°. The reason why most space stations choose this height is mainly considering its economy: the air resistance here is small enough, it is protected by the geomagnetic field, and it is convenient to transport personnel and materials, and it is easier to observe the earth.

Musk's first batch of Starlink satellites are mainly deployed in a near-circular orbit 550 kilometers from the ground and an inclination of 53°, which basically maintains a safe distance from the space station. Under normal circumstances, Starlink satellites will not pose a threat to the space station.

Starlink's first "orbital shell"

As many as 67 Starlink satellites have been deorbited in the past two years. With the increase in the number of SpaceX launches, more satellites will fail and fall every year in the future. These satellites will inevitably invade the orbit of the space station in the process of moving downwards, which will cause damage to the orbit of the space station. Threats to the operation of the space station.

Scientists are more worried about a scenario known as "Kessler syndrome" than a direct impact: Due to the high density of satellites in orbit, debris from even an accidental collision can affect other satellites, This caused more impacts and more debris, eventually rendering the entire low-Earth orbit unusable.

Effects of "Kessler Syndrome"

In order to protect the astronauts and avoid possible collision threats, the Tiangong space station is designed to place the astronauts' living areas in the small column area of ​​the core module of the "Tianhe". Risks posed by space junk.

But data from the National Academy of Sciences shows that when a 1-kilogram object collides with a spacecraft at a speed of 10 kilometers per second, its destructive force can shatter a 1-ton spacecraft. Therefore, it is not a good idea to just carry it hard. Once the space station is hit with a big hole, the rapid loss of pressure will still kill all the astronauts.

Imaginary image of the impact on the International Space Station

Considering that satellite debris and other space junk have posed a serious threat to spacecraft, we need to increase investment in space observation while doing protection, so as to quickly identify, identify and track about 900,000 spacecraft in low-Earth orbit. For space debris larger than 1 cm, guide the space station to adjust its orbit if necessary to avoid possible impact.

The International Space Station has made nearly 30 orbital maneuvers to avoid collisions since its launch, and in recent years, such maneuvers have been increasing year by year. It is estimated that the Tiangong Space Station will also need to raise the orbit to avoid collisions in the future, provided that we can judge at least 6 hours in advance Danger. Whether or not Musk's Starlink satellites pose a direct threat, we need to plan ahead to be safe.