This article is from WeChat official account:qubit (ID: QbitAI), author: Zheng Ji Yang, Xiao investigation, the title figure from: vision China
As for the “Starlink” (Starlink) of SpaceX under Musk, something worrying still happened.
After the previous vigorous launches, astronomers complained about affecting normal observations.
Subsequently, space enthusiasts also worried, what if these satellites become space junk occupying orbits, or even “locked up” the earth’s crust?
Not only does it affect other countries to explore space, but if there is a “crisis” on the earth, the way out will be blocked.
Unexpectedly, the above worries became reality.
Jonathan McDowell, a scientist at the Harvard-Smithsonian Center for Astrophysics, compared data from SpaceX and the U.S. government and found that about 3% of the more than 800 Starlink satellites that have been launched into the sky have failed.
The so-called “failure” means that these Starlink satellites are no longer controlled by ground commands and cannot change orbit.
Professor McDowell said that although the 3% failure rate is not high, considering the large scale of SpaceX’s satellite Internet program. Even if 3% of the satellites are out of control, in the long run, the number will be quite large.
According to the latest documents from the International Telecommunication Union (ITU), SpaceX plans to launch up to 42,000 satellites, each weighing approximately 227 kg.
If the failure rate does not improve, Starlink can produce more than 1,200 “dead” satellites in the future……
Such a large amount of space junk is enough to make every national aerospace agency “frightened”. Maybe someday the spacecraft launched by itself will be damaged.
A group of SpaceX Starlink satellites to be launched
SpaceX officials have already been asked this question.
But now how many Starlink satellites in space have failed, SpaceX officials did not give a specific number, and did not respond to the 3% failure rate.
And according to SpaceX’s distribution to the Federal Communications Commission from May to June this year (FCC) revealed that since the deployment of Starlink, several of them have lost their mobility.
How terrible is the 3% failure rate
Professor McDowell who discovered this problem explained:
The failure rate of their (SpaceX) is not terrible, no worse than anyone else’s failure rate. But what is worrying is that in such a huge satellite system, even a normal failure rate will result in a large amount of bad space junk.
Professor McDowell is worried about the Kessler phenomenon (Kessler Syndrome) caused by a large number of scrapped satellites. This is the most terrifying.
The Kessler phenomenon was proposed in 1978 by Donald Kessler, a space debris research expert at the NASA (NASA) Kind of theory.
He thought,If the density of space junk in low Earth orbit is high enough, cascade collisions will occur. A piece of debris is collided to produce multiple debris, and these debris will continue to collide with other space junk to produce more debris.
This will make the low-orbit area full of space junk, making it difficult for low-altitude satellites to survive in this area, and even affect the launch of higher-orbit satellites.
The most serious consequence is that it affects the ability of generations of people on earth to explore space and completely “locks up” human beings on Earth for hundreds of years.
Now, the huge launch volume of the Starlink project makes people worry that Kessler’s hypothesis is becoming a reality.
FCC documents show that SpaceX plans to build 12,000 satellites, while ITU documents show that SpaceX plans to build 42,000 satellites.
In these two cases, a 3% failure rate corresponds to 360 or 1,260 satellites with each 227 kg out of control.
According to the (SDO) data of the European Space Agency’s Space Debris Office, as of February 2020, there are currently 5,500 satellites in Earth orbit, of which About 2,300 are still in operation.
This means that if Starlink builds a complete system, it will increase the number of unoperable satellites in space by 11% or 40%.
If you consider the amount of debris from satellite collisions in orbit, the problem looks even more serious.
In addition to “dead satellites,” SDO estimates that there are currently 34,000 objects in Earth orbit with diameters greater than 10 cm, 900,000 objects between 1 cm and 10 cm, and 128 million objects between 1 mm and Between 1 cm.
The mock image is already scary.
European Space Agency’s simulation of space junk larger than 1mm
European Space Agency escaped
It is worth noting that Starlink’s threat to spacecraft is not alarmist.
In September 2019, the European Space Agency (ESA) experienced a thrilling scene.
According to orbit calculations, the European Space Agency’s atmospheric dynamics monitoring satellite Aeolus had a 0.1% probability of colliding with the Starlink satellite.
Although the probability of 0.1% seems to be small, the collision probability in space reaches 0.001%, which requires intervention in the satellite orbit.
And the mass of these two satellites is not small, Aeolus is about 1.36 tons, and the mass of Starlink is about 227 kg. The speed of artificial satellites is more than 10 times that of bullets.
Once the two collide, the consequences will be disastrous.
NASA simulated the consequences of a collision between space debris and a spacecraft in a test
Later, because SpaceX “has no plan to take action”, the European Space Agency had to actively change the orbit of its satellite at the last moment to avoid accidents.
SpaceX later explained that they missed ESA’s email due to an “error” in the communication system.
In the end it was a “false alarm”,But this incident is enough to sound the alarm.
So SpaceX, is there really no security and self-destruct solution? Is it reliable?
Safety and self-destruction of “Starlink”
SpaceX introduced itself that Starlink satellites can de-orbit into the atmosphere and self-destruct under normal operation.
At the same time, there is an automatic collision avoidance system to ensure the safety of satellites in space.
However, once a maneuverability failure occurs, the aforementioned capabilities need to be reassessed.
Satellite self-destruction
Ion engines are the core of power in satellite components. The de-orbit of Starlink is inseparable from the operation of the ion engine.
It appeared in the 1960s, and its principle is to ionize the gas first, and then use the electric field force to accelerate the charged ions and eject them to form a reaction force to achieve propulsion.
Usually, the industry uses xenon ions as the ion source of ion thrusters (fuel).
In order to save costs, SpaceX chose krypton ion. Although krypton is less easily ionized than xenon, the price of krypton ions is nearly 10 times cheaper than that of xenon ion sources. This is due to commercial considerations.
In addition, in order to further save costs, SpaceX has only configured one ion engine in Starlink satellites.
However, this is a safety hazard, because usually a spacecraft will be equipped with multiple engines to prevent the failure of a certain engine and cause the satellite to become disabled. This move by SpaceX will undoubtedly increase the failure rate of Starlink satellites.
So, how does the ion engine perform when it is off-orbit?
When a satellite needs to change orbit or de-orbit, such as a collision or self-destruction of the satellite, the ion engine can increase or decrease the speed to realize the separation from the original orbit.
Analyze the satellite’s self-destruction. When the satellite’s lifespan is about to end, the ion engine will work backwards, reducing its speed and orbit, so that the satellite will soon fall into the atmosphere.
Based on the special structural design, the satellites entering the atmosphere can burn quickly and decompose into small particles that meet safety standards without threatening the ground.
However, once you lose your mobility, the situation is different.
Whether it is a communication system failure or a problem with the ion engine, it means that the satellite has lost ground control and is alone in space.
But what needs to be added is that even if a satellite fails and loses its maneuverability, it is not completely self-destructive.
It can be done through natural descent-satellites slowly lower their orbits by thin air resistance, and eventually enter the atmosphere, but this is a long process.
In this process, satellites are no different from space junk, and they will also pose a serious threat to the normal working spacecraft.
Collision avoidance
In addition, the threat caused by failure of maneuverability is not something that Starlink satellites have their own autonomous collision avoidance system to avoid.
Because of the normal operation of the autonomous collision avoidance system, communication and power are both indispensable.
As shown in the schematic diagram, the satellite can use the space debris threat information data transmitted from the ground, or get instructions, use its own four momentum wheel system, and cooperate with the ion propulsion system to achieve collision avoidance.
For example, the so-called autonomous collision avoidance system is not about seeing a stone and then avoiding it, but like air traffic control.
This system can ensure that the satellite actively avoids other spacecraft or space debris under normal operation, but it cannot be a “fuse” to avoid other spacecraft in the event of a failure.
So in terms of principles and consequences, although Starlink satellites claim to have self-destruction and collision avoidance functions, they are all designed based on the normal operation of the satellite. Once a failure occurs, the result will be the same-resulting in space junk.
So far, as to how to deal with the aftermath, Musk and SpaceX have not given a backup plan at all.
Never mind the consequences of development
What’s more frightening is that this is more like an arms race.
SpaceX “turned a blind eye” to the possible consequences, and other companies avoided talking about it.
The bankrupt OneWeb launched 74 satellites. The company originally planned to launch 48,000 satellites; Bezos’ Amazon also has an Internet satellite Kuiper plan, which is expected to launch 3,200 satellites; even Apple was revealed by Bloomberg. There are similar plans…Around the world, many commercial companies have also joined the battle for resources.
When Musk’s Starlink project was exposed, some people commented from the perspective of “thick and dark”:
Internet satellites are a good way to achieve network coverage in remote areas, but if the immature technology leads to a “space disaster”, it will not be worth the gain.
Reference link:
https://phys.org/news/2020-10-starlink-satellites.html
https://www.businessinsider.com/spacex-starlink-internet-satellites-percent-failure-rate-space-debris-risk-2020-10
https://www.esa.int/ESA_Multimedia/Videos/2019/02/Distribution_of_space_debris_in_orbit_around_Earth
https://techcrunch.com/2019/05/24/spacex-reveals-more-starlink-info-after-launch-of-first-60-satellites/< /span>
https://www.reddit.com/r/spacex/comments/gaayqm/spacex_ion_thrusters_and_where_does_this/
https://www.planet4589.org/space/jsr/jsr.htmlhttp://www.viaspace.cn/Article/20191113.html p>
This article is from WeChat official account:qubit (ID: QbitAI), author: Zheng Ji Yang, Xiao check