The Earth’s orbit is becoming increasingly unsafe due to the overwhelming number of active satellites, akin to a highway during rush hour where every vehicle is speeding.
Ten years ago, there were only about 1,000 active satellites orbiting Earth. However, in the next decade, that number could swell to tens of thousands, or even hundreds of thousands, surrounding our blue planet.
For many years, experts have warned that Earth’s orbit is becoming too crowded. So, how many satellites can humanity launch before things become unsafe?
Old satellites are making the space around Earth congested. (Photo: ESA/ID&Sense/ONiRiXEL).
“The situation will resemble a federal highway during rush hour in a snowstorm, with everyone driving too fast. But the difference is that there will be many federal highways intersecting without traffic lights,” described Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, about the orbital scenario if the massive satellite networks of SpaceX, OneWeb, and Amazon come to fruition.
“The total number of conjunction events in 2022 is predicted to be 134% higher than in 2020 and 58% higher than in 2021, exceeding 4 million,” said Hugh Lewis, a professor of space engineering at the University of Southampton.
According to information submitted by SpaceX, the company founded by billionaire Elon Musk, to the U.S. Federal Communications Commission (FCC) last December, SpaceX’s automatic collision avoidance system has performed 26,037 collision avoidance maneuvers in orbit for its Starlink satellites over two years, from December 1, 2020, to November 30, 2022. This means that each of the nearly 4,000 Starlink satellites launched by SpaceX so far has conducted an average of 12 collision avoidance maneuvers.
However, the current number of Starlink satellites is still less than 10% of what SpaceX plans to deploy. In the next 10 years, the number of Starlink satellites in orbit could increase to 42,000. Additionally, there will also be another 4,000 satellites planned by OneWeb, 3,200 Kuiper satellites from Amazon, and 13,000 satellites in China’s Guowang system.
According to FCC documents, SpaceX asserts that each of its satellites has enough fuel to perform 350 collision avoidance maneuvers over a projected lifespan of five years. However, Lewis calculates that this level of 350 could be reached very soon, even before these satellites reach the end of their lifespan.
The currently active satellites are just part of the problem. The European Space Agency (ESA) estimates that the near-Earth space contains about 36,500 pieces of space debris larger than 10 cm, around 1,000,000 pieces ranging from 1 to 10 cm, and 130 million pieces smaller than 1 cm. Moreover, the number of smaller pieces continues to increase as large objects collide at high speeds and break apart.
A batch of SpaceX’s Starlink satellites ready to be launched into orbit. (Photo: SpaceX).
So, how many satellites can Earth’s orbit safely accommodate? The answer is not straightforward. Lewis notes that some orbital altitudes are more hazardous than others.
For instance, Starlink satellites operate at an altitude of 550 km. Objects at this altitude typically do not drift in space for long after ceasing operation. Even if the propulsion system fails and cannot bring them down into the atmosphere to burn up, they will naturally descend within a few years due to atmospheric drag.
However, this natural “cleaning up” ability diminishes with increasing altitude. “At altitudes above 1,000 km, the atmosphere does not do much because it is too thin,” Lewis explains. OneWeb’s satellite network operates within this altitude range, as does the smaller network from Globalstar.
Most companies operating satellite networks commit to ensuring that their satellites have enough fuel to descend into the Earth’s atmosphere at the end of their missions. However, the potential for technical malfunctions still concerns experts. In 2012, ESA was unable to remove the 8-ton Earth observation satellite Envisat from its planned orbit at 772 km. It is now one of the most dangerous pieces of space debris and will continue to orbit our blue planet for centuries.
“In 5 or 10 years, we will have around 20,000 to 100,000 satellites. With 100,000, I seriously doubt that everything can be operated safely,” McDowell shared.
