by In the first half of 2024, satellites from SpaceX’s Starlink fleet performed nearly 50,000 collision avoidance maneuvers. This reflects the number of satellites in orbit and raises fears of collisions between satellites if we continue to launch more satellites unchecked.
Considering how much of our telecommunications and navigation now comes from space, not to mention the observational data that informs us about climate change, the fear of a catastrophic crash – resulting in a loss of such vital services – is understandable .
But according to Andy Lawrence, Regius Professor of Astronomy at the University of Edinburgh, it is more treacherous than that. “The idea that there will eventually be some kind of catastrophe is not entirely correct. It’s more like the infamous ‘boiling the frog’ problem,” he says.
The idea is basically that if a frog falls into boiling water, it will immediately jump out. But if it were placed in cold water to which heat were gradually added, it would not perceive the danger and be boiled alive.
“It’s exactly like climate change. You know it’s gradually getting worse, but where do you say ‘stop’ and how do you make it stop?” says Laurens.
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To orbit the Earth, a satellite must move at a speed of at least 7.8 km/s (4.8 miles/s). At this speed, collisions would release a huge amount of energy, shattering the spacecraft involved and creating large clouds of debris that could destroy other satellites.
Such crashes have already occurred: in 2009, the functioning US satellite Iridium 33 and the inoperable Russian Cosmos 2251 collided at a speed of 11.7 km/s (7.3 miles/s), destroying more than 2,000 pieces traceable debris and many smaller pieces emerged.
There are now more than 13,000 satellites in orbit, of which approximately 10,000 are functioning. In January 2023, the decommissioned IRAS (Infrared Astronomical Satellite) space telescope from the US, Britain and the Netherlands came within 15-30 meters of the US Gravity Gradient Stabilization Experiment (GGSE-4) satellite, which has not been used since 1972 works.
A month later, NASA’s scientific TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics) satellite passed just 10 to 20 meters from a defunct Russian satellite, Cosmos 2221. Although it functions, TIMED is a non-maneuverable spacecraft, which means that which operators on Earth could simply watch and hope for.
The space tracking company LeoLabs provides commentary on the conjunction, as these close passes are called posted on X: “Too close for comfort.” The subsequent message thread pointed out that if these two satellites had collided, it would have produced 2,000 to 7,000 fragments large enough to track from Earth. Since there are currently approximately 12,000 traceable pieces of space debris, such an event would have contributed significantly.
While Lawrence doesn’t believe a single catastrophic event will happen, he says one day a collision could take away something important to many people. “If you suddenly can’t watch the Super Bowl game, or if an important military asset is damaged, people will realize that something has to be done.”
Satellites have been a feature of our world since 1957, when the Soviet Union launched Sputnik 1, to the surprise of everyone. But the huge increase in the number of satellites in orbit in recent years means the risk of these fast-moving objects colliding has never been greater.
The dramatic rise of satellites has been driven by companies looking to build space-based internet services. To provide acceptable response times, the satellites must be in low Earth orbits, where they speed around the world every 90 minutes. To guarantee unbreakable coverage and sufficient bandwidth, hundreds, thousands, if not tens of thousands of satellites are therefore needed.
Starlink is the largest of the satellite constellations, having put more than 7,000 satellites into orbit as of 2019. To reduce the risk of collision, the satellites are maneuverable: the built-in software performs a maneuver if the chance of a collision is greater than 1 in 1, 100,000.
This is useful, but some experts worry that the increasing number of satellites will overwhelm the software’s ability to handle it. (Starlink did not respond BBC Science Focus‘s request comment on this.)
In 2023, Dr. Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, addressed this concern on the news website space.com, saying “we are operating at the edge of what is safe.”
And it’s not just orbital space that could be at risk from the increasing number of satellites. In an early effort to combat space debris, NASA and ESA issued guidelines a decade or two ago stating that an operator must dispose of the satellite at the end of a satellite’s lifespan or after 25 years (whichever comes first). to delete. Usually this means it is burned up in the Earth’s atmosphere, but this could only shift the problem.
“You’re filling the atmosphere with aluminum and nitrous oxide, so it’s also about air pollution,” says Lawrence.
In April, NASA confirmed that a piece of discarded cargo from the International Space Station had survived its return to Earth and fallen to Earth, leaving a large hole in the ceiling and floor of a Florida home. Fortunately, no one was injured.
It clouds our view of the universe
As the number of satellites around Earth grows, so does the interference astronomers experience when studying the sky. At visual wavelengths, satellites can leave streaks on images. At radio wavelengths, satellites can transmit signals that drown out the precious whispers from deep space.
“As we industrialize space, which is a good thing, there will be challenges for astronomy,” Prof. Brian Cox recently said. BBC Science Focus. “How you balance those things is the challenge for the coming decades.”
A study with the LOFAR (Low Frequency Array) radio telescope in the Netherlands below found that the latest V2 mini Starlink satellites emit unintended radio waves that are up to 32 times brighter than the previous generation. That is 10 million times brighter than the faintest objects that LOFAR can detect.
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