Satellites and space trash threaten ozone layer and space safety

Every year, we shoot several thousand satellites and other objects out into space. When satellites die, they become space trash that threatens aerospace safety.

Outer space has a trash problem.

“And the problem is only going to get bigger and bigger,” says Rannveig Færgestad.

Færgestad studies aerospace technology at NTNU’s Department of Structural Engineering. In her Ph.D., she has developed computer models that show what happens when pieces of space debris collide with spacecraft. With an average speed of 7 kilometers per second, even a tiny piece of junk can cause a lot of damage.

Rocket debris and satellites

Space trash consists of rocket remnants, fuel and whole or parts of defunct satellites. Much of this debris moves through the low Earth orbits below 2000 kilometers in altitude, or is on its way down into the atmosphere. This debris burns up in the layer of air surrounding the planet because air resistance creates intense friction.

All spacecraft that carries humans are covered with various types of protective shielding. Færgestad is conducting research on these kinds of shields in order to make them as safe as possible.

One of her supervisors is former astronaut Kevin Anthony Ford from NASA (the National Aeronautics and Space Administration). He has completed three space missions and has served as commander of the International Space Station (ISS). He is now part of a team of advisors who continuously assess the safety situation for the ISS.

“The team now says that space trash is the greatest risk,” said Færgestad.

A tenfold increase

More than 20,000 objects have been launched into space since the Russian Sputnik 1 satellite kicked things off on 4 October, 1957. That amounts to 50 thousand tonnes. Some of the debris has returned to Earth, but according to the European Space Agency (ESA), 10,000 tonnes are still floating around in orbit.

In the summer of 2025, there were more than 14,000 active or derelict satellites orbiting Earth. On average, an uncontrolled object crashes somewhere on Earth once a week.

According to the United Nations Office for Outer Space Affairs, almost 2900 satellites, space probes and other objects were launched in 2024. That is more than ten times as many as a decade ago.

If we continue to launch the same amount of equipment into space, the risk of collisions will only increase. The risk could become so great that developing shields strong enough to withstand such powerful impacts would be both challenging and expensive. Researchers warn of collisions that could trigger massive problems, wreaking havoc in many systems, such as communication and navigation, TV signals, banking services, and climate and weather forecasts.

In the worst case, collisions could destroy entire orbits.

“In the worst case scenario, it could simply become difficult to use these orbits for anything practical,” explained Færgestad.

“The ESA’s collision models show that even if all launches were to stop abruptly this year, the number of collisions would continue to increase over the next 200 years. Many companies already have large teams of engineers working to keep satellites safe and steer them away from collisions,” Færgestad said.

Moving the ISS

There are always people on the ISS and China’s Tiangong Space Station. If there is a risk of the stations being hit, they can be moved slightly to avoid a collision. In fact, the ISS astronauts perform these types of maneuvers at least once a year.

“The most catastrophic scenario is if something hits a part of the space station containing people. If a hole forms, the station will lose pressure and the astronauts would die instantly,” Færgestad said.

Centimeter-sized pieces are particularly dangerous. So far, they have not hit the parts of the space station that house the astronauts, but they have created a clearly visible hole in a robotic arm on the ISS.

Elephant in the room

It could be said that Elon Musk is the elephant in the room with regard to outer space issues. He is the world’s richest man and controls the Starlink satellite network. The goal of Starlink is to provide internet access to the entire planet. Ukraine, for example, is entirely dependent on Starlink for its military communications and drone operations in the war against Russia.

Starlink alone has launched almost 8000 satellites since 2018, and they have been given the green light to launch a total of 40,000. Other satellite mega-constellations, i.e. large private networks, have similar plans. On 28 April 2024, Amazon launched the first 27 of over 3,000 planned Kuiper satellites. Communication networks like OneWeb, Telesat and China’s StarNet are all waiting in line.

This means that the number of satellites is skyrocketing.

In a 2021 article published in the journal Nature, researchers from the University of British Columbia in Canada warned that rocket launches and mega-constellations could harm the ozone layer that protects us from UV radiation. A number of research groups have since followed up on this finding.

A typical satellite weighs around 250 kilograms. Sooner or later, they stop working, just like your TV or washing machine. They then return to the atmosphere, burn up, and release around 30 kilograms of aluminum dust, which can harm the ozone layer.

Experts warn that this kind of dumping could cause a large-scale, uncontrolled change in the natural chemistry of the atmosphere.

Many satellites die every day

Many of the first Starlink satellites have already reached the end of their useful life. In January 2025 alone, 120 of them had lost enough altitude to fall into the atmosphere and burn up. This is completely according to plan, and satellite trackers at the Harvard Center for Astrophysics state that 4 to 5 derelict Starlink satellites burn up every single day.

Scenarios developed by American researchers suggest that these satellite mega-constellations could collectively add 360 tonnes of aluminum oxide compounds to the atmosphere each year when their satellites are decommissioned and die. The particles fall slowly, so it could take 30 years before they reach the ozone layer—and we see the effects.

“That is really quite worrying,” said Færgestad.

Beyond enabling communication and navigation services, satellites are widely used to monitor the environment and climate. They monitor sea levels, algal blooms, melting glaciers, landslides, floods, overfishing and climate change.

Agencies are working to tackle the problem posed by the aluminum dust from dying satellites, including through the ESA’s Zero Debris approach. Any company that is launching objects into space must now have a plan in place for what they are going to do with them when the equipment stops functioning.

For satellites in low Earth orbit, engineers can use the last remaining energy in the satellites to slow them down. As a result, they lose altitude and burn up when they reach Earth’s atmosphere.

Satellites in the highest orbits can be moved to designated graveyard orbits. These are located so far away that there is no risk of collision.

For larger objects, such as capsules or spacecraft, the aerospace industry has chosen the most remote place on planet Earth: ‘Point Nemo,” or the “Oceanic Pole of Inaccessibility,” in the Pacific Ocean, which is more than 2600 kilometers from the nearest land. There, at a depth of 3000 meters, lies the world’s largest spacecraft graveyard.

Every gram costs

In autumn 2025, Færgestad will defend her Ph.D. at NTNU. She says that awareness of safety in unmanned spaceflight is increasing. Satellites and space probes will now also be protected by shields.

Every gram of equipment launched into outer space costs money, which is why everything is focused on reducing weight. Færgestad’s research is helping make the shields as light—and as safe—as possible. On the ISS alone, there are hundreds of types and combinations of shields. Different parts are made from different materials and will react differently if they are hit. Therefore, they also require different protection.

Layer upon layer upon layer

The protective shields are 10–15 centimeters thick and consist of multiple panels made of materials such as Kevlar, carbon fiber, fiberglass and foam. The exterior is usually aluminum, with an air cavity between each panel. If a piece of space debris comes hurtling through space and hits the shield, the air cavity between the panels absorbs some of the impact.

“Exactly what happens when something strikes the shield depends on its speed, temperature and the material it is made from,” she said.

If the debris is moving slower than 3 kilometers per second, it will break up into smaller pieces. At speeds of 7 kilometers per second or more, everything is vaporized into a cloud of molten droplets. The air cavities dampen the impact of the fragments in the cloud of debris, spreading the energy over a larger area in the subsequent layers.

The physics of these collisions is extremely complex and difficult to describe in computer models.

“We are talking shock physics,” said Færgestad.

This involves understanding how materials behave under the most extreme stresses that exist—such as explosions, meteorite impacts and hypervelocity collisions in space.

Tests in Italy and the United States

In order to create computer models that can simulate what happens as accurately as possible, the researchers also conduct physical tests. The tests are needed to check whether the computer models reproduce what happens in reality as accurately as possible.

Færgestad has tested panels at NASA’s hypervelocity laboratories in New Mexico and the University of Padua in Italy. These facilities have gas guns capable of firing projectiles at speeds of up to 7 and 5.5 kilometers per second, respectively. All the tests were filmed using high-speed cameras that capture up to one million frames per second.

She is very pleased with the results; the behavior observed in the laboratory tests appears to align very closely with her computer simulations.

The 30-year-old has chosen a very specialized field of study in which she is one of very few researchers in Norway. Slow progress is being made, one step at a time.

“It is probably not the kind of work that makes you think, “Wow, this is going to get me a Nobel Prize,'” said Færgestad.

“But what we know and how we understand thing are getting better. The tools are getting better. The computers are getting more processing power. We are trying to make the toolbox for everyone working in aerospace bigger, better and as reliable as possible,” she said.

Making equipment safer also means it will also last longer before it stops working and turns into dangerous space debris.