Outer space has a trash problem, according to researchers

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

She studies aerospace technology at NTNU’s Department of Structural Engineering. 

In her PhD, she has developed computer models that show what happens when pieces of space debris collide with spacecraft. 

With an average speed of 7 kilometres 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 satellites that no longer work.

Much of this debris moves through the low Earth orbits below 2,000 kilometres 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. It’s these shields that Rannveig Færgestad studies to make them as safe as possible.

The greatest threat

One of her supervisors is former NASA astronaut Kevin Anthony Ford. He has completed three space missions and served as commander of the International Space Station (ISS). 

He is now part of a team of advisers that continuously assess the safety situation for the ISS.

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

Tenfold increase in launches in 10 years

More than 20,000 objects have been launched into space since the Russian satellite Sputnik 1 kicked things off on October 4, 1957. 

That amounts to 50,000 tonnes. Some of the debris has returned to Earth, but 10,000 tonnes are still floating around in orbit, according to the European Space Agency (ESA).

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

In 2024, nearly 2,900 satellites, probes, and other objects were launched, according to the United Nations Office for Outer Space Affairs. That's more than ten times as many as ten years 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.

Orbiting space debris

In the worst case, collisions could destroy entire orbits.

Orbits are like roads in space. For example, the paths planets follow around the sun or satellites follow around Earth.

In these orbits, gravitational force and centrifugal force are balanced: gravity pulls inward, while speed prevents the planet or satellite from falling in.

Space has traditionally been considered so vast that leaving things there was thought to be unproblematic – not unlike how the oceans were once viewed on Earth, writes the Norwegian Space Agency.

However, there are certain orbits around Earth that are very important, and in these areas, space is not unlimited, the agency continues.

Orbits are in many ways a limited natural resource. And at certain orbital altitudes, there are already considerable amounts of space objects – both active satellites and debris.

The number of collisions will continue to increase

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

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,” says Færgestad.

The ISS moves annually

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 manoeuvres 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,” says Færgestad.

Centimetre-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.

Elon Musk is the elephant in the room

It could be said that Elon Musk is the elephant in space. He's the world’s richest man and controls the Starlink satellite network. The goal 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 8,000 satellites since 2018. They have been given the green light to launch a total of 40,000. Other satellite mega-constellations – large private networks – have similar plans. 

On April 28, 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, quite literally, skyrocketing.

Satellites can harm the ozone layer

In a Nature article from 2021, 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 aluminium 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 retirement age. In January 2025 alone, 120 of them had lost enough altitude to fall into the atmosphere and burn up. 

That's completely according to plan, and satellite trackers at the Harvard Center for Astrophysics show that four to five 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 aluminium 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's really quite worrying,” says Færgestad.

Must clean up

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 aluminium dust from dying satellites, including through the ESA’s Zero Debris approach. 

Any company that launches objects into space must now have a plan in place for what they are going to do with them when the equipment stops functioning.

Graveyards in the ocean and outer space

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 the 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 over 2,600 kilometres from land. 

There, at a depth of 3,000 metres, lies the world’s largest spacecraft graveyard.

Every gram costs money

Færgestad says that awareness of safety in unmanned space travel is increasing. Satellites and space probes will now also be protected by shields.

Every gram of equipment launched into outer space costs money. Therefore, everything revolves around minimising weight. Færgestad’s research helps make the shields as light – and safe – as possible. 

On the ISS alone, there are several hundreds types and combinations of shields. Different parts are made from different materials and will react differently if hit. They therefore also need different kinds of protection.

Layer upon layer upon layer of protection

The protective shields are 10-15 centimetres thick and consist of multiple panels made of materials such as Kevlar, carbon fibre, fibreglass, and foam. The exterior is usually aluminium.

There is 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's made from,” says Fægerstad.

If the debris is moving slower than three kilometres per second, it will break up into smaller pieces. At speeds of seven kilometres or more, everything is vaporised into a cloud of molten droplets. 

The air gaps dampen the impact of the fragments in the cloud of debris, spreading the energy over a larger area in the subsequent layers.

The most extreme stresses

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

“We're talking shock physics,” says 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 US

To create computer models that can simulate what happens as accurately as possible, researchers also conduct physical tests. 

These tests are needed to check whether the computer models reproduce real-world results as precisely 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 kilometres 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 behaviour in the lab tests appears to align very closely with her computer simulations.

Larger toolbox

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

“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,” says Fægerstad.

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

Astronaut? Yes, absolutely!

Ever since she was in upper secondary school in Drøbak and attended the European Space Camp at Andøya, Færgestad has been passionately interested in aerospace and space technology.

In autumn 2025, she will start working as a Space Debris Mitigation Engineer for the Italian company Thales Alenia. This is one of the major aerospace companies in Europe. They have built a lot of the components for the ISS. 

Currently, they are building modules for the planned space station that will orbit the Moon, and they are designing spacecraft for lunar landings and unmanned vehicles destined for Venus.

"How long would you have to think about it if you were offered the chance to become an astronaut?" 

“There’s nothing to think about. If you get an opportunity like that, you seize it,” she says.

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Read the Norwegian version of this article on forskning.no

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