Space is vast and largely empty, but the space around our planet is becoming increasingly cluttered. In today’s post, we’re talking about what space debris is, why it’s a problem and how it can be kept under control.
What does ‘space debris’ mean?
Essentially, ‘space debris’ refers to objects in space that can’t be controlled and have no function. It’s commonly used to talk about manmade objects orbiting Earth, although meteoroids could also be considered space debris.
A communications satellite isn’t space debris, because it does something useful: it relays information from one place to another. If the satellite’s systems fail, though, and it continues to orbit without performing its function, it becomes space debris.
If a satellite is destroyed in orbit, it will break into many pieces of space debris. Some pieces will fall towards Earth and burn up in the atmosphere, but many will remain in orbit, cluttering up the space around our planet.
Why is space debris a problem?
Although space debris is often small, it travels at very high speeds and can damage or destroy operational satellites if it collides with them, in the same way that, although bullets are small, their high speed makes them extremely dangerous.
Space debris is also a self-replicating problem. If space debris destroys an existing satellite, it can cause large quantities of new space debris, as happened in 2009 when a derelict satellite, Kosmos 2251, collided with the operational communications satellite Iridium 33. Both satellites broke up into hundreds of smaller pieces, littering Earth’s orbit.
If space debris continues to accumulate, it will become harder to operate satellites around Earth. According to ESA’s infographic ‘The Cost of Avoiding Collisions’, each of ESA’s Earth-orbiting spacecraft needs to be moved approximately twice per year to avoid a potential collision with space debris. As the quantity of space debris increases, the need to move satellites in order to avoid collisions will also increase, burning valuable fuel.
A notable recent event that created space debris was the Russian missile test that destroyed the defunct Russian satellite Kosmos 1408 in November 2021. The satellite’s destruction resulted in over a thousand pieces of space debris. Some of these pieces burned away in Earth’s atmosphere, but many remain in orbit, and will continue to orbit for years.
Shortly after the missile test, the astronauts above the International Space Station (ISS) were told to shelter in heavily shielded capsules, in case the space station was damaged by the debris. You can read a BBC article about the missile test and the resulting concern for the ISS here.
Space debris can also impact on Earth’s largest and oldest satellite. In March, part of a rocket hit the moon, creating a new crater. Whereas debris falling towards Earth will partly or fully burn up in the atmosphere, the moon has no atmosphere to prevent impacts. Of course, there’s usually no one on the moon to be endangered by this.
How much space debris is there?
ESA’s page ‘Space debris by the numbers’ keeps track of the quantity of debris currently in orbit around Earth. As of July 2022, about 31,000 pieces of space debris are being tracked by space surveillance networks.
However, many pieces of space debris are too small to track, and these pieces can still present a danger to satellites. ESA reports some estimates of the quantity of space debris orbiting Earth:
- Approximately 130 million objects between 1 mm and 1 cm in diameter
- Approximately 1 million objects between 1 cm and 10 cm in diameter
- Approximately 36,500 objects greater than 10 cm in diameter
What can we do about space debris?
Unfortunately, we don’t currently have a feasible way of gathering or deorbiting the space debris that already exists, although there has been speculation and research on the topic. Not far from our labs at Harwell Science and Innovation Campus, you’ll find the UK branch of Astroscale, an international company dedicated to space sustainability and tackling the debris problem.
One theoretical technique is the use of a laser that can alter the orbit of space debris and cause it to fall into the atmosphere, rather wonderfully named a ‘laser broom’.
At the moment, most space debris mitigation techniques focus on two areas: preventing new space debris from being made, and preventing the existing space debris from causing damage.
As mentioned, many larger pieces of space debris are tracked, which means it’s possible to anticipate and avoid collisions with operational satellites. Because space debris can’t be controlled, satellite operators will need to move the operational satellite out of the way to avoid an anticipated collision. This is one of the reasons satellites need fuel; for more about this, take a look at our article ‘How are satellites powered?’
Satellites can also be shielded against smaller pieces of space debris. To protect the space station itself and the astronauts aboard it, most of the ISS is shielded against debris of up to 1 cm in diameter.
How can we prevent space debris from being made?
Space debris is difficult to clear up, so the best thing to do is to prevent it from being made in the first place. This can be done by disposing of a satellite correctly at the end of its lifespan.
If a satellite is allowed to stay in orbit until it stops working, it becomes space debris, as it will continue orbiting while serving no function and cannot be controlled. If the defunct satellite is then hit by debris, it may break into many more pieces of space debris.
To avoid this, it’s common to slow low-orbiting satellites down as they approach the end of their useful life. When the satellite slows down, gravity takes over; the satellite will be pulled down to Earth and break up in the atmosphere.
It’s harder to get satellites in higher orbit to fall to Earth, so these satellites are sometimes instead pushed into a ‘graveyard orbit’, higher than any functional satellites. However, while these satellites are out of the way and no longer pose a danger to functional satellites, they still ultimately become items of space debris, orbiting the Earth while serving no purpose. Eventually, we may need to clean up this graveyard orbit and make better use of it.
In the future, hopefully, we’ll develop ways to gather and recycle space debris. For now, by responsibly disposing of satellites before they stop working, we can help to keep Earth’s orbit clear enough to be a safe environment for useful satellites.
For more about satellite disposal, take a look at our article ‘What happens to old satellites?’
Darwin Innovation Group is a UK-based company that provides services related to autonomous vehicles and communications. If you’re interested in working with us, take a look at our careers page. If you’d like to know how we can help your organisation make use of autonomous vehicles, contact us. You can also follow us on LinkedIn or Twitter.