How space debris threatens modern life
Matthias Maurer had been on the International Space Station (ISS) for just three days when he was woken in the early hours of Monday November 15 by an alert from Mission Control in Houston. Fragments of a defunct satellite were hurtling towards the space station and the crew was ordered into their escape shuttles. A direct strike could spell the end of the ISS, and of their mission.
“We had a moment of quiet,” Maurer told the Financial Times after returning to Earth last month. “You can imagine . . . you train for so long, in my case 13 years, and then suddenly, after a few days, it’s maybe all over.”
It took several hours for the crew to realise that the debris storm was not the result of a random collision between a satellite and a piece of space junk. Instead, Russia had deliberately fired a missile at the inoperative Cosmos 1408 satellite, in a blunt demonstration of military force that sent shards of hardware speeding randomly around the planet at thousands of kilometres an hour.
Russia’s missile test was condemned internationally, not just because it had endangered the lives of the ISS crew, Russian cosmonauts included. It also stoked the environmental crisis threatening human activity in space and, in particular, the emerging “new space” economy of low Earth orbit (LEO), the area between 150km and 2,000km altitude.
The space around Earth is littered with roughly 9,000 metric tonnes of debris, according to Nasa. After 65 years of space flight, derelict spacecraft, spent rocket stages, hardware released during missions, exploded motors and more are zooming uncontrollably around earth at speeds of 25,000 km an hour.
Roughly 70 per cent of that debris is in low Earth orbit. This region has traditionally been home to science missions such as the Hubble telescope and the International Space Station, where astronauts from different nations have for 20 years studied microgravity and the space environment.
Now, thanks to the Russians, it’s even riskier. “The statistical probability of collision for satellites with mission-terminating debris in the 300–800km altitude range has likely doubled due to this event, and will remain high for many years,” according to LeoLabs, a US-based startup which uses radar to track objects in space.
The scale and intensity of debris presents a serious challenge to the burgeoning space economy in low Earth orbit, where falling launch costs and smaller cheaper satellites have opened up a market potentially worth up to $3tn over the coming decades.
Satellites delivering weather and communication services, Earth observation or climate change monitoring, such as the Sentinel-1, fly in low earth orbit. LEO is also used for surveillance, both public and not so public.
And increasingly it is where companies such as OneWeb, Amazon, Telesat and SpaceX, which has already launched thousands of Starlink satellites, intend to build mega constellations delivering high speed internet access to the remotest parts of the globe.
“We humans use an increasing level of technology that is only provided by space-based platforms,” says Moriba Jah, associate professor at The University of Texas and chief scientific adviser to space tracking startup Privateer. “Everything from the global internet, navigation, financial transactions and climate change monitoring, or looking at the war in Ukraine — without space we would still be in the dark ages.”
There are roughly 5,000 operational satellites in orbit, some 4,000 of which are delivering services from low Earth orbit. A further 3,000 dead satellites are also circling the planet.
Almost half of those working satellites were launched in the last three years. Over the next decade, that rate of growth will accelerate.
Elon Musk’s Starlink has already launched over 2,000 satellites to provide global internet services and has applied for over 40,000 more. Amazon’s Jeff Bezos plans more than 7,000 for his Project Kuiper. And OneWeb, owned by a consortium including the UK government, has filed for some 7,000 second generation satellites. Others in Canada, China and Rwanda have plans for constellations as big or bigger.
Even if all of these launches may not materialise, the Satellite Industry Association reckons there could be more than 100,000 commercial spacecraft in orbit by 2030.
The scourge of space junk threatens that future. In 1978, Nasa astrophysicist Donald J Kessler outlined a theory of what would happen if space traffic continues to grow and collisions occur. The debris created by those collisions would skitter off into the paths of other satellites, creating yet more debris.
Over time, Kessler argued, a chain reaction of cascading collisions could one day make low Earth orbit hard to access and even prevent manned spaceflight from leaving Earth: a phenomenon since labelled the “Kessler syndrome”.
A cluster of startups has emerged to help navigate this new reality, and perhaps begin the process of cleaning up low Earth orbit. But some experts believe the chain reaction has already begun.
“Even if you stop launching, modelling shows that the number of space objects will still grow because collisions are happening and producing fragments at a higher rate than those that decay,” says Holger Krag, in charge of space safety at the European Space Agency (ESA). “We have gone past the point of the Kessler syndrome.”
It’s not just satellites at risk, says Nasa administrator Bill Nelson. Space debris “is threatening our missions, even human missions. You can imagine on a spacewalk if some of that hit an astronaut’s . . . suit, it would punch a hole in it,” he says. “We have to worry about getting some of this space junk down.”
Even small collisions can have serious consequences, generating a volume of debris up to 100 times the size of the original colliding object.
In 2016, ESA engineers noticed that the solar panel on their Copernicus Sentinel-1A satellite was working at a reduced capacity. From onboard camera footage, they discovered that it was due to a collision with a 1mm piece of debris.
Catastrophic collisions are those which fully destroy one or more satellites.
These can generate hundreds, or thousands, of pieces of debris.
While operating satellites can be avoided by other operators, much of the generated debris is untrackable and over time diverges unpredictably from the original path.
Eventually, this creates the potential for secondary collisions with other satellites or structures, generating more debris.
The debris from the secondary collision becomes a new set of unpredictable objects, eventually creating collisions of their own. This is the chain reaction that Kessler referred to as the “collision cascade”.
Even chips of paint or metal shards as small as 0.3mm have the potential to cause destruction because of the speed at which they move.
Debris can travel at speeds of more than 7km per second, almost 10 times as fast as a bulletand about 25 times faster than a commercial airliner.
At that speed, it would travel from London to Moscow in less than 10 minutes.
A watershed moment
One of the worst collisions of the space age occurred in 2009 when a defunct Russian satellite crashed into an spacecraft operated by US-based satellite operator Iridium Communications at an altitude of about 800km. That created 1,800 pieces of trackable debris larger than 10cm, the smallest that can be accurately identified from Earth.
Some of that debris scattered into lower orbits where the thicker atmosphere caused friction that eventually burned it up. But some debris flew above 1000kms where the atmosphere is thinner and the fragments take longer to decay. Those will present a threat to other satellites in the vicinity for centuries. At this altitude, debris is “quasi-eternal”, according to the Inter-Agency Space Debris Coordination Committee.
Iridium’s collision was a “watershed” moment for debris awareness, says Walt Everetts, the company’s vice president in charge of space and ground services. “It changed the way we think about how we do our operations. Things are very different from 10 years ago. We now have to make sure we maintain a safe space environment for everyone.” Iridium has since invested in more agile satellites allowing greater manoeuvrability in case of a potential collision, he says.
These kinds of collisions are still rare, because space is still a pretty big place. But the number of near-misses is soaring as the satellite population increases, according to Nobu Okada, founder of the Japanese debris removal startup, Astroscale. In 2020, spacecraft came within 1km of an object roughly 2,000 times a month, he says. “Over the last 12 months that has tripled.”
The steep growth of satellite systems and operators has complicated the business of avoiding collisions, says Hugh Lewis, head of the Astronautics Research Group at the University of Southampton. “It is different from 20 years ago where we would worry about a single satellite at 800km altitude and the consequences of that being hit by debris. Now the game has changed completely.”
The Iridium collision focused global attention on the need for better information about where objects are in space and where they are heading. The work of detecting, tracking and cataloguing artificial objects in space has long been done by the US government.
The system is maintained by the Department of Defense, so the data shared was historically limited. The 2009 incident changed that. The “next day” the US began sharing more precise data more widely, says another satellite executive, who asked not to be named.
“There has been a huge improvement in the last 10 years in their transparency,” says Jonathan McDowell, astrophysicist and satellite tracker at the Harvard-Smithsonian Center for Astrophysics.
But no one knows for sure exactly how much junk there is up there. The US Space Surveillance Network has identified more than 23,000 pieces of debris bigger than 10cm. Modelling by ESA suggests the figure could be as high as 36,500.
For every one of those objects, the agency estimates there are 30 more measuring between 1cm and 10cm. This debris, numbering more than 1mn pieces in total, is too small to track or catalogue.
Scientists believe there could be as many as 130mn additional fragments smaller than 1cm, but existing technology cannot give a reliable estimate of how many and where they are.
Without that knowledge we will never know the limits of safe and sustainable space activity, says Privateer’s Jah. “If we get on a plane, what we don’t hear is, 'By the way there are random bullets flying through the air so good luck’,” he says. “Right now that is a real risk . . . in space travel. I want space to be more predictable.”
Not every collision in space is accidental.
Military exercises such as Russia’s anti-satellite test (ASAT) in November, which took place 500km above Earth, have also created new clouds of space junk. The US-based Secure World Foundation, a private organisation that lobbies for sustainable space practices, estimates that tests by the US, China, India and Russia have generated more than 6,000 fragments big enough to track, with lifespans of up to 50 years or more.
And it was a military test that created the world’s single largest debris-creating event.
In 2007, China shot down an old weather satellite, Fengyun-1C, flying at 863km altitude. That test is estimated to have increased trackable debris by 25 per cent, with fragments eventually spinning into orbits from 175km to 3,600km above the Earth.
Fourteen years later, Pentagon officials concluded the shattered satellite still accounted for 10 per cent of all trackable debris. Of the more than 2,000 pieces of catalogued debris generated, 79 per cent is not expected to re-enter the atmosphere within 100 years.
Another 15 per cent will have taken more than a year to re-enter the atmosphere.
Only 6 per cent of the debris re-entered the atmosphere within a year, largely due to the altitude at which the test was conducted.
Just two weeks ago, an Iridium satellite had to dodge a fragment of Fengyun-1C. Such manoeuvres use up fuel, shortening the life and increasing the cost of commercial satellites.
The US has also conducted several ASAT tests, the last in 2008. Operation Burnt Frost brought down a failing reconnaissance satellite flying at 247km altitude, which meant 99 per cent of the resulting 174 pieces were pulled into the Earth’s atmosphere within months.
Under 600km altitude, space is often described as “self-cleaning”. Objects naturally fall back into the atmosphere within five years. So most of the debris from Cosmos 1408, which was flying at just under 500km when the Russians struck it with a missile, is expected to re-enter the atmosphere within a couple of years.
But dozens of pieces were scattered into higher altitudes and will still be orbiting in 20 years time, according to Comspoc, which tracks and predicts the trajectory of space debris. Even those that deorbit quickly pose a threat as they could cross the paths of ascending satellites. The risks to Starlink spacecraft, the biggest operator in low Earth orbit, have increased 8 per cent, estimates Comspoc.
Taking out the trash
In April, the US became the first nation to declare a ban on anti-satellite weapons tests. It was a significant move in the global campaign to clean up space. But experts say it will take much more to ensure a sustainable space environment. First, the major space faring nations will have to clean up their trash.
The 20 most dangerous objects in low Earth orbit are old Russian rocket boosters, weighing 9,000 kg each and orbiting some 800km above the Earth, according to research published last year. But objects abandoned by China, Japan and the ESA some 20 years ago rank in the top 50. A collision with any of these objects would almost certainly be catastrophic.
ESA estimates the removal of just five to 10 of these objects a year could be enough to stabilise the volume of debris, as long as new objects are not added. But cleaning up this mess will cost billions. “There is huge potential liability from all that existing debris and most governments don’t want to deal with that,” says Brian Weeden of the Secure World Foundation.
Nor do governments appear ready to agree globally enforceable rules for the exploitation of space that could minimise future debris. Currently there are no internationally agreed “rules of the road” for space: how many satellites can be launched into orbit, how to share information about where spacecraft actually are or who has to avoid whom.
Despite the tens of thousands of catalogued pieces of debris orbiting Earth, as well as the millions more that are impossible to track, there is still time to avoid the worst.
Laurence Blacketer, senior scientist at UK space situational awareness company NORSS, says Kessler will take decades or even centuries to play out. “This is not a looming disaster that will turn into a catastrophe tomorrow,” he says. But action now could have a “massive and valuable” impact on the years to come, he adds. “It is simultaneously not a disaster, but also the most important time to act.”
The space industry broadly follows guidelines for best practice to mitigate the creation of debris, such as deorbiting a satellite within 25 years of the end of its mission or ejecting residual fuel to avoid explosions.
But it has taken years to win support for these benchmarks at the United Nations, which plays a significant role in space governance, and they are still not legally binding. Now they appear inadequate given the pace of change in low Earth orbit.
Iridium, for example, was able to take an entire constellation of 65 satellites out of orbit within an average of 19 days after the end of their missions. Twenty-five years now looks far too long.
“The mitigation measures they came up with were for a different era,” says Lewis of Southampton University. “There is still a lot of understanding left to do in terms of what this new space era looks like.”
With the global space economy forecast to grow by 74 per cent by 2030, some companies have spotted an opportunity literally to clean up.
Astroscale, a Japanese startup founded in 2013, is developing a vehicle capable of removing dead satellites. ESA and the UK Space Agency are funding its first mission, planned for 2024.
Europe’s Airbus has tested a harpoon in space and successfully snared a small, square satellite known as a cubesat with a net in 2019, with the UK’s University of Surrey Space Centre.
A process that Astroscale is testing to safely retrieve defunct satellites or debris by using a servicer satellite with a magnet. It matches the speed and orientation of its target before retrieving it and then re-entering the atmosphere.
But cost and the absence of enforceable rules may prove obstacles. “Why would you pay millions of pounds for your satellite to be removed from orbit when nobody’s making you do it?” says Alexander Hall, from Future Programmes at Airbus.
An alternative could be to extend the lives of spacecraft with in-flight maintenance, bringing down the costs of operation. Northrop Grumman is developing a robotic servicing vehicle due for launch in 2024. Some researchers are even exploring the possibility of recycling satellites, says Hall, using robots to disassemble old dead structures whose parts can be used to build new spacecraft in orbit.
“We can transform the space ecosystem if we can make satellite servicing just an everyday, normal thing,” says Chris Blackerby, chief operating officer of Astroscale.
In the meantime, the race to populate unregulated space is heightening concerns that another catastrophe could be around the corner, intensifying the Kessler syndrome.
“Near Earth, space is a finite resource,” says Jah. “If everyone gets to launch what they want, where they want, when they want, without coordination then . . . space become unusable.”
For Matthias Maurer, who splashed down on May 6 after 176 days in space, that would be a tragedy. “It makes me very, very sad to see we are repeating in space what we have done on the planet’s surface,” he says. “Space is like the ocean — a resource you cannot claim for one country. People think space is so big, if I leave my trash here no one cares. But there is only so much debris the planet can afford.”
