Space debris
Also known as: space junk, orbital debris, orbital space debris
Space debris, or space junk, is human-made material left in orbit that no longer serves a purpose: dead satellites, discarded rocket stages, and fragments from collisions and explosions.
Because objects in orbit travel around 28,000 kilometres per hour, even a paint fleck can damage a spacecraft. While agencies track tens of thousands of larger pieces, millions of tiny fragments can't be tracked at all, and the rush of new constellations makes the problem more urgent.
Space debris, explained at three levels
At home
Picture a highway where broken-down cars are never towed and their scattered parts keep moving at full speed. That is orbit today. Dead satellites, old rocket stages, and fragments from explosions keep circling at about 28,000 km/h, so even a small bolt hits harder than a bullet. Working satellites and the space station have to share the road with this junk and steer around the biggest pieces.
At work
Space debris is any human-made object in orbit that no longer works. It matters to business because GPS, weather data, satellite internet, and imaging all depend on satellites that debris can damage or destroy. Operators spend fuel and staff time dodging it, insurers price it into coverage, and regulators increasingly require plans to remove satellites at end of life.
At home
Military and commercial radars and telescopes track objects larger than about 10 centimetres, tens of thousands of them, and publish their orbits. Software predicts close approaches, called conjunctions. When the risk is high, a satellite fires its thrusters to shift its path; the space station does this a few times a year. Fragments between 1 and 10 centimetres are too small to track but big enough to destroy a satellite, so spacecraft carry shielding.
At work
Operators receive conjunction warnings from services such as the US Space Force's space-track.org and commercial trackers like LeoLabs. Each warning carries a collision probability, and teams set thresholds for when to manoeuvre. Large constellations automate this and perform thousands of avoidance burns a year. End-of-life good practice means deorbiting low satellites, moving GEO satellites to a graveyard orbit, and passivation: draining leftover fuel and batteries so old hardware can't explode.
At home
How long debris lasts depends on altitude. Below about 500 kilometres, air drag pulls objects down within years. At 800 kilometres or higher, they can stay for decades to centuries. The real danger is Kessler syndrome: one collision creates thousands of fragments, which raise the odds of the next collision. While space looks empty, in my opinion a few bad collisions in crowded bands could make those orbits unusable for generations.
At work
Governance is thin. The 1967 Outer Space Treaty and the 1972 Liability Convention assign responsibility to launching states but don't require cleanup. Practical rules come from IADC guidelines, ISO 24113, and national licensing, such as the US FCC's five-year deorbit rule. Active debris removal, such as ESA's ClearSpace-1 mission, is still experimental. Failure modes include dead satellites that can't deorbit and anti-satellite weapon tests. I'd require deorbit plans in any satellite procurement.
Real-world examples
At home
Lena saw a news story about the International Space Station adjusting its orbit to avoid a piece of debris. She was surprised to learn this happens regularly.
At work
Thomas is a flight dynamics engineer at a Canadian satellite operator. He reviews collision warnings daily and plans small thruster burns when a debris fragment comes too close to one of his company's satellites.
Common confusions
- Space is so big that debris can't really hit anything. — Useful orbits are crowded bands, and at about 28,000 km/h even small fragments can disable a satellite. Operators dodge debris regularly.
- Debris falls out of orbit quickly on its own. — Low debris re-enters within years, but debris a thousand kilometres up or higher can stay in orbit for centuries.
For analysts
Anyone operating or depending on satellites should ask providers about their end-of-life and collision-avoidance practices. In my view, responsible debris practices are becoming a procurement question, not just an engineering one.
History & origin
NASA scientist Donald Kessler warned in 1978 that collisions could create a cascade, now called Kessler syndrome, where debris breeds more debris. China's 2007 anti-satellite missile test destroyed a weather satellite and created thousands of trackable fragments. In 2009, the defunct Russian satellite Cosmos 2251 collided with a working Iridium satellite, the first accidental collision between two intact satellites. Russia's 2021 anti-satellite test forced International Space Station crew to shelter. Regulators responded: the US FCC adopted a rule in 2022 requiring most US-licensed LEO satellites to deorbit within five years of mission end. In my view, orbit is a shared resource being treated like a free dump, and the bill will come due unless rules get stricter.