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
Space is getting littered with old satellites and broken rocket parts. Because they move so fast, even tiny pieces can damage working satellites or the space station.
At work
Debris is a business risk for anyone relying on satellites, from GPS to communications, because collisions can knock out services.
At home
Tracking networks follow objects bigger than about 10 centimetres. When a risky close approach is predicted, satellites fire small thrusters to dodge. Small fragments can't be tracked, so spacecraft carry shielding.
At work
Operators receive conjunction warnings and plan avoidance manoeuvres. Large constellations perform these manoeuvres often. Good practice includes deorbit plans, passivating batteries and fuel at end of life, and sharing position data.
At home
Low satellites fall back and burn up within a few years, but debris higher up can stay for centuries. In my opinion, the scariest part is that a single big collision could make certain orbits unusable for generations.
At work
Policy issues include enforceable international norms, liability under the 1972 Liability Convention, active debris removal missions, space traffic management, and limits on anti-satellite weapons testing. Atmospheric effects of frequent satellite re-entries are also an emerging research concern.
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.