Space Debris: The Nightmare of Modern Satellites

Origin and nature of space debris

Space debris originates from defunct satellites, abandoned rocket stages, fragments from collisions, or explosions in orbit. More than 36,000 objects larger than 10 cm are currently being tracked. Their relative speed, which can reach \(v \approx 7.8 \, km/s\), gives these debris formidable kinetic energy during impacts.

Table of major space debris-generating events

Sources: NASA Orbital Debris ProgramESA Space Debris Office.

Kessler Syndrome: Alarming Risk Projections

The Kessler Syndrome is a catastrophic scenario proposed in 1978 by American astrophysicist Donald J. Kessler (1940-). It describes a domino effect in space where the density of orbital debris becomes so high that collisions between objects generate even more fragments, creating an uncontrollable chain reaction. In the long term, some orbits could become unusable for decades, threatening GPS navigation, telecommunications, and Earth observation.

Main consequences of space debris

• Saturation of low Earth orbit (LEO) by thousands of hypervelocity fragments.
• Increased risk of collisions with operational satellites, threatening telecommunications, navigation (GPS), and Earth observation.
• Blockage of access to space for decades, rendering some orbits unusable.

Table of space debris consequences

Proposed solutions to limit the problem

To prevent near-Earth space from becoming a dumping ground, space agencies and companies are working on various solutions. Two main approaches are distinguished: avoiding adding new debris and cleaning up existing debris.

• Mitigation: To avoid creating more debris, when a satellite ends its mission, it should be removed from orbit instead of being left abandoned. International guidelines recommend deorbiting it within 25 years, where it burns up like a shooting star.
• Remediation: To recover existing debris, projects are testing nets, harpoons, or robotic arms capable of capturing debris to deorbit it. In 2018, a European mission, RemoveDEBRIS, proved this was possible.
• Use of ground-based lasers: The idea is to point a laser from the ground to give a small push to debris, enough to change their orbit and make them fall faster.
• Electric propulsion and drag sails: Some satellites could carry large sails that increase air resistance, helping them descend more quickly at the end of their life.
• International coordination: No single nation can manage this problem alone. This is why the UN and several international organizations are trying to impose common rules to hold all space actors accountable.

Scenarios for the evolution of space pollution

The future of the orbital environment depends directly on the choices made today regarding debris management. Experts envision three main scenarios:

• Optimistic scenario: Strict application of international rules (deorbiting within 25 years, passivation of stages, better coordination of launches). In this case, the density of debris could stabilize at a manageable level, allowing sustainable use of near-Earth space.
• Trend scenario: Continuation of the current rate of launches and debris production, with only partial mitigation efforts. There would be a slow but continuous increase in fragments, making some orbits increasingly risky and costly to exploit.
• Pessimistic scenario: Multiplication of accidental or deliberate events (collisions, anti-satellite tests), triggering a Kessler Syndrome. Chain collisions could render low Earth orbit (LEO) largely unusable for decades, with a major impact on telecommunications, navigation, and scientific research.

These scenarios show that inaction greatly increases the risk of uncontrollable escalation. Conversely, rapid and ambitious international cooperation can maintain space as a common good accessible to future generations.