Space Debris Basics

What is the Future Trend?

The amount of debris on orbit in the future will depend upon whether the creation or removal rate dominates. Currently, the only mechanism for removal is orbital decay through atmospheric drag, which ultimately leads to reentry. This mechanism is only effective in a restricted range of low Earth orbits. At higher orbits, it takes hundreds to thousands of years for objects to reenter, and so there is no effective removal mechanism. Historically, the creation rate of debris has outpaced the removal rate, leading to a net growth in the debris population in low Earth orbit at an average rate of approximately 5 percent per year.

A major contributor to the current debris population has been fragment generation via explosions. As the debris mitigation measure of passivation becomes more commonly practiced, it is expected that explosions will decrease in frequency. It may take a few decades for the practice to become implemented widely enough to reduce the explosion rate, which currently stands at about four per year.

In the near future, there will be an increase in the number of individual intact objects launched by man. The trend in space technology is moving toward smaller satellites operating cooperatively in coordinated constellations. This trend is mainly due to the revolution in commercial satellite-based communications systems, and satellite microtechnology. As satellites become smaller, they will become more vulnerable to the smaller debris population. Hundreds of satellites have been proposed for operation in low Earth orbit.

While functioning satellites in individual constellations will be controlled to maintain constellation geometry and hence preclude collisions among themselves, traffic will increase through each constellation due to associated operations and maintenance of their neighbors. In addition, satellite failures will eventually occur, resulting in uncontrolled satellites that drift through operating constellations. The close proximity of satellite orbits may result in increased collision risk as well as increased risk of multiple losses if a satellite breakup occurs and forms a debris cloud with constrictions.

Because of the increased number of larger objects, lack of sufficient debris mitigation efforts such as collision avoidance could eventually result in collision-driven population growth. Various technical models for population growth have been developed by the international community. Most models agree that rapid population growth can occur in the absence of appropriate debris mitigation. They also agree that the population level required to trigger rapid growth in a given orbital region will be achieved before rapid growth is observed. Few models agree in predicting when such growth might become significant.