Simulating the Evolution of Lethal Nontrackable Population for Low-Earth-Orbit Sustainability

The vast majority of the orbital population today is unobservable and untracked because of their small size. These lethal nontrackable objects will only become more numerous as more payloads and debris are launched into orbit, increasing the collision rate. In this paper, the long-term effects of collisions are simulated using an efficient Monte Carlo method to simulate the future low-Earth-orbit environment, including lethal nontrackable objects, which are typically ignored due to the large computational resources required. The results show that simulations that do not incorporate lethal nontrackable debris would omit a large number of debilitating collisions with active payloads and catastrophic collisions to a smaller extent. This shows the importance of simulating small debris in the long-term evolution of the orbital population, which is often omitted in the literature. This increased debris population and, consequently, the risk to orbital payloads diminishes as smaller, lethal, nontrackable objects are considered. An efficient and validated model is used to simulate these numerous small objects. Several future cases, such as the launches of registered large constellations, improved postmission disposal rates, and no-future launches, are explored to understand the effect of the inclusion or exclusion of lethal nontrackable objects.