Game Theoretic Analysis of the Space Debris Dilemma Final Report

In this study we analyse active space debris removal efforts from a strategic, game-theoretical perspective. Space debris are non-manoeuvrable, human-made objects orbiting the Earth. They pose a threat to operational spacecraft, especially in low-Earth orbit. As a consequence, active debris removal missions have been considered and investigated by different actors (space agencies, private stakeholders, etc.) as part of a strategy to alleviate the problem, thus protecting valuable assets present in strategic orbital environments. An active debris removal mission is a costly endeavour that has a positive effect (or risk reduction) for all satellites in the same orbital band. This leads to a dilemma: each actor has an incentive to delay its actions and wait for others to respond. Specifically, each actor is faced with the choice between acting now or postponing to take action, i.e., either take an individually costly action of debris removal, which has a positive impact on all players; or wait until others jump in and do the ‘dirty’ work, as this will be at their own benefit and reduce their own costs. The risk of the latter action is that, if everyone waits the joint outcome will be catastrophic leading to what in game theory is referred to as the ‘tragedy of the commons’. Such a scenario is unlikely if we look at the current debris population and the threat it poses, but it may become increasingly realistic as the debris population grows further and as more and more private stakeholders enter the business of exploiting the Earth orbital environment. We introduce and thoroughly analyse this dilemma using empirical game theory in a two and three player settings and in terms of strategic properties and equilibria of the game, and show how the cost/benefit ratio of debris removal strongly affects the game dynamics. Our results are based on simulations of the long term evolution of the debris population accounting for new launches, new collision events, orbital decay and possible player actions such as debris removal.