Energetic cost and viability of the proposed space debris mitigation measures

At the international level several mitigation measures are proposed to reduce and minimize the debris growth in Earth orbit. The deorbiting of payloads and upper stages at the end of their operative lifetime is one of the most favored options. The spacecraft should be deorbited either directly into the atmosphere or into disposal orbits with selected residual lifetimes (for example, 10, 15, 25, and 50 years) as a result of air drag. The possible introduction of storage zones (both in low Earth orbit and in geostationary Earth orbit) is also discussed. The effects of the different mitigation measures on the long-term evolution of the debris population are analyzed. The need for deorbiting to stabilize the debris population and stop its growth is confirmed. The introduction of low-Earth-orbit (LEO) storage zones is still able to reduce significantly the growth of the number of objects, even though it does not stop it. On the other hand, the adoption of such storage zones might only delay the problem. In particular, the use of the lower proposed storage zone, above 1700 km, will give way, in the next decades, to an increased number of collisions in LEO as a result of the accumulation of a large number of objects in that region. Whereas the only way to guarantee a long-term stability of the environment will be to adopt only the deorbiting mitigation measures, it is shown that a mixed strategy, involving deorbiting to 25-year residual lifetime disposal orbits and reorbiting to a storage zone above 2000 km, appears to be the best compromise between the debris mitigation problem and the practical operational issues (that is, in terms of ?V required to accomplish the maneuvers).