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 de-orbiting of payloads and upper stages at the end of their operative lifetime is one of the most favored options; the spacecraft should be de-orbited either directly into the atmosphere or into disposal orbits with selected residual lifetimes (e.g. 10, 15, 25, 50 years). The possible introduction of graveyard zones (both in LEO and in GEO) is also discussed. in this paper the effects of the different mitigation measures on the long term evolution of the debris population are analyzed. The need of the de-orbiting to stabilize the debris population and stop its growth is confirmed. The introduction of LEO graveyard zones is still able to significantly reduce the growth of the number of objects, even though not to stop it. On the other hand, the adoption of such storage zones might only delay the problem; especially the use the lower proposed graveyard, above 1700 km, will give way, in the next decades, to an increased number of collisions in LEO, due to the accumulation of a large number of objects in that region. Nonetheless it is shown that a mixed strategy, involving de-orbiting to 25-year residual lifetime disposal orbits and re-orbiting to a storage zone above 2000 km, appears to be the best compromise between the debris mitigation problem and the practical operational issues (i.e. in terms of DeltaV required to accomplish the maneuvers).