Comparison of chemical propulsion solutions for large space debris active removal

In recent years, the development of active removal missions, to face the growing risk of catastrophic collisions and new debris generation due to the high density of orbital debris in LEO, is widely discussed in the international space community. Besides legal and political issues, active removal solutions are strongly hampered by the high costs involved. Chemical propulsion might represent the preferred way to carry out the controlled reentry of large abandoned objects, and, in the perspective of cost reduction, hybrid rocket technology is considered a valuable option, due to the potential lower fabrication and operational costs, if compared with bipropellant liquid systems. The possibility to use nontoxic propellants, besides their lower prices, reduces the complexity of handling, storability, and loading operations, decreasing the connected costs and avoiding the need of a special staff. Solid rocket technology allows for very small and compact motor units, although without throttleability and reignition capability and characterized by lower safety level than liquid and hybrid systems. This study deals with the preliminary design and mass budget of solid, liquid, and hybrid propulsion modules, as well as their comparison, to be used for active removal of large abandoned rockets in LEO.