This thesis analyses possible Active Debris Removal (ADR) mission architectures by comparing them on multiple levels. The objective is to determine if the proposed mission concepts, selected from already existing models, are suitable for the removal of critical debris under the environmental impact, costs and mitigation strategies points of view. A preliminary functional analysis is developed to determine the requirements, and the main functions that ADR satellites shall accomplish. Then, the proposed architectures are sized and their mass breakdown is analysed, being the starting point for the Life Cycle Assessment (LCA). Data for the Life Cycle Inventories is gathered from both previously developed LCAs and guidelines, while in some cases processes and materials are modelled autonomously.