The applicability of COSYSMO, a systems engineering cost model, is explored in the context of space systems through the analysis of two main assumptions. First, the WBS elements of the model are mapped to a prototypical WBS for space systems. Second, the life cycle phases assumed in the model are mapped to the phases outlined in the latest National Security Space acquisition policy. Through the analysis of these assumptions, the applicability of COSYSMO to space systems can be improved. Moreover, techniques for performing partial estimation of systems engineering by systems engineering activity and life cycle phase are provided to further the applicability of COSYSMO to space systems.