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Engineering changes and their propagation through a system provide insight into the complexity of a system. In an effort to identify systematic trends, we have analyzed two very different JPL-led space mission projects to classify the change activity and assess change propagation. The projects selected are a Mars lander mission, Mars Science Laboratory (MSL), and an Earth-orbiting mission, Soil Moisture Active Passive (SMAP). Change in space system development is recorded with engineering change requests (ECRs). ECRs can be regarded as an indicator of the progression of work. We employ time analysis of ECR initiation throughout the lifecycle, correlate ECR generators with ECR absorbers, and consider the distribution of ECRs across subsystems. Further, we analyze ECR-document and ECR-ECR networks to assess project interaction. These analyses give us insight into the similarities and differences between these projects. For both SMAP and MSL, similar subsystems generate or absorb change. However, SMAP followed a progression in which change was damped over time, whereas MSL often saw acceleration of change. The two projects also differed with regard to change management, with SMAP using a hierarchical approach while MSL interactions were more widely distributed.