Adaptability can have many different definitions: reliability, robustness, survivability, and changeability (adaptability to requirements change). In this research, we focused entirely on the last type. We discuss two alternative approaches to requirements change adaptability. One is the valuation approach that is based on utility and cost of design changes in response to modified requirements. The valuation approach is theoretically sound because it is based on utility and decision theory, but it may be difficult to use in the real world. The second approach is based on examining product architecture characteristics that facilitate changes that include modularity, hierarchy, interfaces, performance sensitivity, and design margins. This approach is heuristic in nature but more practical to use. If calibrated, it could serve as a surrogate for real adaptability. These measures were incorporated in a software tool for exploring alternative configurations of fractionated space satellite systems.