Abstract The choice of architecture in the design of large-scale complex systems has an enormous bearing on the cost, performance and adaptability of the system. It is often the case that the operational environment of the system changes over time, necessitating evolution of the architecture. In this paper, tradespace graphs of candidate space-based relay networks for NASA׳s Space Communication and Navigation (SCaN) program, focusing on the Tracking and Data Relay Satellite (TDRS) system, are analyzed in order to examine the potential pathways through the tradespace for a specified planning horizon. We utilize a method that enumerates architectures as vertices in a tradespace graph, taking into account both the fixed properties of the architecture and the variable ages of its assets. We then examine what real options can be put in place to enable future flexibility given uncertainty about the lifespan of existing TDRS assets. In a separate set of analysis, these time-expanded graphs are used to price the potential inclusion of hosted payloads against a range of possible architectural decisions.

Highlights • A time-expanded tradespace graph is presented, which enumerates architectures as vertices in a tradespace graph, taking into account both the fixed properties of the architecture and the variable ages of its assets. • This formulation incorporates the lifecycle of satellites, giving decision-makers the opportunity to plan for a fixed horizon. • The real options to enable future flexibility are examined, given uncertainty about the lifespan of existing TDRS assets. • It was found that extending the lifetime of the TDRS constellation by an extra five years results in a cost and benefit improvement on average over a given 30 year development cycle. • The time-expanded graphs are used to analyze the effect of utilizing hosted payloads against a range of possible architectural decisions; significant savings were demonstrated over a 30-year development path.