ABS = Activity Breakdown Statement OPF = Orbiter Processing Facility DES = Discrete Event Simulation RLV = Reusable Launch Vehicle

Future reusable launch vehicles are considered to have potential benefits compared to expendable systems. These benefits can arise from reductions in turnaround time, recurring operations costs (labor and materials), and life cycle cost. Yet quantifying these operability and affordability effects, in some manner beyond using historical analogies, has proven difficult for the systems analysis community. SpaceWorks Engineering, a division of SpaceWorks Engineering, Inc. (SEI) has developed, through research and quantitative modeling, an activity-based simulation to predict turnaround time, recurring ground operations cost, and other operations metrics for future launch vehicles. This development goes beyond traditional historical modeling efforts and particularly focuses on modeling activities associated with the propulsion system. The model is implemented in the discrete-event simulation software Arena, commercially available from Rockwell Automation. Inputs for the analysis model include descriptions of the basic vehicle concept of operations, mission models, and performance information. In the early part of the twenty-first century, both the theoretical underpinnings and actual simulation software capabilities are present to create a usable, activity-based systems analysis capability for metrics related to reusable launch vehicle operability and recurring operations affordability