Satellite failures that once led to end-of-life may eventually be addressed using robotic servicing platforms. The ability to model and simulate the physical interaction between two free-floating spacecraft is a key aspect of robotic servicing, and understanding how large appendages such as solar panels, antenna arrays and booms affect the combined system dynamics may be critical to mission operations. This research presents a model of the coupled rigid- and flexible-body satellite dynamics that can be implemented on a robotic satellite simulator. The coupled dynamics are validated against a commercially available dynamics software package, and robot hardware-in-the-loop tests are conducted to demonstrate how the dynamics model is able to predict the response of a robot mass simulator outfitted with physical appendages. Through both validation efforts, a flexible-body simulation is developed to observe the resulting dynamics of a given satellite system on-orbit.