Abstract — USARSim began as a human-robot interaction (HRI) research tool but has since found use in a much wider community and for purposes we had never envisioned. This paper describes a six year HRI research program at the University of Pittsburgh using the simulation. Our original work involved teleoperated control of single robots and primitive simulations. In the most recent experiment teams of operators were controlling 24 robot teams in a high fidelity environment. In between we developed and tested measures of coordination demand, tried out news ways for managing video generated by teams, and investigated scaling effects as operators controlled increasing numbers of robots. This paper provides a brief chronology of this research summarizing their designs and findings. I I.