Orbiter (simulator)

''Orbiter'' was developed by Martin Schweiger, a senior research fellow in the computer science department at University College London, who felt that space flight simulators at the time were lacking in realistic physics-based flight models, and decided to write a simulator that made learning physics concepts enjoyable. It has been used as a teaching aid in classrooms, and a community of add-on developers have created a multitude of add-ons to allow users to fly assorted real and fictional spacecraft and add new planets or planetary systems. Provided by Wikipedia