This is a FREE game. It has been around for many years. It is not for the Mathematically challenged or those that dont understand Physics of Solids and Celestial Mechanics. There is much more in there besides the Orbiter. This is not an Arcade Game. The guy running the site, (Assuming it is the same guy I have spoken with many times over the years) is a very good person and will provide you with some advice on this game.
Regards,
KayBay