Kerbal Space Program - Principia - Doing Gravity Properly

Kerbal Space Program uses only single gravitating bodies in its physics model this is a pretty good approximation for most things, but for those that want more realism there's Principia. http://forum.kerbalspaceprogram.com/index.php?/topic/62205-wip105-principia-version-buffon-2016-02-22-n-body-and-extended-body-gravitation/