I'm hitting a strange issue with this method. First, a bit of background: I'm updating the old NeatherdyneMassDriver mod.  Now, one of the things it does when being armed (using a manual event) is to look at the entire FlightGlobals.Vessels list using this: for (int i = 0; i < FlightGlobals.Vessels.Count; i++) The code only looks at vessels which are loaded. The strange thing is that upon first runthrough of this after launching a vessel, the GetWorldPos3D re