If I understand correctly, Generation Ships are using sub-lightspeed tech. Which means that they can be no more than ~500ly from their starting point. This is quite a small bubble, given how many CMDRs there are in that space. So why haven't we found any of them yet? I'm assuming this is an indication that they're not actually in the game yet? Or am I missing something? A 500ly bubble is bigger than I'm making out here, but with Advanced discovery scanners capable of pinging whole systems in a second, I think the tech should be available to make finding them a relatively simple task.