Spencer M. answered 08/09/19
Willing to teach the ropes of academic and creative writing!
There's no consistent way to make a great ending, and it depends greatly on what you want the book you're writing to be like. In your case, I think it's possible that everything being neat and tidy is just the problem. There's nothing wrong with a thread never quite getting wrapped up, with an outcome of a story not quite being clear, with a character's problems not being fully resolved. As good as it is to be consistent with tracking your plot threads, it's also important, maybe especially in sci-fi, to leave the reader with questions after the book is finished. How did that side story wrap up, how will this character deal with the things that they've experienced- leave them wondering!