Can you clarify that fast travel mechanic? I'm trying to get to a couple of systems but it keeps telling that I can't fast travel there, and I genuinely can't figure out since it's not fuel related.
So on the Star System map (where it shows Sol, Alpha Centauri, etc) the red dots are systems you haven't travelled to, and the white are ones you have. You need to upgrade your grav drive and Astrophysics skills to reach certain systems (such as Bohm in the far right corner) as they're outside your travel range based on your ship. But lets say you travel to Bohm, and you're on the edge of the map, and you want to travel back to Jemison in Alpha Centauri. If you are on the Star System map and click on the Alpha Centauri system, it will pop up on the right with a red box giving you a warning saying something like "this route is unexplored" and won't let you fast travel. However, if you click INTO Alpha Centauri to where it gives you a view of the planets, and go click on New Atlantis and click the "Land" button, it'll immediately fast travel you to New Atlantis DESPITE the previous screen telling you that you didn't have a route there.
So it means as long as you have gone to a star system, you can always fast travel back to the planets in that star system. I haven't tested it on planets in the star system that you haven't travelled to before but I cannot imagine it is any different. The reason that this sucks is twofold: first, you get conflicting information from the menu. One menu tells you there isn't a route home, suggesting you manually hop between systems to get back, the second menu ignores that and immediately lets you travel. Now it's fine for there to be fast travel in a game if you want that as a system, but why do you get warnings on one screen while on the other it lets you travel with no issues? It's confusing. This leads into the second main issue which is the competing gameplay styles eat at each other. You have fast travel like any Bethesda game, but it eats at the space exploration component. You have space exploration, and it eats at the Bethesda game component. You're upgrading your ship and travelling really far away as part of a progression system, and then it doesn't matter since you can fast travel. Or you're trying to complete a quest, and your hopping lightyears away in an instant to run a fetch quest. It's irrational, and as I keep going back to, as Todd Howard said "schizophrenic." If you go to the far edge of the map, the most desolate, high level planet possible, don't worry because you can immediately fast travel home at the click of a button! It undermines what it would be like to travel all that way. Worse yet is you can get random events that undercut the experience. E.g. I was on Bohm, far edge of galaxy and the furthest planet in the Bohm system, and a ship of colonists lands and starts walking around. I upgraded my skills and ship (only time you need to do this is to initially get to further systems, then no longer matters) to get here, and some random bunch of NPCs lands to make this remote ice planet feel active. Worse yet, wasn't the first time I had that random event. Like I said the two game elements, a Bethesda experience and a space exploration game, don't work in harmony and actively cannibalise one another.
But to answer you direct problem about it not being fuel related, as I said, either upgrade your Astrophysics skill or your grav drive. Likely you'll need a combination of the two.