When I launched a Tier 1 rocket on Mars, I realized that tier-based travelling system is a complete disaster - it wasn't even possible to go back. I was thinking about a better system of space travelling and got this: there are some factors, that affect your radius: remaining fuel, rocket tier, boosters and gravity. The space catalog should make a circle (let's leave squares to keep logic, this time) centered where you launched your rocket and when you select your destination, it should tell you how much fuel is it going to cost you to get there. for example: if you had 600mB of fuel left, your range was 400Mm and moon was 362Mm from you, it would take 543mB of your fuel, since 534mB/600mB=362Mm/400Mm With this travelling system, planets should be moving far slower to add another aspect to space travelling - timing. I'm not talking about 1 Earth year to take 5 real life days. That would be realistic, but hardly acceptable for most players. So it should be like 1 earth year = 96 in-game days (like in terrafirmacraft) or even less.