> But you also have to carry the fuel you'll burn with you, so the more fuel you have, the more fuel you'll need
Isn't this the entire point of using methane as fuel so that they can build a gas station once they get there so that return fuel is not required to be considered in this equation?
I'm not talking about fuel that you need to get back, we're still at the "leaving Earth" case. The point is that you need, say, 1000 tons of fuel to leave the Earth. Your rocket then will weigh [weight of empty rocket] + [weight of payload] + 1000 tons. And it is this mass that the engines will have to push while ascending. Of course, the fuel gets spent as you ascend - by the time you reach orbit, your rocket is now 1000 tons lighter.
The refueling idea is so that for example you don't need to carry the fuel needed to get to the moon or Mars all in one rocket. You just need to carry enough to get to the refueling orbit - which is much less.
