[z3t4]

You could also add 3-4 extra stages and put an even bigger tanker into space. But I guess there will be diminishing returns due to the crushing weight. It would probably be cheaper to make many smaller unmanned vessels and boost them via an electromagnetic rail, then assemble it in orbit.

[samstave]

Why not launch a bunch of larger payload tanker bays, empty, then link them together in orbit and then send Many smaller multiple regular trips to fill it up such that you have an orbital fueling station?