[SJC_Hacker]

Establishing a permanent presence on the moon would be a stepping stone to further exploration of other planets. (Mars in particular.)

Since its only a 3-4 day trip, with transfer windows every month (and non-optimal ones essentially constantly). resupply missions and rotating astronauts/personnel are going to be much easier. Much less of a gravity well to deal with.

The plan would be for in situ resource extraction and manufacturing. With enough of a human presence, projects like local construction of spacecraft become feasible. And something like a mass driver would be much more feasible on the moon. A big enough one and you're even considering interstellar probes ...

It would require a consistent, sustained effort. But not astronomical in US budget terms. Maybe $20-$30 billion/year (about of 3-4% the defense budget)

[Zigurd]

Anything beyond Earth orbit requires either multi-stage expendable rockets, which isn't economical for supporting a moon base, or in-orbit refueling that has better economics than expendable rockets, which depends on cheap rapid reusability. If you can't land, refuel, and fly without refurbishing the launch system, rocket engines, etc. you can't ship fuel to orbit cheaply enough to justify in-orbit refueling.

Starship is a vastly better attempt at more of these goals than STS. But if it misses cost, or payload, or reliability goals it won't solve this problem. It is even possible that it will take too many attempts in which a ship and 39 engines are expended to even get close.

[philwelch]

Or we can get the fuel from the moon. The moon has water ice, which means it has hydrogen and oxygen, which you can use as rocket propellant.