It's the interplanetary spaceship, a vehicle that remains in space, goes from one place to the other, always returns back to Earth Orbit.
I like the idea too, but I'm afraid we underestimate the fuel problems.
After every mission , it will have to be refurbished and it means doing it in 0G, in the vacuum of space and transfering tons of something either very toxic (hydrazine) or very volatile (LH2) or very heavy (LO2) and having to bring it from Earth and its extremely deep gravitational well.
And what about the years of solar radition exposure...The moisture problems (like Mir and ISS encountered)?
The spaceship will have to be extremely reliable and quick to refurbish (rapid rotation period, not on Earth, but in space) if it's going to fulfill on time the missions assigned to it after the first one.

Raoul