Your design is well thought, but I managed to improve it a little:
The main trick is that the upper tank is not full:
Even with only half its capacity, the ion engines are so efficient that it's enough to perform the mission. It's also less weight so I can reduce the number of engines.
Changing the Valiant by 2 Kolibris allowed to save one more ton.
Then, the mission:
LEO reached! Then the Moon part:
Now lift-off and back to Earth:
Sadly, the ion engines broke when landing. I should have fired the ion engines to help it to slow down.
I did it with 22.52 tons, but it's probably possible to improve it again. In particular, keeping the Valiant and removing a bit of fuel from the tank may be a better move to save mass. And a single Valiant still gives a better kick than 2 Kolibris.
Even with only half its capacity, the ion engines are so efficient that it's enough to perform the mission. It's also less weight so I can reduce the number of engines.
Changing the Valiant by 2 Kolibris allowed to save one more ton.
Sadly, the ion engines broke when landing. I should have fired the ion engines to help it to slow down.
I did it with 22.52 tons, but it's probably possible to improve it again. In particular, keeping the Valiant and removing a bit of fuel from the tank may be a better move to save mass. And a single Valiant still gives a better kick than 2 Kolibris.