Mapscripts doesn't have space.
You have to play on scenario - that is premade map, accessed trough custom game. Their names start with Space Map.
Do you have iron, titanum and bauxite mines connected to lunar cities?
Also you need to connect all space colonies with space routes.
On github I removed supply ships (ones, that can build four different buildings on Moon).
It was overcomplicating early space colonization.
Now those buildings will be buildable on Moon.
They are extra cheap and require Commercial Spaceport in empire, just like Supply Ship required it.