How do we get the whole thing off the ground?
I read of a beautiful idea in a scientific magazine called Omni. It suggested the use of virtual reality systems to control robots on the moon. This would enable us to build the first colony more efficiently because robots need only raw energy. We send a rocket to the moon, on the rocket we put machine tools and intelligent systems, with which can build both more machinery and the necessary superstructure to house a biosphere. We now have the ability to use our hands at a distance.
The high cost to the human race's colonisation of space, is caused by the complexity and danger of reaching and leaving escape velocity within the earth's atmosphere whilst carrying the fuel up from the earth's surface with which to do so.
The Space Shuttle turned out to be an expensive dangerous white elephant, the reason the Shuttle was so expensive is, because of its complexity with millions of different manufactured parts. There is another route, we can reach the edge of space no problem Burt Rutan proved this with Space Ship one, when he won the 'X' prize by reaching over 100 km twice in one week. Yes the Shuttle was 'reusable' but in name only. They could not have turned that around in a week. One idea could be to create rocket fuel on the moon, there is lots of water on the moon, use solar energy to split the moon's water into hydrogen and oxygen which makes very good rocket fuel. Use the rocket fuel to fuel a space tug, use the space tug to accelerate and decelerate Space Ship One, to and from escape velocity in the safety of a vacuum.