[Ductapemaster]

I love that we have ideas and theoretically a combination of technologies that can take us to Mars and beyond in a short timeframe. The way I see it is that while chemical rockets are un-economic, as you point out, for a large scale colony, what humanity needs is a demonstrated need and a catalyst to get us to explore the more exotic propulsion technologies like nuclear + ion drives + hydrogen.

Chemical rockets will take us from 0 to 1, and the economics will drive the next technological development to take us from 1 to n. I think it will work the same way as when telegraph wires were exploding around the US and we realized copper resources were a limiting factor. Did we give up and say "well, let's wait for the next technology"? No, we kept building the wires and other industries sprouted up to handle the demand (notably recycling).