The New Scientist discusses a recent study that advocates using of an ion beam generator on the moon to allow the use of far smaller rockets to move from the moon to other locations in space. The ion beam generator would need several hundred megawatts of electrical power from either a large solar cell array or nuclear power.

I have discussed the need on my website to make gigawatts of power on the moon and in orbit in order to begin serious development and colonization efforts.

An alternative to ion beams would be magbeam, a plasma based approach for accelerating spaceships

The Lifeboat Foundation supports space habitats and Asteroid shields

The beam approaches all require large power sources. The fastest way to achieve this would be to build a lightweight nuclear power source on the earth and launch it into a high orbit (a lagrange point) or the moon.

The power could also be used to power mining and industrial machinery on the moon which has uranium and thorium and the raw materials to make more nuclear reactors. Containment and waste issues on the moon would be less of an issue until colonization happened in a big way. The colonization is better place in rotating structures in orbit, so the moon could be a power and material source for primarily orbital colonization.

Large scale structures for solar power and for space stations could be made with mostly existing or near term technology using magnetically inflated cables Using superconducting wire a lightweight structure could be launched that would unpack from an existing rocket and then expand to be 1 kilometers in diameter or more.

The main points are large scale space architecture is possible in the near term. Large power sources are needed and can be built. We can create viable space habitats with large viable populations properly engineering the technology that we have now. This would be superior to the lunar program that NASA has proposed which lacks the scale necessary to establish viable Lifeboat colonies.