We can now achieve "space rail technology." The design I mentioned would allow manned space travel at a kilogram cost of under a dollar, would cost roughly $1 trillion to build, over the course of 10 years, creating many construction jobs. Funds can come from the DoD, which will be a major user.
The vacuum tunnel, at a depth of 1 1/4 miles, and diameter of 3 meters, would allow a mag-lev train to accelerate with no air resistance to roughly mach 30, pulling on passengers at a constant 5 Gs. Over the last 65 miles, track would slowly curve upward, eventually reaching a 9 degree angle at the top of the man-made mountain. Max Gs should be ~10 down, for 1 sec in the curve, and ~13 "eye's in" for 1 sec at the tube exit, doable by healthy adults.
This makes human space colonies plausible.