Colonizing, terraforming & developing Mars and mining the asteroids should take centuries.
There are lots of other things to do and ways to do it. Consider--
After two more 2004 flights — one on Sept. 29 and another on Oct. 4 — the piloted vehicle won the $10 million Ansari X Prize for repeated flights in a privately developed reusable spacecraft. SpaceShipOne was a space plane designed and fabricated by Scaled Composites, a company owned by aerospace designer Burt Rutan.Oct 2, 2014
--how much the private sector could do w/ a ten billion dollar prize. While it cold literally move mountains into space, it would hardly be missed from our current candidates' half (Trump) or quarter (Hillary) $T for roads'n'bridges.
I think that a lot of the nonsense we see today, including liberalism and the obsession with sexuality and gender, is the result of the lack of a real frontier.