The question that arises when people dream about colonies on Mars or any other large scale space project is how to pay for them. Governments have been somewhat stingy when it comes to financing national space programs since the end of the Apollo program. Private companies, even run by deep-pocketed people like Jeff Bezos and Elon Musk, have limited resources. However, as notes, a number of ways exist to raise cash to start spreading out into the solar system. The key. According to Philip Metzger, a planetary scientist at the University of Central Florida and a co-founder of NASA Kennedy Space Center's Swamp Works laboratory is Space Mining and related industries.

As most people who follow space know, trillions of dollars in minerals exist in Earth-approaching asteroids and on the moon that companies such as Planetary Resources and Moon Express hope to get at. Naysayers note that the cost of transporting these materials to Earth is prohibitively expensive. No problem, suggests Metzger. Space mining can feed three profitable businesses that can be profitable enough to fund anything, including Mars colonies. The businesses include:

Space-based fuel depots. Mining operations on the moon or asteroids can extract water and refine them into rocket fuel to be stored in space-based fuel depots. The fuel can be used by spacecraft headed between the Earth and the moon or out into deep space or to maintain satellites far beyond their current operational lives.

The latter idea has been advanced by Rep. Jim Bridenstine, who has been mentioned as a possible NASA Administrator.

Space-based Internet. The demands for data transmission on the Internet is growing exponentially. The key to handling the expanding demand is building relay stations in space, 3D printed from materials mined on the moon and asteroids.

Space-based solar power. The idea of making solar collectors in orbit and beaming power back to Earth is an old one. Instead of launching the pieces of such power stations from Earth, they can be built entirely of material mined on the moon and asteroids, 3D printed and then assembled where needed.

Therein is a business plan for opening up the High Frontier of space. Mine the moon and asteroids, build fuel depots, space-based Internet and solar power, then ploy the profits to build colonies. What can be simpler?