Ithekro wrote:All that needed is a way to make if profitable, and/or viable as trade. Even if it is mostly trade between various colonies, with only monetary/technological trade back to Earth (or "rare" something or other that gets a good price Earthside). Than its is sustainable if the commerce is basically moving needed resources from one point to another around the Solar System to support life in those place. Even if mostly all the trade is just to keep those colonies alive early on, that is a step forwards. It could take a hundred or two hundred years to get them to a point where they are doing anything but survival trade economies, but eventually, they should become viable on their own.
There are two economies that are closely linked, but not congruent. On one hand, there is the economy in monetary terms. In that market, space exploration can be made profitable with fiscal or technological trade. The other economy trades in resources. Westerners aren't for the most part aware of its existence, because we did live in unparalleled surplus for the last century.
A lot of people think that when oil deposits get rarer, price for oil will rise and make exploiting more challenging deposits worthwhile and thus the supply of oil and energy will remain the same. However, we need resources for this exploitation, meaning the EROI keeps sinking. The danger of a low EROI is that we can be lacking the energy surplus to maintain higher industry, extensive schooling or the ability to feed the population. We've had an EROI of 100 barrels/barrel in 1900. It's fallen now to 14 barrels/barrel. The effects of this aren't linear, from 100 to 20 is only a reduction from 100% to 95%. The change from 10 to 9 however can be massive.
To get to the point of my depressive post, we might not have a century left in us to get projects up and running that do not provide a quick benefit in resources.
So the best way to make space exploration sustainable would be to find ways of harvesting energy in space and sending it back down to earth. Perhabs LEO based solar farms tethered by a space elevator/power line could be worth it. Or harvesting fissible materials in asteroids and planetoids and using those to sustain our dependency on artificial fertilizer.