NSS Space Settlement Art Contest Resources Page
What is a Space Settlement?
The Milestones in the NSS Roadmap for Space Settlement include both bases and settlements. What is the difference? The difference can be a matter of both purpose and degree, so a more extended discussion is warranted. Exact definitions are also difficult or impossible, because no matter what criterion you use, there may be exceptions. There is certainly room for some artistic license here!
A space settlement or space colony is a place in space where people live, generally for an indefinite period of time, and at least some raise families there. By comparison, space stations or Mars/lunar bases are places where people go for limited periods to work, and are generally completely or very heavily subsidized. Space settlements are generally larger, ranging up to the size of a full-fledged city, and are further along the curve toward self-sufficiency and economic viability.
Is size or population a defining criterion? Not really. Although a "settlement" is generally larger, does it reach the category of "settlement" when the population reaches 500? 10,000? One million? McMurdo Station, the largest permanent research base in Antarctica, is capable of supporting a population of 1,250 people, yet it is still a fully subsidized research outpost with no intention of "settling" the continent of Antarctica, and there are no children there.
Is permanence a defining criterion? Not really. Again, McMurdo Station is considered "permanent" whereas a mining settlement might run out of ore and either move or be closed down. Historically, lots of settlements are no longer inhabited, but that does not mean they did not qualify as settlements.
Is self-sufficiency a defining criterion? Not really. A space settlement might rely heavily on imports yet still be economically productive and viable, and be able to balance imports with exports.
Is lack of economic subsidy a defining criterion? Not really. A University town is certainly subsidized to a significant extent, yet it is clearly a place where people can live, work, raise families, and even retire.
All of these things are factors, but none of them alone provide clear lines of demarcation. Of all the factors, "economic self-sufficiency" is probably the most important. But there is still something of a continuum between "base" and "settlement" and the artist certainly has significant leeway here.
Good examples of "requests for proposals" of space settlement designs can be found on the website of the International High School Space Settlement Design Competition. For example, an RFP for a settlement in the asteroid belt can be found on that site here and might provide some inspiration for artistic rendering.
The following references may also be useful.