Science Fiction Economics

There are probably those about who believe that economics is some kind of science fiction especially in certain hands, but in the comments to this article in Making Light, about aliens as some kind of force for socialism as far as I understand it, there's a link to a list of academic papers on The Economics of Science Fiction of interest to me would be the Paul Krugman one on "The Theory of Interstellar Trade", but it seems that you can't get this anywhere on the Internet.