I think, all futuristic utopias are broken about the very essence of human nature. What kind of socialism can there be if we have not overcome pride and greed? The desire to be "better" or "higher", richer sooner or later can take possession of a person, and then he will have no business before socialism and equitable distribution of resources. For one hypothetical idealist, there may be several persons who care only for their own well-being. This also results in economic and logistical difficulties, which makes it virtually impossible for an endless extraction of resources outside our planet, at least in the coming decades.