Yet another classic science fiction trope that real-world science is reaching towards: a team of scientists have come up with a design for a space station named "Luna Gaia" that works on similar principles to a biosphere – a "closed-loop" ecology where almost all waste products are recycled by the system. [Image credited to NASA]

The ISS runs on a type of closed-loop system already, but the recycling processes are largely based on chemical reactions; the biosphere design would use plants and algae instead, as far as is practically possible, and should be theoretically capable of sustaining twelve astronauts for three years. The diet sounds a bit dull, though …