This instructable is for realistic extraterrestrial design. Star wars/trek have mostly got it wrong- too much like earth. This instructable is for creating things like the daggerwrist or skewer from Wayne Barlowe's Expedition. Remember the number one rule: Don't make things too much like earth
http://www.instructables.com/id/How-to-Make-a-Hypothetical-Planet-and-Its-Inhabita/