How to create a Zero G script for my game?

I'm relatively new to Lua but I'm in the middle of creating a game that takes place in space. How would I make the characters move around like they are in Zero G? For example, how you character in space engineers moves about. Note, I mean Zero G meaning they can go in any direction and not fall as if they where locked to a celestial bodies gravity. 

EDIT: I think I'm going about this the wrong way. You know how admins can say fly: me? Well how can I make all players have that upon entering the game? Unfortunately this question was reported for some reason. If you have the answer I would still love to hear it via PM. Thank you.