My concept can be condensed down into a sentence. I think most stories can, no? I think you mean like one word or a single thing. They could rob me in three words. And don't say you can rob me in two. or can't they? It's all very spooky.
It's in the execution. Copyright protects the execution. Copyright is for something in a fixed form. A screenplay. A short story. A painting. A dance.
Ideas are not in a fixed form.
And no one is going to rob you. For several reasons.
1. Your idea... in three words... can't be all that specific and unique--even if you think it is.
2. People really aren't out there stealing ideas, it's more trouble than it's worth..
3. No one is going to steal your space opera idea, because no one wants to produce Space Operas... But, let me be more specific: No on is going to produce Space Opera UNLESS it is tied to an existing Intellectual Property. Guardians of the Galaxy. Star Wars. Star Trek.
(Now, MAYBE, someone might want to produce it independently... which means a LOT less money... and less reach.)
If, indeed, you have the script, and you want to be a professional writer, this might serve as a great sample to get you an agent or a manager--not the sort of agent, but, a real one who can be your advocate and get you into rooms. But, the chances of getting THIS script made... it's very small. That's a reality of the business.
If this is a TV script, it's going to be the same thing. This might help get you an agent or a manager, but, no one is going to buy a script that is a Space Opera from an unknown, untested writer. Unless it is TOTALLY amazing. And even then: they would take it away from you and have someone else run the show.
However, if this is a hobby, and you want to do it for fun. Yeah, then, maybe Kickstarter would be the route. But, as others have said, you need proof of concept. Drawings. Video. And don't ask for the sky. Projects that don't have Star Trek or Star Wars attached to them don't do well on Kickstarter. Even well known writers don't reach their goals. David Gerrold was trying to launch Star Wolf... and he couldn't get the money.
Is it just two guys in a ship 'cause if it is then you have something fairly digestible to the two titans - Trek and Wars. I hate it when writers don't want to hear your ideas. I have them copyrighted, but I hear you can't copyright an idea and call it intellectual property because it's in the public domain but I think that is bullshit, and you know what I think they can do with all their derivative rights especially when they run me over.
Public domain is a specific term. It means work that was once held by copyright is no longer protected by copyright and is free to use by anyone. You could sell your own edition of Shakespeare for example. Or use characters from Sherlock Holmes in your story or screenplay.
Ideas are just that. Ideas. They are not related to the term Public Domain.