Here is the absolutely most important thing you should know about writing a science fiction novel.
Your brain will try to trick you. It will tell you that you can't do this. You don't know enough about physics, or chemistry, or genetics. You don't know how to world build on a grand scale--heck, you can't even give good directions to the nearest parking garage, how did you expect to world build?
What you need to know is that this is no different than the fear of failure associated with writing a picture book, or a book in verse, or a romance. This is the same fear of inadequacy every writer feels with every book. Oh, it's dressed itself up in science fiction trappings (I don't know, maybe a homemade Star Trek uniform?) but it's the same monster, you betcha.
I'm writing my first science fiction novel, and it took me a while to understand this. But after a bit (OK, a few months) I realized that I recognized this beast who told me I wasn't smart enough to make this world work. This was the same beast who told me I wouldn't ever figure out pacing. The same beast who told me I couldn't plot my way out of a paper bag. The same beast who says to me, even as I type this, "You know, Kate, maybe you only think you've gotten better at pacing, and who says you figured out how to plot your way out of a paper bag? Nobody's bought one of your novels yet, have they? And now you've decided to write something more ambitious?"
The monster of fear can only be killed by writing word after word. But whatever you're writing, if it's a new genre for you, don't let the monster fool you with tricky disguises. For goodness sake, don't let it distract you with your lack of knowledge of electronic engineering or fishing in medieval times or maritime law or iambic pentameter.
Can someone send me some fear of success to balance out my fear of failure? Wait, it doesn't work that way? Sigh. I guess it's back to sheer stubbornness and coffee.
-- Kate, Miss Perfecting the Pages