A while back I came across the ultimate all-in-one-place science reference for Science Fiction writers. It’s a site called Atomic Rockets, located at ProjectRho.org and run by a guy named Winchell Chung. It’s essentially a site dedicated to giving writers/game-designers/movie-producers the serious scientific lowdown on living/working/travelling/fighting/anything in space or on another world. On the sliding scale of hard sci-fi versus soft sci-fi, it’s about as hard as the depleted uranium doped ceramic composite on an M1a2 Abrams main battletank.
Do you want rocketships? This site will teach you exactly how they REALLY work, along with ideal design, engines both actually-in-existence and only-theoretical, methods of radiation shielding, styles of navigation depending on power and engine type, possible crew structure, and more.
Do you want FTL? This site will punch you in the head on why it’s impossible, then run you through a list of how, IF YOU MUST HAVE FTL, you can avoid making it galactically stupid FTL and circumvent a variety of plot-holes and other problems that can be caused by poorly thought out versions. It will also show you how a clever FTL mechanism can CREATE all kinds of plot gold for you and allow or block any number of military scenarios and civilization structures.
Do you want Lasers? This site will teach you about the three major kinds of laser weapons, why current lasers are NOT the most awesome technology to ever exist, how lasers might be employed on a ship and what drawbacks they would have, etc, as well as linking to some other sites that have EVEN MORE information, including spreadsheets for designing hypothetical laser weapons and then testing their penetration. Also, if you want something else, there are particle beams, rail guns, nukes, etc etc etc.
Do you want handheld weapons of doom? This site has all of them. I mean it. ALL OF THEM. Okay, maybe not. But close. Lots on anything that’s actually conceivably possible, and debunking on the kinds that are just totally idiotic. Also, it has laser rifles, and how they would actually work, with pictures of how they might look and calculations for penetration, power use, etc.
Do you want Galactic Civilizations and aliens? Yes. Of course this site has that. Lots and lots of that. There are reams of discussion on that. From charts on the kinds of governments, to discussions of each of them, to the cyclical rise and fall of nations, to how trade works within an empire and how it might work in space (including how you might come up with excuses for lots of it).
Do you want stealth space ships? Winchell Chung will take your dreams of stealth ships and smash them into teeny tiny pieces with a brick bat made of physics.
If you want it in your sci-fi story, this site probably has information on it, and then some discussions, and some charts, and maybe some equations, a bunch of links, and plenty of etcetera. Reading through it all (okay, maybe half of it all… or a third… a quarter? THERE IS SO MUCH!) made me rethink the technology of my whole sci-fi universe, and I am SO GLAD that it did. My sci-fi is still pretty soft, but it’s also so very much better than it was, and now it’s immensely more detailed and consistent than I had imagined possible.
So take it from me. If you do any kind of science fiction and desire the least little bit of internal consistency in your storyverse, then GO to this site and read through it. Let it knock you around and challenge you and force you to think. No, you DON’T have to be as realistic as Winchell pushes you to be, but once you’ve gone through his site, you will KNOW when you are cheating, and if you decide you have to, you will be able to do it consistently in a way that enhances your story. Honest.
(Warning: My one caveat to my otherwise unreserved recommendation of this site is this: every page is plastered with covers from vintage sci-fi novels. That means shiploads of scantily clad space babes from the sixties, seventies and eighties, including one or two damsels in peril that are as naked as the Venus De Milo (that means entirely naked, to any of you Philistines). If you’re someone who would find such images a dangerous temptation, then I urge you to stay away. If you aren’t at all bothered, then just ignore this warning and go check out the site.)