Specifically, my space ships do not behave like ships in space.
I lay the blame at everyone else who ignores physics. I’ve seen two authors do it right – David Weber nails it in the Honor Harrington books (though I’ve read some criticism of the main character being a bit too shiny and brilliant), and Jay Allen’s Crimson Worlds series gets it right all the time.
The problem is that absent any intervening force, an object will continue to move in the same direction (vector) and velocity forever. Once your ship is going a gazillion miles per hour, and the ship you’re going against is going a gazillion miles per hour, you’re going to have a moment in time to engage with your weapons, assuming your weapons aren’t long range missiles, which have a different problem. These are slashing attacks. You fly by the other guy and shoot all your weapons at once. Then, you either hit the brakes (that is, fire engines in the opposite direction) and turn around, which may take a week, or you modify your vector to do a loop. The higher your velocity, the bigger the loop.
So you can do engagements slow and deal out damage, or you can go in fast and get out fast.
And then there’s ship shape. You don’t need aerodynamics in space. Just a good frame that holds everything together. Shape means nothing. You’re only limited in size by stuff like dock size, or magic transfer gate (call them wormholes if you want) size, or stuff like mass vs. acceleration and fuel and all that.
This isn’t even addressing the idea of fuel for your massive ship. I’ve seen get-your-HE3-from-gas-giants with cloud scoops which seems okay on the face of it but ignores the difficulties of gas giants and their deadly magnetosphere radiation, gravity, storms, and how do you float in something lighter than you? Hydrogen and Helium. Go ahead. Solve that one. I’ll wait over here.
Thought so. You don’t have an answer. Nobody else does, either.