I've read through the older threads and I can see how a lot of the principles still apply in my low-speed SF world -- you can get to a thousand km/s, but you're going to need planets handy for slingshots and braking maneuvers. We're not interstellar, needless to say. We can still throw rocks, though, just at lower speeds.
Anybody see any major problems if I try to downshift the tactics you all have been discussing?
Yep. I agree with most of your points here. Except the one about KKVs. Depending on their exact specifications, they can be defended against (the big ones). A big KKV is quite visible, and all you need to defend against it is to hit it head on with another one. If there is time enough to aim and accelerate an intercepting KKV after detection, singular big planet killers aren't as dangerous as someone getting close and firing a large number of smaller ones.
Originally Posted by Dommo
Another exception i can think of would be art and other luxury goods (with certified exoplanet origins). With luxury goods, people don't pay for the object, they pay for the exclusivity, and while it might be cheaper to replicate an identical painting (or locally gene-engineer an exotic creature) i'm quite certain people would be willing to pay interstellar freight costs just to get the "real" thing. Like they do now with diamonds.
Originally Posted by Dommo
Although you'd probably need some other reason for starships to exist at all (maybe passenger transport) so the goods would be transported as a secondary freight, otherwise i still doubt economic viability.
No immediately, but keep in mind that changing the parameters of one thing (i.e. speed of ships and kinetic weapons) will change their relation. I.e. if kinetic weapons are too slow, you'd use nuclear warheads (or antimatter) instead of simple impactors.
Originally Posted by carlaviii
Depending on the available missile technology a laser might be the longest range weapon of a spaceship, or just point defence. Etc.
Actually, I think I modeled this correctly in my game a few years back - consider that, in my game Fire On The Suns (FOTS), a freighter of any decent size is going to run you on the order of a couple dozen RPs (resource points). Any decent planet is going to have an average value output of around 200 RPs per turn. A typical, well-trained and equipped military unit is going to cost another dozen or more RPs and require at least one transport freighter to carry it to the target. In order to have enough force to successfully insure a successful invasion, you need at least a dozen or more ground units (and accompanying support) in the least case (many more if you're trying to invade a home world).
Finally, the world may not just surrender even if your ground units wipe out all organized resistance (unlikely as surviving defenders which successfully disengage immediately "go bush" and become cadre forces which can organize against the invading force). You could end up in a years-long effort to garrison and control an enemy planet which drains RPs out of your overall imperial budget for years.
Many players in FOTS have just found it cheaper and easier to "nuke the site from orbit" and then move on (habitable worlds tend to be plentiful in the game depending on your species environmental requirements).
Sounds pretty good to me. You'd have a sliding scale of increasing resource costs moving from just nuking the whole planet to strategic kinetic bombardment to an invasion with ground forces.
The more intact you want to take the planet, the more expensive it will be (and never actually profitable).
A secondary factor would also be the uniqueness of a given planet. Suppose that it had unique lifeforms that had no known likeness in the known universe, or suppose it was a planet that had a really long and extensive cultural history, in those cases I might see there being a reason to not outright nuke the world. (It might be analogous to destroying a national park, or bombing the great wall).
However, Lhun is right on the economics. There is no real return on investment in trying to take most planets intact. There's the rare case of something like a low gravity moon/planet that is used for an industrial base. Something like that might be worth not outright destroying since it could vastly speed up the construction of your own infrastructure, but for a lot of situations given the resource intensity that interstellar travel is, you'd be best off just wiping the slate clean.
One of the things I did in FOTS was index a species environmental requirements. Since planets are also indexed based on solar position and solar type this tends to mean there are quite a lot of gas giants and frozen rocks. Depending on the technology available any world can be useful, but those frozen rocks can be very expensive to colonize. Since it's a game this makes inhabitable planets cheaper, but not inexpensive to colonize depending onnyour environmental requirements. To a race that likes frozen rocks half the worlds in a typical system might look like home though only a few are going to be valuable enough to really make an all out effort to colonize to their fullest potential.