>Relativistic weapons
I'm not convinced of the overwhelming power of RKKVs against major space-faring civilizations. Velocity works both ways; if you're travelling fast enough to break a planet, then hitting a random pebble will completely vaporize you. Interception actually gets easier in some ways as speed approaches c; less time to react, but destruction of the projectile becomes easier.
Besides, either you're assuming that objects retain their velocity coming out of FTL, or else you'll have to make a very interceptable run-up to ramming speed, which would require your projectile have its own escorting fleet, and if you've already got a fleet in-system why tie it down with an escort mission instead of just using nukes?
>Another fun scenario is unless you have ludicrously large fleets chances are good your ships are spread so thin across your territory as to be useless for defence
Which means any combat will likely turn into a planet-burning race, unless ground defenses are generally equal or superior to orbital attackers and will take long enough to reduce that reinforcements will arrive. Which would still technically be a planet-burning race, just a slow and inconclusive one.
Space Ships Tabletop Games and Pics General
I will user, if only to steal idea from it.
In the setting I'm working half assed, only capital ships or tenders like Jump ships from Mechwarrior have FTL capabilities without going in a space gate. It's a expensive way (I'm using antimatter as the rare fuel because I want to limit the space magic as much as I can, unless the elder races are involved) and it has a limited weight limit and distance, but to go to ungated systems or atack heavily defended systems is pretty handy.
Stargates are conected to the system stars and are constructed be an elder race than change incredible large quantities of rare metals in echange of incredible advanced tech, and space gates are one of the most demanded item because is comparatively cheap and useful (in part are subsidized be them, to allow the younger races to trade more easily). Jump systems can't be used near strong gravitational points like planets or stars, so a FTL atack tend to be slow enough for at least a report of the imminent atack. It isn't instantaneos too, weeks of space voyage in the wrap/space gate dimension bubble(working in the name), than can be intercepted. I have to really work on it I know.
>RKKV
II see what you're saying in terms of fleet resources. It could be cute to redirect and speed up a comet to intercept a colony to force the enemy to move some ships to deal with it, leaving a weakness at wherever those ships were before. A bit far fetched, I know.
>ground campaigns
I think space superiority would settle it pretty quickly. Sure you'll have deal with guerrillas and that's fun stuff storywise, but the assets you're invading the planet for in the first place can be seized and held if you have ships in orbit no problem. Unless your objective was the hearts of the people.
What's the most interesting balance of power dynamic? Space UN makes me groan, but I like the out-numbered and out-tech'd civilisation struggling to win against a superior enemy.
I like the power dynamics of a galactic empire in the process of collapse, mostly because it's the best environment for PCs to murderhobo through. The last remnants of central authority mostly shooting at each other, suddenly-isolated garrisons fending off rioters nightly, corporations scrambling to become nations out of sheer self-defense in the power vacuum as every minor power starts carving out their own little empires, pirates joining forces in vast fleets to pillage entire worlds. For sheer density of stuff happening it's tough to beat.
Galactic Cold War could also serve as a good setting, with spies, space privateers, two superpowers fighting a proxy war for resources on a planet, bounty hunters, etc, etc.
Yeah, that's my second-favorite. And generating plots is as easy as opening a history book!
Low level space western/pirate in an dying empire is the best, lawlness, plunder and oportunities for roleplaying than nearly write themselves.
What are good ways to rid off heat in space? After generating loads of heat between power generators than convert terawatts of energy, weapons than use GJ and all that a simple radiator is enough?
Mass Effect mentions starships using heatsinks in extended battles, and releasing water droplets from the front to cool the hull.
Other than that, you get the handwavium of heat being recycled into more power somehow, or getting dumped into hyperspace.
I prefer a sorta-kinda Alcubierre drive for space settings I write.
Sorta-kinda because it has a limitation I'm not sure the real thing has: It's ridiculously sensitive to tidal forces. If the force of gravity differs too much from one end of the Alcubierre metric to the other- on the order of micronewtons per square meter- the metric goes wonky in weird, unpredictable, and usually catastrophic ways.
The smaller the Alcubierre metric is, the closer it can safely approach astronomical objects in FTL. Larger spacecraft have to drop out farther away and come in on reaction drives
It creates a nice tension between how small you make the Alcubierre spacecraft and how big it has to be to carry what it needs to complete its mission. This results in a wide range of sizes and capabilities for Alcubierre ships.
Small enough ships, around 20-30 meters can Alcubierre deep enough into a stellar system that they can shuttle between some of the planets. In military operations, these can sally from carriers from across the stellar system, like some sort of space fighter.
It also allows FTL interdiction, by using Alcubierre technology to generate disruptive gravity perbutations over a wide area. Along with the ridiculous small sizes required this prevents uninterceptable IPBMs-they can be reliably intercepted and destroyed close to their target, and even if they hit they have to be really, really tiny, with not a lot of volume for mass or warhead.