>>11832698>If we're using antimatter weaponsIf people on planets have antimatter you can bet your ass people in space have it too, and in greater quantity since how much you can make is directly tied to how much energy you are working with as a civilization.
That being said, it doesn't matter what weapons tech you consider, a 99% c projectile isn't going to stop a billion tons of iron, while it's certainly gonna cost a lot more. For one thing really fast projectiles don't even act like fluids when they collide with solid objects, they actually act more like radiation, because they move too fast for any interaction other than direct nuclei-on-nuclei scattering to have significant effect. For another, their ability to transfer momentum is garbage, they mostly just dump heat into whatever they hit, which means in the most effective case scenario your 99% c projectile is going to turn that billion ton slug of iron into several million slugs of iron massing around a ton each, and that's going to cause just as much damage if not more when it strikes the planet.
I think you're missing something obvious, which is the fact that any dyson-swarm like civilization warring with a civilization on a planet is not only going to have an immense population and resources AND high ground advantage, they're also going to have an immense technological advantage, because MOST of the people will be living in that swarm, which means MOST of the innovations will be made there, and of course since they will be living in by far the harsher environment they will have MOST of the motivation to actually develop and improve pretty much any technology you can imagine.
Finally, dyson swarm crowd-sourced laser array BTFOs any planet. A single gigawatt laser firing from one in a thousand habitats blasts the surface of any planet with millions of terawatts of light and heat, and requires basically no effort.
