magic9mushroom
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It's about 40 metres per second for that example to create an orbit whose perigee brushes the Earth. And yes, that is going to hit the planet at fairly close to terminal velocity (of whatever remains after ablation), somewhere. "Somewhere" being operative; atmospheric nonuniformity is going to give you a rather embarrassing hit cone reminiscent of the balloon bombs when performing an entry at that kind of grazing angle. I'm suspecting that the delta-V minimum for vaguely-accurate fire is going to be similar to that needed to hit space targets.As I said, though, the minimum energy to drop an impactor from orbit is immensely lower than that needed to hit something in orbit from the ground.
You can't drop a 100-ton rod from orbit unless you can de-orbit it. If you simply release an object in orbit, it stays in orbit, because that's what "orbit" means. Also, firing something fast enough to reach spacecraft in orbit (as opposed to achieving orbit themselves) isn't actually as difficult as you make out. Modern high-powered rifles reach 1.2 km/s muzzle velocity, remember.1. Firing something that fast is either impossible or really, really hard and expensive. While you can release a rod from orbit that can be as big and as heavy as you want. Gravity works no matter the mass of the object you're using, but trying to use another method to achieve the same amount of kinetic energy is going to be much harder (You can drop a 100 ton rod from orbit, but I don't think that we have any kind of cannon that can launch this kind of mass at the same speed).
2. Another advantage of striking from orbit is that you can easily strike at any part of the world (well, a single satellite will only be able to target some parts without having to relocate, but my point stands), an installation on the ground doesn't have that kind of mobility.
Also, the reciprocal of your #2 applies. You can shoot at a lot of places on the ground, but a lot of places on the ground can shoot at you too.