That is an oxymoron. You are either orbiting or going "really fast" but you can not be doing both. (In the context in question single-digit miles per second is not "really fast", it's just the cover charge.) You can pour arbitrary amounts of energy into a kinetic kill projectile, and there is no known reasonable way of defending against such a thing except to not be where it hits.
Just as people worry about nuclear weapons and biological weapons, we get planet-killing kinetic projectiles rather earlier than we get anything else useful from space. In fact if we put our minds to it, and were willing to be patient, we could probably do it today. The same tech we're looking at to divert existing planet killing asteroids can just as easily be turned to tweaking one of their existing orbits towards us instead of away.
That is an oxymoron. You are either orbiting or going "really fast" but you can not be doing both. (In the context in question single-digit miles per second is not "really fast", it's just the cover charge.) You can pour arbitrary amounts of energy into a kinetic kill projectile, and there is no known reasonable way of defending against such a thing except to not be where it hits.
Just as people worry about nuclear weapons and biological weapons, we get planet-killing kinetic projectiles rather earlier than we get anything else useful from space. In fact if we put our minds to it, and were willing to be patient, we could probably do it today. The same tech we're looking at to divert existing planet killing asteroids can just as easily be turned to tweaking one of their existing orbits towards us instead of away.