A bullet travels at a relative speed of about 250 to 1250m/s. A ~10g projectile moving that fast has an energy of 600-16000 joules.

Everything in low Earth orbit is moving at 7600m/s. A ~10g projectile moving that fast has an energy of 580,000 joules. Getting hit by something moving that fast is roughly equivalent to getting hit by a whole ammo case of bullets at the same speed. There is no armor that can protect you; Even the most solid objects behave like fluids at this relative velocity, potentially incurring more damage from the explosion / shockwave splatter than a thinner object that would allow you to overpenetrate.

A cardboard box of ball bearings with a handgrenade in it in LEO being triggered could wipe out nearly everything up there, and depending on the exact altitude it could effectively mine LEO and prevent humanity from using it for a long time, with a selectable duration between months or millennia depending on altitude.

"Space warfare" in LEO is a matter of everybody walking around with a personal nuclear weapon strapped to their back that can be activated on a hair trigger. We may well wipe everything out by accident, if it gets too crowded or because somebody stubbed their toe. Regardless, there is no selectivity, and any actor with space launch capability can blot out our access at will in ways that will outlive them.

Basically our only hope of continued use is things that persuade us to refrain from attempting to incorporate space into a theatre of war. That box of ball bearings should have higher stakes on the escalation ladder than a tactical nuclear strike. And it probably shouldn't be there in the first place.

> Everything in low Earth orbit is moving at 7600m/s. A ~10g projectile moving that fast has an energy of 580,000 joules.

What matters is the relative velocity of the projectile towards the target. I practice it will be smaller or larger (if the bullet is incoming). But steering an incoming projectile is way harder.