Railguns that could accelerate and dump pieces of metal anywhere in world from high orbit. Militaries would drool over the idea of controlled falling meteors for strategic bombing
Ramen. We really need to get into primary schools subjects such as meditation, ethics, moral and "care for humanity" instead of having people get educated to go into military and "drool over weapons to kill more effectively".
Well, that would work if people/government don't break treaties of all kind on daily basis. Solution must be in roots not a patch on top of pile (of bullshit we created over time)
a) it's kind of hard to hide a launch system where the fueled-up booster stack on the pad weighs two and a half times as much as a Saturn V and the launch is visible with the naked eye from a hundred miles away.
b) There is a reason we don't use Trident D-5 SLBMs (or the Russian equivalent) for precision conventional explosive strikes on targets which otherwise require long range bombers with intricate in-flight refuelling arrangements to hit: something about not scaring the other folks with strategic nukes into thinking we've initiated a first strike and hitting the big red end of the world button.
TLDR: even the big guys don't mess with space-based or sub-orbital weaponry. The risk of a misunderstanding is non-trivial and the perceived costs are far too high.
Are we trusting the militaries of the world won't make gray goo or 100% lethal bioweapons because those would kill everyone, or will that just happen because it can, no point in even talking about it?
Of course we can and should talk about it. It's important to at least theorize what others might realize in order to be prepared. That's all I wanted to add.
"we are so dominant in space I pity the adversary who would come against us" Lieutenant General Franklyn Blaisdell, Deputy Chief of Staff of the Air Force for Air and Space Operations
A railgun still obeys Newton's third law. The gun would need a mass much larger than the bullet, or it's the gun that will fly away from the earth (so it won't be reusable for future bullets). This makes putting the gun into orbit too costly, or else the bullets too small.
It's probably most cost efficient to de-orbit the entire satellite, and include a rocket that fires upwards when it reaches a certain low height, to make it exceed its natural terminal velocity.
Most naturally dangerous asteroids (near passes) are being publicly tracked, so people would notice you attaching a rocket and nudging it off course. Bringing a whole new asteroid from the belt is feasible (or will be soon), but it takes a lot of time, so you need to do it in advance. But if you put an asteroid in orbit, astronomers (at least) are going to notice and ask questions, which they wouldn't do for a satellite with a cover story.
I wonder what one might do with a few square kilometers worth of foil shaped like a concave mirror and a lens or two. Perhaps the atmosphere is too efficient at absorbing light, but an equivalent of frying ants with a magnifying glass sounds pretty scary to me.
I think we would all be better off if we didn't develop even more effective ways of killing each other...