If only there were some way to lift a bunch of cheap kill vehicles into orbit that could be used for both detection and interdiction of incoming rocks with little notice...

(I know, it's not exactly that simple. But still.... ;) )

Let me do that and I will ready it to drop on your head whenever I want and then I'll hold that threat over you constantly.

I mean, I already live under the constant threat of nuclear armageddon from "conventional" ICBMs. So if you're going to suspend kill vehicles over my head that can also save the world from an asteroid... There's gonna be a lot of international politics to work out, but I'm not gonna be the one stopping you. ;)

I've got to be honest. I'm not going to bother with the asteroid part. I'm just going to tell you that what they're for. After all, you can't check.

There's lots of things I can't check. I delegate.

I would assume the "working out the international politics" part includes "a multinational effort among nuclear-armed countries that spot-checks the kill vehicles can actually do the thing claimed to do."

Any rock you can tackle on little notice is a rock that wouldn't have done much anyways. Anything with the size to have significant impact on Earth is gonna require years of lead time to tackle; you'd need to start changing its orbit well in advance.

No disagreement that less delta-V is needed for big rocks far out in their orbit, so early detection is cheaper.

... but in terms of whether stopping is possible, I believe that depends on the amount of kinetic energy you can apply to it. I'd have to sit down and do some real math to determine the practical stopping power of a kill fleet, but to give a thumbnail comparison: each Starlink sat is about 500 lbs, which is about the weight of one B57 nuclear bomb, with a yield of 5-20kt. There are about 660 Starlinks in orbit now... A constellation of kill vehicles of the same size could have the ability to deliver an upper-bound of 13.2 megatons of explosive energy. According to one source (https://www.space.com/39971-asteroid-destruction-nuclear-bom...), 3 megatons should be sufficient (though the parameters for individual delivery of smaller payloads vs. one big nuke would of course be different).

This is, of course, all a terrible idea; nobody's gonna be comfortable with a mega-constellation of nukes in orbit.

I'm pretty skeptical of this experimental approach scaling up:

> The scientists found that a 500-joule-per-gram laser blast was required to break apart a model space rock 0.3 inches to 0.4 inches in diameter (8 to 10 millimeters), if that blast were directed at a premade cavity in the "asteroid." Without the cavity, the necessary energy was about 650 joules per gram.

Really cheap heavy-lift launch capability would be a big help. Developing that capability is exactly what Starlink is intended to fund.