The downside of hypersonic missiles is that they are travelling so fast, hitting a stationary object in the air will do significant damage - even raindrops can

The downside of hypersonic missiles is that they are travelling so fast, hitting a stationary object in the air will do significant damage - even raindrops can do damage. So if you detect the incoming hypersonic missile and just fill the sky in front of it with metallic particles, you're good. CSIS calls it "twenty-first century flak".