[CodeWriter23]

The Patriot Anti-Missile system had plenty of successes and a few failures broadcast on live TV during the first Gulf War.

But I think the idea is to only use them when the launched missile is on a trajectory to hit a target you want to defend. First, it costs money. Second, each time a defensive missile is deployed, there is inherently some information leakage about the defensive capability. So if you're going to make such a disclosure, you want it to count.

[LyndsySimon]

Patriots in the Gulf War were pretty good at shooting down incoming Scud missiles - but Scuds are fairly slow short-range missiles, with a range of ~200-700km depending on the version.

This was probably a Hwasong-12, with a range of ~5,000km. It would be a much more difficult target to hit, especially at maximum altitude or on terminal approach (where it would be traveling very fast indeed).

Patriots have gotten much better since the first Gulf War and we have other systems designed to shoot down ballistic missiles, but it's still a very hard problem that we've not completely solved. It seems likely that the reason we've not shot down a North Korean test missile is that there is a high enough possibility of failure that it wouldn't be worth the risk.

[CodeWriter23]

I'm sure there is great optimization possible from 80's tech, which out of computational necessity, communicated by satellite to mainframes at NORAD. And if you think about it, a defensive missile doesn't have to outrun an offensive one. It just needs to be in the right place at the right time. It doesn't have to have pinpoint accuracy either; errors can be corrected by sizing and/or clustering the defensive payload.