The earlier interceptors were for ballistic missiles. They are traveling at hypersonic speeds but have high trajectories (so radar can see them earlier) and can't maneuver for significant parts of their flight (so they are easier to track and target).

FWIW they were cancelled because they didn't have a particularly good kill ratio and proliferation and MIRV meant you'd need a ton of them to prevent an attack landing (and doing so would involve a significant number of nuclear blasts pretty close to the targets anyway). Deterrence was more credible.

The weapon you linked to is an anti ballistic missile. The difficulty is not purely in how fast the target is going, but how much it maneuvers, the duration at which it can sustain those speeds, and the altitudes at which it operates. The article addresses this early on.

Weren’t those anti ballistic missile missiles all nuclear armed themselves?

And doesn’t the parent article to the Sprint article make it clear that they we didn’t deploy them because fall out shelters combined with building more nukes was deemed more cost effective at saving lives.

Spirit is a nuke. Not really something we want to be detonating in the atmosphere.

I think you are missing something;

The ABM systems we built in the early cold war worked by having nuclear payloads. We could absolutely not hit an incoming ICBM with the tech at the time, so we just slapped a nuke on it and hoped we could get within 1km at detonation.

Importantly, it was a completely dead end. They had no response to MIRVs and could not be built in sufficient numbers to deal with any actual launch. We threw them out because they were in fact useless.

Generally, we have moved away from Nuclear ABM systems because detonating a hundred warheads above a city is very unlikely to work out well.

Intercepting a cold war era ICBM turned out to be feasible with newer technology, and we currently have $2 billion missiles that can feasibly intercept ICBMs (at low quantity).

>No maneuvering boost-glide hypersonic vehicle has ever been fired in combat against a defended target

Nobody has fired one of those against a target because almost nobody has a functioning maneuvering hypersonic vehicle. Basically just China I think.

I would expect "real" hypersonic weapons like that are basically uncounterable. The physics just gets too obnoxious. Interceptors will struggle to get better than a coin flip, and they will be too expensive to use on anything else so they won't be general purpose, so equipping them will be full of tradeoffs.

That's the entire point of hypersonic weapons. $3 billion dollars to make that high value target go away, with extremely high probability. They replace 50 bombers launching still quite expensive anti-ship weapons at scale, which is the strategy it replaces.

This of course has rather negative implications for the concept of force projection in future wars. Which is why China made a hypersonic weapon.

Wikipedia notes both the Spartan and Sprint missiles as having nuclear warheads. That was reasonable-ish, since Wikipedia also notes them being cold war-era anti-ICBM weapons. Less bad to have your own interceptor nukes going off "near" your city than to have enemy nukes scoring direct hit on it.

In contrast, modern hypersonic weapons have plenty of use cases where they'd be fitted with conventional warheads, and used against targets like US Navy ships.

There is plenty that could go wrong if USN ships mounted nuclear interceptor missiles, ready to launch on a moment's notice...