Ugh, this is why the term "hypersonics" is misleading. Ballistic missiles ARE hypersonic systems, they travel faster than Mach 5. And that's not just me being pedantic. The Kinzhal missile is regularly touted as a "hypersonic" including in this thread. But the Kinzhal is just a ballistic missile, it's actually just an air-launched version of the Iskander.

Which interceptor would be used against a target largely comes down to whether the intercept is endo- or exo-atmospheric. The SM3 is an exo-atmospheric intercepter: it's designed to collide with the target in the vacuum of space. The SM6 is an endo-atmospheric interceptor. SM3 can be used against ballistic missiles, including both traditional re-entry vehicles and hypersonic glide vehicles, before they enter the atmosphere. The SM6 can be used against anything in the atmosphere: including ballistic missiles in the terminal descent phase.

> Again, the versions of Patriot handed over to Ukraine are not the latest versions, so their performance might not be illustrative. And we don't know the strategy used by Ukraine; they might feel like bigger salvos are worth bringing down hypersonics.

So why even bring it up? Kinzhal is just a slightly faster ballistic missile, the fact that it can be intercepted in ideal conditions is not new. What matters is the interception probability and the engagement envelope, so what's the point to bring it up and then immediately discredit whatever useful inference can be made while still jumping to a conclusion?

SM6 is just an upgraded SM2, it's intended for BMD just the same - it's just better at it, but not better enough for the Red Sea situation.