Pretty sure that at some point in the next 2 weeks all hell is going to break loose in Ukraine. A new front is going to be opened up and an absolutely massive push is going to happen with the fresh troops deployed. It's coming.

Missile Defence and You: A short primer on how to stop your things from exploding

I saw someone posted here about the US maybe providing some anti-missile defence to Ukraine, so I thought I'd pour a few drinks and offer some even more layman thoughts.

In this conversation, missile defence specifically refers to the task of defending against strategic missiles. Active defence against guided AT missiles is an entirely different role with its own concerns.

Up front, I think the effectiveness of anti-missile systems has been overstated. Especially in the case of systems being sold, but even for private systems, there is always incentive to oversell the effectiveness. The Iron Dome, for instance, has mostly been tried against relatively low tech unguided rockets. The Patriot missile system has a high success rate against Iraqi scuds (though disputed). These examples do not give a clear picture of how effective such systems would be against modern strategic missiles (either cruise or ballistic).

There is also the CIWS, which in popular culture has a mythical ability to shoot down missiles. This has barely even been tested in real world situations, let alone against modern missiles. There is a ground deployable variant, which I'm sure is a bundle of fun.

Hypothetically, these are the sorts of the systems that would be sent to Ukraine. Even if Patriot missiles had a 100% kill rate per missile, to send enough missiles to counter the Russian cruise missile onslaught would severely deplete the US of Patriot missiles. Obviously, they don't, and it's also doctrine to fire two or more patriots per incoming target. Each missile costs around $6M, courtesy of Raytheon. This is also ignoring the fact that air defence systems are massive fire magnets due to their RADAR systems, which could take down multiple Patriot systems without actually any patriots being fired or destroyed.

Note on doctrine of firing more than one missile: If a single missile has a 90% chance of taking out a target, two missiles would have a 99% chance of taking out a target. I think these are the numbers that the Iron Dome runs with, give or take. Sometimes the reason the first missile fails will also cause the the second missile to fail, so the logic doesn't always pan out, but there it is.

Missiles are easiest to shoot down, usually, as they're approaching a target. You can't have a "fence" of AA systems even if the range bubbles line up. Or, you can, but their interception rate will be substantially lower if not non-existent. This is especially true for shorter ranged systems like Avengers and CIWS, assuming they're effective to begin with. This means that if one wanted to protect all the critical infrastructure in Ukraine, you would need a huge amount of defence, what seems to me far more than the war materials already sent to Ukraine. While man-portable equipment is arriving in droves, heavier equipment is being sent in drips and drops.

Many modern cruise missiles have a few tricks to avoid being shot down. The Kalibr has both a system that allows it to jink to evade incoming fire, as well as a high speed super-sonic mode that activates as its closing in. I would assume that most modern and even previous-generation cruise missiles at least have the jink capability, which dramatically reduces the effectiveness of all missile defence and drops the CIWS's effectiveness to zero.

I did see someone mention jamming, which is less trivial than it sounds. It would effectively amount to an entire other missile alongside a cruise missile, which may as well be another cruise missile. Perhaps the cheapest way of overcoming missile defence systems is to send missiles in waves. This also means that if the missile defence system fails, you also have more ordnance heading to target.

I think, also, the US is a little cagey about selling air defence systems to "unreliable" allies. Ukraine has had a problem with a lot of weapons not making it to the front, something I'm sure we won't see bite anyone in the ass later. US military power is, in the modern day, built off air supremacy, and losing control of their strategic air defence assets would not do. Furthermore, in any potential conflict, US military equipment would be facing off, which doesn't do well for arms sales. The success rate of any system in the most televised active combat zone in history would also be hard to hide.