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Missile defense is NP-complete

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Re: Missile defense is NP-complete

#71

Post by wavefunction »

DivingForGold wrote: post #61
jsw97 wrote: post #8

The author explains that this problem is actually adversarial, in the sense that the attacker gets to observe defenses and allocate warheads and decoys accordingly. Thinking of our current circumstances, this suggests another cost of war: our offensive capabilities, as well as our defensive capabilities become more observable. Our adversaries are studying our strengths and weaknesses in Iran, and they will have a muc…

Did I miss this ? Missing from the discussion is that Iran's cluster munitions in each single missle have absolutely overwhelmed Israels defense and would likely do the same to US military as well. Also to consider, Iran's $20,000 drones versus our $1 million dollar interceptors.

You could counter multipayload missiles by hitting the missile earlier in its trajectory before the payloads deploy, that was the plan for MIRV nukes but it requires usually forward interceptors or perhaps energy weapons we don't yet have.

Re: Missile defense is NP-complete

#73

Post by Noumenon72 »

jmyeet wrote: post #45

Pardon the pun but this is an arms race and the defenders are going to lose. There are broadly five classes of missiles (one isn't a missile per se): 1. Ballistic. These are traditional rockets, basically. While rockets are designed to reach orbit or leave the Earth, a ballistic missile basically goes straight up and comes down. The higher it goes, the further away it can get because of the ballistic trajectory and t…

[flagged]

Re: Missile defense is NP-complete

#74

Post by dlisboa »

SegfaultSeagull wrote: post #20
jsw97 wrote: post #8

The author explains that this problem is actually adversarial, in the sense that the attacker gets to observe defenses and allocate warheads and decoys accordingly. Thinking of our current circumstances, this suggests another cost of war: our offensive capabilities, as well as our defensive capabilities become more observable. Our adversaries are studying our strengths and weaknesses in Iran, and they will have a muc…

Or perhaps they will learn they are outmatched, lack the resources and technological capabilities to compete, and deterrence will have been established.

Very few countries lack the technological capabilities to produce these kinds of drones.

What most countries don't have is, for lack of a better term, the resolve Iran has shown. Venezuela could have built drones and resisted just the same, but it's internally divided enough that it was possible to strike a deal with an inside faction and have a coup from within.

Re: Missile defense is NP-complete

#75

Post by nerfbatplz »

SegfaultSeagull wrote: post #20
jsw97 wrote: post #8

The author explains that this problem is actually adversarial, in the sense that the attacker gets to observe defenses and allocate warheads and decoys accordingly. Thinking of our current circumstances, this suggests another cost of war: our offensive capabilities, as well as our defensive capabilities become more observable. Our adversaries are studying our strengths and weaknesses in Iran, and they will have a muc…

Or perhaps they will learn they are outmatched, lack the resources and technological capabilities to compete, and deterrence will have been established.

The Iranians just hit an F35 with a proverbial box of scraps they put together in a cave. The Chinese military must have experienced collective euphoria when they saw that.

Re: Missile defense is NP-complete

#76

Post by jmyeet »

jsw97 wrote: post #8

The author explains that this problem is actually adversarial, in the sense that the attacker gets to observe defenses and allocate warheads and decoys accordingly. Thinking of our current circumstances, this suggests another cost of war: our offensive capabilities, as well as our defensive capabilities become more observable. Our adversaries are studying our strengths and weaknesses in Iran, and they will have a muc…

In strategic circles, this was a common thought in the 12 day war: Iran was essentially mapping and testing defenses.

As evidence of this, the US was forced to hastily move THAAD ground station radar from South Korea because Iran destroyed a bunch of them in the Gulf [1][2]. Bear in mind there aren't many of these and they cost half a billion dollars each.

Further evidence of this is how quickly it happened. Iran most likely had detailed contingencies and battle plans for this kind of event.

As an aside, this is what militaries do. They plan for things. So whenever you see some conspiracy about how government X reacted to situation Y quickly and thus had foreknowledge, you can ignore it. Military planners are paid to make up fictional situations and figure out how to respond. That's what they do.

Weapons are the ultimate export. You use them and blow them up and the customer has to come back and buy more.

[1]: https://www.theguardian.com/world/2026/mar/11/redeployment-u...

[2]: https://www.cnn.com/2026/03/05/middleeast/radar-bases-us-mis...

Re: Missile defense is NP-complete

#77

Post by icegreentea2 »

dlisboa wrote: post #55
myrmidon wrote: post #29

Earlier quoted context omitted.

This is absolutely true, but there is a strong counterpoint: You also learn the limits of your own systems and how to operate them most effectively yourself (and better than adversaries can, too). Just to pick a recent example: Russian air defense in the early stages of the Ukraine war was dismal (more specifically: defense against big, slow drones like Bayraktar), despite having sufficient AA capability "on paper"--…

There is an assumption here that the value in improving defenses is the same as improving offensive weapons. That is not the case in the assymetry that drones provide and Russia is the first example. Russia has not been able to improve AA capabilities to the point where it's "safe", for any definition of the word, neither has Israel. Israel and Gulf states often tout over 90% interception rate yet it's really at the…

Air defenses do not need to be 100% effective to be... effective.

Russia cannot keep Ukraine from targeting their oil infrastructure, yet here Russia is, still fighting on. Ukraine cannot prevent Russia from targeting their energy infrastructure or apartment buildings, yet here they are, still fighting on.

If we're talking about strategic/civil air defense, then you must figure out what's tolerable to your population (and how to increase and maintain that tolerance), and then figure out all the means to reduce the incoming attacks to below that tolerance. That must include the full spectrum of offensive, counter offensive, defensive, and informational options.

Re: Missile defense is NP-complete

#78

Post by wat10000 »

bluGill wrote: post #28
owenmarshall wrote: post #16

Two more sobering axes to introduce: cost and manufacturing capability. Numbers are hard to find for obvious security reasons, but using the numbers most optimistic to the defender[0] suggests an adversary using a Fatah type hypersonic is spending 1/3rd the cost of an Arrow interceptor, and is launching missiles that are produced at a much faster rate. Interception is deeply asymmetric in favor of the attacker. [0] h…

There are too many potential attackers though, and not everyone is sane. So you don't really get a choice about it. The cost of the interceptors needs to be considered in relation to the cost of what it protects. If the interceptor means an attacker doesn't kill my kids then it was worth the cost. If the interceptor keeps a multi-million dollar building around then interceptor at a million dollars is still cheap, eve…

Unfortunately, necessity doesn’t imply possibility. It could simultaneously be true that you must build interceptors to protect yourself, and that you can’t build enough.

It only makes sense to consider the cost of what’s protected if it’s actually protected. If your million-dollar interceptor protects a multi-million-dollar building from a $100 missile, and then that building is hit by a second $100 missile, was it worth it?

That’s the math that has prevented missile defenses from being deployed on a large scale despite being technologically possible for well over half a century now, and despite the fact that a single interceptor might be saving an entire city from a nuclear warhead.

An interceptor costs at least as much as what it intercepts. Take into account miss rates and the cost of defense is a multiple of the cost of offense. Add in the fact that the attacker can concentrate an attack but the defender has to defend everywhere, and multiple warheads on a single missile, and the cost of defense multiplies further.

If defense costs 10x more than offense (a conservative estimate, I’d say) then that means you need to dedicate 10x of your economic capacity to it than your attacker does. If your attacker dedicates more than 10% of what you can put into defense, you lose. Defense can work, but it needs to be against a far weaker enemy. Thats why the most prominent example is Israel defending against neighboring non-state actors. Israel is wealthy enough, and the groups shooting at them are poor enough, that the math works out in the defender’s favor. Iran is a rather different story. And of course defending the US against the likes of Russia and China is a fever dream.

Re: Missile defense is NP-complete

#79

Post by maratc »

DivingForGold wrote: post #61
jsw97 wrote: post #8

The author explains that this problem is actually adversarial, in the sense that the attacker gets to observe defenses and allocate warheads and decoys accordingly. Thinking of our current circumstances, this suggests another cost of war: our offensive capabilities, as well as our defensive capabilities become more observable. Our adversaries are studying our strengths and weaknesses in Iran, and they will have a muc…

Did I miss this ? Missing from the discussion is that Iran's cluster munitions in each single missle have absolutely overwhelmed Israels defense and would likely do the same to US military as well. Also to consider, Iran's $20,000 drones versus our $1 million dollar interceptors.

Cluster munitions are great against infantry in open field; less so against population centres equipped with advance warning systems. As it stands, they fail to even cause the damage worth offsetting by firing interceptors. The damage these inflict on Israel is not unsustainable, and they don't do much to create deterrence.

Given a choice of conventional 500-800 kg warhead or cluster munitions warhead, I think that the nations in the current conflict would prefer being on the receiving end of cluster munitions (as a less bad option) every time.

Re: Missile defense is NP-complete

#80

Post by falcor84 »

gzread wrote: post #48
marcosdumay wrote: post #40

Earlier quoted context omitted.

You seem to be implying that there is a long history of countries starting wars against the USA?

More like the USA starting wars against countries, and those countries not immediately surrendering, to which the USA is shocked.

I think that there's a more general issue here with the US and the West in general having a mindset built up on playing Risk and Civ, which considers the foreign country as a whole as their opponent, whereas in practice, the adversaries are a multitude of individuals, for almost none of whom a surrender is the rational choice, especially (as sibling comments pointed out) when part of their reasoning and authority is based on a divine mandate.
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