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Missile defense is NP-complete

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Re: Missile defense is NP-complete

#181

Post by OrangePilled »

hedora wrote: post #157
OrangePilled wrote: post #130

Earlier quoted context omitted.

Bearing in mind the three constraints quoted, which of these do you think a country's deployed directed-energy weapons (e.g., US, Israel, Russia) would be useful against: https://missilethreat.csis.org/country/iran/

You don't really have to guess. None of those countries are using directed energy weapons, and they're all repeatedly getting hit by Iranian technology (so they have an incentive to test whatever they have).

> None of those countries are using directed energy weapons

The USS Preble is equipped with HELIOS and is in Iran. [0] The US has also used "dazzlers" there too (as mentioned in the linked X thread). [1]

Israel's Iron Beam was used against Hezbollah's drones (Iranian tech), with apparently limited return for it, this could explain why it won't be seeing action in Iran. [3][4]

The only alleged case of Russia using DEWs was in August 2025. [5] Admittedly, it was a reach for me to even name them.

As cost-effective (and cool-sounding) as DEWs are meant to be, there's a reason the US and Gulf states are beckoning Ukraine for help. At the same time, the Pentagon want's to ramp up development with 3 years and the US military at large seems to be bullish on lasers...[6]

[0]: https://xcancel.com/sebastienroblin/status/20361510681621877...

[1]: https://www.armyrecognition.com/news/navy-news/2026/u-s-navy...

[3]: https://www.jpost.com/defense-and-tech/article-889677

[4]: https://www.jpost.com/defense-and-tech/article-889701

[5]: https://t.me/milinfolive/154597?single/

[6]: https://www.defensenews.com/industry/techwatch/2026/03/18/th...

Re: Missile defense is NP-complete

#182

Post by pjc50 »

elfly wrote: post #176
ceejayoz wrote: post #99

Earlier quoted context omitted.

Except this looks likely to exhaust the US/Israel alliance, if it continues long, leaving China in the "US in/after WWII" spot in the analogy.

USA won't injure or kill 1 in 25 of young adults in the Iran war, unless somehow Iran does have a nuke and wants to use it, come on.

Quite possibly would end up killing or injuring that many Iranians, though.

Gaza is up to 10% of the population killed or injured in the Oct 7 reprisals: https://costsofwar.watson.brown.edu/paper/HumanTollGaza

Re: Missile defense is NP-complete

#183

Post by pjc50 »

teleforce wrote: post #144
lejalv wrote: post #53

Earlier quoted context omitted.

Stakes for whom? >100 kids got murdered the first day of this "low stakes" war

Imagine the NATO reaction if on the very first day of Russo-Ukrainian war offensive is by Russia performing missiles bombing murdering 100 kids studying in Ukraine primary school. Trump candid reaction to the Iranian school incident when asked by reporter was "I can live with that".

There were significant civilian casualties right from the start of the war in Ukraine, and several massacred villages.

Russian air defense shot down a civilian airliner mostly full of Dutch nationals and the response was just condemnation and tweaking the sanctions a bit.

Re: Missile defense is NP-complete

#184

Post by maratc »

dlisboa wrote: post #153
pc86 wrote: post #132

Earlier quoted context omitted.

What Iranian drone did a trillion dollars in damages? I'm not saying the general thrust of your argument is wrong, quite the opposite. But that's a big number for one drone.

A trillion seems large but it's not that absurd. The drone that shut down 17% of Qatar's LNG capacity is said to have caused 20 billion USD worth of annual lost revenue. They said it'll take up to 5 years to rebuild so that could be 100 billion USD in lost revenue, plus whatever it costs to do the rebuild. A trillion dollars worth of damage seems possible if spread over some years for some countries in the Gulf where…

> that could be 100 billion USD in lost revenue

that could be 100 billion USD in deferred revenue, if we assume that LNG is not going anywhere from wherever it's sitting underground, and will be simply extracted and sold later

> plus whatever it costs to do the rebuild

That is the real cost, which I would assume is nowhere near billions

Re: Missile defense is NP-complete

#185

Post by [deleted] »

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…

[deleted]

Re: Missile defense is NP-complete

#186

Post by gpderetta »

O3marchnative wrote: post #164
consumer451 wrote: post #151

Earlier quoted context omitted.

Lasers are not "all weather" weapons as far as I am aware. Clouds, snow, fog, rain, and just humidity all degrade their performance greatly.

The recently announced "Golden Dome" project intends to get around this issue by putting a vast constellation of satellites into orbit. Each satellite would likely need a serious source of power in order to use its laser. Assuming that's just an engineering problem, then the issue becomes coverage. That is, depending on the adversary's capabilities, you'd need an absolutely massive constellation in orbit [0]. [0] htt…

The idea has been around for a while: https://en.wikipedia.org/wiki/Brilliant_Pebbles

> https://en.wikipedia.org/wiki/Golden_Dome_(missile_defense_s...

> President Donald Trump signed an executive order directing the United States Armed Forces to construct the [...] Golden Dome

Well, that's just taking the piss!

Re: Missile defense is NP-complete

#187

Post by icegreentea2 »

jcul wrote: post #114

Really interesting. Forgive my ignorance, but I thought Israel's "iron dome" offered a very effective defense. Is this just from short distance missiles from neighbouring countries? This article seems to indicate it's very difficult to achieve a high success rate against multiple missiles. Admittedly I probably need to read up on this more.

There are multiple tiers of missile (and ballistic missile defense).

Especially with ballistic missiles, the longer the range, the faster the inbound warhead will be in the terminal phase (roughly). So longer range ~= faster meaning more difficult to intercept.

"Iron Dome" is the name generally used to describe Israel's lowest tier set of defenses. Very roughly Iron Dome is designed to defend against stuff that you could plausibly fire from the back of a truck, and have a max range of around ~50km.

Very roughly, these were intended to take on something like GMLRS (realistically, massed volleys of unguided rockets) - these are rockets that one or two people could conceivably manhandle, and are traveling in the neighborhood of Mach 2-3. One of the key innovations of Iron Dome is its ability to quickly ascertain and design on which rockets were unlikely to strike valuable areas, and only engage the actually threatening ones.

The next tier up is David's Sling, and then Israel's wider set of high performance anti-ballistic missile systems. Returning the the range speed thing, we'd need something like a medium range ballistic missile to get from Iran to Israel. For something like the Shahab-3, that's like ~Mach 7 during re-entry.

If we step up to IRBMs (so something that China might use to strike at Guam), we're probably talking like Mach 10.

Re: Missile defense is NP-complete

#188

Post by O3marchnative »

hedora wrote: post #159
koakuma-chan wrote: post #143

Earlier quoted context omitted.

From the article, "Each GBI costs approximately $75 million, and as of 2024, 44 are deployed across Alaska and California [3]."

I'm quoting the missile cost. I think they're quoting the launchers + a few missiles. (Also, lower bounding the cost improves the argument that they're too expensive to be practical.)

Author here. The $75M is specifically for Ground Based Interceptors (GBIs). This is the U.S.'s ICBM mid-course interceptor. There are other interceptor types in the current U.S. arsenal:

Patriot PAC-3 (~$4M): Nations burnt through 600-800 in the first few days of Operation Epic Fury. There are reports that they're being used for drone defense.

SM-3 (~$10-30M): Ship-launched

SM-6 (~$4-5M): Ship-launched

THAAD (~$12-15M): Terminal phase, high altitude

GBI (~$75M): intended for interception of ICBMs (reported as the hardest type of missile to intercept)

Each type of interceptor is optimal for certain type of threats, which is yet another constraint on the optimization problem.

Re: Missile defense is NP-complete

#189

Post by dlisboa »

maratc wrote: post #184
dlisboa wrote: post #153

Earlier quoted context omitted.

A trillion seems large but it's not that absurd. The drone that shut down 17% of Qatar's LNG capacity is said to have caused 20 billion USD worth of annual lost revenue. They said it'll take up to 5 years to rebuild so that could be 100 billion USD in lost revenue, plus whatever it costs to do the rebuild. A trillion dollars worth of damage seems possible if spread over some years for some countries in the Gulf where…

> that could be 100 billion USD in lost revenue that could be 100 billion USD in deferred revenue, if we assume that LNG is not going anywhere from wherever it's sitting underground, and will be simply extracted and sold later > plus whatever it costs to do the rebuild That is the real cost, which I would assume is nowhere near billions

> that could be 100 billion USD in deferred revenue, if we assume that LNG is not going anywhere from wherever it's sitting underground, and will be simply extracted and sold later

That's not how revenue works at all.

Re: Missile defense is NP-complete

#190

Post by mrguyorama »

pjc50 wrote: post #179
9cb14c1ec0 wrote: post #102

Earlier quoted context omitted.

To be clear, that F35 was being incredibly careless, flying low in broad daylight. All the stealth features of an aircraft are useless if you can look at it with your own eyes. In any conflict with China, F35s would not be flown that way.

In a direct conflict with China, the ICBM exchange would destroy the F35s on the ground.

China doesn't seem to think so. China believes they need to fight those F35s in the air.

Why would the opening salvo be ICBMs?

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