Missile defense is NP-complete • Hacker News Board

Re: Missile defense is NP-complete

#321

Post by dilyevsky » Wed, Mar 25, 2026, 6:05 AM UTC

jandrewrogers wrote: post #149

owenmarshall wrote: post #109

Earlier quoted context omitted.

This leans towards my belief that the US is fundamentally fighting last century's war against adversaries that have _massively_ evolved. Look at the Ukranians: they are currently fielding an entire suite of counter-drone tech: fast pursuit systems to hit Russian drones on launch, cheap FPV drones for last-mile intercept, integrated radar/acoustic monitoring to target and respond to launches... and of course, the Russ…

This betrays your ignorance of drone defense tech. The US had APKWS (anti-drone guided missiles) operational in the 2010s and these have been widely deployed. They are effective and cost less than a Shahed. These are just mods of an existing dirt-cheap rocket for which the US has an effectively unlimited supply. The Europeans have similar systems under development. The US has deployed high-power anti-drone laser syst…

Not to mention US is at the forefront of drone interceptor tech which are particularly useful against Shaheds: https://en.wikipedia.org/wiki/Merops_(weapon)

Re: Missile defense is NP-complete

#322

Post by WalterBright » Wed, Mar 25, 2026, 6:11 AM UTC

YeGoblynQueenne wrote: post #271

breppp wrote: post #211

Earlier quoted context omitted.

I don't think we are arguing the same thing. I am arguing that even without any air defense, Iran would have difficulty hitting its targets in Israel with ballistic missiles due to low accuracy. When adding interception rates they have a real problem in attacking strategic facilities, air bases is a good example, which would be much more important than desalination plants. You can then see that they shifted to comple…

Shahed drones have a maximum range of 25000 km [bbc_1]. The distance from e.g. Isfahan to Tel-Aviv is ~1592 km [google]. Shaheds can reach Israrel from Iran. As to them all being intercepted, in the 12-day war that seemed to be the plan, i.e. force Israel to waste interceptors on cheap drones [bbc_2]. That seems to have changed in the current conflict. _______________ [bbc_1] With a maximum range of 2,500km it could…

During WW2, the British used Spitfires to shoot down V1s. The V1s, pushed by a simple pulse jet, I presume are much faster than the drones. So some WW2 aircraft could be re-armed and used to shoot them down cheaply.

The British also employed a belt of radar-guided flak guns to shoot them down.

I don't hear any comparisons with the V1s, so my idea must be stupid, but I'm not seeing the flaw in it.

Re: Missile defense is NP-complete

#323

Post by 15155 » Wed, Mar 25, 2026, 6:14 AM UTC

jmyeet wrote: post #85

delichon wrote: post #4

Add multiple decoys and the missile math tends to become an argument for the importance of preemption. Han shot first for a good reason.

If you haven't, I'm going to recommend you to listen to an episode of Dan Carlin's Hardcore History , specifically The Destroyer of Worlds [1]. Why? Because it goes into the change in strategic thinking brought on by the atomic age (and, soon thereafter, the thermonuclear age). And there was an element of US strategic thinking that argued for a preemptive strike against the USSR. The episode also goes into the argume…

> hydrogen bomb, a weapon that could never really be used and arguably not even necessary when we already had the atomic bomb.

Two-stage designs are far more cost-effective and compact.

Re: Missile defense is NP-complete

#324

Post by 15155 » Wed, Mar 25, 2026, 6:20 AM UTC

Havoc wrote: post #295

mattmaroon wrote: post #256

Earlier quoted context omitted.

Well, it’s less about the value of the interceptor and more about the value of what the drones are heading for. If it’s a desalination plant that makes 20% of your freshwater, eight missiles are probably well worth it because a lot of people can die. Middle Eastern countries have much more condensed critical infrastructure and economic targets than we do. Iran has expected a war like this for decades and been continu…

That logic right there is why the US is going to lose. That math only works in isolation The Ukrainians don’t think about today’s tradeoff but also about tomorrows. They learned that when when a three day special operation turned into four years. You have to match your best defenses against the best expected incoming attack- across time- even if it means taking a hit. Yes desalination plant included The us doctrine o…

Ukraine has no feasible means to actually act offensively, meanwhile, the United States is a nuclear weapons state.

Pose a credible-enough threat and atomic deletion will ensue.

Re: Missile defense is NP-complete

#325

Post by maxglute » Wed, Mar 25, 2026, 6:22 AM UTC

drak0n1c wrote: post #316

nerfbatplz wrote: post #75

Earlier quoted context omitted.

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.

The "pen-testing" discoveries go both ways. In Iran, Chinese HQ-9B surface-to-air missile systems and YLC-8B anti-stealth radars failed to intercept any aircraft. In Venezuela, Chinese JY-27A early warning radars failed to detect approximately 150 incoming U.S. aircraft. In Pakistan, Chinese HQ-9B and HQ-16 systems failed to intercept Indian strikes.

Not really. US, a competent operator of US made platforms losing hardware to Iranian box of scraps is different than third party operators vs overmatch environment, i.e. Pakistani had pathetic amount of IADs vs India, and by all accounts VZ didn't even integrate theirs.

IADs not integrated by marginal operators =/= stealth radar didn't work aka, physics of stealth detection is basic, and parsimonious likelihood is US gave up strategic intangibles for VZ and IR side shows. Even if IADs wasn't integrated it would still be worthwhile for PRC to send out stealth radars knowing they'd get glassed because it's rounding error investment to get near F35s without luneburg. At the end of the day, these radars are networked/uplink to beidou3 for a reason, their primary function for PRC is to serve as cheap telemetry gathering nodes that gather strategic US ephemera like stealth profiles, ew, order of battle and beamed it back to CETC.

Re: Missile defense is NP-complete

#326

Post by WalterBright » Wed, Mar 25, 2026, 6:25 AM UTC

falcor84 wrote: post #305

marcosdumay wrote: post #193

Earlier quoted context omitted.

> when part of their reasoning and authority is based on a divine mandate If you are atheist is becomes rational to surrender to the people that are invading your house and killing your friends at random?

Yes. Absolutely. If there are invaders who are killing everybody around me and telling me that they'll stop and generally let me be if I surrender and agree to live in a democracy, I expect that I'll be very inclined to accept. Maybe afterwards, if I see it's not working out, I may still consider guerrilla resistance down the line, but I don't see the benefit of fighting and most likely dying just for the sake of def…

Fighting is rational when the alternative is being killed.

FDR made a big mistake announcing that he was going for unconditional surrender. This resulted in Germany fighting to the bitter end. Hitler dragged it on to the last few hours - he knew what was going to happen to him when the war ended.

Re: Missile defense is NP-complete

#327

Post by WalterBright » Wed, Mar 25, 2026, 6:35 AM UTC

mrguyorama wrote: post #195

mamonster wrote: post #136

Earlier quoted context omitted.

>The damage these inflict on Israel is not unsustainable, and they don't do much to create deterrence. Has there been a study on this? What is the GDP loss of having however many Israelis go to bunkers due to incoming ballistics instead of working ? If a trash cluster missile that costs 100k USD to build causes 1mio USD worth of GDP to not be produced (numbers completely made up) then it's very worth it.

Ballistic missiles do not cost only 100k USD to build. They are very unlikely to ever be that cheap. Rocketry requires enough precision to not explode on the launcher. Ballistic missiles with conventional munitions are only useful for point targets. Cluster munitions like Iran uses are an admission that they aren't targeting specific systems, aren't expecting to penetrate defenses, or other reasons why they would was…

> None of the harassment campaigns done by the Nazis for example really amounted to anything.

I hate to say it, but the aerial bombing campaign against Germany in WW2 was not terribly effective. The Germans were quick to decentralize the factories, and burning down houses did not impair the war effort much.

What did work was bombing the oil infrastructure. Germany ran out of gas.

What also worked was using the B-17 fleet as bait for the Luftwaffe. The Luftwaffe could not help but rise to defend the country, and then they were shot down by P-51s and P-47s and Spits. The goal was to erase the Luftwaffe, and it worked. (Even though German warplane production increased, the pilots were dead and irreplaceable.)

Re: Missile defense is NP-complete

#328

Post by tliltocatl » Wed, Mar 25, 2026, 6:45 AM UTC

pc86 wrote: post #172

iso1631 wrote: post #129

Earlier quoted context omitted.

It's America that's waging this war, having attacked Iran for no reason the world can see It's somewhat similar to Russia waging a war in Ukraine, although I can see some reasons for Russia to attack Ukraine (mainly territory)

If "I want this land" is a legitimate reason to initiate a war then basically anything is a legitimate reason.

You are confusing reason as in "why they did it" vs "why they ought to do it".

Re: Missile defense is NP-complete

#329

Post by tliltocatl » Wed, Mar 25, 2026, 7:02 AM UTC

skywhopper wrote: post #10

trollbridge wrote: post #7

Earlier quoted context omitted.

A lot of things involving rockets and putting things in space have changed since the 1960s.

Have they, really? * Small rockets can now land themselves. Anything else?

Vastly cheaper and more powerful control and guidance systems (and cheaper, if only a bit cheaper, radars too).

Re: Missile defense is NP-complete

#330

Post by jounker » Wed, Mar 25, 2026, 7:02 AM UTC

WalterBright wrote: post #322

YeGoblynQueenne wrote: post #271

Earlier quoted context omitted.

Shahed drones have a maximum range of 25000 km [bbc_1]. The distance from e.g. Isfahan to Tel-Aviv is ~1592 km [google]. Shaheds can reach Israrel from Iran. As to them all being intercepted, in the 12-day war that seemed to be the plan, i.e. force Israel to waste interceptors on cheap drones [bbc_2]. That seems to have changed in the current conflict. _______________ [bbc_1] With a maximum range of 2,500km it could…

During WW2, the British used Spitfires to shoot down V1s. The V1s, pushed by a simple pulse jet, I presume are much faster than the drones. So some WW2 aircraft could be re-armed and used to shoot them down cheaply. The British also employed a belt of radar-guided flak guns to shoot them down. I don't hear any comparisons with the V1s, so my idea must be stupid, but I'm not seeing the flaw in it.

A v1 was 30 feet long with a 20 foot wing span, and had no evasive capabilities.