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Comment by 40acres | Hacker News Reader

I've read a few stories about the lack of confidence in America's missile defense systems. We have THAAD missile [0] in Asia as a counter punch to North Korea but from what I've read confidence in the system is pretty low.

Israel's Iron Dome [1] system seems to be effective but I would assume there are differences in the system and proximity of Palestine to Israel and the missiles fired that allow it to be so effective.

As a further point, the fact that our missile defense systems are so poor just emphasizes how reckless our approach to North Korea is, their missile technology is getting better and better while our defense system is unproven and yet top Trump administration officials talk about war as if it's not a big deal. Truly scary stuff.

[0]: https://en.wikipedia.org/wiki/Terminal_High_Altitude_Area_De... [1]: https://en.wikipedia.org/wiki/Iron_Dome

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I think Iron Dome has a high success rate due to the type of missile. Mostly 80mm unguided 'Katyusha' and 122mm 'Qassam' unguided rockets, which are destroyed by multiple interceptor missiles with proximity fuzed explosive warheads.

I was in Tel Aviv in 2012, when larger Fajr-5 330mm rockets were fired at the city and I saw several of them being successfully intercepted, a few thousand meters out from their targets. Sadly there was one rocket that hit Tel Aviv, killing several people, and another 'failure' of sorts when debris from an intercepted Fajr-5 landed in a Tel Aviv street, however the warhead did not explode and it was simply falling at terminal velocity... Iron Dome also has an interesting optimisation mode where it tracks the impact point and will not waste a salvo against the incoming threat if it will land somewhere harmless like the sea or open countryside.

Yes, this was my thought too. Rockets fired at Israel are generally cheap, short-range subsonic jobs, not substantially harder to shoot down than a World War 2-era V-1 buzz bomb. Medium-range and intercontinental ballistic missiles reach speeds of many thousands of miles per hour, making them much harder targets to intercept.

>Rockets fired at Israel are generally cheap, short-range subsonic jobs,

not exactly. Most seems to be manufactured either in Iran or China and a follow on or similar development off basic USSR/Russian systems, like Grad, Uragan, Smerch - these rockets have speed anywhere between 2M and 3M. It is outside of capabilities of many air defense systems on the merit of the speed alone. Add to that multiple rockets in a salvo. Iron Dome being capable of dealing with that is a very huge achievement.

I'm going to hazard a guess that it's actually very hard to make a sub-sonic rocket!

The Qassam rockets are little more than large, deadly fireworks rockets (see an image: https://usdiaspora.files.wordpress.com/2014/07/qassam-rocket...)

There are bigger ones than that of course, but the smaller ones are certainly subsonic.

The 'Katyusha' and 'Qassam' rockets are subsonic, or perhaps just transonic in the case of the Katyushas (which are quite varied)

"The Qassam's speed in the air is 200 meters per second." (= ~750km/h)[1]

The Katyusha rockets fired from Gaza are commonly quoted to hit Tel Aviv in 2 minutes (35km in 2 minutes = ~1000 km/h)

[1] https://www.haaretz.com/news/iron-dome-system-found-to-be-he...

there is a range of rockets used by Hamas https://www.globalsecurity.org/military/world/para/hamas-qas...

The 'Qassam' are the low-end of Hamas rockets, and they are locally made low quality stuff. The rest is imported military grade production.

>The Katyusha rockets fired from Gaza are commonly quoted to hit Tel Aviv in 2 minutes (35km in 2 minutes = ~1000 km/h)

Judging by the distance and the name Katyusha, it is probably Grad (https://en.wikipedia.org/wiki/BM-21_Grad) rockets as by looks and function it most closer resembles Katyusha. The Grad is 122mm and it is the starting system in that type of weaponry and its rocket speed is ~700m/s. The higher-end, 200mm and 300mm, systems fly a bit faster and much farther (typically Chinese versions are even faster and longer range than original Russian).

The Katyushas can't hit Tel Aviv. From Gaza, the only system that can threaten Tel Aviv is the Fajr-5, which were fired at it for the first time in 2012. The linked chart [0] shows that most Katyusha/Quassam rockets have a maximum of ~30km range, whereas the Fajr-5 can make the ~75km to hit Tel Aviv. The warning time given is 60-90s (i.e. from when the air raid sirens sound to impact or interception) so with a margin of error on the slow side, they do 75km in 2m which is ~2250 km/h or Mach 1.8, definitely supersonic. I think I was wrong about the smaller rockets though, which are subsonic.

0. https://en.wikipedia.org/wiki/Palestinian_rocket_attacks_on_...

You're saying that the majority of rockets fired from Gaza are not made in Gaza? That contradicts everything that I've read about them.

"Rockets fired at Israel" includes foreign-manufactured rockets fired from Lebanon.

I have nothing at all to say in favor of the Trump approach other than that talking about not-war with North Korea is truly scary stuff as well, as their capabilities are increasing by leaps and bounds. There just seem to be no good answers there.

The key feature of Iron Dome is it won't try to intercept rockets that aren't going to hit a populated area, which means the Israelis don't go broke shooting $100k interceptors at $50 rockets that were going to hit anything anyway.

It's a tool designed to deal with the unique situation in which the Israelis find themselves. It's not any better at intercepting modern guided ballistic missiles than other systems.

THAAD is in a league of its own... It hasn't had its real world effectiveness tested yet, but its miles better than what Patriot could provide.

I would also expect a lot of disinformation around the subject, both about how these systems work, and about their failure modes.

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