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[Il Palazzo]

Meh, that's a lot of assumptions to make the argument stick.
They have enough brainpower to construct an advanced nuclear device, but not to go borrow a book on fundamentals of astrodynamics from a library? Or is their targetting technology worse than WWII-era tech?
Sounds like wishful thinking.

[Starver]

I don't think pen and paper are enough. Even if assuming you're accounting for the non-ballistic (i.e. powered) parts of the 'ballistic' flight and the curvature of the Earth, there's the winds to encountered at various heights, in air of varying pressure (1 to practically zero back to 1 atmospheres), and calculations would need to be made with the current weather conditions in mind, every single launch, and I bet that the error bars are still massive.

You need in-flight adjustments (practically) all the way down as much as you need them going up, with these beasts. (Assuming that they know where they are, and OTS GPS devices won't work at these speeds and (all but the lowest altitude segments of) these trajectories. So homegrown receivers, or hacked ones from the rest of the world, would be needed.)

If they haven't got that, they've got a Big Dumb Rocket that they can land on the right country, but I doubt they can even be confident of hitting Guam if they tried... Which won't stop them trying, if they want to, but that's just another reason to not want to.

[Reelya]

@Il Palazo, If you read about ICBMS, they do in fact use sophisticated active tracking systems. You're implying none of that is needed.

https://en.wikipedia.org/wiki/Intercontinental_ballistic_missile#Flight_phases

Strategic missile systems are thought to use custom integrated circuits designed to calculate navigational differential equations thousands to millions of FLOPS in order to reduce navigational errors caused by calculation alone. These circuits are usually a network of binary addition circuits that continually recalculate the missile's position. The inputs to the navigation circuit are set by a general purpose computer according to a navigational input schedule loaded into the missile before launch.

There are a lot of variables you just can't really predict ahead of time, e.g. turbulence.

Also if you look at the cost of ICBMs they're some of the most expensive weapons systems ever devised. Only a tiny handful of countries (6) even possess ICBM launch capabilities,  because of how expensive they are.

The idea that a tiny, low-pop and incredibly poor country with a terrible education system could create a viable ICBM launch system with all the multi-discipline knowlege that goes into that is making a "lot of assumptions". They have one dude who's good with launching rockets, they lucked out with that. That doesn't mean he's necessarily good at designing anything else, and doesn't imply they have the range of skilled professionals they'd need to pull this off. It's propaganda.

[Il Palazzo]

Sure, if you need to deliver a groundburst within a thousand metres of a missile silo. We're talking about hitting an island.
The Germans managed to reliably hit cities in the 1940s using gyroscopes for guidance.

[Reelya]

Those were launched right on the other side of the English Channel however. North Korea to Guam is a little further than that.

[Starver]

320km V2 range vs ten times that distance to get to Guam. Area of (greater) London, 1500kmē, area of Guam, 540-odd. V-weapons were somewhat keyed towards random terror/uncertainty (nothing strategic), and NK is only really going to be able to aim at randomised nuclear terror...

[Il Palazzo]

Launch velocities are comparable though, and there's less atmosphere to pass through.

The idea that a tiny, low-pop and incredibly poor country with a terrible education system could create a viable ICBM launch system with all the multi-discipline knowlege that goes into that is making a "lot of assumptions". They have one dude who's good with launching rockets, they lucked out with that. That doesn't mean he's necessarily good at designing anything else, and doesn't imply they have the range of skilled professionals they'd need to pull this off. It's propaganda.

Yes, yes. And the tiny, low-pop and poor country totally didn't build a nuclear device. And the actual working ICBMs. But when it comes to targetting, oh boy, that's too hard.

Look, peeps, it might very well be that they somehow dun goofed on targetting. But evidence shows that they have the brains and the means to engineer high-tech devices, so assuming that they really did spectacularly fail in this particular case is unwarranted.

[martinuzz]

After a few more of these 'dud' launches over Japan landing in the deep sea, KJU is going to push the remote detonator button and cause a tsunami that will sink Japan as promised.

[Reelya]

There's a lot more to it than just getting a rocket up.

e.g. the biggest NK nuclear test so far was about 8 kilotons. The Davy Crocket, an American nuke that's launched from a Mortar-like device by hand has a yield iof 10-20 kilotons. So they can blow up things that are about half the yield of the WWII bombs. Sure that's still scary, but just being able to replicate designs the USA made 70 years ago doesn't imply a necessary genius at engineering, and doesn't necessarily mean they've miniturized whatever they have enough to get that payload on their 3400 km rocket.

Then, with the targeting of Guam, it's 10 times the distance as the V2s flew, and they hit within an 18 km accuracy. Guam being 550 km^2, you'd need to hit within a 23 km accuracy, so you need basically the same accuracy as the V2 but over 10 times as far. There's no evidence that they have this tech or anyone specialized in it at all.

Next, you have reentry, none of the NK long range missiles have had a payload that's survived re-entry yet. It's unlikely they have anyone who has expertise in this particular area so they're just winging it by trrial and error right now. There being less atmosphere in the way isn't a selling point. You go up and come down a lot faster meaning much more air resistance, and the need for specialized re-entry tech.

The thing is, you gotta hit Guam within a few km, then the payload needs to carry one of their nukes, and it needs to detonate at the right altititude to be sure of doing damage. All of that sounds pretty unlikely right now. They have one scientists who's good at getting missiles to launch, doesn't necessarily mean they have the technical eco-system to make everything else work, and once you have it, it's expensive to maintain that capability. America doesn't launch any ICBMs, but just maintaining the ability to do so is very expensive and requires huge amounts of manpower / brainpower.

[smjjames]

You don't need a computer to aim a ballistic missile. Pen and paper is sufficient.

That's irrelevant. My point is that if they were able to pinpoint where these missiles were going to impact the surface, they would make a big deal of it. They keep silent about it however, and that's out of character. Which implies that these rockets are very innaccurate. What that suggests to me is that their tech isn't accurate enough to land a payload it's capable of carrying close enough to a target where it would damage said target.

Which is why the extremely specific threat at Guam was such a surprise, they don't normally say the equivalent of "hold my beer, you're gonna watch me hit bullseye at coordinate xyz".

[Reelya]

Ok then let's see them do it. They can in fact pick a random spot in the ocean at the same distance and tell us they're going to land a missile at that point. The fact that they don't do this, but make loose threats against Guam suggests that they lack the accuracy to actually hit Guam, but they don't want us to know that. The threats against Guam would be far more believable if we could point to previously announced flight paths for NK missiles and could extrapolate an accuracy capable of actually hitting it.

Also, ICBM systems aren't the same as just landing a whole rocket some distance away by ballistic aiming. They have 3-4 total stages similar to space rockets, so you have to make sure every stage operates correctly, then the payload needs to detonate in the air above the target rather than just hitting the sea or the ground, which would probably make it a dud.

[smjjames]

I'm sure they do it internally, whether formally or informally. But you do have a point about announcing flight paths (SOP in most countries when launching something), which NK never does.

edit: I doubt even NK would want to waste a warhead in a test unless they want to actually test said warhead. I suspect we could see such a test at some point. The previous one which went over Japan disintegrated into pieces midflight, don't know what happened to the most recent one.

[Il Palazzo]

e.g. the biggest NK nuclear test so far was about 8 kilotons

Under which rock have you been living?
https://en.wikipedia.org/wiki/2017_North_Korean_nuclear_test

[Reelya]

Sorry I haven't been watching the news for the last couple of weeks so I missed that. It's definitely scary, but it's designed to be like that.

http://www.bbc.com/news/world-asia-41139741

NK propaganda is basically that they detonated the warhead seen in the above picture, which will fit in their missile shown. The question is whether we take that propaganda at face value, do we interpret the narrative exactly the way that North Korea is telling us to interpret it? Maybe all the facts are exactly like the North Koreans have set it up for us to be reported to, but then again we also need to trust that the information coming out of North Korean press releases is true if we do that. Of course we should be worried but we should also be skeptical of information which is only confirmed by North Korean press releases.

The range of possibilities is that they detonated a hydrogen bomb, or they detonated a larger version of the fission bombs they've already demonstrated. 100 kT is well within the limits of what a fission device can be created to deliver, the biggest fission device tested by the USA was 500 kT in 1952. So a 100 kT fission device is something that could be made with only late 1940's level technology, and it's direct extrapolation of things the NKer's are already known to have working.

In fact the first hydrogen bomb ever tested had a yield of 10 megatons and weighed 82 tons. The device they just tested is far closer in yield to 1950-era fission devices than it is to early hydrogen bombs. If they successfully went straight to miniaturized hydrogen bombs without needing to go through all the in-between development work the USA did to miniaturize their designs, that's ... kind of harder to believe than the idea that they're bullshitting. There's basically no way you could bypass all the development legwork and research without outright copying existing designs, and since this doesn't appear to be a copy, then I'd question that.

[Il Palazzo]

I agree there's likely a huge amount of posturing and propaganda on NKs side. But let's not forget about the (whether or not intentional) propaganda of the West, which has been constantly painting NK as crazy and inept. They've proven to be able to achieve high-tech feats, which do require a technological and knowledge base larger than just one lucky guy doodling in a garage. Let's not deny that they can do this shit.
Now, do they currently already have a fully functioning missile that could hit what they want to hit? I don't know, and neither do you.
But if they don't have it yet, then they're going to soon - all those tests are not just for show, they provide them with data on what is and what isn't working.