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Looking forward to hearing "The Song of General Kim Jong-Il"
December 21, 2012 5:52 PM   Subscribe

Almost Everything You’ve Heard About the North Korean Space Launch Is Wrong
posted by Simon Barclay (41 comments total) 16 users marked this as a favorite

 
As anyone in the imagery analysis field can tell you, LEO imagery satellites have their limitations. They exist in limited numbers, travel in predictable orbits, can only observe what’s directly underneath them, and have a revisit time measured in many hours to days.

We should start using the infinite and unpredictable kind that can see through solid rock.
posted by DU at 6:16 PM on December 21, 2012 [2 favorites]


Man, am I getting tired of headlines telling me how ignorant I am.
posted by Etrigan at 6:22 PM on December 21, 2012 [18 favorites]


Actually, pretty much everything you've heard about North Korea, ever, is wrong. Bruce Cumings' excellent book on North Korea, published a few years back, retraces the long and insane history of the US and North Korea, starting with the terror-bombing and massacres of the Korean War. Apparently, neither Kim Jong Il nor Kim Il Sung were even remotely crazy, despite American media efforts to portray them as such. Also, we carried out large scale massacres of their civilians, bombed almost every city in the country to rubble, and seriously considered nuking the country to prevent the Chinese from invading. What's interesting to me is how consistently unwilling to reexamine their preconceptions our lazy media are, over a period of decades. Same narrative for half a century.

None of which is to excuse or avow what is apparently a pretty disgusting dictatorship. But hey, our press is backing Al-Qaeda in Syria, so there you go...

Also: very interesting article, thanks.
posted by jackbrown at 6:45 PM on December 21, 2012 [6 favorites]


While it is true that this was a satellite launch trajectory, the distance between satellite launch capability and ballistic missile capability is much much smaller than the distance between satellite launch capability and no launch capability.
posted by notme at 6:45 PM on December 21, 2012 [3 favorites]


Holy balls, this article is actually rather good. That's a lot of data and a good overview to the conclusions packed in there. The shift in rhetorical tone when describing the North Korean satellite was a little jarring, but jeez that's a well-supported explanation.
posted by lazaruslong at 6:48 PM on December 21, 2012 [1 favorite]


Okay, so here's a question: when talking about the HEO satellites, since it's being sling-shotted around the Earth like that, does the satellite's velocity increase and decrease relative to its position? Intuitively, it makes me think that it zips around the nadir section quickly and slows down to hang in the apogee section.
posted by lazaruslong at 6:59 PM on December 21, 2012


Lazaruslong, your intuition is correct. Kepler's second law applies to all bodies in orbit, including satellites around planets as well as the planets around the sun.
posted by autopilot at 7:05 PM on December 21, 2012 [1 favorite]


I was stunned by the rhetorical difference between the supposedly super-scary North Korean satellite and fascinating yet mysterious X-37 launched by the US Air Force just a couple days earlier. Both are certainly military demonstrations in space, but just one was presented as a threat to anyone.

lazaruslong: That's correct. An object in orbit around another is at its greatest speed relative to the object at periapsis and its slowest speed at apoapsis.
posted by ddbeck at 7:09 PM on December 21, 2012 [3 favorites]


Okay, cool. So that makes me wonder if there's a....risk calculus threshold for a maximum HEO satellite trajectory? If that makes sense? What I mean is, if the idea is to have a satellite that hangs for a long amount of time over a specific point, then the shallower the ellipse the better. But that shallowness also means increased speed and proximity to the Earth. So in the event of some kind of malfunction, the shallower the ellipse the nastier the possible result of a crash, right? Cause it would be hauling more ass and slamming in at a steeper angle?
posted by lazaruslong at 7:10 PM on December 21, 2012


lazaruslong: Even highly elliptical orbits can be stable. Provided the lowest altitude of the satellite is high enough to avoid most atmospheric drag, the satellite can remain in orbit for many years, whether ground control is maintained with the satellite or not. And generally, crashes aren't a major concern with these satellites, since they rarely have sufficient mass to survive reentry to the ground. They just burn up into a fine dust, like a little manmade meteor.
posted by ddbeck at 7:15 PM on December 21, 2012


Ah right, I was making an assumption that a malfunction would result in a crash when instead it would just burn up and stuff. Of course, thanks to that post about realistic space warfare a while back, I wonder if you could design an HEO object that looked like it was a satellite from its trajectory and orbital design but was in reality a super dense block of matter or something that would survive reentry to function as a kinetic weapon in 10 years time after launch.
posted by lazaruslong at 7:22 PM on December 21, 2012


LazarusL, the danger to a satellite's stability is never the high point of its orbit; it's the low point. It's drag at the perigee that slows the sat down over time eventually bringing it down. The difference at perigee between a high-apogee sat and a low-apogee one is that the high-apogee sat is going faster, because more momentum is needed to swing it back up to the apogee. If it's experiencing drag, it gets a bit worse of a hit than a more circular sat that isn't going as fast when the air gets thick.

In practice, the way elliptical satellites fail is that their orbits get circularized; before the perigee starts to noticeably degrade the apogee does, because the sat is losing the momentum it needs to heave itself back to apogee. Once the orbit gets more circular the sat starts spending more and more time at low altitudes with drag, and eventually it falls out of the sky in exactly the same way as a sat that never got over 100 miles up.
posted by localroger at 7:31 PM on December 21, 2012 [4 favorites]


Man, am I getting tired of headlines telling me how ignorant I am.

Almost everything you've heard about condescending headlines is wrong!
posted by SpacemanStix at 7:34 PM on December 21, 2012 [20 favorites]


lazaruslong: I wonder if you could design an HEO object that looked like it was a satellite from its trajectory and orbital design but was in reality a super dense block of matter or something that would survive reentry to function as a kinetic weapon in 10 years time after launch.

You could build a hunk of something dense with rocket attached to de-orbit at the opportune moment to hit a target on the ground, and it wouldn't look different from any other satellite as viewed from the ground. But observers could still notice the increased mass of the object by its orbit and the seemingly oversized launch vehicle. It'd be plain that you were up to something, though not what specifically.
posted by ddbeck at 7:44 PM on December 21, 2012 [1 favorite]


Man, am I getting tired of headlines telling me how ignorant I am.

Could your ignorance of headlines kill you in your sleep? More at 11, and Sam with the latest weather!
posted by potsmokinghippieoverlord at 7:50 PM on December 21, 2012 [2 favorites]


Yeah, I find the condesending headlines annoying, particularly since this is the only article i'd read on it.

As far as the mass thing, I was thinking the same thing about the mass being obvious - but can you actually tell how massive something small like a satelite is by its orbit? It doesn't seem like it would have enough mass to have much of a measurable effect on other objects. Maybe by how much the atmosphere slows it down in leo?

Also, I don't think an object needs to be that heavy to survive rentry, it just needs a heat sheld able to absorb the energy - like the mars rover had.
posted by delmoi at 8:24 PM on December 21, 2012


What a bizarre article. Why does the author think North Korea bothered to launch a satellite in to orbit? Do they really think broadcasting "The Song of General Kim Jong-Il" to the world is going to be a meaningful statement? Does anyone rational in North Korea think that building a space program is actually valuable to their scientific development? This, a country that can't keep the lights on at night or even feed its people? The entire country is a military dictatorship horrorshow; they're not amateur space enthusiasts. The only plausible theory is that this is a demonstration of ballistic missile capability. Sure is a nice pairing with their demonstrated nuclear weapons capability. Both technologies are sad and ænimic, but frightening in combination.

(Bonus link: trajectory of the satellite, should you want to try to spot it or hear whether they manage to enable the supposed transmitter).
posted by Nelson at 9:12 PM on December 21, 2012 [1 favorite]


There was a North Korean space launch?
posted by dirigibleman at 9:19 PM on December 21, 2012 [1 favorite]


In fact there was.
posted by Pudhoho at 9:34 PM on December 21, 2012


Calling the launch proof of the ineffectiveness of the Barack Obama administration’s “strategic patience” approach, Cumings, 69, said Washington would be better served to favor active dialogue over ineffective sanctions.
posted by dhartung at 10:16 PM on December 21, 2012


The article struck me as having a lot of actuals facts for being in Wired. Neat!

It also seems to argue that satellite technology isn't applicable to ballistic missiles. Not neat.
posted by jiawen at 11:02 PM on December 21, 2012


delmoi: As far as the mass thing, I was thinking the same thing about the mass being obvious - but can you actually tell how massive something small like a satelite is by its orbit? It doesn't seem like it would have enough mass to have much of a measurable effect on other objects. Maybe by how much the atmosphere slows it down in leo?

Also, I don't think an object needs to be that heavy to survive rentry, it just needs a heat sheld able to absorb the energy - like the mars rover had.
I'm not feeling well so I don't have it in me to work out all the details, but I note that the greatest engineering achievement of humankind delivered approximately 130 tons into LEO, and less than half of that into a lunar trajectory. The best known kinetic orbital bombardment system was nicknamed "Thor's Hammer" by Jerry Pournelle who came up with the concept in the '50s. The payload would be a tungsten rod 20 feet long and a foot in diameter that weigh around 8 tons each, and according to Wikipedia would deliver the energy equivalent of 11 tons of TNT to the target. Point being, I don't think putting anything massive enough to be really worrisome into orbit could be done unnoticed.
posted by ob1quixote at 12:02 AM on December 22, 2012


While it is true that this was a satellite launch trajectory, the distance between satellite launch capability and ballistic missile capability is much much smaller than the distance between satellite launch capability and no launch capability

It's none. The ΔV needed to put a given mass into LEO is much higher than the ΔV needed to put the same mass into a ballistic arc to hit anywhere on the planet. So, if you orbit 1000kg, you can put much more than 1000kg anywhere on the planet.

What this launch said was very clear. North Korea has the ability to build ICBMs. Indeed, this launcher may well be an ICBM with some minor changes -- this, after all, is how we did our earliest manned launches. The Mercury-Redstone was built off the PGM-11 Redstone IRBM with a longer fuel tank, the Mercury-Atlas was built off the SM-65D Atlas ICBM, and the Gemini capsules were launched by the Titan II GLV, which was a derivative of the LCM-25C Titan II ICBM.
posted by eriko at 6:55 AM on December 22, 2012 [1 favorite]


Any elliptical orbit is stable if your spacecraft can overcome lithospheric drag. However, the design of such a craft would need to be less like an ICBM and more like a TBM.
posted by autopilot at 9:07 AM on December 22, 2012 [3 favorites]


The article is right in saying that the trajectory for a ballistic missile is different to that for an orbital launch, but to say this:
Some of the same technologies are needed for long-range missiles and for space launches — most notably rocket motors, high strength-to-weight fuselages, and guidance software. But they’re not the same thing. All evidence points to a satellite launch, despite headlines like these.
is a bit ridiculous. They say "some of the technologies" and then go on to describe... all of it! There's very little technical difference between a ballistic missile launcher and a satellite launcher - in fact we use ballistic missile designs for quite a few satellite launches - Early manned flight and the currently used Rockot are notable examples.

If you want to test a ballistic missile without causing a military response, disguise it as a satellite launch. Once you're able to successfully launch and control a liquid fuel rocket, the difference between a satellites trajectory and a missiles trajectory is a few lines of code.
posted by leo_r at 9:10 AM on December 22, 2012


autopilot: "Any elliptical orbit is stable if your spacecraft can overcome lithospheric drag."

If you're having trouble with lithospheric drag, then achieving orbit isn't your first concern; lithospheric drag means you're having a little problem with... crashing. Perhaps you meant atmospheric drag? (Sorry if you meant that as a joke.)
posted by jiawen at 9:50 AM on December 22, 2012 [1 favorite]


If you're having trouble with lithospheric drag, then achieving orbit isn't your first concern;

Yes. Aerobraking is a very valid way to help shed velocity and enter a stable orbit. Lithobraking, however, is not nearly as useful.
posted by eriko at 10:05 AM on December 22, 2012 [1 favorite]


Lithospheric drag is now going to be my new euphemism for crashing into the ground.
posted by RobotHero at 10:07 AM on December 22, 2012 [1 favorite]


jiwaen, a TBM can (slowly) overcome lithospheric drag. An ICBM can only make it part of the way through before being retarded by the increased density of the lithosphere.
posted by autopilot at 10:36 AM on December 22, 2012 [2 favorites]


Lithobraking, however, is not nearly as useful.

As a braking method, though, it is extremely effective.
posted by localroger at 11:37 AM on December 22, 2012 [2 favorites]


Man, am I getting tired of headlines telling me how ignorant I am.
Man, am I getting tired of Americans telling me shit about North Korea.
posted by fredludd at 12:16 PM on December 22, 2012


What I found particularly interesting about this article is that the techniques used to launch the satellite into the required orbit were relatively complicated, and demonstrated some level of sophistication that I (perhaps naïvely) didn't expect. There is likely more to North Korea than most people suspect -- for better or worse.

The fact that they deliberately avoided overflying other people's countries, and they notified the appropriate agencies about where the debris was expected to land, indicates that they might not entirely be the monsters they're being depicted as. Or maybe it's just meant as a ploy to make them seem like good global citizens!
posted by Simon Barclay at 1:09 PM on December 22, 2012


a tungsten rod 20 feet long and a foot in diameter that weigh around 8 tons each ... 11 tons of TNT to the target. Point being, I don't think putting anything massive enough to be really worrisome into orbit could be done unnoticed.
Huh? Why not? You put a heat shield on a nuke, deorbit over a large city and then have it detonate when it gets close enough to the ground to cause damage. Looking at the chart on this page a 100 kiloton yield nuclear weapon can weigh as little as 100 kilograms, and there lower yield nukes (around 10 tons of TNT) weighing just around 30kg (as far as I can tell from reading a log/log chart). A 1-ton nuke can have a 10 megaton yield.

In other words, people have built nuclear weapons that deliver as much energy as the tungston rod and are light enough to pick up and carry in your arms.
posted by delmoi at 1:10 PM on December 22, 2012


The fact that they deliberately avoided overflying other people's countries, and they notified the appropriate agencies about where the debris was expected to land, indicates that they might not entirely be the monsters they're being depicted as. Or maybe it's just meant as a ploy to make them seem like good global citizens!
Well, it proves they have the ability to control and predict their rocket precisely, it requires more sophistication then launching it without altering the trajectory. Pretty good, given they've never been able to launch anything before.

Anyway, this missile at it's current technology level can't really be used to deliver weapons very effectively in a war. They launch from a platform and it takes time to setup - just like a shuttle launch. If a war ever happened we could easily take out the missile while it's on it's platform. They need to be able to launch from bunkers the way the US and Russia were able to do back in the day (and still can, I guess - although launching from subs is the preferred method now, I think)
posted by delmoi at 1:30 PM on December 22, 2012


delmoi: In other words, people have built nuclear weapons that deliver as much energy as the tungston rod and are light enough to pick up and carry in your arms.
I don't disagree about the prospect of orbital nukes being much more alarming. I was responding to your apparent concern about kinetic weapons disguised as a satellite. My point was that putting anything into orbit that is massive enough to cause enough conventional damage to worry about wouldn't be worth the effort. At $450M each, they could build two and a half Unha-3s for what it cost to build one Saturn V.
posted by ob1quixote at 2:12 PM on December 22, 2012


autopilot: thanks, I wasn't getting your joke, and now I know why: I didn't know the acronym TBM.

Hmm, how does a TBM overcome lithospheric drag? Maybe with some really special technology.
posted by jiawen at 7:40 PM on December 22, 2012


As a braking method, though, it is extremely effective.

It is very good as a braking method, and utterly amazing as a breaking method.
posted by eriko at 7:53 PM on December 22, 2012 [1 favorite]


delmoi: "In other words, people have built nuclear weapons that deliver as much energy as the tungston rod and are light enough to pick up and carry in your arms."

Kinetic weapons are filed under, "Ideas that sound plausible, but could be done easier and cheaper through other means." Maybe on a planet with a significant ring system they might be more workable?
posted by Chrysostom at 9:02 AM on December 23, 2012


Oh my goodness, there's a sci-fi story right there. Planet with a massive ring system with different countries and merchant conglomerates in a constant state of kinetic-weapon warfare induced by the selective deorbiting of non-essential moons. One day a the wrong shepherd moon gets deorbitied and the apocalypse begins. Only one woman can save them all, and herself.
posted by lazaruslong at 11:14 AM on December 23, 2012


Oh my goodness, there's a sci-fi story right there.

In The Mote in God's Eye it's implied that this happened on a solar system scale in the deep past of the Catholic aliens, and in order to save their species they removed the entire asteroid belt to the Oort cloud.
posted by localroger at 11:29 AM on December 23, 2012 [1 favorite]


I like that book a lot! It's on the shelf right next to me, actually. I loved the idea of the cyclical Apocalypse museums that could remind the next civilization of the advances made by the previous ones, but only if they had sufficient technology / science to be able to unlock the locks on the doors to the tech rooms. Kind of the basis for my comment in the genetic data thread here, now that I think about it.
posted by lazaruslong at 11:34 AM on December 23, 2012


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