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Iran’s aerospace program has been so active in the last few years it should be possible to say something about their development philosophy: the technological arc or trajectory they are following. For instance, why did they “jump” from SCUD-type missiles to the Shahab-3-type? Why didn’t they put a higher priority on clustering engines in order to achieve greater ranges before moving on to the Shahab-3? Many of my friends believe they should have. A large portion of their argument is centered on the fact that they believe Iran would have established a missile capable of hitting Israel much sooner if they had done that, perhaps as early as the mid-1990s. Of course, such arguments place an extraordinary amount of emphasis on such a military objective, especially when Iran’s nuclear program was much, much less advanced.

I’ve always thought, however, that Iran did make a strategic decision about the direction its missile development program was going in. But it was not a military-strategic decision but an industrial-strategic decision even if there were military advantages to be had further down the road. I believe Iran decided they needed to assimilate the technology for producing large engines indigenously and that this was a much higher priority for them than early production of a longer range missile. New images released at the same time as the “Kavoshgar-3” sounding rocket (with its animal passengers) was launched. Two amazingly important images were released:

A new, large, two-stage rocket with the Iranian space agency logos on it. The second stage appears to be the same stage (and nose fairing) as the Safir’s second stage.

Assuming that the smaller diameter second stage is the same as the Safir’s second stage (with a diameter of 1.25 meters), then the much larger first stage is consistent with a diameter of 1.95 meters. That is, of course, considerably smaller than twice the Shahab-3’s diameter of 2 times 1.25 (or 2.5) meters. So it is fair to ask “What can you put in there?” I think the answer is a cluster of four “Nodong engines.” And, voila, the Iranians show a new rocket power plant with a cluster of four Nodong engines at the same gathering where Pres. Ahmadinejad watched the Kavoshgar-3 launch:

An Iranian rocket scientist unveils the new cluster of four Nodong engines, known as the Phoenix (if Google translate is working properly). The yellow struts above the engines are for transmitting the thrust to the rocket’s airframe. Their presence implies that the first stage will use jet vanes for thrust vector control.

Phoenix, the name of the new power plant, is an interesting name. I’m not sure what the Iranian mythological implications are but as a Westerner, to me it means rebirth in fire. Perhaps they are implying the rebirth of this engine design in a new form. Of course, it is always dangerous to use one cultural point of view to analyze another culture’s literary allusions.

The yellow struts rising above the engine cluster (and their multiple turbopumps, perhaps four? one for each engine?) are for fastening the power plant to the rocket body and for transmitting the thrust they develop. They are angled slightly outward for increased structural strength. Pads at the top of the struts are the connections with corresponding strong points inside the first stage. But is the first stage wide enough to accommodate this cluster?

To answer that question, I have had to go through a chain of photo-interpretation; each of which undoubtedly contributes a certain amount of uncertainty or error to the final answer. First, I had to determine the diameter of the Nodong engine. (I know these are Shahab-3 engines, but I am so used to calling them Nodongs, it would be too painful to switch. Let it be known that I think these engines are indigenously produced in Iran, though Iran probably bought or licensed the production line for them from North Korea.) I get a diameter for the combustion chamber, just below the strong points for the struts, of 0.57 m.

Then, transfer this diameter to the image of the Phoenix power plant:

The top of the Phoenix power plant, showing the combustion chambers and the full diameter of the struts. Calculations by the author indicate that this cluster of four engines would certainly fit inside the large rocket body shown above.

Using this combustion chamber diameter as a reference point on length, I get a total separation between opposite pads at the top of the struts of 1.87 meters. Of course, a rather long chain of analyses was needed to estimate this length. And even the assumption that the farthest right strut pad and the farthest left strut pad represent the full diameter of the support system introduces a certain amount of uncertainty (though that is reduced by a cosine theta effect). Nevertheless, this is remarkably close to my estimate for the diameter of the new rocket’s first stage. Close enough to convince me that this is the new first stage’s power plant.

Note that there are at least superficial differences between this rocket’s first stage and the DPRK’s U’nha-2’s first stage. If nothing else, Iran has designed the airframe itself. (I am being extra cautious about this, my own feeling is that Iran has designed the entire first stage itself. But that is such a key step in my understanding of Iran’s missile development trajectory, that I am hesitant to state it as a conclusion.)

So what do I think has happened? First, Iran purchased a production line for Nodong engines (and the other components of the Shahab-3 missile) from North Korea. However, though the years of producing them, flight testing Shahabs, and modifying them with the design and production of the Safir and other rockets, Iran has fully assimilated this technology and they are moving on to the next stage of development—clustering large engines (they obviously gained some highly important experience with the cluster of two engines on the Safir’s second stage)— and they are probably doing this largely on their own.

Note: a future post will estimate the range of this missile using the “hypothesis” developed here.

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The infrasound signals from North Korea’s 4 July 2006 missile launch.

Infrasound has become an accepted CTBT monitoring technique in recent years with 60 infrasound stations world-wide as part of the CTBTO network. They also, however, detect a bunch of other atmospheric phenomena, as Bharath Gopalaswamy has illustrated. I am particularly interested in using these facilities (or perhaps I should say this phenomena) to study missile proliferation and have worked with Bharath on just this question. In particular, I think it would be useful to determine when North Korea’s 2006 Tae’podong-2 failed or Iran’s August 2008 Safir launch failed. (The analysis has proved complicated with one acoustic event, such as the staging of the rocket, potentially showing up at several different times in the recorded signal. Each time corresponds to a different acoustic flight path such as 3 vs. 4 bounces off the stratosphere. Since a rocket trajectory consists of a number of such acoustic events, it becomes fairly complicated to unwrap the signal; especially since the timing depends on wind speeds and directions and could vary for the different paths. I hope to post more about this analysis as we progress.)

This helps illustrate how one person’s useful technique for detecting clandestine nuclear explosions is another’s intelligence gathering. In particular, I understand that India considers this nothing but an intelligence gathering exercise. Should the international community deny itself such a useful tool because it could be used to gather information about a country’s missile development? Or should countries recognize that firing a rocket is an inherently open process and that certainly their neighbors could set up their own infrasound stations and monitor what is going on regardless of whether or not the international community does? And, of course, the US and perhaps Russia are observing the rocket launches with infrared-sensitive satellites.

You can probably guess which way I come down on this question. I might also mention that if the CTBT actually goes into force, people like me will no longer be able to access any of the information from any of the CTBTO stations, including seismic signals. That’s what the treaty says. So public scrutiny of missile proliferation will, hopefully, be denied this important tool. But governments who sign the CTBT will be able to use it so the question is still important for policy makers.

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click on the image for a larger version

The Iranian video apparently showing some of the manufacturing stages of the Safir two stage rocket still has a lot of information that needs to be analyzed. One important aspect is a brief montage of this furnace and a cylinder obviously cooling down. I think it might be a rotatable vacuum furnace for brazing the Safir’s second stage engines but I’m not an expert on that technology. We have, as I have recently found out, a world full of expertise in the ACW community that I would like to exploit to answer some of these questions. So the problem for the ACW-community is if anyone else has a better idea/knowledge about this thing. The cylinder is shown here and is obviously cooling off, with the outer radius cooling off faster than the heavier mass/smaller surface area support pipe. My guess, and I’m not the artist that Jeffrey obviously is, is shown here.

If this is a vacuum furnace, it appears in the same region of the video as engine construction and I think it would be one more piece of important evidence that Iran is fabricating its own engines.

Note: I have brightened and increased the contrast of the furnace image but there appears to be some thing attached to the front face on the non-adjusted photo that could just be the cylinder.

This post became part of series that consists of:
0) Do You Know What This Thing Is?

1) Iranian Furnances

2) The Jet Vane Hypothesis

3) The How of Proliferation, Part 1

4) The How of Proliferation, Part 2

5) Iran’s Composites Infrastructure

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click on the image for a larger version

Unfortunately, there was a mistake in the range of the original plots. (These things happen when you rush to get things put up on the blog as soon as possible. Im sorry about that!) The observed pitch angle is still very shallow but less so that I originally thought. However, I am still of the opinion that this trajectory is more consistent with an ICBM type flyout that tries to maximize range than a space launch vehicle. Here is my original post:

This question is not going to be answered with one set of data but the pitch program, as determined by the contrail observed in the DigitalGlobe/Globalsecurity.org image is more consistent with an ICMB trying to maximize its range than a space launch vehicle. The one remaining uncertainty, for me, was DigitalGlobe’s time of imaging. They reported 11:32:00 local time, which seems very round to me. So I thought I’d look at the effects of a 30 second uncertainty in when the image was taken. That is shown in the graph of trajectory above. It’s much shallower than I would have expected if it was trying to maximize the orbit. So I am now favoring the hypothesis that North Korea was testing both the missile and an important part of the guidance program of an ICBM with this test. Since the missile appears to have succeeded in second stage separation and ignition, then this was a highly significant accomplishment for them.

Update: I have come to realize, surprise, surprise, that I have not explained myself very clearly. I want to apologize to my readers; my only excuse is that I got very excited about this analysis. Hopefully, this image should help explain things.

click on the image for a larger version

If you look at this image, the contrail, as projected against the ground is in the lower right corner and are represented as circular targets. ( You can find a GoogleEarth overlay of the contrail here.) The points in the “orbital plane”—the plane the rocket travels in, are shown as diamonds with little sticks connecting them to the ground (and are in the center left). These are the reconstructed points through which the rocket actually passed. If you were to connect the ground points with their corresponding trajectory point and continue on into space, they would all intersect at the location of the Worldview-1 satellites. And if you were to draw a line through the places where the space points’ sticks touch the Earth, it would pass through the launch pad, even if it doesn’t look like it would from this perspective.

Update: After discussions with David Wright, I went back and re-checked my calculations and, unfortunately, there was a problem with calculating the positions of the contrail from the alternate satellite positions. In particular, the position assuming the image was taken 30 seconds later than DigitalGlobe stated seems to indicate a considerably steeper raise to the missile so it is possible that could account for differences between this and David’s model. We will have to see if that timing is more consistent. The trajectory is so sensitive to this timing because the image is taken at such a slanting angle. I doubt that DigitalGlobe or any other image provider would normally take such oblique angles. However, it is also clear that DigitalGlobe was trying to maximize its chances of seeing the launch. I suspect all the different commercial (and governmental?) satellites were also imaging the launch pad at large angles. I would guess that DigitalGlobe could see the launch site for at about 5 minutes before and 5 minutes after it passes directly over the launch site. That in itself improves the chances of seeing the launch to about 1%. If you include the other photoreccon satellites, this probability could “climb” to 5% or greater. So this was hardly the “1 in a million” chance that some satellite would photograph it that has been bandied about.

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click on the image for a larger version

The amazing satellite image by DigitalGlobe and presented by GlobalSecurity.org of the Unha-2 in flight can be used to determine the portion of the powered trajectory as it crosses those altitudes where contrails are normally produced. The graph above, which I calculated from that image and the position of the worldview-1 satellite at the time the image was taken, shows some of the points that any simulation of the rocket will have to fit. This, together with the splash down zones will add significant constraints to certainly the first stage. Some wonk-readers have wondered about both the direction and position of the observed contrail as projected against the Earth’s surface. This can be simply explained by the oblique viewing angle of the satellite (which had a latitude of 33 N degrees and a longitude of 126.6 degrees E and an altitude of 489.7 km) at the time the image was take and the fact that the rocket itself was over 4 km above the surface of the Earth.

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Images from the ground of the Unha-2 launch are starting to come in. Besides an amazing satellite image by DigitalGlobe and presented by GlobalSecurity.org of the the Unha-2 in flight, there are North Korean television images starting to appear in the West. (I should mention that the flare at the of the rocket’s contrail is not the rocket plume but rather indicates that the CCD camera on board the satellite saturated.) I’m going to be analyzing these images and hope to write more but I wanted to get these out as soon as possible.

There are a few comments I’d like to make:

1) The first stage is not quite as large as I thought based on a slanted satellite view. It’s much closer to half the rocket length than the 2/3 that I originally thought. I think I was mislead by the projection of the interstage as seen from a funny angle.

2) While you cannot see the individual nozzles on these images, you have to say its more consistent with a cluster of engines than a single engine. ( See this image of the missile in flight.)

3) The diameter is the first stage appears quite large. More work needs to be done on measuring it.

4) No fins are visible on these images or the one the of the missile in flight. While fins are not needed to insure a rocket’s stable powered flight, some analysts had automatically put them on their models.

5) No clear indication one way or another (at least with the cursory viewing of them I’ve made so far) of vernier engines or gimbaled engines.

Update: It’s a cluster! I cannot tell for sure whether or not its 2 or 4 engines but it is definitely a cluster. New info is coming so fast and furious that it’s almost worth missing the Carnegie conference.

By the way, so many of you are viewing this site, I am having a very hard time posting updates! This must be a good sign, but it’s causing me a lot of problems with lost work.

Update: The cluster of engines seems to use a single turbopump. Its still possible, of course, that each nozzle has its own turbopump but given the location of the exhaust exit, Im guessing that its a single pump. This implies a both a reduction in weight and an increase in sophistication on North Korea’s part. This image is a lot more convincing when you look at it in the video because you can see the exhaust plume from the turbopump pulsing.

Update: Gimbaled engines or jet vanes? I cannot tell for sure (if you look at the image of the turbopump exhaust I point to above) there appears to be four (you can see two spaced approximately 1/4 the way around the stage’s circumference) members sticking down from the airframe to below the nozzles. These could be either structural members to support the rocket on the launch pad or extensions for bringing down jet vanes to the level of the nozzle exits. I frankly think the support structures is a more likely alternative so I’m guessing the first stage is guided by gimbaled engines.

Update: I didn’t mean to rule out vernier engines. They are certainly still a possibility.

Update: The DigitalGlobe/GlobalSecurity.org image of the Unha-2 contrail is going to prove to be an analytical goldmine! I have made a rough GoogleEarth overlay of it it. Now, to find out the exact time the image was taken and use these to triangulate the Unha-2’s trajectory during early flight!

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Screen Capture from a FNN Video, click here for the entire video.

So, for about five minutes this morning, the Japanese Self-Defense Forces thought North Korea had launched its satellite rocket. (Good thing they didn’t launch anything in response.) One of the interesting things about this false alarm was that it was reportedly seen by a radar that I and a few experts who know a lot more about radars than I do, weren’t aware of. It’s the J/FPS-5 radar and has been called Japan’s “next generation of ballistic missile tracking radars.” There is apparently a prototype near Chiba, near Tokyo, and one that just went operational in Shimokoshiki-shima [island] in Kagoshima Prefecture. (I’ve marked the general areas on a GoogleEarth image.) I think I would not have placed a radar all the down in Shimokoshiki-shima (if I have the right Island) if I was going to view missiles flying out of North Korea. Perhaps it might be a good place to observe (and direct?) a missile defense engagement?

ps As I write this, dawn must be coming to the Korean peninsula. It can get exhausting waiting for this thing to launch!

pps. Perhaps the existence of the J/FPS-5 is one reason why the Sea-based X-band radar hasn’t left Pearl Harbor?

Update: It must be a rule: as soon as you post something, the answer comes flying through the door. The J/FPS-5 is a detection radar and Japan will eventually surround itself with them. Take a look at this slide from an MDA briefing.

Update: (11:10 pm EDST) North Korea launched its Unha-2 rocket today at about 10:30 pm EDST. No word yet on if it put anything into orbit. Of course, if it did put something into orbit, it would be crossing the United State’s satellite tracking radar fence in Texas right about now for the first time. (Well, actually not. It would be at about 40 degrees South this time. So the US will either have to track it with other assets to determine its orbit—the most probable eventuality—or wait 5 or 6 hours for the US to pass underneath its orbit. Its late and Im tired.)

Update: (6:45 am EDST, 5 April 09) As of now, still no orbital object cataloged in the NASA satellite database as coming from this launch.

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In all the excitement and hubbub about Iran’s launch of the Omid satellite yesterday, there was other news that should warrant our attention. North Korea has, apparently, been seen shipping large missile bodies to its Western launch range. While described as a “Tae’podong 3” or upgraded Tae’podong 2, it already seems like old technology some how. What we should look for is signs that the North has imported technology from Iran and is moving away from stacking SCUD-type missiles on top of each other.

I’ve heard some interesting comments about this launch though I can’t seem to find the references when I need them. In particular, I’ve heard that launching from its new Western launch site would allow both the first stage to fall well short of Japan but also allow the upper stages to be considered already “in space” by the time they pass over Japan. I’m uncertain as to the space law involved but I would have assumed that the only meaningful milestone would have been for the satellite to already have reached orbital speed by the time it crosses Japan. Somehow I doubt that is will be the case. Furthermore, if North Korea does use a third stage, as it did with the Tae’podong 1, then the second stage would almost certainly not be “in space” as it over flew Japan.

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…and the middle one (after surveying all the beautiful Italian people) says “Know any good books about missiles?”

And the last one says “Why, yes! I like the books from the ‘50s and ‘60s.”

And the first one in says “And then the frog said, ‘I feel all white and fluffy!” But that’s another story.

So James has asked me what books I can recommend for learning about missiles and he also suggested that it would make a good easy blog. Here is my short list:

1) Handbook of Astronautical Engineering by Heinz Hermann (ed.) Koelle. Hands down the best book for actually learning about missiles. When ever I have mistakenly first tried a different book, I always come back to this one.

2) Aerospace Vehicle Design: Spacecraft Design (vol. 2) by K. D. Wood. If you want to calculate something quickly, this is the book to go to. Its just full of interesting and important empirical relations.

3) Rocket Propulsion Elements by George Sutton and Oscar Biblarz. Ok, they are always coming out with an new edition so perhaps its not really from the 60s any more, but people expect to see it in such a list. But seriously, If you have Koelle, you really don’t need anything else.

I like books written in the ‘50s and ‘60s because they weren’t pure mathematics and actually explained things. That, of course, is an interesting sociological “observation.” You might disagree and I’d like to hear your thoughts. Also, if you know of any other great books on missiles, let’s start a list! Of course, we all run the risk of starting a run on these books, so make sure you have your copy before posting it! Books from the ‘50s and ‘60s are starting to be worth their weight in gold.

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I remember having a conversation with a missile engineer some time ago about the North Korean Nodong missile; he said “no one in their right mind would field a missile that has only been successfully tested once!” At the time, that made a lot of sense to me. But exactly how many tests do you need? And more importantly, how do you decide how many tests you need? These questions should all be determined by the reason why tests are performed in the first place.

I think I understand bullet testing. When developing a new bullet, you test it millions and millions of times to make sure they work right in all imaginable situations and that you have a high degree of confidence that they will work. But, of course, bullets only cost a dollar or two each so there is little problem with running a standard quality control test program to allow you to achieve real confidence they are going to work. National missile defense tests cost about $100 million each so we are never going have the “95% confidence that the system works 95% of the time” that some critics of missile defense have been advocating. (I’m not against that in principle; I’m just saying it’s never going to happen. Any missile defense development program has to be adjusted to that reality.)

I was reminded of my conversation with the missile engineer when NASA announced it was awarding SpaceX part of a $3.5 Billion dollar contract to deliver supplies to the ISS based on a single successful test flight. SpaceX is quickly becoming my favorite sociological experiment in missile development. Touted as a more cost effective way of getting into space, SpaceX has hired former NASA engineers and uses government facilities without, I’m sure, contributing to paying off their development costs; just some sort of use fee. But now, it seems, that the real way they are going to save money is not to have the sort of expensive testing program we might expect from a government development program. This isn’t going to be a rant against SpaceX, which as I say, is one of my favorite sociological experiments (which also doesn’t imply that I think they are doing the right things!) The problem is, I’m not sure what the government would use that development program for, anyways. If we are not using flight tests to determine statistical reliability, perhaps only one successful test is really all that is needed. If so, what does that tell us about countries just starting the development of their missiles?

Tests Associated with Various Development Programs

Program	No. of Tests	No. Successful Tests
Falcon-1 (SpaceX)	4	1
W-76	4	2*
RS-24	3	3
Al Samoud I (Iraq)	37	33
Al Samoud II (Iraq)	24	22
Nodong (DPRK only)	2	1
Taepo’dong I (DPRK)	1	0**
Taepo’dong II (DPRK)	1	0

*I have arbitrarily dropped the two tests with anomalous results from the successful column. **First 2 stages successful.

Integration Tests

One reason I like the Falcon-1 test series so much is illustrated by the reason the third flight test failed. Developed by engineers and scientists who have had plenty of experience developing other missiles, this missile failed (I believe) because they were concentrating so much on economic factors, namely the reuse of the first stage engine. If you want to reuse an engine, you don’t want to go firing pyrotechnics that blow holes in the nozzle to quickly drain the fuel. On the other hand, if you don’t quickly and reliably shut the engine down, the remaining fuel might cause the first stage to continue to produce a little bit of thrust and hence risk bumping into the second stage engine and breaking it as they separate. That is exactly what happened. Could SpaceX have caught this error if it had run more ground checks? If so, were they cut to reduce design costs? I hope you see why I like it so much.

The RS-24 is another interesting case that seems to be devoted to testing an integrated system. Pavel Podvig has made a very convincing argument that the RS-24 is a Topol-M missile with more than one warhead uploaded onto its bus. In that case, perhaps it shouldn’t need very many flight tests to get it up to speed. In fact, one might think that only the post-boost bus needs testing. But perhaps even that doesn’t need much testing since some claim that the Topol-M’s bus was tested for more than one warhead without loading any more on it by simply maneuvering as if it did have the warheads. (Some Russians claim exactly the same thing for some US post-boost buses. The US responds to those charges by claiming that additional maneuvers were needed for range safety reasons. And so it goes.) On the other hand, as the Falcon-1 test series shows, integrating different components does introduce new modes of failure. Were three tests enough? Apparently so, since Russia has said they will now introduce the RS-24 into their arsenal.

Statistical Uncertainty

The US philosophy of testing nuclear weapons is perhaps the hardest to understand; not least because so much is buried in secrecy. One could have imagined that, since the US performed over 1054 nuclear explosion tests (it appears that some tests had more than one explosive device tested at a time) and “developed” a total of 112 nuclear weapons, they could have used these tests to establish a reasonable statistical reliability for each weapon. After all, this corresponds to nine tests per bomb design with a significant number left over for testing one-point-safety, which would be reassuring. Except that the US testing philosophy was never to test to this level.

Instead, our nuclear tests were supposed to develop weapon designers’ expertise; an expertise from which they could judge the reliability of a nuclear design without further testing. This must rely on two assumptions that are probably true most of the time: 1) that the non-nuclear components are tested individually and as a whole enough times to establish a statistical reliability for the non-nuclear functioning of the design and 2) the nuclear process involves so many “particles” that statistical fluctuations cannot have a significant effect on the design’s function.

Some doubt that the later is true for the W-76, a mainstay of the submarine leg of our nuclear triad. Critics have suggested that the possibility that a macroscopic instability exists that violates the second assumption. It is also one of the few warheads for which the US has released information on its testing. It had a total of four tests during its development and apparently two of them had “anomalies.” They could have had anomalously high yields, or anomalously low yields, or anomalies that didn’t affect the yield; the open literature doesn’t say. However, we know that one anomaly resulted in a retest and the other in a change in a component (but no retest). Fortunately, there have probably been enough tests of the W-76 with the few stockpile surveillance tests done in the later years of testing to establish a reasonable statistical reliability, especially when more than one warhead is devoted to each target.

Other Countries
Given these examples of developed countries’ R&D programs, Iraq’s development of the Al Samoud I and II are very reassuring. Not only did they use flight tests to iron out the bugs, they went on to what we would call an extensive operational test and evaluation series. The last 11 Al Samoud II flight tests were for verification of the “firing table,” determining the range under various conditions such as changes to the pitch program etc. (One of these failed, so the operation failure rate of the Al Samoud II was probably around 10%.) Still, I cannot help suspecting that somebody in a powerful position might have made a lot of money for each test flight flown. Hence their large numbers. Still, if other countries followed this sort of a testing program, we would never miss their development of an ICBM.

North Korea, on the other hand, doesn’t seem to need nearly as many flight tests. Apparently only one successful test was needed for DPRK to start selling its Nodong missile abroad. Various analysts have come up with ingenious reasons for this and they could very well be right. But, on the other hand, do we really understand why and how we test complex systems well enough to claim to understand North Korea’s? I am full of doubt.

Note added: Just to be clear, when I say I think there have probably been enough stockpile surveillance tests of the W-76 to give a reasonable statistical confidence to the W-76’s reliability, that was not the intention of the surveillance tests. In fact, this statement is based only on my estimates of the numbers tested that I derived from a correlation analysis and published in Jane’s Intelligence Review in July 2005. As I hope I made clear, the reliability of nuclear weapons is officially based on the judgment of the designers and not on tests. Perhaps not surprisingly, that is probably the case with all the other tests considered here.

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