Geoff FordenBuild New or Buy Old?

Up until about a year ago, potential home owners in the US had to ask themselves “Do I want to buy new or go with an existing home?” (Now, of course, there aren’t any potential home buyers.)

Missile proliferators have had to ask themselves a very similar question and they too almost always answered: “I’ll buy old and renovate to suit my special circumstances!” The reasons are almost identical as well. Buying new (or, in the case of the missile proliferator, developing a new missile indigenously) is too much trouble, it is too risky that they might fail, or they realize that they really don’t know enough to properly manage new construction and will probably be ripped off by the contractor they hire.

North Korea is the stereotypical example of this with almost all (all?) of their missiles derived directly from Soviet missiles. I hedge on that because Robert Schmucker has some very interesting ideas that it is even more direct than that. Iran, on the other hand, appears to be like the homeowner who first buys a starter house and then sets his sights on a custom built home.

Iran’s starter house was a Nodong factory they almost certainly bought from North Korea; we know, after all, that North Korea offered to sell Iraq a complete Nodong factory shortly before the Second Gulf War started. Iran did what most homeowners do with a starter house: they remodeled.

— They “knocked out the kitchen wall” by lengthening the propellant tanks and thereby increasing the range.

— They also “put on a new roof” by upgrading the warhead design to make it more stable during reentry.

(Surprisingly, most developing missile proliferators don’t seem to fully appreciate that an unstable warhead with an erratic incoming trajectory is what they want to avoid terminal missile defenses. My guess is that stable incoming trajectories are a sign of competence in a field where prestige plays a dominant role. Who are they trying to impress? I would hazard that it’s their own government; the people who fund them!)

In the language of the theory of technology diffusion, Iran used the Nodong factory to assimilate the engineering and shop-floor know-how of liquid propellant missiles.

Now, with the Safir, they are moving on to improving that technology in an evolutionary way. The next step will be to innovate and I would guess that would come in two areas: (1) new propellants and (2) lighter airframe materials. There are real advantages to such an indigenous path to acquiring the technology. The question is how far they are away from success in those two areas.

The US Missile Defense Agency seems to feel that the Iranians are possibly within a single year of, but no more than six years away from, having an ICBM capability — here is a chart from MDA:

Click on the image for a larger view.

The most charitable thing I can say is: you got to be kidding!

These graphics are from a briefing by Gen. Obering in May 2008 (remember that date!) — after the flight of the Kavoshgar-1 but before either the Safir of the Sejil. Lets consider these missiles one-by-one, starting on the left.


Ashura. Obering labels the first missile as the Ashura but it looks remarkably like the Sejil—minus the boxes on its side. Since Gen. Obering lists it as already having flown in May of 2008, he presumably confused it with the Kavoshgar. But why does it then appear to be a two stage missile when we know that the Kavoshgar had only a single stage? I think we are seeing some of the problems with intelligence gathering, analysis, and use. Drawing the “Ashura” that way represents a remarkable intelligence success. They obviously had some very good inside information from the Iranian missile development program: the same “baby bottle nosecone” as the Sejil and roughly—as near as we can tell from the graphic—the right proportions between the first and second stages. Not shown in the composite I’ve shown here is that MDA shows the “Ashura” as considerably larger than Shahab-3, I’m not sure how it stacks up to the Shahab-3B but I believe the Sejil can be transported in the same TEL. Unfortunately, it appears that somebody, perhaps the “user” (?), has ignored all the differences between their “Ashura” and the Kavoshgar—namely that the Kavoshgar was a single stage missile—to try to show that the threat was closer than it really was last May. (By the way, the Obering graphic does appear to show jet vanes.)

Possible SLV. The SLV is somewhat better since it shows a nosecone very similar to the nosecone actually used; again, something of a success for the intelligence analysts who must have spotted the nosecone in pictures from Ahmadinejad’s February visit to the Iranian Space Center. Even here, however, the threat it represents is exaggerated but, this time at least, it is almost understandable coming from an intelligence estimate. The graphic shows the SLV, which I take to be the Safir, as having a second stage almost as large as its first stage. When you size a multistage missile, an optimal approach to designing the different stages is to assume that each will produce the about same change in velocity that the other stages produce. That implies a second stage size similar to the first stage while the actual Safir has a second stage noticeably smaller than its first stage, and it might well run into structural problems if it made the second stage any bigger since the current missile has a length to diameter ratio of about 17; at the up end of the rule of thumb for structural stability. Nevertheless, we are left with the question of why the IC missed the fact that the non-flight mockup of Safir showed a second stage more in keeping with the actual Safir. Did the IC simply not believe that mockup was an actuate portrayal of the Safir? If so, were they unduly influenced by an organizational imperative to enhance the threat by making the missile seem more capable? It obviously wouldn’t be the only example in this graphic!

Projected ICBM. Consider the “Projected ICBM” shown here as the last Iranian missile. It appears to be a two stage missile (it’s hard to know for sure what the IC intends, but the cable raceways running down the right side of the missile seems to indicate they think this will be a two stage missile.) We will consider this in more detail tomorrow, in the last of this series of posts and another techno-wonk one! But let me borrow some of the results to say that a 750 kg payload (including the nuclear device and its reentry body) to say that a two stage missile with an deadweight fraction of 10% and an average specific impulse of 240 s implies a total mass of 120 tons! (This has been calculated using constant mass fractions and specific impulses to facilitate tomorrow’s discussion.) That’s a very massive missile! So massive, in fact, that the cluster of four Nodong engines we discussed yesterday would only yield a thrust to weight ratio of roughly one at liftoff. (And would be so under-powered that they would only loft the payload a total of about 4000 km.) For comparison, the Nodong has a thrust to weight ratio of over 1.8 at liftoff. Tomorrow we will discuss what it take for Iran to achieve even this and how long it might take them to field such a missile if they remain on the SCUD-type technology arc.

North Korea North Korea seems to have taken the other path: renovating existing missiles to produce some sort of hybrid.

Taepodong 1. In its Tae’podong I missile, North Korea stacked an existing solid-propellant third stage (some say it used the booster from an SA-2 air defense missile) on top of a SCUD-B on top of a Nodong missile. This missile failed during its third stage and, if I had to guess, I would say that spinning its third stage to stabilize it produced higher burning rates that increased its chamber pressure beyond what it could stand. The failure of the Tae’podong II, however, was more telling about North Korea’s development path. (And why doesn’t the Obering graph indicate it failed? I’m afraid that, too, is a clear example of inflating the threat.)

Taepodong 2. Less is known about the Tae’podong II. However, many analysts believe it used a design borrowed from an old Soviet missile for the first stage and, perhaps, a Nodong for the second stage. It is, of course, not known for if it had a third stage though if it intended to put a satellite into orbit it would make sense for it to have one. (By the way, I completely agree with the sentiment expressed by Jochen Schischka that the Tae’podong II is, in some sense, a “virtual” missile.) The missile, however, is reported to have failed some 42 seconds after liftoff, a number that suggests to me that it failed because the combined forces due to aerodynamic drag, acceleration, and gravity, caused this rather kludged design to collapse.

I notice that I haven’t had a chance to discuss “reverse engineering” (RE) of missile designs and the problems such an acquisition path introduces. Perhaps I will get a chance to discuss that sometime in the future since MDA’s IRBM is arguably a reversed engineered SS-N-6. I’ll just say that many proliferators are seduced by RE’s supposed advantages by borrowing somebody else’s engineering effort but they rarely succeed. (See my paper on WMD acquisitions paths )

Tomorrow, in the last post for this series, we will “design” the “Projected ICBM” in a return to techno-wonk posting. It will, however, concentrate on scaling up SCUD-type technology and will not discuss, at least in much detail, the possibility of a solid-propellant ICBM.


  1. Tal Inbar


    Just a quick note on the Ashura missile which appeared on Gen. Obering’s presentation:

    I think Gen. Obering is right on his remark that the Ashura missile was test flied, and he certainly didn’t mixed up with the Kavoshgar (which in is basically a “baby bottle” Shahab 3 b painted white/ green).

    The Ashura looks remarkably like the Sejil—minus the boxes on its side. That is correct and you can give the US Intelligence the credit of being the first to describe this missile correctly at open forum. The sejil is at best a variant of the Ashura. More likely, it IS the Ashura (remember the Iranian habit of calling the same weapon system in different names).

    We KNOW that various Iranian officials talked about a two stage missile (Ashura) since 2007, And there are credible reports of a test launch (which failed) on that year.

    I really don’t understand the thesis that Obering replaced the Kavoshgar with Ashura.I think that the Kavoshgar is missing from the drawing because the US Intelligence KNEW that it is simply a regular Shahab 3B, and NOT a 2 stage missile used as testbed for space purposes, as claimed by Iran.

  2. Geoff Forden (History)

    Check the dates; Obering lists the “Ashura” as having flown sometime before May 2008. The only explanation that I can think of is that he confused it with the Kavoshgar. Unless you think the Sejil flew before May 2008?

  3. Tal Inbar

    To the best of my knowledge, Ashura missile was test fired on 2007. Until proven otherwise, to me, Sejil is a different name to the Ashura. BTW, there is an earlier version of Obering presentation, dated February 28, 2008, AFTER the Kavoshgar was launched, and in that version the Ashura is not described as a missile that has flown.


    so in that regard you can not claim that he was mixing the launches of Kavoshgar and Ashura.

    I will try to find the Iranian statements on the launching of an Ashura missile back in 2007.

  4. Josh

    The 2010-2015 date range for the projected ICBM seems derived from periodic NIEs on the ballistic missile threat. This particular date range seems to have appeared for the first time in September 1999.

    Careful readers will notice that the Sept. 1999 NIE reflects disagreement between different agencies and therefore equivocates quite a bit. It contains many fine examples of the estimative language previously described by Jeffrey.

    Concerning the testing of the Ashura, ACT’s Peter Crail reported the following:

    “[Iranian Defense Minister] Najjar did not make any reference to a test of the Ashura but there are indications that an unsuccessful test occured in November [2007]. During a Dec. 6 press conference in Washington, Chief of Russian General Staff Yuri Baluyevsky said that he was told in meetings with the Department of State and National Security Council that Iran tested the Ashura on Nov. 20. A Russian diplomat told Arms Control Today that the test was not successful.”

  5. Tal Inbar


    I was referring to the failed test of November 2007. Thanks. The fact that Obering’s presentation does not indicate a flight test of the Ashura until April 2008 is interesting, since the US intelligence knew exactly what happened on November 2007.

  6. Murray Anderson (History)

    You say, correctly, that the stages should be designed to give the same delta-v, but that means that the second stage should be much smaller than the first, not the same size, because the first stage has to boost the second stage and warhead, while the second stage just has to boost the warhead.

  7. Geoff Forden (History)

    A second stage is somewhat smaller than the first stage but not a lot smaller. Take a look at this comparison of the Titan II (a large two stage ICBM) and the Safir. Note also that I’ve most probably included the Safir’s guidance section in its second stage but have excluded it from the Titan II. The proportions of the two stages of Titan II are much more in line with what MDA has shown for the Iranian SLV than the Safir. (Full disclosure: I’ve “photoshopped” in the engine section of the Safir. If I left it out and, instead, only looked at the fuel tanks, the relative proportions would seem even more different!)

  8. Allen Thomson (History)

    On the estimative language in the NIE, it’s important to read the discussion of “could” and “likely” in the preface. There’s a further explanation of how those words are used in , which appears to be a transcript of testimony by National Intelligence Officer Robert Walpole before the US Senate Government Affairs Committee on March 11, 2002.

  9. Jochen Schischka (History)

    To Tal Inbar:

    Based on the information available to me on this issue, i must say that in my opinion a flight test of the Ashura missile in november 2007 is anything but certain. It might also have been only a ground test (in any case necessary for such a development!) or the official announcement of this missile program.

    BTW, makes a distincton between the “Ghadr-110” and a “Ghadr-110A” (which is interpreted there as a three-stage missile) – could this perhaps translate into the “Ashura” (initial configuration as shown in the MDA-drawing) and the “Sejil” (altered configuration, maybe with additional “sidepipes”/retrorockets)?

  10. Jochen Schischka (History)

    Considering unstable warheads:

    A militarily useful missile should possess the ability to actually destroy a selected target (opposed to a pure terror- or “propaganda”-weapon that exclusively aims at striking fear by symbolic actions – like the V-2-bombardment of London or the Al-Hussain-shots at Tel-Aviv – or which is not intended to be used at all, except as a political bargaining token), isn’t it?

    So the effective radius of destruction of the warhead should ideally be about the same as the maximum deviation or at least the CEP that can be expected for the missile at a certain range, right?

    A randomly-maneuvering unstable warhead without doubt would be even more unlikely to land anywhere near the intended target, so it would perhaps be able to penetrate a missile shield, but so what? There is no point in shooting something down that won’t hit anything anyway!

    Since i expect the CEP of the iranian missiles to be at least in the order of several kilometers (i see no sign for anything other than a Horizont-Vertikant-guidance system, basically the same as on the Scud – converse evidence welcome!), a fast, straight-flying (“baby-bottle”) RV with a high ballistic coefficient and a nuclear payload (20+ kt – anything other than a nuclear payload simply doesn’t make sense with such a small-volumed RV anyway) seems to me to be a much smarter approach to an actually deployable weapon than a potentially “unstoppable”, rampantly-tumbling conventional warhead (nukes are usually triggered by radar fuses – which are useless if they point to the sky in the wrong moment) with an area of effect of 30 to 50 meters…

    As far as i can tell, the change to the triconic RV clearly indicates a shift in the iranian intentions.

  11. Jochen Schischka (History)

    Considering (RevEng-)R-27/SSN-6/Serb in North Korea/Iran:

    I’d be very surprised if these countries should in fact have mastered the technology of the closed-cycle-high-pressure-main engine of that missile (on the other hand, the belonging open-cycle-twin-chamber-vernier-engine is rather low-tech in comparison…).

    Again, until hard photographic evidence to the contrary surfaces, i’m inclined to interpret the dreaded “NoDong-B” as nothing else than the Ghadr-1.

  12. Murray Anderson (History)

    The second stage of the Titan II was a lot smaller than the first. According to David Stumpf in “A History of a Cold War Missile Program” page 49 the length of the first stage was 70 feet and that of the second stage was 20 feet. The relative masses were were in roughly the same proportion. Other sources give somewhat similar figures. For example, page J-2 (p 104 in the pdf) of Nasa Launch Vehicle Handbook, dating to 1961 gives a stage mass breakdown of 257K lbs versus 63K lbs for first and second stages respectively (available at

  13. Maggie Leber

    I suppose an “erratic incoming trajectory” is a valid way to avoid terminal missile defenses….as long as you don’t much care what you hit.

  14. Geoff Forden (History)

    Let’s consider exactly what an erratic trajectory is and what effect an unstable warhead would have as well as what a strategic target for a conventionally armed ballistic missile might be. (After all, if the weapon can fulfill a strategic mission, then it has a military utility.) First, here is a picture of an incoming Al Hussein missile. It has its warhead still attached but because the body extension of the Al Hussein, it was unstable when empty. The height of the warhead at this moment was about 10 km. (The annotation comes from Ted Postol, who has no responsibility for this post.) Note that the erratic motion tends to cancel itself out, though nobody is talking about hitting a hardened silo with this weapon.

    Here was the Al Hussein’s target:

  15. Jochen Schischka (History)

    And thus, as i tried to explain – without usefulness to the military!

    A weapon that has only a marginal statistical chance to transport its warhead close enough to damage or destroy the intended military target (as in “i’ll have to launch 100.000 missiles to statistically have a chance for one hit on that strategically important building”) has, since you could neither afford launching a sufficient number nor hope that your enemy would allow you to do this, NO ACTUAL MILITARY VALUE!

    Weapons with such characteristics are mere terror- (if actually used) or propaganda-weapons (if not actually used – in my mind the preferable option)!

    By the way, i don’t want to say that an “unstoppable” weapon in this context is worthless – in contrast, this would be highly beneficial for mentioned terror- or propaganda-affairs.

    But fear alone never has won any real war so far (at least, not that i’d be aware of…)!

  16. Jochen Schischka (History)

    On the issue of the proportions of the stages of a two-staged missile:

    That depends on the intended purpose and design philosophy!

    If you plan on launching a satellite, i’d allocate only enough delta-v-capability (about 2-3 km/sec) to the lower stage to insert the upper stage into a height-optimized trajectory and generate the rest (about 7-6 km/sec, drag- and gravity-losses included) for a circular orbit with the upper stage. This has the advantage of 1.) minimization of losses by leaving the atmosphere and the gravity-field as slow as reasonable (aero-drag) on the shortest way possible (aero- and gravity-drag) and 2.) maximizing your engine-performance by using ambience-pressure-optimized rocket engines (the lift-off-engine can only have a limited area ratio!) and fuel combinations (LOX/LH2 offers high Isp, but low mass-flow -> comparable low thrust and efficiency at sea level). Of course, this approach requires a coast-phase after staging so that the upper stage can take full advantage of the lower-stage trajectory. And this leads to the problem of igniting a liquid-fuel-engine under free-fall-conditions (solvable by ullage motors). Retrorockets on the lower stage prevent a collision with the (still inactive immediately after staging) upper stage in this scenario if necessary.

    On the other hand, on a surface-to-surface-missile i’d use the mentioned 50-50 delta-v share in combination with an upper-stage-ignition while the lower-stage engine still pushes the upper-stage-propellants into the upper-stage turbopump and combustion-chamber. Only after lower-stage-cutoff/-burnout would i then disconnect the already accelerating upper stage from the lower stage by explosive bolts. But for this to work properly, openings in the interstage-section are required, so that the exhaust-gasses of the upper-stage-engine can escape (classical examples are the Titan-II, the DF-5 or the Taep’oDong-1), which are sometimes covered-up by “blow-out”-panels. Coast-phases would only be counterproductive for a range-optimized trajectory (where only two things count: velocity and angle at cutoff).

    A proliferator with limited resources will more likely follow a third, makeshift-like approach by using whatever is available to him (see Taep’oDong-1 or Al-Abid), making predictions on the intended purpose of specific missiles somewhat difficult.

  17. Pedro

    So what would be the reason for the Sejil to have a free-flight phase which the retro rockets on the first stage indicate? The reason for free-flight phase is to avoid strong elliptical paths for satellites, is there any reason for its use with military missiles?

  18. Jochen Schischka (History)

    This is exactly what i also don’t understand (yet), especially since the burnout-height of the Sejil-lower-stage should range below 20 km (-> still considerable aero-drag).

    On the other hand, the soviet R-14/SS-5/Skean single-stage-liquid-missile also used retrorockets, obviously in this case to avoid a collision with the separated warhead.

    Maybe the Iranians have a problem with after-acceleration of the not-thrust-terminated first stage (although obviously other multi-staged solid-fueled missiles don’t share this problem)? Could this be connected to a non-functional upper-stage (e.g. to demonstrate successful staging to radar-observers)?

    It would be VERY interesting to know if the retrorockets were (or will be) present on the initial (or a possible future) configuration of the Sejil (could this be the name-changing difference to the Ashura?)!

  19. Geoff Forden (History)

    There are boxes all over these missiles but there is one right up near the nose cone of the Safir that, to me, looks very similar to the one on the Sejil that is immediately below one of the four boxes that mark the start of the second stage. I thought that on the Safir it might be video camera(s) for recording the staging and nosecone ejection. What do you think?

  20. Jochen Schischka (History)

    To Geoff:

    Interesting thought. I’ve also been puzzling over what these small boxes could be. Did you notice that in both cases, Safir and Sejil, there are two symmetrically arranged boxes on opposite sides of the body (on the sides II and IV of the Safir and at I and III in case of the Sejil)?

    On the Safir, i tend to the interpretation that these are fairings for ullage-motors (-> see liquid-stage ignition under free-fall conditions), although the positioning would be somewhat unconventional (but not necessarily unreasonable);

    I can only speculate on what the small boxes on the upper end of the lower stage of the Sejil could contain. Maybe some sort of staging-related spring-mechanism or pyrotechnics (since this is exactly adjacent to the plane of separation of both stages)?

    BTW, in my last comment i should have written “the sidepipes”, since we can still not be absolutely positively sure that these structures really are retrorockets (although i think the chances for this are not bad)…