By Michael Elleman
22 September 2016
North Korea’s ground test of a powerful, liquid-fueled engine on September 20, and the launch of three modified-Scud missiles earlier this month renewed allegations that Pyongyang and Tehran are collaborating on ballistic-missile development. The accusations are mostly speculative, based largely on the apparent similarities of ballistic missiles and satellite launchers appearing in both Iran and North Korea. A detailed examination of the designs employed by the two countries casts doubt on claims that the two countries are co-developing missiles and satellite launchers, exchanging detailed design data, and testing prototypes for each other. Pyongyang and Tehran may share test data on a limited basis, and perhaps trade conceptual ideas. But there is little evidence to indicate the two regimes are engaged in deep missile-related collaboration, or pursuing joint-development programs.
During its war with Iraq in the 1980s, Iran’s cities and petroleum infrastructure were repeatedly attacked by Baghdad, which possessed a sizable arsenal of Soviet-supplied aircraft and Scud-B ballistic missiles. Lacking reliable access to the skilled technicians and spare parts needed to maintain and fly its Western-supplied aircraft in the aftermath of the 1979 Islamic Revolution, Iran was unable to respond to and punish Iraq for the assaults. Tehran was thusly driven to acquire ballistic missiles and artillery rockets from willing exporters for its counter-strike capabilities. Libya and Syria initially shipped a limited number of Scud-B missiles to Iran, with allowed the Islamic regime to target Baghdad and other large Iraqi cities in the mid-1980s. In need of a much larger arsenal of missiles, Iran turned to North Korea for its longer-term requirements. Pyongyang shipped between 200 and 300 Soviet-built Scud-B and Scud-C missiles to Iran during the latter years of the war and into the early 1990s. Iran renamed the missiles Shahab-1 and -2, respectively.
The transactional relationship between Iran and North Korea continued throughout the 1990s, with Pyongyang providing missile-maintenance infrastructure and training, as well as medium-range Nodong missiles, which Iran dubbed Shahab-3. When Tehran test fired its Shahab-3 in July 1998, it was only the second known launch of the Nodong, with North Korea having successfully flown the missile just once, in 1993. Iran continued to flight test the Shahab-3, as did Pakistan, another recipient of the Nodong, which it calls Ghauri. The preliminary flight trials conducted by Iran and Pakistan showed promise, though Iran was concerned that the Shahab-3’s maximum range was less than 1,000 km. Consequently, Tehran’s engineers and missile specialists modified the Shahab-3 to create the 1,600-km range Ghadr missile, which was initially test flown in 2004.
It is unclear how deeply involved North Korea was in Iran’s program to modify the Shahab-3, and create the Ghadr missile. While it is reasonable to assume that some flight-test data were shared, interviews with Russian and Ukrainian specialists aiding the Iranian missile program during the late-1990s suggest that cooperation between Pyongyang and Tehran was isolated and not comprehensive. Iran’s compartmentalisation of the missile programs would have impeded deep technical collaboration with North Korea, if not preventing it altogether. Moreover, if the security procedures in Iran continue today, it is unlikely Pyongyang and Tehran are actively cooperating on missile and satellite-launcher development, though critical materials and components may continue to flow from one country to the other.
Four Allegations of Possible Collaboration and Cooperation
Those arguing that Iran and North Korea are cooperating on missile development cite four observations. Two of them center on the similarities in the evolutionary versions of Pyongyang’s Nodong missiles and Tehran’s Shahab-3 and Ghadr systems. The third observation focuses on the solid-propellant technology recently used by North Korea to propel its submarine-launched ballistic missile, the KN-11, which some argue is identical to that employed by Iran’s two-stage, medium-range Sajjil missile. The fourth, and most often citied observation, and the one said to be corroborated by official US government sanctions, claims that Tehran and Pyongyang are cooperating on the development of large rockets used to loft satellites into orbit.
As discussed above, to overcome shortfalls in the reliability and reach of the Nodong missiles imported from North Korea, Iran modified the Nodong/Shahab-3 to create the Ghadr missile. The evolution in design was incremental, with several versions of the improved Shahab-3 tested in Iran. North Korea, which launched only one Nodong prior to 2006, presumably retained the original design. There are no publicly available photographs of the Nodongs tested in 2006, so it is impossible to know if any modifications were introduced by North Korea. The first public appearance of the missile occurred in 2010, when the Nodong was seen during in a military parade in Pyongyang. The Nodong that appeared in the parade was a mock-up, though, at first glance, it looked similar to the Ghadr, including the complex shape of the nosecone. This led some to conclude that North Korea and Iran collaborated on its design, and by extrapolation, possibly the flight-trials conducted in Iran during the 2000s.
In August 2016, North Korea’s KCTV aired video of Nodong missiles being fired from their respective mobile launchers near Hwangju and roughly 40-km south of Pyongyang. The missiles resembled those seen in the 2010 parade, with the Ghadr-like nosecone design. It is reasonable to conclude from these occasions that engineers from the two countries shared at least some nosecone-design information. However, a closer examination of 2016 launches reveals definitively that the similarities between the North Korea’s new Nodong missile and Iran’s Ghadr do not extend beyond the shape of their nosecones. Indeed, the external dimensions and features, other than the similar nosecones, are quite different. Figure 1 illustrates two prominent differences. The Ghadr’s rear fins are much smaller than those found on either version of the Nodong, and the Ghadr’s airframe and propellant tanks have been lengthened to carry more fuel. The original and new Nodong airframes appear to be the same, only the nosecone has been altered.
Figure 1. Key differences between North Korea’s Nodong and Iran’s Ghadr missiles.
It is interesting to note that the minimum distance between North Korean territory and Tokyo is just over 1,000 km. If the new Nodong is a clone of the original version, but with a new nosecone and smaller warhead, it has a maximum range of about 1,000 km, when launched with a 700 kg payload. To ensure pre-launch survival, Pyongyang would presumably want to deploy and fire the missile from deep within its territory, which requires a reach of 1,200 km or greater. In other words, North Korea has great incentive to extend the Nodong’s range, yet it does not appear to have adopted the Ghadr’s design.
In September 2016, North Korea fired three missiles, again from mobile launchers situated on a highway near Hwangju. The missiles travelled about 1,000 km before crashing into the East Sea, though within Japan’s air defense identification zone. Most observers initially suspected that the missiles launched were Nodongs because the longest-range alternative is the Scud-D, which has a range limit of just over 700 km. Pyongyang reportedly developed a Scud-D missile with a range of just over 700 km. Video of the launch appear to show a Scud-B warhead placed on a Nodong airframe, with a short flange connecting the two. An Iranian missile with a similar nosecone and airframe configuration was seen in Tehran a dozen years ago, leading one analyst to conclude that North Korea and Iran collaborated on the design. But again, closer scrutiny of the missiles and an analysis of the trajectories expose a different story (see Figure 2). The missiles were extended range Scud missiles, or Scud-ER, having a diameter of 1.0 m, and an overall length of about 12.6 m. The diameter and length of the Scud-B and –C are 0.88m and 10.944 m, respectively. The Scud-D has the same diameter as the –B and –C versions, though its length is 12.4 m. The Scud-ER is very different than the Shahab-3—with the so-called NRV nosecone—seen in Iran in 2004.
Figure 2. Key differences between North Korea’s Scud-ER and Iran’s Shahab-3 missiles.
Iran, unlike North Korea, has pursued both liquid- and solid-fueled missiles since its dual-track approach to missile acquisition started in the early 1980s. Iran now possesses a family of short-range missiles, including the Fateh-110 and Fateh-313, which were developed over a period of at least two dozen years. Tehran is also developing a two-stage, medium-range missile, the Sajjil. The Sajjil program likely began in or about the year 2000. The first ground tests of the 13.5-metric ton, stage-one motor reportedly occurred in 2005. The Sajjil, though dubbed Ashoura at the time, underwent its initial flight test, which failed, in 2007; a successful test occurred in 2008, though only the first stage was active. Flight-testing continued until 2011, when launches abruptly stopped before the missile was fully developed. The reasons behind the halt in testing remain unclear.
North Korea, on the other hand, has limited experience developing and producing solid-fueled missiles. The largest solid-rocket motor manufactured by Pyongyang before 2016 weighs only one-metric ton and propels the KN-02 missile, a copy of the Soviet Tochka. The KN-02 has a maximum range of about 100 km, though versions of the original Tochka can reach beyond 120 km. In April 2016, North Korea conducted a ground test of a large solid-fueled motor and test launched at least two solid-propellant missiles from an underwater platform, likely its GORAE-class submarine. The KN-11, submarine-launched ballistic missile (SLBM) is a two-stage system. Each stage consists of a solid-propellant rocket motor substantially larger than any tested by the North before, excepting the April ground test. Learning to manufacture large-diameter, solid-fueled rocket motors typically requires decades of effort, as illustrated by the history of Iran’s program, as well as others. Yet, with no public reporting of large solid-motor development in North Korea prior to 2016, the KN-11 emerged suddenly and flies successfully to a distance of 500-600 km.
The sudden, unexpected appearance of the solid-fueled KN-11 led to speculation that Iran may have aided Pyongyang’s efforts to design, develop and manufacture large-rocket motors, or perhaps supplied the motors to North Korea outright. Tal Inbar, an Israeli analyst who closely follows the missile and space programs of Iran and North Korea, asserts that the KN-11’s 1.25 m diameter motors are the same as those found on Iran’s Sajjil missile. He further states that the KN-11 is built using a propellant that is “identical to the technology developed in Iran.”
The exact dimensions of the KN-11 are difficult to extract from the photos and videos released by Pyongyang. However, the relative dimensions are readily derived from the photos. Based on the performance of the KN-11, the missile’s diameter is likely between 1.2 and 1.5 m. The length of the KN-11’s first stage is then between 3.5 and 4.4 m; the second stage is between 1.5 and 1.9 m long. The Sajjil has a diameter of 1.25 m, with first- and second-stage lengths of 9 m and 5.6 m, respectively. The relative dimensions—the ratio of the length to the diameter—of the KN-11 stages are clearly different from those of Iran’s Sajjil. Further, the external features of the Sajjil reveal stage separation apparatus that are not visible on the KN-11, indicating differing design philosophies. Both missiles do use jet vanes for steering during the boost phase of flight, though the vanes themselves are slightly different. Finally, it is possible that the propellant formulation used by the KN-11 and Sajjil are very similar, though this should be expected. Most solid-fueled rockets use a variation of what is called a composite propellant formulation, so it would be surprising if the KN-11 and Sajjil differed significantly.
Figure 3. Key differences between North Korea’s KN-11 and Iran’s Sajjil missiles.
Lastly, many observers note the similarity between the satellite-launch vehicles, or SLVs, used by Iran and North Korea, and speculate that the two countries are collaborating on large rocket development. It is true that the Taepodong-1 SLV launched by Pyongyang in 1998, and Iran’s Safir SLV have first stages powered by the Nodong engine. It is also true that the first stage of the North Korea’s Unha SLV and Iran’s Simorgh SLV use a cluster of four-Nodong engines, and the upper-most stages of both SLVs are propelled by the steering engines originally employed by the now-retired Soviet R-27 SLBM. But a closer look at the SLVs reveals differences inconsistent with close cooperation between Pyongyang and Tehran.
The most obvious difference is that the two North Korean SLVs operate using three stages, whereas Iran’s two SLVs are two-stage systems. This likely reflects the more conservative design approach taken by North Korea, where until late-2015, engineers had limited experience developing new missiles and launchers. The paucity of missile-development testing, and learned knowledge accrued from testing activities, likely led North Korean specialists to over design the Taepodong-1 and Unha launchers to ensure each succeeded in lofting a specified payload to a certain orbit. There may, however, be other reasons behind the decision to employ three rather than two stages. Regardless, the divergent design philosophies argue against deep cooperation.
The decision to power the first stage of the Taepodong-1 and Safir with a Nodong engine was very likely driven by that lack of viable alternatives. Neither North Korea nor Iran have the experience and wherewithal to design and develop a powerful liquid-propellant engine indigenously, so therefore each had to rely on the engines available for use. The roughly 27-ton thrust Nodong engine was a logical engineering choice for small SLVs. The alternative would have been to cluster two or four Scud engines together to form the power unit for a first stage, though such configurations would have required a new and larger diameter airframe.
When North Korea, and later Iran, began the design of the Unha and Simorgh SLVs, respectively, the most powerful engine available was still that associated with the Nodong missile. Again, the lack of viable alternatives drove both countries to design a first stage powered by a cluster of four Nodong engines, with each engine relying on its own turbo-pump assembly to deliver propellant to the combustion chamber. It was, and remains today, beyond the technical capacity of either country to design, develop and build a larger pump capable of simultaneously feeding all four engines.
The Unha and Simorgh both employ four small engines to steer the first stage. Arguably, this feature suggests some level of design cooperation. However, beyond the use of four small engines, the two designs diverge. Each steering engine of the Unha receives its propellant from the turbo-pump of an adjacent Nodong engine by tapping into the fuel and oxidizer lines of the nearby engine and diverting a small portion of the flow. In other words, each Nodong turbo-pump feeds a Nodong engine and a steering engine. Iranian engineers, on the other hand, adopted a different design for the Simorgh. All four steering engines of the Simorgh are supplied propellant by a single Scud-engine turbo-pump assembly placed at the center of the Nodong engine cluster. The Iranian design delivers up to 13 tons of additional thrust compared to the Unha.
Covert Development of Long-Range Rocket Booster
In November 2013, Bill Gertz reported that Iranian missile technicians had visited North Korea in secret to jointly develop a new “80-ton rocket booster” for long-range missiles or SLVs. Two months later the US Treasury Department issued sanctions against several persons and entities, including the Shahid Hemmat Industrial Group, or SHIG, the firm responsible for development of Iran’s liquid-fueled missiles, and two individuals, Seyed Mirahmad Nooshin and Sayyed Medhi Farahi. The Treasury Department notice specifically mentions that Nooshin and Farahi had travelled to North Korea, and that the two “have been critical to the development of the 80-ton rocket booster.”
It is unclear if the 80-ton rocket booster specified in the media and Treasury Department reports describes the overall size of multi-stage booster rocket, or just that of the single stage of a larger SLV. In either case, the description might apply to the Unha or Simorgh SLV. The overall mass of the Unha SLV is about 87 metric tons, and the Simorgh SLV is roughly 85 metric tons. The first-stage masses of the Unha and Simorgh are approximately 70 and 76 metric tons, respectively. It is within reason to conclude that the reports apply to either the first stages of the two SLVs, or the multi-stage configuration of the Unha or Simorgh. It would not be surprising if Iran and North Korea held discussions about their respective space programs, and the general technical details of their SLVs. Iran has, in the past, presented technical papers about its space program and SLVs at international meetings, so sharing general design and performance information is not unprecedented. However, as discussed above, the significant design differences of the Unha and Simorgh first stages indicate that the two countries are not co-developing rockets and that there may be limits to just how much technical information Tehran and Pyongyang share, or employ.
The recent ground test of an 80-ton thrust engine by North Korea raises additional questions, and might be the focus of the Gertz article and the Treasury Department notice. The engine tested is likely a version of China’s YF-20 design, of which there are several varieties. The YF-20 engine uses high-energy propellants, similar to the combination employed by North Korea’s Musudan, or KN-10, intermediate-range ballistic missile, and generates roughly 80 tons of thrust. North Korea announced that the engine tested produces 80 tons of thrust, and was for lifting satellites into geosynchronous orbit. The Treasury notice specifically mentioned an 80-ton booster; it did not refer to an engine. Nonetheless, perhaps the intelligence reporting that informed the sanctions lacked the necessary detail to distinguish between a rocket and engine, or the authors of the notice did not appreciate the differences. If the report was referring to the amount of thrust produced by the booster’s engine, then it is possible that Iran and North Korea are working together on a new rocket. If so, the booster rocket itself would necessarily weigh fewer than about 65 metric tons, and even less if it is the first stage of a larger system.
Evidence available in the public domain indicates that North Korea has, for several decades, supplied Iran with complete missiles and critical components for larger missiles and SLVs. The transactional relationship very likely results in information exchanges, including the sharing of flight-test data, possibly more. But, the evidence to date is inconsistent with design collaboration or joint-development efforts between the two countries. This could change, especially as North Korea presents new capabilities. Given Pyongyang’s history of shipping missile components to Iran and others, and its willingness to support the secret construction of a nuclear reactor in Syria, it is possible, if not likely, that North Korea would ship advanced engines to Tehran, including the engine most recently tested. Therefore, the international community must remain vigilant and closely monitor the missile and SLV activities in both countries. Signs of deeper collaboration between Iran and North Korea must also be closely monitored, since deeper cooperation has the potential to accelerate the development efforts on both parties.