Financial sanctions and oil embargoes imposed since December 2011 by the United States and European Union respectively have tightened the economic pressure on Iran and, along with United Nations Security Council sanctions imposed in June 2010, could yet deal a knock-out blow to the country´s development of long-range ballistic missiles.

There is mounting evidence to suggest that, whereas the sanctions regime has not prevented Tehran from operating an increased number of centrifuges for uranium-enrichment activities or adding to its stockpile of fissile material, it has stymied efforts to develop and produce the long-range ballistic missiles capable of striking potential targets in western Europe and beyond. If sanctions continue to disrupt Tehran´s access to the key propellant ingredients and components needed to produce large solid-propellant rocket motors, Iranian attempts to develop and field long-range ballistic missiles could be significantly impeded, if not halted altogether.

Liquid-propellant missiles

Soon after the start of the Iran–Iraq War in 1980, Tehran initiated a two-track effort to acquire ballistic missiles and related technologies to compensate for its barely operational air force. The first track focused on the immediate acquisition of short-range, liquid-propellant Scud-B missiles from Libya, Syria and North Korea for use against Iraqi cities during the latter stages of the war. The perceived success of the missile attacks led Iran to purchase additional 300km-range Scud-Bs from Pyongyang, along with 500km-range Scud-Cs, in the 1990s, which it renamed Shahab-1 and -2.

Wishing to threaten targets as far afield as Israel, Iran began procuring medium-range No-dong missiles,known locally as Shahab-3s, from North Korea in the mid- to late-1990s. The imported No- dong/Shahab-3 missiles, as received and initially tested by Iran in 1998, had a maximum range of only 900km, meaning that they could only reach Israel if launched from sites near Iran´s border with Iraq. In a quest to enhance pre-launch survivability, Iranian engineers spent almost a decade modifying the Shahab-3 to create a longer-range version of the missile, dubbed Ghadr-1. The Ghadr-1 has a maximum range of roughly 1,600km when carrying a relatively light payload of 750kg and is believed to have entered military service some time after 2007. If fitted with a heavy payload, such as a notional first- generation nuclear warhead weighing upwards of 1,300kg, the Ghadr-1´s maximum range would be reduced to roughly 1,100km.

Iran does not have the capacity to design, develop and produce new, more powerful liquid-fuelled engines, and this is unlikely to change over the next decade. Available evidence also indicates – but does not prove – that Iran cannot reliably build the liquid-propellant engines that power its current inventory of Scud and No-dong/Ghadr-1 missiles, a shortfall that likely leaves the Islamic Republic susceptible to supplier controls and unable to add to its stockpile of operational liquid-fuelled missiles. Iranian engineers may one day establish a capacity to produce near-copies of the Scud and No-dong engines, but such endeavours are rarely successful – replica engines do not perform as well as the originals and often prove to be unreliable.

The relatively low energy output of the Soviet-legacy engines available to Iran will certainly complicate attempts to develop and deploy longer-range missiles. Intermediate-range missiles founded on No-dong and Scud engines and capable of reaching western European cities, for instance, would necessarily weigh 60–70 tonnes, making them at least four times heavier than the Ghadr-1 and ten to 12 times heavier than the Scud-B. An intercontinental-range missile would be even larger, weighing as much as 120 tonnes. While it might be possible to deploy missiles weighing 60 tonnes or more on road-mobile launchers, they would be operationally cumbersome and vulnerable to pre-launch attack because of the extended launch-site fuelling times and the substantial logistics and support infrastructure that must accompany the missiles. Silo-basing would be a more viable option, but deploying missiles at known and fixed sites would leave them vulnerable to pre-emptive attacks by an advanced military power, such as the US.

Solid-propellant missiles

The second missile-acquisition track pursued by Iran focused on developing an indigenous capacity to manufacture solid-propellant systems. The approach did not yield immediate results beyond the production of artillery rockets for use during its war with Iraq. However, over the past two decades Iran has established the technical wherewithal to build increasingly larger, more powerful solid- propellant motors capable of propelling longer-range systems.

Presently, Iran is developing a two-stage, solid-fuelled missile with a maximum range of about 2,000km. Once fully developed, the missile, known as Sajjil-2, will offer Iran three significant strategic benefits. Firstly, solid-propellant missiles can be launched more quickly than their liquid-fuelled counterparts, and they require a much smaller logistical infrastructure to support operations, two factors that enhance pre-launch survivability. Moreover, because of their compact design and construction, solid-propellant missiles can be more easily fitted on road-mobile launchers. Secondly, the Sajjil- 2´s range–payload capacity is superior to that of the Ghadr-1, which would allow the former to be launched against targets in Israel from less vulnerable sites deep inside Iranian territory, even when carrying a heavy 1,300–1,500kg warhead. And finally, Sajjil technology will provide a foundation upon which larger, longer-range missiles could be developed indigenously, should Tehran seek such a capability.

The development of the Sajjil-2 began about a dozen years ago with the acquisition of the necessary production equipment and infrastructure, most probably from China. In May 2005, then-Defence Minister Rear Admiral Ali Shamkhani announced that Iran had successfully ground tested a large solid-propellant rocket motor, which would later emerge as the roughly 13-tonne first stage of the Sajjil-2 missile. The initial but unsuccessful flight test of the new missile, known at the time as Ashura, was conducted in November 2007. During a second test launch the following year, the missile, now named Sajjil, was apparently equipped with only an active first stage; the second stage was an inert dummy. A successful Sajjil launch in 2008 was followed by three flight tests of a two-stage Sajjil-2 missile in May, September and December 2009. The progressively shorter interval between tests – a typical feature of development programmes – suggests that Iran was enjoying success with the Sajjil-2 effort through 2009. Surprisingly, however, Iran did not test the Sajjil-2 in 2010. Not until February 2011 did engineers conduct the sixth flight, roughly 14 months after the December 2009 launch. No additional tests are known to have occurred since February 2011.

Possible reasons for the hiatus

Though the paucity of Sajjil-2 tests over the last 30 months could be interpreted as a signal that Iran has completed the development process and begun deploying the missile to military units, this is highly unlikely. Iran has not undertaken a sufficient number of test launches to validate the performance and reliability of the new missile. Given that solid-fuelled missile-development efforts elsewhere have required a minimum of a dozen test launches, and more typically 20 or more flights to create a combat-ready system, the Sajjil-2 would require at least another half-dozen flight tests. Having historically applied disciplined engineering management practices to its missile and space-launcher development efforts, there is nothing to suggest that Iran would expect its military to accept an unproven strategic weapon system.

Iran´s missile-related activities suggest that the reason for the hiatus is not that it is seeking to avoid provoking international opprobrium for violating UN sanctions.UN Security Council Resolution 1929, adopted in June 2010, specifically declares in Paragraph 9 ´that Iran shall not undertake any activity related to ballistic missiles capable of delivering nuclear weapons, including launches using ballistic missile technology´. But Iran has repeatedly ignored this proscription and other elements of the UN sanctions. The Sajjil- 2 and Ghadr-1 were both tested in February 2011, in clear violation of UNSCR 1929. The Qiam, a modified Scud-C missile also capable of carrying a nuclear weapon, was initially flight tested in August 2010. And during war games held in early summer 2011, and again in July 2012, the Shahab-3 and other shorter-range missiles were fired under operational conditions. Finally, Iran placed two satellites into low-earth orbit using the Safir carrier rocket, whose first stage is based on the Ghadr-1 missile. Another satellite launch is scheduled for this summer.

The discovery of a major design fault in the new missile could also be responsible for the suspension of testing. Interruptions in missile-development programmes are common and expected. However, programme delays caused by design defects discovered during preliminary flight testing are typically measured in months, not years. Moreover, five of the six test launches conducted to date appear to have succeeded, at least partially, suggesting that the basic design of the Sajjil-2 is sound.

Explosions at the Bid Ganeh missile facility some 40km southwest of Tehran in November 2011 could also have derailed the missile-testing programme, by robbing Iran of its core solid-propellant missile- production and -testing expertise. Major-General Hassan Tehrani Moghaddam, the so-called ´godfather´ of Iran´s missile programme, was killed in the blasts along with more than a dozen of his colleagues. But even though replacing key personnel and resurrecting development activities, including the production line, could possibly delay the programme by years, the explosions occurred nine months after the last Sajjil-2 test in February 2011 and two years after the sudden break in flight-testing activities. Also, the engineering discipline exhibited during the development of the Shahab-3 and Ghadr-1 missiles, the Safir space launcher, as well as the Sajjil-2 efforts to date, indicates that Iran has institutionalised the fundamental knowledge, production practices and technical procedures that led to these earlier successes.

Supply-chain disruption

The most likely explanation, however, centres on Iran´s inability to establish a reliable supply chain for the high-quality solid- propellant ingredients needed to produce the Sajjil-2.

Solid-propellant rocket motors run on a mixture of oxidiser salts, aluminium powder and other minor ingredients bound together by a rubber-like substance that acts as a fuel constituent and provides structural integrity to the end product. After undergoing rigorous quality checks, each ingredient is introduced into a large, specialised mixer; once combined, the ingredients are poured into a motor casing and cured to form a solid, homogeneous mass with the consistency of a pencil eraser. As the size of the solid-propellant motor increases, the complexity of the production process and the need for high-quality ingredients and strict adherence to quality- control measures becomes increasingly critical to success.

Obtaining propellant ingredients from the same producer and using the same production process bolsters the quality-control process. More important, perhaps, is the fact that using the same supplier for each propellant component minimises the potential introduction of minor deviations in the chemical and physical characteristics of the ingredients. Indeed, seemingly benign or undetected deviations can have a substantial and unpredictable effect on the mechanical and combustion properties of the fabricated rocket motors. For this reason, solid-fuelled rocket-motor manufacturers are loath to change suppliers during serial production.

Iran may have the industrial capacity to produce some, or even most of the key propellant ingredients to support the manufacture of small solid-fuelled rocket motors, such as those that power the two-tonne Zelzal and Fateh-110 systems. However, the quality of locally produced ingredients very likely falls short of the requirements for the production of the much larger Sajjil-2 rocket motors.

Iran´s history of importing key propellant components underscores this assessment. The panel of experts responsible for overseeing UNSCR 1929 compliance, for example, reported the interception in Singapore on 30 September 2010 of 302 drums of pure aluminium powder destined for Iran from China. The seized aluminium powder was suitable solely for solid-propellant production. Diplomatic cables made public by WikiLeaks provide additional evidence of Iran´s worldwide search for propellant ingredients, including attempted acquisitions from India and China.

With each change in supplier, for each component ingredient, Iranian engineers would need to have revalidated the production line for Sajjil-2 rocket motors, a costly, time-consuming process that would require additional ground tests to confirm performance and reliability. Worse yet from the Iranian perspective, production engineers may not be able to manufacture rocket motors that behave in a predictable and repeatable fashion because of uncontrollable and possibly undetected deviations in the constituent propellant ingredients. Lacking a reliable rocket-motor production line, Iran cannot pursue a viable development effort capable of distinguishing between design faults and manufacturing defects, or of validating missile performance over a range of operational conditions. And for the same reason, Iran will find it profoundly difficult to manufacture large rocket motors for an operational missile with predictable performance and reliability.

While it is impossible for outsiders to identify the precise reasons behind the stalled Sajjil-2 programme, it is reasonable to conclude that trade sanctions have disrupted Iran´s access to key propellant ingredients and compromised development efforts. If true, and if future applications of sanctions prevent Iran from establishing a reliable source of propellant ingredients regulated by the Missile Technology Control Regime, the Islamic Republic will not be able to create missiles capable of threatening western Europe, much less the United States, before the end of this decade. (Copyright ©2006 - 2012 The International Institute For Strategic Studies)