Strategic Comments  – Volume 15, Issue 1 – February 2009

Iran's missile development

 Further tests needed to cement recent advances

The November 2008 test launch of Iran's new Sajjil missile indicated a significant shift in the country's missile-development programme. The immediate strategic impact will be limited, since neither the range nor the payload capacity of the Sajjil is substantially greater than that of Iran's existing Shahab-3 missile. However, the transition from the liquid-propelled Shahab to production of the multi-stage, solid-fuelled Sajjil would be important if shown by further tests to be sustainable.

Iran's active approach to rocket development was further highlighted by the February 2009 launch into space on a domestically produced rocket of its first home-made satellite – a milestone that coincided with the 30th anniversary of the Islamic revolution.

The Sajjil is estimated to be able to carry a maximum one-tonne payload 1,500–1,800 kilometres. While these capabilities are similar to those of the Shahab, the technical capacity required to build a medium-range, solid-fuel missile is of a different order to that needed for its liquid-fuel equivalent. If progress could be extended beyond the initial Sajjil launch, Iran might be able to begin the design and development of a new generation of long-range missiles. Solid-fuel missiles can be launched more quickly and are thus less vulnerable to pre-emptive strike.

Iran's missile strategy

During the Iran–Iraq War of the 1980s, Tehran initiated a two-track effort to develop ballistic missiles to compensate for its barely operational air force. The first track focused on the immediate acquisition, from Libya and later North Korea, of short-range (300-km), liquid-propellant missiles based on the Soviet Scud. Tehran integrated these systems, dubbed Shahab-1 and -2, into the military and in the mid 1990s established the infrastructure to assemble the missiles locally – although it still relied on foreign supply of components.

In the late 1990s, Iran began to import, and possibly assemble imported components of, the North Korean No-dong missile. Improvements, made reportedly with Russian and possibly Chinese assistance, were incorporated into the No-dong around the turn of the century, resulting in the Shahab-3. This is now the mainstay of Iran's missile forces and the foundation for its nascent space programme, which test-launched two sub-orbital missiles in 2008 as well as launching the home-made Omid satellite in February 2009.

While this first track addressed Iran's immediate needs for an extended-range strike capability, there are technical obstacles to extending missiles' capability when using imported technology. The second track pursued by Iran centred on developing an indigenous capability to manufacture solid-propellant systems. Focusing on small, extended-range artillery rockets, Iran had established the capacity by the late 1990s to design, develop and produce solid-fuel rockets with ranges just beyond 250km. These single-stage Zelzal and Fateh-110 missiles, whose range has been increased to 400km in recent years, are powered by one motor containing one-and-a-half to two tonnes of solid fuel.

While full details of the Sajjil missile and its test launch are unavailable, it is obviously much larger than any solid-propellant missile previously produced by Tehran. Judging from videos and pictures, the Sajjil's first-stage rocket motor alone contains up to ten tonnes of solid propellant and is capable of generating 55–65 tonnes of thrust (see above). The knowledge, equipment and experience needed to produce such a motor go far beyond that behind the two-tonne motor used by the Zelzal and Fateh-110. The technological leap represented by the Sajjil missile is further underlined when the difference between liquid-fuelled and solid-fuelled rocket engines is considered.

Liquid-fuelled rockets

Liquid-propellant engines involve a complex combination of mechanical parts, including pipes, valves, regulators, pumps, turbines, injectors, nozzles and a heat-resistant pressure vessel. These force the oxidizer and fuel from on-board storage tanks into a combustion chamber, where they are mixed and react to generate high temperatures and pressures. The resultant combustion gases accelerate through the engine's exit nozzle, propelling the missile.

In theory, a team of engineers could disassemble an existing engine and, with access to the necessary industrial infrastructure and dual-use production equipment, manufacture exact copies of the components. These parts could then be reassembled into a working engine with the same performance characteristics as the original. In practice, this process is difficult. Iraq, for example, attempted to reverse engineer the Scud ballistic missile, but never fully succeeded. North Korea may have had greater success, although some analysts believe that not even Pyongyang can make a complete engine without imported components.

However, even if engineers succeeded in replicating a liquid-fuel engine, they would not be able significantly to improve its performance. Nor could they design or build a more powerful variant without access to the original development and design documentation or access to the initial designers. Indeed, reverse engineering cannot impart the experience and knowledge accumulated during the original development, design, testing and redesign process. It cannot reliably reveal critical design tolerances or material compatibility requirements.

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