The Iranians developed this variant in order to incorporate a steerable re-entry vehicle during the terminal dive phase of the missile's trajectory. The regular Shahab-3 has spin stabilization, but the 3B reportedly includes a rocket-nozzle control system. This nozzle-control system is supposed to enable the Shahab-3B to be guided and course-corrected during all phases of the missile's flight.
Iran announced that it successfully tested a solid-fuel motor for its Shahab-3 in May of 2005. The Shahab-3 previously was reported to use liquid-fuel technology. The Shahab-3 ballistic missile had been known as a single-stage device. Military experts said the development of a second motor demonstr ated a significant improvement in Iran's missile program. Former top Russian defense official Gen. Leonid Ivashov said he was not surprised by such progress.
