October 22, 2012

Bill Sweetman and David Fulghum Washington and David Eshel Tel Aviv

If Iran is going to pose a threat to Israel, it has to pose a credible one. The most catastrophic outcome for Iran's leaders is a nuclear attack that fails and leaves the nation a pariah, looking down both barrels of a justifiably enraged and very well-armed adversary.

Determining a nuclear threat's credibility involves weapons, delivery systems and defenses, both conventional and otherwise. The decision to use nuclear weapons against Japan rested on many factors, some so obvious now that we do not think about them: Japan no longer had any means to retaliate; qualms against the use of weapons of mass destruction had long been abandoned by the Allies with the use of heavy bomber raids; and a reliable delivery system was in place, to the point where a small flight of B-29s could raid Japan in daylight with a high probability of success and survival.

Iran's route to constructing such a force involves the parallel development of intermediate-range missiles and nuclear warheads. So far, no nation has succeeded in doing this either quickly or inexpensively. Conventionally armed, non-precision-guided missiles fired over regional distances are insufficiently accurate to do more than threaten random destruction and widespread disruption in large urban areas, while Iran is not within sight of any alternate delivery means for a nuclear device.

The rates at which the U.S. and Soviet Union produced both nuclear-capable missiles and warheads during the Cold War obscure the fact that both were costly and slow to produce in their early stages. They require a number of unique technologies (from high-temperature materials and liquid- or solid-rocket propulsion to nuclear material production and explosive devices). Engineering is complicated by the fact that a full-scale test necessarily destroys the device.

Iran has been assessed by some sources as having “hundreds” of Shahab-3 missiles—evolved from the Russian R-11/R-17 Scud via the North Korean Nodong—but fewer launch complexes. Although the missile is road-mobile on a semi-trailer towed by a Mercedes tractor, as a liquid-fueled weapon it has to be accompanied by fuel transporters and erected before refueling, rendering it an obvious, vulnerable target. (This is why the U.S. replaced the liquid-fueled Redstone by the solid-fueled Pershing after six years in service.) The solid-fuel Seijil—which requires a different industrial base to produce casings and propellants—is still in the testing stage.

Israeli researchers believe that Iran is working on disparate parts of a nuclear weapon system in parallel. “That's why they are conducting R&D work on the trigger mechanism and explosives behavior simultaneously,” Ephraim Asculai, senior research fellow at Tel Aviv University's Institute for National Security Studies, says. “Indications are that they did this work at [the nuclear research center at] Parchin. They had a working design. They had a metal vessel to contain the initiating and timing mechanism. The IAEA [International Atomic Energy Agency] asked to visit. The Iranians said, 'No.'

“They have the Shahab 3 and are working on solid propellants,” Asculai says. “And there is intelligence that they have been trying to fit a warhead to those missiles. They probably have several sets of warheads without the fissile materials.”