Israel's new “Iron Dome” counter-rocket, artillery and mortar system has racked up a success rate above 80% since being fielded last year, but its weak link—as with most missile defense systems—is too few interceptors.

Israel plans to solve this problem in the short term by doubling the Rafael's Tamir interceptor manufacturing capacity. But some U.S. lawmakers are pushing the Pentagon to step in and coproduce the missile on U.S. soil, not only as a backstop for the Israel Defense Forces' supply but as a domestic capability that could protect deployed soldiers.

Iron Dome is the newest layer of Israel's budding air and missile defense capability. The Arrow-2 covers intermediate-range missiles. The PAC-3 and “David's Sling” systems handle the range between Arrow-2 and Iron Dome, which is designed to counter threats launched from 4-70 km (2.5-45 mi.).

These weapons are largely launched by Hamas and Hezbollah. Though many lack guidance—and some land harmlessly in unpopulated zones or the sea—Israel had to devise a way to counter them in order to maintain normal daily activities inside its borders, despite the threat, says Ilan Berman, vice president of the American Foreign Policy Council.

Four Iron Dome batteries, each capable of defending a medium-sized city, are deployed in southern Israel, and two more will follow next year, says Lt. Col. Merav Davidovits, missile defense liaison for the Israel Defense Forces in Washington. During a briefing Oct. 2 hosted by The Heritage Foundation conservative think tank, she declined to identify the current or planned capacity of the Tamir interceptor production line.

However, since the system was fielded in 2011, Iron Dome has intercepted roughly 100 rockets, a success rate of 80-90%. To avoid wasting interceptors, developers designed the system to discriminate among targets. The feature, called “selective engagement,” allows for the command-and-control element to assess the anticipated impact point of a rocket or mortar during its flight; it automatically disregards those headed for unpopulated areas or the sea.

“The system was successful not only with a single interception but also in a salvo situation,” Davidovits says, noting that often the Israel Defense Forces felt Hamas and Hezbollah were testing its limits by changing tactics, including launching rockets at night or during bad weather, or by trying to overwhelm defenses with salvos of threats. “We thank them for all the lessons learned that we gained,” she said. Israel has added undisclosed improvements based on operational experience.

The production ramp-up is needed in part to address the salvo threat; adversaries can simply try to launch enough offending weapons to deplete the Israeli stockpile. Israel hopes to eventually deploy up to 13 Iron Dome batteries.

Davidovits attributes the success of the system to a simplified development approach. “The magic was that we developed only what we needed,” she says. Development began in 2007 and the first intercept took place in July 2009.

Meanwhile, in Washington, some House lawmakers are pushing for U.S. coproduction of the interceptor. This would likely be headed in the U.S. by Raytheon, which coproduces the Stunner missile with Rafael for the longer-range David's Sling defense system.

House defense authorizers, like their appropriations counterparts, offer $680 million for Iron Dome in the fiscal 2013 budget. But the authorizers take a step further, stipulating that the U.S. requires data rights.

Senate authorizers and appropriators budget only $210 million for Iron Dome for this fiscal year.

The Pentagon lacks a sophisticated counter-rocket, artillery and mortar (CRAM) system, forcing soldiers to “duck and run” when a launch is detected, says Randy Jennings, a defense consultant at P-51 Consulting. “All too often, the Pentagon has a 'not-invented-here' mind-set against foreign-developed weapon systems,” he says.

The U.S. Army issued a request for information for CRAM capabilities in August. Though research is being funded for laser solutions, the time and cost to field would likely exceed that required for coproducing a version of Iron Dome in the U.S., Jennings says. “Coproduction is inevitable,” he adds. The U.S. would spend roughly $1 billion in its development and fielding in Israel, he calculates.

Davidovits declined to specify a per-missile cost for Tamir, but some reports put it at $50,000 per interceptor. Though this is far more expensive than the offending weapons, Israel has found value in the cost-avoidance from preventing the loss of life and property from constant attacks.