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Missile-Killing Interceptors Eyed By Israel, US
This article first appeared in Aviation Week & Space Technology.
Killing tactical ballistic missiles so that explosive, biological or radioactive debris fall near a foe's launch sites is a key problem for those mapping out defenses in an era of proliferating, short-range missiles and long-range rockets.
New concepts are taking two forms -- striking enemy missiles while they are still in space, or destroying them in the first minute or two after launch. And it is becoming glaringly apparent that the solutions are different if the foe is nearby or far away.
Israel, for example, does not have a weapon that can be launched from an aircraft to catch enemy missiles when they are most vulnerable as slow and very bright targets during the first few minutes of flight.
The Israelis flirted with air-launched boost-phase intercept (BPI) in their MOAB UAV/missile program of the 1990s, and the U.S. had a parallel Raptor/Talon project. But both projects were shelved to await technology advances, including more energetic rocket motors, satellite-based battle management and smaller, lighter missile designs.
However, operational introduction into the Israeli arsenal of the advanced Arrow 3 interceptor missile and the Stunner interceptor for the David's Sling system may open the door to a period of rapid development for air-launched weapons that can be carried by unmanned aircraft.
The Stunner interceptor, designed and built by Rafael in a cooperative program with Raytheon, is a low-cost design that targets threats such as cruise missiles, medium- and long-range artillery rockets and short-range ballistic missiles. It has two stages: The first is a solid-fuel, rocket motor booster; the second is a curious asymmetrical kill vehicle with advanced steering for increased agility. A three-pulse motor provides additional thrust at critical moments of flight. A multi-mode sensor package -- electro-optical and millimeter wave, electronically scanned array radar -- provides all-weather performance against small, maneuvering targets. The Stunner is larger than Raytheon's AIM-120 medium-range air-to-air missile but smaller than the Arrow 3 interceptor.
As for Israel Aerospace Industries' (IAI) Arrow 3, it now forms the longest-range, highest-altitude (exoatmospheric) layer of Israel's ballistic missile defenses. It is "half the size of Arrow 2 and 21 in. in diameter, [and] no other interceptor has the same kinetic capability or agility," says a senior Israeli official with insight into the Arrow program. While Arrow 3 is a big step toward developing BPI, Israeli planners say they still need better unmanned aerial systems and much smaller, longer-range interceptor missiles.
"It could be used from aircraft, ships and submarines, but the obstacles are not small," he says. "The main challenge is time-of-flight [from the orbiting aircraft to the boosting missile]," the official says. "It has to be faster and more agile so that it can divert to another target or change the interception point. Iran is 2,000 km. away. How fast can you predict its path? BPI is not that realistic right now."
The speeds necessary for a long-range missile interceptor are variously predicted at 5-6 km. (3.1-3.9 mi.) per second. The airborne launch of such a system is acknowledged to offer the advantage of having less dense atmosphere to push through and a launch-speed advantage of around 300 mph. But for now it is considered more expensive than other missile defense options.
However, the threat is changing and may require a more advanced, long-range solution because the next generation of enemy ballistic missiles is expected require insurance that none can penetrate Israel's air and space defenses.
"The main challenge is the requirement for zero leakage," the Israeli official says. "Arrow 2 is effective against older, less sophisticated targets. Arrow 3 is more flexible [and at $2-3 million per copy, it is] an order of magnitude cheaper than [the American-built] SM-3 ship-based air defense missile. It mitigates the assumed threats from Iran and Syria, but future threats will require us to think about and develop new resources to address different missile types, scenarios and warheads."
For example, ballistic missiles with nuclear, chemical or biological warheads should be destroyed quickly so that they fall back onto the country that launched them. That exposes the pressing need for Israeli or U.S. unmanned aircraft to orbit close enough to the Iranian border that missiles being launched in the east can be targeted early in flight.
"So far, there are no real programs for using Arrow 3 for BPI and ascent-phase intercept," the Israeli official says. "However, the geography, detection, line-of-sight and time-of-flight issues are doable. Arrow 3 is a much more capable missile in flight. It can be carried by a fighter, but there is no requirement to do so."
Raytheon has built and tested a modest BPI program for the U.S. Company researchers and engineers took parts from the AIM-120 and added the AIM-9X infrared seeker as well as a two-stage rocket motor for longer range and active maneuvering in the last stage of flight. The initial Network-Centric Air Defense Element (NCADE) version is designed for long-range rockets and short-range ballistic missiles, and it has shot down other missiles in a series of live-fire tests from F-16s.
The view of Israeli aerospace analysts is that BPI can be useful at relatively short ranges, but it is a much more difficult and perhaps too expensive solution for missile defense at 1,000-2,000-km. ranges.
"It's an excellent idea as long as the target is in the atmosphere," says Yoram Shimoni, group director of marketing for IAI's Systems, Missiles and Space Group. "If you are not very close to the launch site -- for example, 1,000 km. away -- it doesn't work if it's an atmospheric-type air-to-air missile or even the NCADE or PAC-3. There is no way to [aerodynamically] steer above 70,000 ft.
"In a conflict with North Korea, the U.S. can hang out 20-40 mi. off the coast," says an Israeli-based analyst. "The [North Koreans] have no significant airpower to shoot you down, so you can try to catch the missiles as they are being launched. That's not the case with Iran," which in a conflict could launch missiles at Israel from sites in the eastern part of the country that are more than 1,000 mi. away.
Photo credit: Raytheon