A successful boost-phase ballistic missile intercept by a modified Sidewinder missile Dec. 3 could indicate the potential for a significant leap forward in intercept technology for the boost phase, an area in which ballistic missile defense systems have been slower to mature.
A simulated ballistic missile in the boost phase of flight was intercepted in a test conducted at the White Sands Missile Range in New Mexico Dec. 3. After a troubled test in September, a Network Centric Airborne Defense Element (NCADE) seeker — mounted on an AIM-9X Sidewinder airframe — destroyed a target sounding rocket in boost phase for the first time. The test is noteworthy not only for success, but for the established systems NCADE leverages. Boost-Phase Intercept Ballistic missile defense (BMD) is divided into three basic phases of intercept: boost, midcourse and terminal. Before NCADE, technologies to intercept ballistic missiles in the boost phase of flight were slow to mature — a phenomenon with roots in both historical and technological issues. Boost-phase intercept requires relatively close access to territory or airspace adjacent to missile launch sites (compared to midcourse- or terminal-phase intercepts, which must be further back). The current BMD renaissance has its roots in the Reagan-era "Star Wars" program, which sought to create a national missile defense shield tailored specifically to Soviet intercontinental ballistic missiles (ICBMs). At that time, reliable access to territory appropriate for boost-phase intercepts of ICBMs deep inside the Soviet Union was not realistic. (click to enlarge) On the technological side, boost phase requires the fastest reaction time, since a missile is only in the boost phase for a few minutes. The ballistic path in this phase is also characterized by a more uneven flight, due to the shifts in acceleration when a stage burns out and separates and the next stage ignites. This also requires a more discerning seeker, as there can be times during boost phase when a discarded stage and the missile are both in the seeker's field of vision. But, for all its difficulty, boost-phase intercept has several attractive aspects. Despite the unevenness of acceleration in the boost phase, this is the slowest phase of flight, as the missile travels against gravity rather than with it, as it does later in flight. Also, the missile has the largest radar cross-section during boost phase, and the large early stages are not only much easier to track, they are also full of generally very explosive propellants. Furthermore, fragments and debris from a missile destroyed in boost phase will not pepper the target area as they do in terminal-phase intercepts. Current Technologies Some of the problems boost-phase intercepts used to face have been solved by the inexorable progress in microprocessor speeds, price, size and durability. In other words, seeker heads or guidance systems have gained more computational capacity due to the rapid improvement in computer technology in the last few decades. That capacity can be leveraged to more quickly plot intercepts and deal with some of the complications of boost-phase intercept. Thus far, two major programs have been the focal point of U.S. investment in boost-phase technology: the Airborne Laser (ABL) and the Kinetic Energy Interceptor (KEI). The ABL program is working to mount a weaponized megawatt-class laser inside a Boeing 747 freighter airframe. If successfully developed, the ABL will be able to patrol off the coast of nations like North Korea and quickly engage multiple missiles as they are launched. However, the ABL program dates back to the Reagan era and requires developing a revolutionary new technology — almost never an easy, simple or cheap task (simply cramming the laser inside an airplane is a major accomplishment). The KEI program is similarly ambitious. Though not as revolutionary in nature, KEI is really a follow-on technology, a generation more advanced than the more rudimentary ground-based midcourse defense interceptors currently stationed in Alaska and California. The program seeks to build a mobile missile capable of intercepts in the boost, ascent and midcourse phases — a broad spectrum of engagement criteria requiring a responsive and flexible system. NCADE This is where NCADE, now in its second year, comes in. The successful Dec. 3 test was admittedly a rudimentary "second-try" test. It is also too early to say just how successful NCADE will prove, and its engagement envelope may be limited to short- and medium-range ballistic missiles. NCADE also has a competitor in a Lockheed-Martin program to launch a modified Patriot Advanced Capability 3 (PAC-3) interceptor from aircraft. But ultimately, NCADE seeks to mount the seeker tested Dec. 3 (on the AIM-9X) on the longer-range Advanced Medium Range Air-to-Air Missile (AMRAAM), along with a second stage. The second stage will roughly double the AMRAAM's range, extending it out to 100 miles (giving the aircraft some stand-off distance). The AMRAAM is a well-established and proven missile (albeit in a different mission profile). It has already seen successful adaptation to a variety of ground-based modifications. The AMRAAM is also compatible with not only most U.S. fighter aircraft, but many foreign — notably Israeli and Japanese — fighters as well. Integration work would of course be necessary, but the commonality could make a mature NCADE as readily deployable as the PAC-3 system has already proven to be. In other words, the phase of BMD intercept that has long languished behind the others in terms of progress saw a promising development Dec. 3. If it proves successful, it will offer a near-term and comparatively cheap technology that could be distributed to and deployed around the world — and even (given its size) potentially mounted on unmanned aerial vehicles like a modified Predator-B. Such a development would be a major step forward in the BMD field. The NCADE system is not constrained by fixed concrete silos in Alaska, California or Poland. It does not even require the deployment of a BMD-capable destroyer or cruiser equipped with Standard Missile-3 interceptors (of which the U.S. Navy hopes to have 18 outfitted by 2010). A successful NCADE program translates into a major step forward for BMD, making it easier to hit more missiles sooner in more places around the world — especially places like Iran and North Korea, whose periphery is easily accessible to U.S. aircraft.