The Network Centric Airborne Defense Element is a low-cost concept for intercepting short- and medium-range ballistic missiles in boost phase using a modified version of the main air-to-air missile carried on most U.S. fighter aircraft today.

The weapon's explosive charge is replaced with a second propulsion stage and a heat-seeking sensor is installed in its nose, thereby converting it into a ballistic-missile interceptor that rams vulnerable missiles in boost phase with sufficient force to destroy them.

The information needed to guide the weapon to the vicinity of its target is provided by netted sensors on and off the host aircraft, which is why the phrase "network centric" is used in its name.

Compared with most other missile-defense concepts, NCADE is relatively simple and inexpensive. Because it relies on hardware already available in the joint force, it will cost less than a half-billion dollars to develop and can be operationally available in four years.

The unit cost of each round will be less than a million dollars, which is a fraction of what other missile interceptors cost. And while it will cost more per interception than the Airborne Laser, it presents few of the technical challenges associated with the latter system.

Its main drawback is that it probably cannot successfully engage longer-range missiles, which constitute the greatest threat to the U.S. homeland. For that reason, it is best thought of as a complement to the Kinetic Energy Interceptor and Airborne Laser, rather than an alternative.

Aside from its low cost and simple design, one of the most appealing features of NCADE is that it would fit within the design constraints of existing tactical aircraft such as the Lockheed Martin/Boeing F-22 Raptor and the Lockheed Martin Lightning F-35 Joint Strike Fighter aircraft, enabling them to participate directly in missile-defense missions.

In its modified form, the Advanced Medium-Range Air-to-Air Missile used for NCADE would have the same configuration as munitions already carried by those planes, so few changes would be required to the airframe or support systems.

Many of the wireless links required to access off-board sensors, such as U.S. Air Force radar planes, already exist. The weapon also can be adapted for use on unmanned combat aircraft such as the Air Force's Reaper, enabling defenders to maintain a continuous presence near enemy launch sites during periods of heightened tension.

A somewhat similar concept called Air Launched Hit-to-Kill has been proposed that would enable Air Force F-15C fighters to carry the Patriot Advanced Capability Three missile for both boost-phase and terminal-phase interception missions.

-- (Part 12: Why mounting interceptor missiles on the F-22 Raptor could provide cheap boost phase ballistic missile defense)

(Loren B. Thompson is chief executive officer of the Lexington Institute, an Arlington, Va.-based think tank that supports democracy and the free market.)

(United Press International's "Outside View" commentaries are written by outside contributors who specialize in a variety of important issues. The views expressed do not necessarily reflect those of United Press International. In the interests of creating an open forum, original submissions are invited.)