Cruise missile defense
Cruise missile defense encompasses a range of doctrine, systems, and techniques for detecting, tracking, and neutralizing cruise missiles and their launching platforms. Mechanisms used for neutralization may be kinetic (i.e., causing physical damage or destruction) or nonkinetic (e.g., electronic warfare and interference with computers or networks).
There will be variations depending on both the launch (air, sea, land, underwater) and target (land, sea) environments for the cruise missile system. With variations for the range of the cruise missile system, defense engagement can take place in any or all of several phases:
- Prior to launch
- During the approach to the target area
- In the immediate target area
Cruise missile defense has both similarities and differences to ballistic missile defense. Both can attack the launcher, but cruise missile launchers are far more likely to be mobile than ballistic missile launchers. Ballistic missiles have an additional boost phase engagement phase that generally does not apply to cruise missiles. Terminal defense against cruise missiles is a different problem than against ballistic missiles; cruise missiles are slower but take much more unpredictable flight paths.
Especially with respect to air-launched cruise missiles, a motto of defense designers was that it was far better to shoot the archer than to attempt to shoot down the arrow. During the Cold War, the U.S. Navy doctrine for protecting carrier battle groups included a concept called the Outer Air Battle, in which a defensive ring was placed outside cruise missile range. That ring consisted of radar aircraft such as the E-2 Hawkeye, and F-14 Tomcat fighters equipped with the long-range AIM-54 Phoenix missile.
The Phoenix was fast and long-ranged, but not especially maneuverable — the set of characteristics optimized to hit large aircraft that carried heavy cruise missiles, or large cruise missiles that flew a straight supersonic course.
While the threat against which the Outer Air Battle was designed no longer exists, it is the Russians that now have what may be the world's best missile, the Novator R-172, optimized for attacking large aircraft at long range. It is not meant solely as a cruise missile defense system, also being a threat to tanker and C3I-ISR aircraft.
The Tomcat/Phoenix system had a "look-down-shoot-down" capability that could also be used against long-range submarine-launched cruise missiles. This continues to be a general characteristic of systems that defend against cruise missiles flying a relatively straight path to the general area of the target. There is a specific optimization of an anti-cruise missile missile to go against this flight profile.
Radar airraft, and now unmanned aerial vehicles carrying radar have a critical role in detecting low-flying cruise missiles. During the 1982 Falklands War, ships did not have enough warning, from the limited radar horizon of shipboard radar, to ready their defenses; the lack of an airborne early warning radar is often considered the most important failing of the British forces. The Argentines had only five Exocet missiles; if they had more, and they had managed to cripple or sink either of the British aircraft carriers, the British counterattack probably would have failed.
Cruise missiles, especially targeted against ships, often take difficult-to-predict final attacks. At a minimum, sea-skimming missiles will "pop-up" close to the target, so that their final attack is as a dive that delivers the most kinetic energy. The missiles also can zigzag, or curve their approaches so they come in from a direction other than the "threat axis" on which known launchers are positioned.
Terminal defense includes both hard-kill mechanisms to shoot down the missiles, and extensive use of electronic warfare. With the increased speed of sea-skimming cruise missiles, autocannon defenses such as the Phalanx close-in weapons system did not have sufficient range, and have been replaced in Western service with the RIM-116 Rolling Airframe Missile, which can engage at long range.