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[Missile Guidance]


A Beyond Visual Range missile usually refers to an air-to-air missile that is capable of engaging at ranges beyond 20 nautical miles. This range has been achieved using dual pulse rocket motors or booster rocket motor and ramjet sustainer motor.

In addition to the range capability, the missile must also be capable of tracking its target at this range or of acquiring the target in flight. Systems in which a mid course correction is transmitted to the missile have been used.

Early air-to-air missile used passive radar guidance, that is the missile used the radiation produced by the launching aircraft to guide it to the target. Later missile tend to use a combination of passive and active radar.

The first such missiles used Semi-active radar homing (SARH). This is where the launching aircraft's radar is locked onto the target in a Single Target Tracking (STT) mode, directing a thin radar beam at the target and swiveling the beam to track any movement of the target. Missiles like the Raytheon AIM-7 Sparrow and Vympel R-27 NATO designation AA-10 'Alamo') will then home in on the reflected radiation, much like a Laser-guided bomb homes in on the reflected laser radiation. Some of the longest range missiles in use today still use this technology.

Newer fire-and-forget type missiles like the Raytheon AIM-120 AMRAAM and the Vympel R-77 (NATO designation AA-12 'Adder') instead use an Inertial navigation system (INS) combined with initial target information from the launching aircraft and updates from a one or two-way data link in order to approach the target from beyond visual range, and then switch to a terminal homing mode, typically active radar guidance. These types of missiles have the advantage of not requiring the launching aircraft to illuminate the target with radar energy for the entire flight of the missile, and in fact do not require a radar lock to launch at all, only target tracking information. This gives the target less warning that a missile has been launched and also allows the launching aircraft to turn away once the missile is in its terminal homing phase or engage other aircraft. The very longest range missiles like the Hughes (now Raytheon AIM-54 Phoenix missile and Vympel R-33 (NATO designation AA-9 'Amos') use this technique also.

Some variants of the Vympel R-27 use Semi-active radar homing (SARH). for the initial guidance and then passive infra-red guidance for the final stage. This type of missile requires active guidance for a longer part of the flight than the fire-and-forget type of missiles but will still guide to the target even if radar lock is broken in the crucial final seconds of the engagement and may be harder to spoof with chaff due to the dual-type guidance.

Despite many years of development, this class of weapon has never been tested in the environment they were designed for. Uses that have occurred have been against unequal advisaries

NexT  {BVR Component}


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Last modified: 10/12/05.