- Beyond Visual Range missile
A Beyond Visual Range
missileusually refers to an air-to-air missilethat is capable of engaging at ranges beyond 20 nautical miles(37 km). This range has been achieved using dual pulse rocket motors or booster rocket motor and ramjetsustainer 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
semi active radarguidance, that is the missile used the radiation produced by the launching aircraft to guide it to the target. The latest generation of BVR missiles use a combination of semi-active and active radar.
The first such missiles were relatively simple
beam ridingdesigns that were soon replaced by Semi-active radar homing( SARH). This is where the launching aircraft's radar is "locked" onto the target in a Single Target Track(STT) mode, directing a radar energy at the target that the missile seeker can "see" as it reflects off the target. The radar antenna must "illuminate" the target until impact. Missiles like the Raytheon AIM-7 Sparrowand Vympel R-27( NATOdesignation AA-10 'Alamo') home in on the reflected radiation, much like a Laser-guided bombhomes in on the reflected laser radiation. Some of the longest range missiles in use today still use this technology.
The first air-to-air missile to introduce a terminal active seeker of its own was the
AIM-54 Phoenixcarried by the F-14 Tomcat, which entered service in 1972. This relieved the launch platform of the need to illuminate the target until impact putting it at risk. The Phoenix and its associated Tomcat radar, the AWG-9was capable of multiple track and launch capability, which was unique to the Tomcat/Phoenix until the advent of AMRAAM in 1991. Newer fire-and-forgettype missiles like the Raytheon AIM-120 AMRAAMand the Vympel R-77( NATOdesignation 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 launch 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-54Phoenix missile and Vympel R-33( NATOdesignation AA-9 'Amos') use this technique also.
Some variants of the
Vympel R-27use Semi-active radar homing( SARH) for the initial guidance and then passive infra-redguidance for the final stage. This type of missile requires active guidance for a longer part of the flight than the fire-and-forgettype 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. Astra missileis an active radar homing Beyond visual range air to air missile (BVRAAM)being developed by Defence Research and Development Organisation (DRDO), India. This is the first air-to-air missile developed by India and when tested successfully India will join a prestigious group of countries that are US, France,Israel,Japan,Russia,South Africa and China who have so far produced such advanced missiles. The single stage, solid fuelled 'Astra' missile is more advanced in its category than the contemporary BVR missiles and it is capable of engaging and destroying highly manoeuvrable supersonic aerial targets.
Despite many years of development, this class of weapon has never been tested in the environment for which it was designed, but has instead mostly been used against poorly equipped adversaries.
Sky Sword II
* [http://www.janes.com/defence/news/jdw/jdw060831_1_n.shtml Meteor blazes path but challenges remain] Jane's Defence Weekly, 31 August 2006
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