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This blog is about missiles and its control surfaces

MISSILE

ACTIVE.:In the active homing system, target illumination is supplied by a component carried in the missile, such as a radar transmitter. The radar signals transmitted from the missile are reflected off the target back to the receiver in the missile. These reflected signals give the missile information such as the target's distance and speed. This information lets the guidance section compute the correct angle of attack to intercept the target. The control section that receives electronic commands from the guidance section controls the missile�s angle of attack. Mechanically manipulated wings, fins, or canard control surfaces are mounted externally on the body of the weapon. They are actuated by hydraulic, electric, or gas generator power, or combinations of these to alter the missile's course.

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SEMI ACTIVE.:In the semiactive homing system, the missile gets its target illumination from an external source, such as a transmitter carried in the launching aircraft. The receiver in the missile receives the signals reflected off the target, computes the information, and sends electronic commands to the control section. The control section functions in the same manner as previously discussed.

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PASSIVE.:In the passive homing system, the directing intelligence is received from the target. Examples of passive homing include homing on a source of infrared rays (such as the hot exhaust of jet aircraft) or radar signals (such as those transmitted by ground radar installations). Like active homing, passive homing is completely independent of the launching aircraft. The missile receiver receives signals generated by the target and then the missile control section functions in the same manner as previously discussed.

MISSILE CONTROL SURFACES

Canard Control:

Canard control is also quite commonly used, especially on short-range air-to-air missiles like AIM-9M Sidewinder. The primary advantage of canard control is better maneuverability at low angles of attack, but canards tend to become ineffective at high angles of attack because of flow separation that causes the surfaces to stall. Since canards are ahead of the center of gravity, they cause a destabilizing effect and require large fixed tails to keep the missile stable. These two sets of fins usually provide sufficient lift to make wings unnecessary. Shown below are twelve examples of canard control missiles.

Wing Control:

Wing control was one of the earliest forms of missile control developed, but it is becoming less commonly used on today's designs. Most missiles using wing control are longer-range missiles like Sparrow, Sea Skua, and HARM. The primary advantage of wing control is that the deflections of the wings produce a very fast response with little motion of the body. This feature results in small seeker tracking error and allows the missile to remain locked on target even during large maneuvers. The major disadvantage is that the wings must usually be quite large in order to generate both sufficient lift and control effectiveness, which makes the missiles rather large overall. In addition, the wings generate strong vortices that may adversely interact with the tails causing the missile to roll. This behavior is known as induced roll, and if the effect is strong enough, the control system may not be able to compensate. A few examples of wing control missiles are shown below.

Tail Control:

Tail control is probably the most commonly used form of missile control, particularly for longer range air-to-air missiles like AMRAAM and surface-to-air missiles like Patriot and Roland. The primary reason for this application is because tail control provides excellent maneuverability at the high angles of attack often needed to intercept a highly maneuverable aircraft. Missiles using tail control are also often fitted with a non-movable wing to provide additional lift and improve range. Some good examples of such missiles are air-to-ground weapons like Maverick and AS.30 as well as surface-to-surface missiles like Harpoon and Exocet. Tail control missiles rarely have canards, although one such example is AIM-9X Sidewinder. A selection of 23 representative missiles using tail control is pictured below.

VIDEO

http://www.youtube.com/watch?v=3RBpK3DqrKw