Aerodynamic characteristics of winged missiles

The aerodynamic shape design and aerodynamic characteristics of winged missiles have the following characteristics: ① In order to meet the requirements of storage, transportation, combat and structure, The wing aspect ratio of tactical missiles is very small, generally not exceeding 3. ②In order to track mobile targets, tactical missiles should have high maneuverability, and the overload coefficient is mostly above 20, or even up to 60.

③ Tactical missiles are often equipped with one or more boosters, which complicates the aerodynamic shape of the entire missile, and there is also the problem of aerodynamic interference when the boosters are separated. ④The launch site of winged missiles is changeable. They can be launched from aircraft or helicopters in the air, or from ships on the surface or underwater.

⑤The flight speed of cruise missiles is not high and they mainly rely on covert penetration. Therefore, various problems with ultra-low-altitude flight arise, such as terrain tracking and wave response. Reducing the amount of radar wave reflection through shape design is also an important means of concealment.

Text

The aerodynamic force, torque and surface pressure distribution generated when the airflow passes around the winged missile vary with the shape and shape of the missile. The law changes with the movement of the missile in the atmosphere (including Mach number, Reynolds number, angle of attack, sideslip angle, rotation angular velocity, sinking and floating speed, etc.). The aerodynamic shape design and aerodynamic characteristics of winged missiles have the following characteristics:

① In order to meet the requirements of storage, transportation, combat and structure, the aspect ratio of the wing of tactical missiles is very small and generally does not More than 3. ②In order to track mobile targets, tactical missiles should have high maneuverability, and the overload coefficient is mostly above 20, or even up to 60. ③ Tactical missiles are often equipped with one or more boosters, which complicates the aerodynamic shape of the entire missile, and there is the problem of aerodynamic interference when the boosters are separated.

④The launch site of winged missiles is changeable. They can be launched from aircraft or helicopters in the air, or from ships on the surface or underwater. ⑤ The flight speed of cruise missiles is not high and they mainly rely on covert penetration. Therefore, various problems arise in ultra-low-altitude flight, such as terrain tracking and wave response. Reducing the amount of radar wave reflection through shape design is also an important means of concealment.

Aerodynamic layout of winged missiles? There are many aerodynamic layout types of tactical missiles, such as normal type, canard type (the stable control surface is located in front of the missile wing), tailless type, and three-group tandem wing type. And long side strip combination type, etc. Missiles do not have problems with takeoff and landing rolls, so cross-shaped and X-shaped airfoil layouts are widely used, which can directly generate lateral aerodynamic force without rolling.

The two sets of wings at the front and rear can be in the shape of ×× and ×, ×, or a combination of a straight line and a cross or an There are also cases where only the tail section rolls freely. Boosters are divided into two types: series type and parallel type. The tandem type is arranged at the tail end of the missile, usually with only one booster; the parallel type is arranged at the side of the missile, which can be only one (cruise missile) or as many as four.

As for winged missiles using air jet engines, the layout of the air inlets also comes in various forms. Most cruise missiles adopt an aerodynamic layout similar to that of an aircraft, and their focus is not on maneuverability but on cruise efficiency.

Aerodynamic characteristics of large angle of attack? High maneuverability requirements and small aspect ratio constraints force the aerodynamic design of tactical missiles to tend towards a large angle of attack. When the angle of attack is greater than 20°, the flow around the missile wing It is a leading edge breakaway vortex type (see vortex).

The leading edge escape vortex can not only avoid the stall phenomenon caused by airflow separation on the airfoil, but also provide considerable nonlinear lift (see wing aerodynamic characteristics). At a high angle of attack, the separated airflow on the side of the missile body will also form a breakaway vortex, providing non-linear lift of the missile body. In order to strengthen the escape vortex and make it stable without breaking, the cross-sectional shape of the missile body can be made oblate, or small edges can be added to both sides of the round missile body.

On the edge strip wing and the turning wing, the edge strip and the inner wing part generate a breakaway vortex, while the outer wing part is still an attached vortex, which is called a mixed flow pattern, which plays a role in delaying the stall, but still Maintain the characteristic that lift changes linearly with angle of attack.

Complex aerodynamic interference issues? In terms of winged missile aerodynamics, aerodynamic interference issues appear to be more important than isolated components. First of all, the size of the missile body is very large, so the aerodynamic interference of the wing body is very serious. The escape vortex of the missile wing and the missile body makes the interference more complicated.

The second is the wash flow interference effect on the rear wing group caused by the leading edge breakaway vortex and trailing edge vortex dragged out by the front wing group, as well as the missile body breakaway vortex. Missiles usually use rocket engines, and the drop pressure ratio at the nozzle is much greater than that of the aircraft's air jet engine. Therefore, the free expansion rate of the jet is very high, which has a serious interference effect on the rear section of the missile (including the wing surface there).

Air-to-air missiles and air-to-ground missiles are carried and launched by aircraft or helicopters, which causes aerodynamic interference problems between the mother aircraft and the missile in the suspension state and launch phase. There are also aerodynamic interference problems between the booster and the missile during the connection state and separation stage.

The maneuverability of unsteady effect tactical missiles is very strong. The rudder deflection angle, elevation angle, sideslip angle, rotation angular speed and translation speed change rapidly. The flight Mach number also changes drastically, so it needs to be considered. Unsteady effects of aerodynamics (see unsteady aerodynamics).

Reducing the radar reflection area? Weakening the radar wave reflection signal plays an important role in improving missile survivability (see stealth technology). This is especially important for strategic cruise missiles and coastal defense missiles that rely on concealment to penetrate defenses. In order to reduce the radar reflection area, the shape of the missile must be changed, which will affect the aerodynamic research and design of the missile.