Last year, the newly developed MAADS air defense system by European MBDA conducted a test fire and successfully shot down a target aircraft simulating an incoming enemy aircraft. It is reported that the air defense system can use two types of missiles - CAMM and extended range CAMM-ER. Although there are some differences in length and aerodynamic layout between the two missiles, they both have gas rudders at the rear. What is a missile gas rudder? What role can it play? Just like the rudder used to control the direction of a ship's movement, the gas rudder of a missile is used to adjust its flight direction. Missile gas rudder is usually installed at the nozzle of the rocket engine nozzle, using the reaction force generated by the gas passing through the rudder surface to control the missile's flight attitude and direction. Its structure includes gas rudder bracket, gas rudder shaft, gas rudder blade, etc. When the gas rudder blade is not deflected, the airflow on both sides passes through symmetrically without generating lateral forces; The rudder shaft drives the rudder blade to deflect, which can change the gas flow injected by the engine, generate control force and torque, and thus cause changes in the missile's flight attitude and trajectory. Unlike air rudders, gas rudders have a certain degree of irreplaceability. Gas rudder can function in an environment without air medium, and can achieve large angle turns of missiles in a short period of time and at low speed flight. Therefore, gas rudder has almost become an essential component for vertically launching missiles. Although the principle is simple, the development process is not easy. This is because the temperature of some gases can reach 3000 ℃, and the gas rudder must withstand high temperature "baking" tests. Some rocket propellants contain aluminum powder, and the solid aluminum oxide particles produced by combustion can erode the rudder surface. These erosion and erosion may cause deformation of the gas rudder, thereby reducing its control efficiency and even causing the gas rudder to fail. Therefore, the material selection of missile gas rudders is quite particular, which requires high melting point, strong anti vibration ability, ability to withstand particle erosion, low cost, easy processing, and mass production. After various tests, tungsten infiltrated copper material has been recognized by many countries. Due to the high density of traditional refractory metal materials, which can increase the weight of missiles, some research and development manufacturers have begun to rely on the precise grasp of the gas rudder ablation process, reasonably control the ablation process, predict control effects, and determine the gas rudder configuration in a targeted manner to achieve the expected results. In addition, the resistance generated by gas rudder blades can also directly or indirectly affect the direction of missile flight. To create a functional missile gas rudder, these issues need to be addressed. The higher requirements for off-axis attack capability of missiles in modern warfare have made in-depth research on missile gas rudders more urgent and crucial. (Lai Xin She)