Gas-dynamic

A gas-dynamic control system is one where the path of an object in flight is controlled by either the generation or redirection of gas flow out of an orifice rather than with the traditional movable control surfaces. There are two major types of gas-dynamic control: thrust vectoring and control jets.

Thrust vectoring involves redirecting part or all of the same gas outflow that is used to generate thrust for maneuvering. Either vanes that are placed in the gas flow jet are moved, redirecting it, or else there is a nozzle around the gas jet which can be tilted in one axis (1D thrust vectoring) or two axes (2D thrust vectoring) in order to direct the gas jet.

Control jets are small orifices in the top/bottom and/or sides of the object to be controlled, through which gas can be ejected. This gas may be tapped from the main engine or generated separately from compressed gas in bottles or by burning fuel. If mounted in the front of the vehicle, a gas jet blowing out the left of the nose will push the nose, and therefore the object, to the right. If mounted behind the center of gravity of the object the opposite effect will occur - a gas jet on the left side will turn the object to the left. Varying the amount of gas exiting the jet will control the amount of force and therefore the rate of turn.

Gas-dynamic control systems are typically found on high-altitude jet aircraft (such as the Sukhoi Su-35, F-22 Raptor and X-15), spacecraft (such as the Space Shuttle), ballistic missiles, air-to-air missiles (such as the Vympel R-73 (AA-11) and surface-to-air missiles (such as the S-400 "Triumf" (SA-20) and 9K332 "Tor" (SA-15)).