Space Shuttle flame deflector system.
In a vertical launch, a flame deflector is any of variously designed obstructions that intercept the hot gases of the rocket engine so as to deflect them away from the ground or from a structure. The flame deflector may be a relatively small device fixed to the top surface of the launch pad surrounded by the framework of the launcher, or it may be a heavily constructed piece of metal mounted as a side and bottom of a flame bucket. In the latter case, the deflector may be perforated with numerous holes connected with a source of water, bending at an angle of about 45° into the line of the exhaust stream. During thrust buildup and the beginning of the launch, a deluge of water pours from the holes in such a deflector to keep it from melting.
See also deluge collection pond.
In a captive test, a flame deflector is an elbow in the exhaust conduit or flame bucket that deflects the flame into the open.