Unsteady control surface loads of lifting re-entry vehicles at very high speeds.

Abstract

Recent research on control surface instabilities of lifting body configurations at very high speeds and with separated flows has led to a new insight into several possible unsteady control surface load problems. These separated flow problems are examined by presenting the most instructive of the numerous dynamic measurements obtained from wind-tunnel tests on simple aeroelastic models at Mach numbers from 3 to 10. The discussion is intended to provide a conceptual framework within which the test results can be interpreted and assessed as to their more general validity and to draw some guidelines as to their possible design significance. The observations include an instability of a type that involved a fluid-dynamical self-excitation of the separated pocket, feeding upon or modulated by tunnel and model disturbances without the necessity for participation of the control surface motion. The key to this type of instability appears to be contained in the recognition and identification of the various feedback mechanisms in the complex fluid and elastic systems and the conditions under which these might become regenerative or self-sustaining.