Sources, mechanisms, and control of roll resonance phenomena for sounding rockets.

An understanding of roll resonance and the sources and mechanisms leading to roll lock-in is developed upon the basis of the steady-state or equilibrium trim resonant response of spinning sounding-rocket vehicles. The primary source of roll lock-in is shown to be the coupling of the lateral center-of-gravity offset with the aerodynamic normal force which results from pitch resonant response to trim asymmetry. The effect of induced roll moment is explained as a special case for mass and configuration asymmetries. Realistic operational criteria are developed based on the equilibrium behavior yielding the worst possible combination of asymmetries for degradation of the roll control of the vehicle. Maximum tolerance limits for center-of-gravity and trim asymmetries (either aerodynamic trim or thrust misalignment) are specified for representative sounding-rocket vehicles and trajectory profiles. These limits were tested and verified numerically with a dynamic motion program and shown to be conservative. Excellent agreement with flight behavior was obtained. Methods for controlling roll rate during flight in the presence of configurational, mass, and thrust asymmetries are developed, and a conceptual design for a fin tip gyro-aileron is illustrated.