Closed-form approach to rocket-vehicles aeroelastic divergence

Abstract

The aeroelastic divergence of a class of rocket-vehicl e configurations is studied in closed form. The class is characterized by having the lateral aerodynamic loads distributed mainly about the vehicle nose and tail. The purpose is to demonstrate the feasibility of a closed-form approach and its usefulness in pinpointing the essentials of, and lending insight into, the phenomenon. The equations of motion are first derived; then, a dynamic frequency-domain stability analysis is carried out, yielding simple formulae for the divergence dynamic pressure and generalized static margin. The predivergence short-period roots behavior is also found. Expressions are derived for the steady-state angle of attack, accelerations, aerodynamic loads, and elastic bending of a perfectly aligned vehicle at divergence and of a misaligned vehicle at predivergence . For application to actual cases, a method is developed by which actual aerodynamic distributions may be converted into a form admissible to the theory. Validity is confirmed by comparison of results with those of a more exact theory and with available experimental data.