Launch vehicle buffeting with aeroelastic coupling effects

Launch vehicle structural responses can couple with transonic flow state tr ansitions at the nose of payload fairings. This self-sustained coupling yie lds a nonlinear equation of motion that can be analyzed using the force-res ponse relationship and the periodicity condition. The traditional analysis approach for this phenomenon, however, linearizes the equation of motion by converting the alternating flow forces into an aerodynamic damping term an d defines a stability criterion as the response amplitude that yields zero net system damping. This work clarifies the relationship between the presen t and traditional methods, and compares results and conclusions. The feasib ility of modifying a launch vehicle response analysis of buffeting (random pressure fluctuations caused by turbulent flow) to include aeroelastic coup ling effects is also explored. The aerodynamic stiffness and damping terms formulated herein are consistent with trends observed in wind-tunnel test d ata. It is shown, however, that the modified buffet analysis can be inaccur ate, particularly when the aeroelastic coupling contribution does not domin ate the system response. (C) 2000 Academic Press.