Aeroservoelastic Stability of Supersonic Slender-Body Flight Vehicles

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T HE coupling between flight mechanics, aeroelasticity, and control system is called aeroservoelasticity. Flight vehicleswith slender configuration can experience aeroservoelastic instability during flight. This type of instability is likely to occur when short period rigid-bodymode, body bendingmode, and control loopmode are not properly phased. On the other hand, stable aeroservoelastic phenomena can affect the planned trajectory of the vehicle. For this reason the extent of aeroservoelastic interaction for guided supersonic vehicles is of considerable importance. The dynamics of the elastic vehicles have been studied in various categories. Meirovitch and Nelson [1] examined the dynamic stability of a spin-stabilized spacecraft containing flexible rod appendages. Meirovitch and Wesley [2] presented an approach for nonspinning variable-mass rockets aeroelasticity whereas Oberholtzer et al. [3], Crimi [4], and Platus [5] investigated the same approach for spinning missiles. Whereas the researchers focused on special cases, an integrated approach developed for nonspinning elastic hypersonic flight vehicles by Bilimoria and Schmidt [6]. To predict the effect of body flexibility on control systemNewman and Schmidt [7] developed a two-dimensional aeroelasticmodel offlight vehicles. The effect of flexibility on the poles and zeros of a general flexible flight vehicle has been studied by Livneh and Schmidt [8]. Thrust effect in the boost phase of flight on the vibrational characteristics of flexible guided vehicles has also been studied by Pourtakdoust and Assadian [9] numerically. Using the previous works of Platus [5] and Bilimoria and Schmidt [6] on the aeroelasticity of unguided flight vehicles, the present work develops an analytical model for the study of aeroservoelasticity of guided supersonic slender body flight vehicles. For this purpose, modal analysis method is employed for the structure, slender body theory is used for aerodynamics, and rate-gyro and actuator dynamics in roll, pitch, and yaw channels are also considered in construction of the model. The solutions to the equations of motion are analyzed for instability prediction. Formulation