Analysis Of Rocket Fairing’s Acoustic Field And Research Of Noise Reduction Technology

The acoustic environment of launch vehicle is very bad during launch period, thus may cause failure to some spacecraft’s electronic equipments of fairing, so it is very important to study the faring’s acoustic environment and then put forward some measures to improve its acoustic environment. The finite element method and statistical energy method were applied to predict the faring’s acoustic, then main plates in faring that affect the noise were analyzed, the scheme that reduce the sound pressure level in faring by sound absorption and damping treatment comprehensive was confirmed.The main parts of faring’s structure is honeycomb sandwich panel, so detailed study was developed for it. Firstly, finite element method was applied for sound insulation quantity calculation of honeycomb sandwich panel and the influence to its insulation quantity from parameters like panel thickness, thickness of honeycomb core, honeycomb core length, height and so on was analyzed. Then, the factor which can influence its lowest resonant frequency by analysis of honeycomb sandwich panel’s model. Last, the results were compared with the experiment, the correctness of the simulation result was verified.In view of the analyzed frequency range is quite wide, and different calculation method suit for different frequency range, so finite element method and statistical energy method was applied respectively to predict its sound field distribution. The faring’s finite element model is established and the coupling of fairing structure and fluid is considered then and the faring’s response under low frequency acoustic field is analyzed during low frequency simulating calculation, then specific sites within sound pressure level in fairing is calculated. The fairing’s statistical energy analysis model is established and divided into fairing structure and spoke subsystem, the main parameters of the statistical energy analysis are confirmed and then fairing absorption coefficient sensitivity is analyzed under middle and high frequency acoustic field.The fairing is divided into multiple panels, the contribution of each panels to the sound field of fairing was analyzed and the major part which contribute the most was confirmed. On the other hand, absorption material and its damp was also studied and various parameters which are suitable for absorption material and damping structure of fairing’s sound field. Last, the scheme of damping and reduction noise for the faring are determined by analyzing and comparing the noise attenuation effect of damping materials and sound absorption material all and part covered in the lining of the fairing.