THE INVESTIGATION OF ACOUSTIC TEST SPECIFICATIONS ON SPACECRAFT STRUCTURE BY NUMERICAL ANALYSIS METHODS

Spacecraft structures are subject to acoustic load and high frequency vibration, particularly during launch, which can impose severe and adverse affect to the structures of the spacecraft and their payloads. Therefore, it is very necessary to execute ground simulation tests to check the spacecraft's adaptability to acoustic environment. In general, spacecraft should to be tested in a large reverberation chamber with severe acoustic levels usually 150dB. However, in acoustic test, the position and number of control/measure microphones, as well as the relationship between the volume of spacecraft and the volume of reverberation chamber are important testing conditions to follow. Unfortunately, the test standard from different countries is different. In this paper, a numerical analysis method based on finite element method (FEM) is developed to predict the sound pressure distribution in the reverberation chamber with spacecraft structure. A mounting system is used to support the spacecraft structure. The FE model for spacecraft structure, the FE model for interior or exterior acoustic domain and their coupling model are established. Acoustic loading is applied by means of point sources with directivity fitted to experimental data. The numerical analysis results in low frequency range are demonstrated. Testing conditions such as position and number of control/measure microphones, as well as the relationship between the volume of spacecraft and the volume of reverberation chamber are further investigated and discussed. The goal is to obtain a clear and correct description for available ground acoustic testing conditions.