| Popis: |
Spacecrafts are exposed to high level of acoustic excitation during launch. The impingement of acoustic energy onto the spacecraft results in random vibration that can potentially lead to catastrophic failure of the components or even the primary structures. Hence, one of the crucial steps in the spacecraft design process involves analytical predictions and test verifications of the structure responses, loads, and internal cavity sound pressure level under launch environment. The prediction of the internal acoustic environment is especially important for the spacecraft that houses sensitive components and/or instruments within its cavities or compartments. In case of manned space missions, excessive cavity acoustic environment may inflict physical injuries to the astronauts. This paper presents a continuation of the analytical correlation effort that was presented in the AIAA SciTech 2015 conference. In the previous study, the authors hypothesized that the shortcomings observed in the boundary element method (BEM) predictions of the cavity sound pressure might have resulted from insufficient modeling of the boundary openings and inaccurate representation of external/input acoustic field around the spacecraft. Thus, the current study focuses on further enhancements to the analytical model and more detailed predictions of the open cavity environment. The cavity sound pressure predictions, as well as the structure acceleration response predictions at various locations on the spacecraft, are compared with the test data from Direct Field Acoustic Test (DFAT). This paper also presents further investigations into resonant characteristics of the spacecraft cavity using acoustic finite element model (FEM), and more precise shaping of the external/input acoustic field using numerical optimization technique. A commercially available vibro-acoustic analysis tool, VA One 2015.0, was used in this study. |
