The sources of vibro-acoustic excitation are mainly due to noise generated by the launcher during ignition, lift-off and atmospheric flight. The vibro-acoustic environment is usually a dimensioning load case for light-weight structures like antenna reflectors and solar arrays. For equipments mounted on the panels of a spacecraft, the dynamic response of the panels to the acoustic load leads to high and, often dimensioning, random vibration loads.
All the equipments of a spacecraft must successfully go through qualification mechanical tests before they are allowed to be flown. For the vibro-acoustic environment qualification, random vibration test is generally specified as qualification requirement for equipments mounted on panels. As for larger appendages, acoustic test in reverberant chamber is the preferred choice.
These equipment specifications have to be derived in the early design process with very limited information on the actual configuration of the spacecraft. Thus, specifications need to be adequate but not too conservative.
Early definition of the specification based often on heritage of test data from other spacecrafts and on empirical data [ECSS-E-10-03A].
The technique used in the analysis for the low frequency range (< 500Hz) is based on the established boundary element / finite element coupling method. The structure of the spacecraft or equipment is considered as elastic body whose dynamic motion caused by the sound pressure load is fully coupled to surrounding the media. The picture below shows the comparison of test and analytical responses at a location on the sun shade of HERSCHEL S/C.
Last update: 12 March 2013