Time/frequency analysis of vibro-acoustic behaviour of a launcher in flight
Abstract
A satellite placed under the cap of a space launcher is submitted to severe vibro-acoustic conditions especially during lift off and transonic phases. This high acoustic level field, which can be damaging for the satellite, is mainly nonstationary. Thus, caution must be taken about results produced by classical Fourier analysis, since they rely on strong stationary hypotheses. To characterize in an appropriate way nonstationary data, time frequency was analyzed by means of wavelet transform. Conceptually, the wavelet transform is similar to a Fourier transform, as there is convolution between the signal and an analyzing window, but it differs in that this window is frequency dependent, leading to a constant accuracy for all frequencies. In addition, the chosen wavelet, Morlet's wavelet, permits a direct reconstruction of the original time signature. This method was successfully applied to the analysis of the Ariane 4 launcher vibro-acoustic behavior. This study was based on real data, signals of transducers located at different places on the launcher and its proximity. Results show the interest of this technique for shock and transient analysis, nonstationarities, identification, and localization in the time/frequency plane.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- October 1990
- Bibcode:
- 1990STIN...9110097F
- Keywords:
-
- Acoustics;
- Launchers;
- Liftoff (Launching);
- Signal Processing;
- Sound Waves;
- Space Flight;
- Transonic Speed;
- Vibration;
- Fourier Analysis;
- Transformations (Mathematics);
- Launch Vehicles and Space Vehicles