Quickly changing acceleration forces (QCAFs) vibration analysis on the A300 ZERO-G.

Experiments that are done under microgravity, e.g. during space or parabola flights, are invariably accompanied and affected by ubiquitous vibrations of the surroundings. Vibrations induce Quickly Changing Acceleration Forces (QCAFs) that interfere with the perception of the earth gravitational field. To investigate their impact on experiments under microgravity we monitored the vibrations of the airplane A300 ZERO-G during parabola flights and analyzed them in their spectral and frequency domains. Power spectra obtained with Fast-Fourier Transforms (FFT) display a complex pattern of various vibrations whose origin, relative phases and intensities remain unidentified. During the zero-g phases (parabolas), when the engines of the airplane are throttled, the vibrations still elicit residual QCAFs of at least +/- 1 g. By means of adequate damping procedures the QCAFs could, however, be reduced by approximately 95%.