Measuring residual accelerations in the spacelab environment

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Measuring residual accelerations in the spacelab environment

Witherow, W.K.

The objective of some experiments performed in space is to study the effect of minimized convection on various processes. The Shuttle orbiter can provide long periods of microgravity for performing experiments. However, residual gravitational accelerations still remain. In May 1985, Spacelab 3 flew on the Shuttle orbiter. The Fluid Experiment System (FES), a multi-user facility, was on board with the Triglycine Sulfate (TGS) crystal growth experiment. The FES is a holographic system that is capable of taking single and double exposure holograms. A series of holograms is recorded during the experiment run. The experiment is analyzed on the ground using the series of holograms taken during the run. The main purpose of the TGS experiment was to examine diffusion limited crystal growth. However, in one of the test cells, tiny crystals were found floating free in the growth solution during the experiment. Since the free crystals were in a viscous fluid, the 'noise' accelerations of the Shuttle were damped out. This made it possible to measure the constant gravitational acceleration by tracking the postions of these crystals throughout the experiment. This paper presents the velocities and hence accelerations obtained by measuring the postion of the free crystals from the holograms.