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Proceedings Paper

Measuring residual accelerations in the Spacelab environment
Author(s): William K. Witherow
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Paper Abstract

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. Accelerometers have been placed in the Spacelab to measure these accelerations. The Accelerometers are capable of measuring inputs as small as 10-6 gs. However, these levels are typically masked by the background `noise' accelerations due to crew activity and mechanical vibrations generated by the experiment facilities. In May 1985, Spacelab 3 flew on the Shuttle orbiter. The fluid experiment system (FES), a multiuser 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 by minimizing convection in the microgravity environment of the Spacelab. The seed crystal was attached to a platform. 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 positions of these crystals throughout the experiment. This paper presents the velocities and hence accelerations obtained by measuring the position of the free crystals from the holograms. An improved experiment is planned on IML-1 in the FES using polystyrene spheres as markers to aid in characterizing the residual accelerations present in the Spacelab.

Paper Details

Date Published: 1 December 1991
PDF: 11 pages
Proc. SPIE 1557, Crystal Growth in Space and Related Optical Diagnostics, (1 December 1991); doi: 10.1117/12.49582
Show Author Affiliations
William K. Witherow, NASA/Marshall Space Flight Ctr. (United States)


Published in SPIE Proceedings Vol. 1557:
Crystal Growth in Space and Related Optical Diagnostics
James D. Trolinger; Ravindra B. Lal, Editor(s)

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