Improving diffusion-controlled microgravity experiments by facility orientation

Abstract

Residual-g (gravity) and g-jitter will be unavoidable sources of undesirable convection during diffusion-dominated fluid science or materials science experiments on the International Space Station. In this paper the facility orientation is proposed as an alternative to passive or active isolation devices, which would be not efficient against any residual-g, to minimize g-disturbances during microgravity experiments. A numerical study for a typical fluid physics experiment shows that both residual-g and g-jitter may be detrimental but also beneficial to achieve purely diffusive conditions, according to the orientation of the residual-g vector and of the vibration direction, relative to the direction of the density gradient. The results of the computations indicate that for the different configurations investigated, corresponding to different relative orientations between residual-g and g-jitter, the experimental facility can be properly oriented to minimize the convection disturbances.