MOTIONS IN FLUIDS CAUSED BY MICROGRAVITATIONAL ACCELERATION AND THEIR MODIFICATION BY RELATIVE ROTATION

It has been recognized fr some time that large reductions in effective gravity can be achieved aboard an orbital spacecraft. As a consequence, many materials science experiments have been conducted in space in order to minimize or eliminate undesirable effects that might result because of convective motions in fluids driven by buoyancy effects. Of particular interest are the low-frequency accelerations caused by the Earth's gravity gradient field, spacecraft attitude motions, and atmospheric drag, since it is known that these can give rise to sustained fluid motion. In order to gain a limited understanding of the effects of these accelerations, the authors examined their magnitude and orientation and, in particular, have calculated the Stokes' motion of a spherical particle in a fluid for various types of spacecraft attitude motions. In addition, the effect of slowly rotating the experimental system relative to the spacecraft has been assessed.