Effect of 1/6 Gravity Environment on Atmospheric Suspension of Simulated Lunar Regolith

抄録

In order to investigate the behavior of suspended particle matter (SPM) in a 1/6 gravity (1/6 G) environment, simulated lunar regolith was diffused in a chamber, realizing a quasi 1/6 gravity environment by parabolic flight. The effect of the 1/6 G environment on the atmospheric suspension was evaluated by means of the cutoff value of an elutriator; the cutoff value in the 1/6 G should be √<6> times larger than at the earth's surface. The results of our experiment confirmed that the falling velocity of SPM in a 1/6G approximates Stokes' law, and the falling time is inversely proportional to the force of gravity. Numerical computation suggested that residual SPM in a convection-free room becomes high in a low-gravity environment or in a high-ceilinged room. These results suggest that once lunar dust intruded into a lunar base, it would take a considerably long time to clean up. Since the suspension time of SPM is different according to the particle size, the exposure risk of SPM will also vary according to the particle size. Considering that the risk depends only on the drifting time, the actual influence of low gravity on fine particles (D_p &le; 1.0 mm in diameter) and on large particles (D_p > 10 mm) in a 1/6G would be negligible. In contrast, for medium sized particles (2.5 < D_p &le; 10 mm) the difference in the drifting time between that on the earth and on the lunar surface is much larger than can be confirmed with the senses. Safety precautions used for this size of particle on the earth should be altered on the lunar surface.