[PPS04-P01] Laboratory penetration experiments conducted at low effective gravity II
Keywords:Regolith, Impact, Penetration
To investigate the penetration of an impactor into granular material as an analogue of planetary regolith, we examined the low-velocity impact of a sphere into a granular layer at low effective gravity in the laboratory experiments. The target granular material was packed in a bucket. The bucket was fixed with two electromagnets; when the electromagnets were switched off, it dropped vertically downward, reducing the effective gravity, which was monitored by an accelerometer. In our previous set-up we used constant-force springs to hang the bucket and the effective gravity averaged 2.5 m/s2 (Nakamura et al., 2019JpGU). In our new study, we used two linear shafts to guide the bucket. The impactor was a 16. 7-mm-diameter glass sphere. A plastic straw with horizontal lines drawn on it was glued to the glass sphere. The penetration process of the glass sphere with the straw was imaged at 960 fps by a camera attached to the bucket. We used 1-mm-diameter glass spheres and 0.7-1 mm peach seed fragments as targets.
In this study, the effective gravity was lower than 0.09 m/s2. The glass sphere collided with the granular target at a relative velocity of between 3 and 4.5 m/s. The final depth of the impactor roughly matched the expected value given by an analytic penetration model (Katsuragi and Durian, 2013).