Presentation Information
[PPS04-P10]Cratering experiments on iron granular targets
*Yuya Yamamoto1, Sunao Hasegawa1 (1.Japan Aerospace Exploration Agency)
Keywords:
crater,impact experiment,iron,Psyche
The asteroid (16) Psyche is classified as M-complex asteroid and a target of NASA's Psyche mission in 2029. The bulk density of Psyche is approximately 4 g cm-3 and comparable to that of stony-iron meteorites such as mesosiderites (Viikinkoski et al 2018). There are several hypotheses regarding the structure of Psyche. One suggests that Psyche is a rubble-pile composed of rocks and metals re-accumulated through repeated impacts, stony-iron meteorites parent body such as mesosiderites (Shepard et al. 2021). NASA’s Psyche mission is expected to observe Psyche's surface crater. These crater information give estimate the surface age of Psyche, the subsurface structure and the composition. However, while there are many experimental studies on impacts on sand and ice, few studies focus on impact craters on metallic targets, particularly iron granular targets. In this study, to investigate the crater morphology on iron granular targets and the effects of target grain disruption and size ratio of the projectile to the target grain on crater formation efficiency, we conducted impact experiments on iron granular targets.
Cratering experiments were conducted by using vertical gas gun sets at ISAS. Granular targets were prepared by using SUS304 spheres with a diameter of 3 mm filled into a stainless-steel container. The SUS grain density was about 8.1 g cm-3, and the target bulk density was about 4.3 g cm-3. A spherical projectile with the size of 1, 2, and 4.7 mm (acetate, nylon, glass, alumina, titanium, SUS, tungsten carbide) were lunched at the impact velocity from 1 to 6 km s-1. Projectiles were impacted perpendicularly onto the target surface. After the experiments, the crater diameter and depth formed on the target surface were measured.
The relationship between crater radius and projectile kinetic energy (Ek) shows that the crater size increased as the Ekincreases regardless of the projectile material. The size ratio of the projectile to the target grain, α= Dp/Dt affected crater formation efficiency. The crater radii for α = 0.67 and α = 1.6 were comparable to dry sand crater. On the other hand, the crater radii for α = 0.33 decreased by approximately 10-30 %. Furthermore, in the region of Ek between 20 and 40 J, the crater radius was almost constant. Using the π-scaling law, the relationship between the normalized crater radius (πR) and normalized gravity (π2) was investigated. The results for α = 0.67 and α = 1.6 were similar to those in previous studies using dry sand and glass bead targets. Conversely, the α = 0.33 results showed a lower crater formation efficiency than previous studies. The quantitatively evaluation of the effects of the projectile-to-target grain size ratio and target grain disruption will also reported in the presentation.
Cratering experiments were conducted by using vertical gas gun sets at ISAS. Granular targets were prepared by using SUS304 spheres with a diameter of 3 mm filled into a stainless-steel container. The SUS grain density was about 8.1 g cm-3, and the target bulk density was about 4.3 g cm-3. A spherical projectile with the size of 1, 2, and 4.7 mm (acetate, nylon, glass, alumina, titanium, SUS, tungsten carbide) were lunched at the impact velocity from 1 to 6 km s-1. Projectiles were impacted perpendicularly onto the target surface. After the experiments, the crater diameter and depth formed on the target surface were measured.
The relationship between crater radius and projectile kinetic energy (Ek) shows that the crater size increased as the Ekincreases regardless of the projectile material. The size ratio of the projectile to the target grain, α= Dp/Dt affected crater formation efficiency. The crater radii for α = 0.67 and α = 1.6 were comparable to dry sand crater. On the other hand, the crater radii for α = 0.33 decreased by approximately 10-30 %. Furthermore, in the region of Ek between 20 and 40 J, the crater radius was almost constant. Using the π-scaling law, the relationship between the normalized crater radius (πR) and normalized gravity (π2) was investigated. The results for α = 0.67 and α = 1.6 were similar to those in previous studies using dry sand and glass bead targets. Conversely, the α = 0.33 results showed a lower crater formation efficiency than previous studies. The quantitatively evaluation of the effects of the projectile-to-target grain size ratio and target grain disruption will also reported in the presentation.