5:15 PM - 7:15 PM
[PPS06-P15] Observation of crater formation process using load cells: Estimating the momentum of the ejecta curtain and apparent-gravity
Keywords:Impact crater, ejecta
Hyper-velocity collisions among planetary bodies are one of the elementary physical processes in solar system. These collisions lead to crater formation and transfer the momentum between the planetary bodies. Therefore, clarifying this process is crucial for understanding the collision evolution of planetary surfaces and planetary defense. Recently, the interest in experimental research on small body collisions has been growing, such as the SCI crater formation experiment by Hayabusa2 and the DART mission, which aimed to modify the orbit of an asteroid through impact. While there have been several studies which investigated the effects of gravity on crater formation, but they needed large experimental setups, which makes such experiments difficult to conduct. To address the challenge, this research conducted a simplified experiment at small laboratory scale using handful devices to restrict the ejection of material during crater formation, which refers to a constrained crater experiment. In the experiment, we developed the new method to measure the load required to stop ejected material using the load cells. Additionally, we propose a new experimental way to investigate the influence the effect of frictional stress and static pressure (imitation-gravity) which generates the friction on cratering. We focus on the momentum of ejected material under restricted condition as well and develop a new method to estimate the momentum transfer efficiency in weak planetary bodies like asteroids.
For the target material, we used quartz sand with a particle size of 0.5 mm to simulate crater formation under gravity-dominated regime. A square aluminum plate with a circular hole in the center was used as a load receiver, and it was placed on a horizontal target surface. The impact experiments were conducted using the vertical light gas gun at Kobe University, and we impacted the projectile at the center of the hole in the plate. The growth of the crater due to the impact was constrained by the size of the hole, and the plate restricted the ejection from the target. During the process, the load on the plate was measured by strain gauge-type load cells. We installed the load cells in contact with the plate. When the collision occurred, the plate was raised according with the ejection or moves of sand from target. We observed the load generated by the motion of the plate during the impact cratering using load cells. In this study, we conducted the experiments using aluminum plates with hole diameters of 20 mm and 30 mm, and impact velocities ranging from 112 to 270 m/s.
The experiments showed that as the momentum of the projectile increased, the load measured by the load cells also increased. However, at the same projectile momentum, we observed no significant change in load influenced by the size of the holes. In this study, the observed maximum load (the difference between the maximum load after the collision and the load before the collision) was used to calculate the average pressure, which was treated as hydrostatic pressure to estimate the apparent-gravity. The estimated apparent-gravity for the 20 and 30mm hole was several times smaller than previous studies. [1] Additionally, by integrating the variation of the load on the load cells with the time, we calculated the impulse applied to the load cells during the collision. We treated the impulse as the momentum of the ejecta curtain restricted by the plate and estimated the momentum transfer efficiency caused by the collision. The results showed that the value was slightly larger than that in previous studies at higher impact velocities.[2]
[1] Matsue et al. (2020), Measurements of seismic waves induced by high-velocity impacts: Implications for seismic shaking surrounding impact craters on asteroids, Icarus, volume 338, 113520
[2] Chourey et al. (2020), Determining the momentum transfer in regolith-like targets using the TUM/LRT electro-thermal accelerator, Icarus, volume 194, 105112
For the target material, we used quartz sand with a particle size of 0.5 mm to simulate crater formation under gravity-dominated regime. A square aluminum plate with a circular hole in the center was used as a load receiver, and it was placed on a horizontal target surface. The impact experiments were conducted using the vertical light gas gun at Kobe University, and we impacted the projectile at the center of the hole in the plate. The growth of the crater due to the impact was constrained by the size of the hole, and the plate restricted the ejection from the target. During the process, the load on the plate was measured by strain gauge-type load cells. We installed the load cells in contact with the plate. When the collision occurred, the plate was raised according with the ejection or moves of sand from target. We observed the load generated by the motion of the plate during the impact cratering using load cells. In this study, we conducted the experiments using aluminum plates with hole diameters of 20 mm and 30 mm, and impact velocities ranging from 112 to 270 m/s.
The experiments showed that as the momentum of the projectile increased, the load measured by the load cells also increased. However, at the same projectile momentum, we observed no significant change in load influenced by the size of the holes. In this study, the observed maximum load (the difference between the maximum load after the collision and the load before the collision) was used to calculate the average pressure, which was treated as hydrostatic pressure to estimate the apparent-gravity. The estimated apparent-gravity for the 20 and 30mm hole was several times smaller than previous studies. [1] Additionally, by integrating the variation of the load on the load cells with the time, we calculated the impulse applied to the load cells during the collision. We treated the impulse as the momentum of the ejecta curtain restricted by the plate and estimated the momentum transfer efficiency caused by the collision. The results showed that the value was slightly larger than that in previous studies at higher impact velocities.[2]
[1] Matsue et al. (2020), Measurements of seismic waves induced by high-velocity impacts: Implications for seismic shaking surrounding impact craters on asteroids, Icarus, volume 338, 113520
[2] Chourey et al. (2020), Determining the momentum transfer in regolith-like targets using the TUM/LRT electro-thermal accelerator, Icarus, volume 194, 105112