14:15 〜 14:30
[PPS02-03] Experimental estimation of regolith scattering behavior when a space lander touches on a planetary body
★Invited Papers
キーワード：レゴリス、室内実験、着陸装置
A planetary lander, which needs to land on and lift up from a planetary surface, needs to be concerned with levitated regolith. Regolith scattered by the landing foot pad might attach to or damage on-board instruments, such as the spacecraft’s camera suite. To design the landing probe, it is necessary to estimate the expected area of the regolith that the probe may scatter. Here we show an experimental approach that was developed to study the behavior of scattered regolith under a vacuum environment. For the probe design, it is necessary to precisely measure the initial ejection angle, ejection velocity, and the amount of regolith that the landing foot pad scatters.
In order to characterize scattered-particle behavior, drop tests in a large vacuum chamber were conducted. A cylindrical mass projectile, mimicking the lander foot pad, fell freely from various heights in the vacuum chamber. The mass lands in a sandbox filled with silica sand and forms a crater with scattered sand particles. During silica sand scattering, a high-speed camera detected particle highlighted by a line laser. Initial ejection velocities and the ejection angles were estimated by processing the images of the impact site, captured by the high-speed camera.
The result of our study revealed that the ejection angle of scattered grains is not sensitive to the impact kinetic energy of the projectile. Our results are consistent with previous studies that showed a similar relationship between impact kinetic energy and ejection angle, but for lower impact energies. Moreover, we find that for impact speeds of ~ 4 m/s, the initial ejection velocity of a majority of the silica sand particle is distributed around 1 m/s.
Our experimental approach can be applied to various kinds of planetary regolith, such as Phobos simulant for the Martian Moons eXploration(MMX). These results help us to understand how to determine the optimal design conditions for a landing probe. Further studies that account for the effect of microgravity and changes to the bulk density and porosity of the regolith need to be undertaken based on drop tower test and numerical simulation.
In order to characterize scattered-particle behavior, drop tests in a large vacuum chamber were conducted. A cylindrical mass projectile, mimicking the lander foot pad, fell freely from various heights in the vacuum chamber. The mass lands in a sandbox filled with silica sand and forms a crater with scattered sand particles. During silica sand scattering, a high-speed camera detected particle highlighted by a line laser. Initial ejection velocities and the ejection angles were estimated by processing the images of the impact site, captured by the high-speed camera.
The result of our study revealed that the ejection angle of scattered grains is not sensitive to the impact kinetic energy of the projectile. Our results are consistent with previous studies that showed a similar relationship between impact kinetic energy and ejection angle, but for lower impact energies. Moreover, we find that for impact speeds of ~ 4 m/s, the initial ejection velocity of a majority of the silica sand particle is distributed around 1 m/s.
Our experimental approach can be applied to various kinds of planetary regolith, such as Phobos simulant for the Martian Moons eXploration(MMX). These results help us to understand how to determine the optimal design conditions for a landing probe. Further studies that account for the effect of microgravity and changes to the bulk density and porosity of the regolith need to be undertaken based on drop tower test and numerical simulation.