13:45 〜 15:15
[PPS03-P02] Simulator for Formation of Rubble-Pile Asteroids Using Open-Source Physics Simulation
キーワード：ラブルパイル小惑星、剛体シミュレーション、サイズ頻度分布
There are various shapes of rubble-pile asteroids. Ryugu and Bennu have a nearly rotationally symmetric top shape, while Itokawa has an elongated shape. Ground-based telescope observations also suggest that there is much diversity in the shape of the rubble-pile asteroids. Even though many factors contribute observed wide variety of rubble-pile asteroids, it is guessed that the size-frequency distribution of fragments of the parent body and their accumulation conditions strongly control them.
The purpose of this research is to investigate the relationship between the conditions for rubble-pile accumulation, including the size-frequency distribution of fragments, and the final shape of the asteroid. This investigation is carried out by simulating the accumulation process of rubble-pile asteroids. In the simulation, the fragments are treated as a rigid body, and basic physical interactions such as contact, friction, rotation, and gravity between fragments need to be reproduced. In this research, we implement these physical processes using open-source physics engine Chrono (https://projectchrono.org/). Chrono can handle physical interactions between objects of various shapes. In addition, while most physics engines used in games and other applications perform single-precision operations, Chrono is capable of double-precision operations. Ferrari et al. (2017, 2020) were early examples attempting to simulate rubble-pile asteroid formation using Chrono, but they were not discussed well the final shapes of rubble-pile asteroids.
This research aims to implement a simulator using Chrono, following previous research, and to simulate with different parameters such as size-frequency distribution, shape, total number, dynamic friction, static friction, rebound, and rolling resistance coefficient of the fragments.
In our test simulation, fragments with a same polyhedron shape with a triaxial ratio of 2:21/2:1 (the average triaxial ratio of rocks in space) are attempted to accumulate to form a rubble-pile asteroid. Two cases of the size-frequency distributions of fragments are tested: a monopolistic case with one largest fragment and an oligopolistic case with four largest fragments. Ten runs have been performed for these two cases, and the final shape of the rubble-piles were examined. It was approximated as an ellipsoid and the triaxial ratio was calculated. As the result, all rubble-piles have larger triaxial ratios than that of the single fragment (2:21/2:1). No difference in the triaxial ratio distribution is found between monopolistic and oligopolistic cases. Order of accumulation may affect the final shape: In a case when one of the largest fragments or the second large fragment accumulates later, the rubble-pile shows an elongated shape. This presentation will explain the detailed parameters and accumulation conditions of the fragments in the simulation and discuss the results.
The purpose of this research is to investigate the relationship between the conditions for rubble-pile accumulation, including the size-frequency distribution of fragments, and the final shape of the asteroid. This investigation is carried out by simulating the accumulation process of rubble-pile asteroids. In the simulation, the fragments are treated as a rigid body, and basic physical interactions such as contact, friction, rotation, and gravity between fragments need to be reproduced. In this research, we implement these physical processes using open-source physics engine Chrono (https://projectchrono.org/). Chrono can handle physical interactions between objects of various shapes. In addition, while most physics engines used in games and other applications perform single-precision operations, Chrono is capable of double-precision operations. Ferrari et al. (2017, 2020) were early examples attempting to simulate rubble-pile asteroid formation using Chrono, but they were not discussed well the final shapes of rubble-pile asteroids.
This research aims to implement a simulator using Chrono, following previous research, and to simulate with different parameters such as size-frequency distribution, shape, total number, dynamic friction, static friction, rebound, and rolling resistance coefficient of the fragments.
In our test simulation, fragments with a same polyhedron shape with a triaxial ratio of 2:21/2:1 (the average triaxial ratio of rocks in space) are attempted to accumulate to form a rubble-pile asteroid. Two cases of the size-frequency distributions of fragments are tested: a monopolistic case with one largest fragment and an oligopolistic case with four largest fragments. Ten runs have been performed for these two cases, and the final shape of the rubble-piles were examined. It was approximated as an ellipsoid and the triaxial ratio was calculated. As the result, all rubble-piles have larger triaxial ratios than that of the single fragment (2:21/2:1). No difference in the triaxial ratio distribution is found between monopolistic and oligopolistic cases. Order of accumulation may affect the final shape: In a case when one of the largest fragments or the second large fragment accumulates later, the rubble-pile shows an elongated shape. This presentation will explain the detailed parameters and accumulation conditions of the fragments in the simulation and discuss the results.