2022-09-20 ローレンスリバモア国立研究所(LLNL)
シミュレーションがしやすく、かつ実際のDART宇宙船に近い挙動をする「中間領域」を見つけるために、さまざまな厚さの円柱や3球体のアプローチも検討した。3球体モデルは、宇宙船の形状をすべて使用した場合の影響のほとんどを説明することができた。この3球体の単純化により、異なるコードやユーザー間で、より多くのDART衝突のモデルを正確に実行することが可能になった。
＜関連情報＞
- https://www.llnl.gov/news/llnl-led-paper-reveals-spacecraft-geometry-effects-impact-simulations-nasas-dart-mission
- https://iopscience.iop.org/article/10.3847/PSJ/ac8932
キネティック・インパクター・ミッションにおける宇宙船形状の影響 Spacecraft Geometry Effects on Kinetic Impactor Missions
J. Michael Owen, Mallory E. DeCoster, Dawn M. Graninger and Sabina D. Raducan
The Planetary Science Journal Published: 2022 September 20
DOI:https://doi.org/10.3847/PSJ/ac8932
Figure 2. (y, z) plane slices through the initial conditions for our various impactor geometries. The insets for the non-DART scenarios are zoomed-in because those impactors are much smaller than the actual DART geometry.
Abstract
The DART (Double Asteroid Redirection Test) mission will impact a spacecraft on the secondary (Dimorphos) of the binary asteroid system Didymos in 2022 September, with the goal of altering the orbital period of Dimorphos about Didymos sufficiently to be observed from ground-based observations. Numerical impact modeling is a crucial component in understanding the outcome of the DART experiment, and while many have investigated the effects of target properties, such as material strength and porosity (which remain unknown), an often overlooked factor is the importance of accurately representing the spacecraft itself in such models. Most impact modeling to date has considered simple impactor geometries such as a solid uniform sphere, but in reality the spacecraft is a complex shape full of different components, open spaces, and thin walled structures. At a minimum, a simple solid representation underestimates the surface area of the impact: for a small body such as Dimorphos (approximately 160 m in diameter), the difference between a spacecraft spanning 20 m (including solar arrays) impacting and a sub-1 m idealized shape may be important. In this paper, we compare models impacting high-fidelity models of the spacecraft based on the CAD geometry with various simplified impactors, in order to assess the potential importance of this effect. We find that the difference between the simplest impactor geometries (such as a uniform sphere) and the real spacecraft is measurable, and has an interesting dependence on the material properties of the asteroid itself.
