Abstract Asteroids are small solid bodies that formed during the early stages of the solar system, even before the formation of our own planet. Asteroids have been known to strike our planet Earth ever since its formation, causing a great threat to all existing life forms. One of the means to avert a potential collision of an asteroid with Earth is to deflect the asteroid away from its trajectory towards Earth by means of an impacting spacecraft. This idea is already part of mission designs such as AIDA (Asteroid Impact and Deflection Assessment). The study of the surfaces of numerous asteroids through spacecraft, ground-based spectroscopic observations and other techniques has revealed that the surfaces of these small bodies are covered with loose, granular, heterogeneous geological material. This is called ‘regolith’. If an impactor were to collide with an asteroid, the physical phenomenon that needs to be understood is the reaction of the regolith to the impact. To understand the deflection of the asteroid, the transfer of momentum from the impactor to the asteroid needs to be characterised. The impact can produce ejecta which would also add momentum to the target. Therefore, there are two components to this momentum gained by target body: (1) direct transfer of momentum from the impactor to the asteroid, (2) momentum caused by ejecta flying in the direction opposite to that of the impactor. The momentum transfer can thus be described by the so-called momentum multiplication factor β, which is the ratio of the momentum gained by the target to the momentum of the impactor at the time of collision. In this work, small-scale impact experiments using polyvinylchloride (PVC) projectiles on regolith-like materials and simulants - sand, glass beads and the Johnson Space Center (JSC)-1A lunar regolith simulant - have been conducted. We used the electro-thermal accelerator of the Technical University of Munich (TUM)/Lehrstuhl fur Raumfahrttechnik (LRT) to determine the momentum transfer from the projectiles onto these regolith targets. We derived relationships between the kinetic energy and the crater mass and characterized the ejecta cloud. We confirmed the dependency of β on the impact velocity of the projectile (impactor) - higher momentum transfer occurs at larger impact velocities. We have also seen a trend that β gets larger for a lower cohesion and higher porosity of the target material. Thus, a thorough understanding of the regolith properties of AIDA’s target asteroid will be crucial towards understanding and determining the momentum transfer.

中文翻译：

---

使用 TUM/LRT 电热加速器确定类风化层目标的动量传递

摘要小行星是在太阳系的早期阶段形成的小型固体，甚至在我们自己的星球形成之前。众所周知，小行星自地球形成以来就袭击了我们的地球，对所有现有生命形式造成了巨大威胁。避免小行星与地球潜在碰撞的方法之一是通过撞击航天器将小行星从其轨道转向地球。这个想法已经是AIDA（小行星撞击和偏转评估）等任务设计的一部分。通过航天器、地基光谱观测和其他技术对众多小行星表面的研究表明，这些小天体的表面覆盖着松散的、颗粒状的、异质的地质物质。这被称为“风化层”。如果撞击体与小行星相撞，需要理解的物理现象是风化层对撞击的反应。为了理解小行星的偏转，需要表征从撞击器到小行星的动量转移。撞击会产生喷射物，这也会增加目标的动量。因此，目标体获得的这种动量有两个组成部分：(1) 动量从撞击器直接转移到小行星，(2) 喷射物以与撞击器相反的方向飞行所引起的动量。因此，动量传递可以用所谓的动量倍增因子 β 来描述，它是目标获得的动量与碰撞时撞击器动量的比值。在这项工作中，使用聚氯乙烯 (PVC) 射弹对类似风化层的材料和模拟物——沙子、玻璃珠和约翰逊航天中心 (JSC)-1A 月球风化层模拟物——进行了小规模撞击实验。我们使用慕尼黑工业大学 (TUM)/Lehrstuhl fur Ra​​umfahrttechnik (LRT) 的电热加速器来确定从射弹到这些风化层目标的动量转移。我们推导出动能和陨石坑质量之间的关系，并对喷射物云进行了表征。我们确认了 β 对射弹（撞击器）的撞击速度的依赖性 - 在更大的撞击速度下会发生更高的动量传递。我们还看到，随着目标材料的低内聚力和更高的孔隙率，β 变大的趋势。因此，