Outline

SoftSphereSim

Introduction

The Particles

Material

Density, Radius, Coefficient of Restitution, Coefficient of Friction

Gravitational Attraction

Spring Repulsion

Friction

The Clusters (Asteroids)

Asteroids are simulated as clusters of balls held together by their own gravitational attraction. To form an asteroid we randomly distribute a predetermined size distribution of balls across a sufficient 3D space for them to exist with no overlap. The cluster is given time to collapse into a stable asteroid held together by the ball force interactions of gravity, friction, and spring repulsion.

The most concise way to describe what we have done is with before and after images shown here:

Note on Cluster Generation

When creating a cluster, we don’t know the space it will need to occupy given its natural formation and resulting packing configuration via particle collapse in self-gravity, so a bit of trial and error is required to obtain a naturally formed asteroid at the desired radius and density.

Shape

We initially chose a simple cartesian random distribution of particles which resulted in “cubeish” clusters. In early collisions simulations we verified that the significance of the impact point on the shape did not significantly affect the outcome of collisions compared to things like impact velocity and impact angle, however, we later discovered that when spinning a “cubeish” cluster about its center of mass, it breaks apart in a very noticeably cube-like structure. This was enough to convince us that we should spherically distribute particles to remove any unforeseen behaviors dependent on that symmetry.

Show before and after cubeish and spherical asteroids from slides.

The Collisions

Target

Projectile

Reference Frame

The Remnant of Collision

Constructive or Destructive?