In the very early stages of planet formation, dust grains trapped in a disk around the young star gently collide with each other, sticking and growing into bigger aggregates. Similarly, particles in planetary rings collide at very low relative velocities and form aggregates leading to many an observed features of Saturn’s rings for example. To better understand these low-velocity collisions and the growth of aggregates, microgravity experiments observing multi-particles systems are required. In particular, collision data for µm to cm-sized particles will help close the current gap in knowledge of how planetesimals are formed, as well as improve our understanding of the collisional evolution of planetary rings.

Q-PACE (CubeSat Particle Aggregation and Collision Experiment) is a 3U CubeSat that will observe a set of 0.1 mm to cm-sized particles colliding at the very low speeds made possible by its microgravity environment in orbit around the Earth. Q-PACE is scheduled for the next launch of the Virgin Orbit LauncherOne rocket, targeting before the end of 2020.


The Q-PACE spacecraft
Figure 1: Q-PACE is a 3U CubeSat. The exterior is mostly covered by solar panels to charge the batteries that power the experiment.

Q-PACE carries out its collision experiments in an Experiment Test Cell, or ETC, that is contained within the 3U body of the spacecraft (Figure 1). The ETC (Figures 2-3) is shaken in a controlled manner by tapping mechanisms in three directions to induce collisions between the particles and the walls of the ETC collision chamber. This then leads to the particles colliding amongst themselves. The particles are backlit, and the collisional evolution is captured by a small video camera for later transmission to Earth.

Top view of the experiment test cell
Figure 2: This image shows the view the camera on Q-PACE has of the particle collision chamber in the Experiment Test Cell, or ETC. At launch, 5 1-cm-diameter quartz spheres and several dozen 2-mm-diameter acrylic spheres were in the ETC collision chamber.
Side view of the Q-PACE ETC
Figure 3: The gears visible on the side of the ETC control the release of meteoritic chondrules and silica dust for later phases of the mission.
The collisional regime to be explored by Q-PACE is placed in the context of other experiments and the known regimes of aggregation and bouncing.


Figure 5: Q-PACE ready for thermal-vac testing.


Figure 4: Q-PACE completed its final vibration test in June 2019.
Measurements are made on Q-PACE to verify its dimensions prior to insertion in the satellite dispenser on the launch vehicle.
Q-PACE Principal Investigator Dr. Josh Colwell and lead software engineer Jonathan Kessluk pose with ceremonial UCF space mascot Dave just prior to installing the spacecraft in its dispenser on the launch vehicle at Virgin Orbit.