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Collisional Particle Evolution

Collisional Particle Evolution

The ‘NanoRocks’ Collisional Evolution of Particles and Aggregates in Microgravity research explores low-energy collisions in microgravity to shed light on the formation of planetisimals, the building blocks of planets.

Customer: The University of Central Florida
Research: Collisional Particle Evolution
NanoRacks Facility: Internal Platform
Mission Duration: 09/2014 – 09/2015
Mission Status: Complete
More Info: From NASA website


Research Overview

  • NanoRocks Collisional Evolution of Particles and Aggregates in Microgravity (NanoRacks-NanoRocks) is an experimental study of the physics of collisions between aggregate types and between monomers and aggregates at the sizes and velocities relevant for planetary formation and planetary ring collisional evolution. This research provides further qualitative and quantitative data in understanding planetary formation evolution on a macro scale.
  • In order to treat collisional evolution in a probabilistic approach, the experimental database for such collisions must be significantly expanded so that there are reliable estimates of the probabilities of certain rare outcomes (such as sticking at large impact speeds). The environment of the ISS with this proposed experiment architecture provides a significant expansion of the number of collisional outcomes observed at low impact speeds.
  • The quantitative increase in data of this type is a geometric expansion and provides further illumination on the nature of planetary formation.

Description
NanoRocks is an experimental exploration of low-energy collisions in protoplanetary disks to better understand the conditions and processes that lead to the formation of planetesimals, the building blocks of planets. The same sorts of collisions also take place in planetary ring systems, such as Saturn’s rings.

The experiment takes advantage of the long-duration and high quality of microgravity on the International Space Station (ISS) to obtain a large sample of collisional outcomes at very low velocities (< 10 cm/s). The experiment consists of chambers containing different populations of particles and aggregates. The chambers are agitated by varying amounts inducing collisions between the particles. Video of the collisions indicate the collision parameters (mass, density and composition of particles, and collision velocities) that lead to sticking, rebound, and fragmentation of aggregates.

In the case of rebound the coefficient of restitution (a measure of the dissipation of energy) is measured. These results have a direct scientific application to the question of the collisional evolution of Saturn’s rings, where particles undergo frequent collisions at speeds as low as 1 mm/s, as well as the conditions necessary for the earliest stages of planet formation.

The age of Saturn’s rings, and hence their origin, remains an open issue. The dissipation of kinetic energy in interparticle collisions is a key parameter in understanding the long-term evolution of the system. The data from the proposed experiments will illuminate the velocity-dependent coefficient of restitution for collisions in planetary rings.

This parameter has a significant effect on the pace of angular momentum transfer across the rings in numerical simulations of rings, but is currently poorly known.

Additionally, the data collected on inter-particle collisions and the behavior of dense particle systems in a low gravity environment informs the development of hardware and procedures for operation on the surfaces of small airless bodies, such as asteroids, where there is very low gravity and surface regolith disturbances may occur.

UCF Physics NanoRocks Payload

Camera image of the experiment tray from NanoRocks.

Applications
Asteroids, moons, planets and the rings of Saturn all form from countless collisions of small particles. As these bodies grow in size, their gravity attracts more rocks and dust, further increasing their mass.

In addition to explaining the physical origins of the solar system, understanding the behavior of dense particle systems in microgravity is important for future missions on small, rocky bodies without significant atmospheres, like asteroids. Results from the NanoRacks-NanoRocks investigation provide new data on particle dispersal and disturbance.

How the Earth formed from a cloud of dust and gas is a fundamental question in science. NanoRacks-NanoRocks studies similar phenomenon on a much smaller scale, by examining several small-particle collisions over a long period of time. Results from the investigation shed new light on how the Earth and other rocky planets coalesced billions of years ago.

Read more about the NanoRocks Research or see the research results PDF.

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