Abstract

Plume surface interactions (PSI) are caused by rocket exhaust impinging on planetary surfaces. PSI-induced environmental changes pose hazards to spacecraft and astronauts; thus, it is crucial to understand the gas-particle dynamics of these systems. We have conducted novel experimental and computational work to study PSI effects in relevant vacuum microgravity environments. To study flow effects and regolith instability we developed a computational model that describes the gas flow through a porous medium based on Darcy's Law. This flow depends on regolith properties, and the resulting subsurface pressure distribution is used to estimate ejecta mass. We find flow behaviors and the resulting ejecta are significantly affected by the surface pressure distribution, pulse duration, and material properties. We have also developed an experimental apparatus, the Gas Regolith Interaction Testbed (GRIT), for studying PSI in vacuum microgravity in the UCF Center for Microgravity Research Drop Tower. It consists of a small, cylindrical vacuum chamber in which a cold gas jet interacts with a bed of regolith simulant. Video data is analyzed to determine PSI trends based on gravity level, nozzle distance, simulant type, and plume duration. We observe PSI effects ranging from perturbation of the granular media to ejection of the entire simulant mass. Phenomena are significantly more pronounced for experiments conducted at microgravity than at Earth gravity (1g). We measure peak ejecta velocities up to tens of m/s, and note how particle properties, jet distance, and pulse duration affect ejecta angle and cratering depth. Our numerical and experimental results have implications for the validity of existing studies of PSI that are conducted in 1g and under ambient conditions, and can be used to inform modeling, lander design, and risk assessment for future missions that will aim to land on or interact with planetary surfaces.

Notes

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Graduation Date

2020

Semester

Summer

Advisor

Britt, Daniel

Degree

Doctor of Philosophy (Ph.D.)

College

College of Sciences

Department

Physics

Degree Program

Physics; Planetary Sciences

Format

application/pdf

Identifier

CFE0008141; DP0023478

URL

https://purls.library.ucf.edu/go/DP0023478

Language

English

Release Date

August 2020

Length of Campus-only Access

None

Access Status

Doctoral Dissertation (Open Access)

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