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Parabolic Penetrometry: What Penetrometry Can Tell Us Through Testing in Microgravity On A Parabolic Flight

Presentation #319.07 in the session Future Missions, Instrumentations and Facilities - Part 2 (Oral Presentation)

Published onOct 23, 2023
Parabolic Penetrometry: What Penetrometry Can Tell Us Through Testing in Microgravity On A Parabolic Flight

Understanding the properties of surfaces on minor bodies in our solar system is an essential step in future planetary exploration. Past missions such as Hayabusa-2 and OSIRIS-REX have landed on asteroids to collect samples and understand what these bodies are made of. However, substantial uncertainty remains regarding the mechanical properties of the regolith covering the surfaces of these bodies. Penetrometry can help to understand these properties such as cohesion, bulk density, grain size and shape. Penetrometry has been mostly limited to ground-based studies such as soil sciences and even cheese maturation. We have a limited knowledge on the background science as to how penetrometry works in microgravity, why it works and what it can show us. We conducted a parabolic flight experiment within which we tested penetrometry in a microgravity environment to understand what penetrometry can show us. The findings are significant and indicate that penetrometry can tell us detailed information on the properties of regolith and will help in future missions in space. We tested penetration velocity, penetrometer tip shapes and different samples to understand whether we can distinguish the differences between these variables in a microgravity environment and compared it to the same experiment run in the lab at 1g. Flat, Hemispherical, 60° and 30° tip shapes were tested. The results showed a clear difference in tip shape reaction. Testing different grain sizes in samples, it was proven that smaller grain sizes still show a larger force than larger grain sizes, and the grain size can be identifiable through the use of penetrometers. Analysing different penetration velocities there are indications that agree with previous research that there are two regimes depending on the Froude number. Slower penetration taking place in a depth-dependent quasi-static regime and faster collisions in a regime dominated by internal drag. The tests we ran on the parabolic flight allowed for Froude numbers in both regimes and indicated a difference between penetration velocities. This knowledge will allow for better preparation for penetrometers and sampling devices on future missions and design of penetrometers and allow for better identification of surface material on other bodies.

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