Modified granular impact force laws for the OSIRIS-REx touchdown on the surface of asteroid (101955) Bennu

Ballouz, R.-L. et al. (2021) Modified granular impact force laws for the OSIRIS-REx touchdown on the surface of asteroid (101955) Bennu. Monthly Notices of the Royal Astronomical Society, 507(4), pp. 5087-5105. (doi: 10.1093/mnras/stab2365)

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The OSIRIS-REx mission collected a sample from the surface of the asteroid (101955) Bennu in October 2020. Here we study the impact of the OSIRIS-REx Touch-and-Go Sampling Acquisition Mechanism (TAGSAM) interacting with the surface of an asteroid in the framework of granular physics. Traditional approaches to estimating the penetration depth of a projectile into a granular medium include force laws and scaling relationships formulated from laboratory experiments in terrestrial-gravity conditions. However, it is unclear that these formulations extend to the OSIRIS-REx scenario of a 1300-kg spacecraft interacting with regolith in a microgravity environment. We studied the TAGSAM interaction with Bennu through numerical simulations using two collisional codes, pkdgrav and GDC-i. We validated their accuracy by reproducing the results of laboratory impact experiments in terrestrial gravity. We then performed TAGSAM penetration simulations varying the following geotechnical properties of the regolith: packing fraction (P), bulk density, inter-particle cohesion (σc), and angle of friction (ϕ). We find that the outcome of a spacecraft-regolith impact has a non-linear dependence on packing fraction. Closely packed regolith (P≳0.6) can effectively resist the penetration of TAGSAM if ϕ≳28° and/or σc≳50 Pa. For loosely packed regolith (P≲0.5), the penetration depth is governed by a drag force that scales with impact velocity to the 4/3 power, consistent with energy conservation. We discuss the importance of low-speed impact studies for predicting and interpreting spacecraft-surface interactions. We show that these low-energy events also provide a framework for interpreting the burial depths of large boulders in asteroidal regolith.

Item Type:Articles
Additional Information:KJW was supported in part through the NASA Solar System Exploration Research Virtual Institute node Project ESPRESSO, cooperative agreement number 80ARC0M0008. P. Michel and Y. Zhang acknowledge support from CNES, Doeblin Federation, the UCA IDEX JEDI “Individual grants for young researchers” program and the European Union’s Horizon 2020 research and innovation program under grant agreement No. 870377 (project NEO-MAPP).
Glasgow Author(s) Enlighten ID:Celik, Dr Onur
Authors: Ballouz, R.-L., Walsh, K.J., Sánchez, P., Holsapple, K.A., Michel, P., Scheeres, D.J., Zhang, Y., Richardson, D.C., Barnouin, O.S., Nolan, M.C., Bierhaus, E.B., Connolly, H.C., Schwartz, S.R., Celik, O., Mitsuhisa, B., and Lauretta, D.S.
College/School:College of Science and Engineering > School of Engineering > Systems Power and Energy
Journal Name:Monthly Notices of the Royal Astronomical Society
Publisher:Oxford University Press
ISSN (Online):1365-2966
Published Online:23 August 2021
Copyright Holders:Copyright © 2021 The Authors
First Published:First published in Monthly Notices of the Royal Astronomical Society 507(4): 5087-5105
Publisher Policy:Reproduced under a Creative Commons Licence

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