The role of shape-dependent flight stability in the origin of oriented meteorites

Khunsa Amin, Jinzi Mac Huang, Kevin J. Hu, Jun Zhang, Leif Ristroph

Research output: Contribution to journalArticlepeer-review

Abstract

The atmospheric ablation of meteoroids is a striking example of the reshaping of a solid object due to its motion through a fluid. Motivated by meteorite samples collected on Earth that suggest fixed orientation during flight—most notably the conical shape of so-called oriented meteorites—we hypothesize that such forms result from an aerodynamic stabilization of posture that may be achieved only by specific shapes. Here, we investigate this issue of flight stability in the parallel context of fluid mechanical erosion of clay bodies in flowing water, which yields shapes resembling oriented meteorites. We conduct laboratory experiments on conical objects freely moving through water and fixed within imposed flows to determine the dependence of orientational stability on shape. During free motion, slender cones undergo postural instabilities, such as inversion and tumbling, and broad or dull forms exhibit oscillatory modes, such as rocking and fluttering. Only intermediate shapes, including the stereotypical form carved by erosion, achieve stable orientation and straight flight with apex leading. We corroborate these findings with systematic measurements of torque and stability potentials across cones of varying apex angle, which furnish a complete map of equilibrium postures and their stability. By showing that the particular conical form carved in unidirectional flows is also posturally stable as a free body in flight, these results suggest a self-consistent picture for the origin of oriented meteorites.

Original languageEnglish (US)
Pages (from-to)16180-16185
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume116
Issue number33
DOIs
StatePublished - Aug 13 2019

Keywords

  • Ablation
  • Erosion
  • Flight stability
  • Fluid–structure interaction
  • Meteorite

ASJC Scopus subject areas

  • General

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