The impact of dust grains on fast fly-by spacecraft: Momentum multiplication,measurements and theory |
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Authors: | JAM McDonnell TJ Stevenson ST Evans M Alexander D Lyons W Tanner P Anz T Hyde A-L Chen |
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Institution: | Space Sciences Laboratory, University of Kent at Canterbury, Kent, CT2 7NT, UK;University of Baylor, Waco, Texas, 76703, USA |
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Abstract: | Energy partitioning during the very high impact speed encountered in a cometary fly-by mission causes a target mass expulsion which leads to a momentum impulse on the target exceeding that of the incident momentum. Theoretical and computational studies are required to provide a basis for predictions of the response at Halley encounter, since experimental data from acceleration of microspheres extends currently only to some 10 kms?1. Such data obtained from the 2 MV Canterbury microparticle accelerator is presented: this demonstrates a target momentum enhancement E which can be approximated by a form E = 1+(V/Vo)β. Over the range 1 to 8 kms?1 the relationship is satisfied by Vo = 2 kms?1 and β = 2. Theoretical considerations of energy partitioning lead to constraints on the extrapolation of this functional dependence to very high velocities and the transition to β ≤ 1 is shown to apply. Results are examined and their significance to impact sensing and spacecraft deceleration discussed. An enhancement of momentum nearer to 12±3 at 69 kms?1 is anticipated for non-penetrating particles, from the ballistic pendulum data, but the ES data indicates a figure considerably higher. |
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