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Master's Thesis 2010:037 MASTER'S THESIS Cumulative Effects of Micrometeoroid Impacts on Spacecraft Lei Zhao Luleå University of Technology Master Thesis, Continuation Courses Space Science and Technology Department of Space Science, Kiruna 2010:037 - ISSN: 1653-0187 - ISRN: LTU-PB-EX--10/037--SE CRANFIELD UNIVERSITY LEI ZHAO CUMULATIVE EFFECTS OF MICROMETEOROID IMPACTS ON SPACECRAFT SCHOOL OF ENGINEERING MSC in Astronautics and Space Engineering (SpaceMaster) MSc Thesis CRANFIELD UNIVERSITY SCHOOL OF ENGINEERING MSc in Astronautics and Space Engineering (SpaceMaster) MSc Thesis Academic Year 2009-2010 LEI ZHAO CUMULATIVE EFFECTS OF MICROMETEOROID IMPACTS ON SPACECRAFT Supervisor: Dr. S. E. Hobbs June 2010 This thesis is submitted in partial (45%) fulfilment of the requirements for the degree of Master of Science ○c Cranfield University 2010. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright owner. Abstract Abstract The geostationary orbit (GEO), which is an ideal orbit for communication and earth observation satellites, is accumulating an increasing number of spacecraft. Lack of atmospheric drag keeps the retired satellites near GEO orbit extremely long. Therefore it is interesting and meaningful to know the long-term effects of micrometeoroid impacts on spacecraft. This thesis aims to study the cumulative effects of micrometeoroid impacts on spacecraft in GEO and quantify the timescale for them to damage the typical spacecraft surface materials that are currently widely used in space missions. The mechanism of hypervelocity impact by a single particle is thoroughly reviewed and a set of damage scaling equations are chosen to evaluate the damage of single micrometeoroid impact. In combination with the implementation of the interplanetary meteoroid flux model developed by Grün et al., the cumulative effects of micrometeoroid impacts on cover glass of solar cells, MLI and radiators are quantified in terms of Volume Ejection Rate (VER) and Area Damage Rate (ADR). Furthermore a simple model is developed to predict the probability of a catastrophic collision between a meteoroid particle and a spacecraft. The results from both long-term effects and catastrophic collision are discussed and compared. The results show that it takes about several 104 years for micrometeoroid impacts to erode away the cover glass material and radiator material, or cover all the MLI surface area, and that after 100 years the chance of a catastrophic collision that can totally fragment the impact target is about one impact per 105 years. According to the study herein only re-orbiting spent GEO satellites to graveyard orbit is not a sustainable enough solution in the long term. I Acknowledgements Acknowledgements The thesis would not have been finished without support from many people. First I would like to thank my family for their constant support and understanding during my study. I would also like to thank Dr. James Campbell for talking with me about his work on hypervelocity impacts and suggestions for my project. I want to express my thanks to my mates Campbell Pegg, Abrar Blauch, Karolina Johansson, and Lin Gao for their support. I would also like to particularly thank my dear friends Cheng Cheng and Wang Meng for providing me very comfortable and quiet places to write my thesis. Finally I wish to thank my supervisor, Dr Steve Hobbs, for his kindness and advices during the whole project. II Table of Contents Table of Contents Abstract ...................................................................................................................................... I Acknowledgements .................................................................................................................... II Table of Contents ...................................................................................................................... III List of Figures ............................................................................................................................ V List of Tables ........................................................................................................................... VI List of Notation ....................................................................................................................... VII 1. Introduction ..........................................................................................................................1 1.1 Background ...............................................................................................................1 1.2 Project aims and objectives ........................................................................................2 1.3 Outline of the report ..................................................................................................2 2. Literature review ..................................................................................................................4 2.1 Space debris and meteoroid environment ...................................................................4 2.1.1 Space debris ....................................................................................................4 2.1.2 Meteoroids ......................................................................................................6 2.2 Micrometeoroid flux models ......................................................................................7 2.2.1 Grün et al. model ............................................................................................7 2.2.2 The ―Divine/Staubach‖ model .........................................................................8 2.2.3 ESA MASTER 2001 .......................................................................................9 2.3 Hypervelocity impact ................................................................................................9 2.3.1 Impact effects ............................................................................................... 10 2.3.2 Ground testing facilities and in situ impact detector ...................................... 11 2.3.3 Impact features ............................................................................................. 13 2.3.4 Impact damage equations .............................................................................. 15 2.4 Spacecraft structure analysis .................................................................................... 17 2.5 Summary ................................................................................................................. 18 3. Methodology ...................................................................................................................... 19 3.1 Single Impact .......................................................................................................... 19 3.2 Micrometeoroid flux ................................................................................................ 20 3.3 Cumulative effects ................................................................................................... 21 4. Analysis of different exposed surfaces ................................................................................ 22 III Table of Contents 4.1 Solar Cells ............................................................................................................... 22 4.1.1 Solar cell structure ........................................................................................ 22 4.1.2 Single impact damage on solar cells .............................................................. 22 4.1.3 Cumulative damage ...................................................................................... 24 4.1.4 Lifetime estimates ......................................................................................... 25 4.2 Multi-Layer Insulation (MLI) .................................................................................. 26 4.2.1 Structure of MLI ........................................................................................... 26 4.2.2 Single impact on MLI ................................................................................... 27 4.2.3 Cumulative damage ...................................................................................... 28 4.2.4 Lifetime estimates ......................................................................................... 28 4.3 Radiator ................................................................................................................... 28 4.3.1 Structure of radiator ...................................................................................... 29 4.3.2 Single impact on radiator surface .................................................................. 29 4.3.3 Cumulative damage ...................................................................................... 30 4.3.4 Lifetime estimate .......................................................................................... 31 4.4 Summary ................................................................................................................. 32 5. Results and Discussions...................................................................................................... 33 5.1 Long-term effects of micrometeoroid environment .................................................. 33 5.2 Probability of a catastrophic collision ...................................................................... 34 5.2.1 GEO spacecraft evolution
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