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Mission Planning for the Mitigation of Hazardous Near Earth Objects

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Mission Planning for the Mitigation of Hazardous Near Earth Objects This page is intentionally left blank. Copyright By Brent William Barbee 2005 Mission Planning for the Mitigation of Hazardous Near Earth Objects By Brent William Barbee, B.S. Thesis Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the Degree of Master of Science in Engineering The University of Texas at Austin December 2005 Mission Planning for the Mitigation of Hazardous Near Earth Objects APPROVED BY SUPERVISING COMMITTEE: __________________________ Wallace T. Fowler __________________________ Cesar A. Ocampo Mission Planning for the Mitigation of Hazardous Near Earth Objects by Brent William Barbee, M.S. E. The University of Texas, 2005 SUPERVISOR: Dr. Wallace Fowler The problem of mitigating the threat posed by hazardous Near Earth Objects (NEOs) is examined and addressed. The concept of hazardous NEO mitigation is presented, along with background on the NEO population and its characteristics. A set of philosophies and hierarchies of decision-making principles and protocols are devised to aid in the design of spacecraft missions to mitigate threatening NEOs, leading to the construction of a generalized approach to NEO mitigation mission planning. The orbital mechanics involved in rendezvousing with a NEO and performing proximity operations in its vicinity for the purposes of science and deflection system deployment are studied. The need and opportunity to perform rigorous asteroid/comet science in the context of NEO mitigation missions is also discussed. The construction of optimal NEO deflection maneuvers is also examined and the particular case of impulsive deflection maneuvers is given more thorough treatment. NEO deflection systems, both practical and theoretical, are analyzed and discussed. In particular, the standoff nuclear detonation deflection method is examined in detail. A case study is conducted in which a fictitious threatening Near Earth Asteroid (NEA) is mitigated using the techniques developed within. vii TABLE OF CONTENTS 1. INTRODUCTION .................................................................................................... 1 1.1 Mission Statement............................................................................................... 1 1.2 Human Opportunity and Responsibility ............................................................. 1 1.3 Current State of NEO Mitigation Readiness....................................................... 5 1.4 Low Frequency, Low Probability, High Impact Events ..................................... 6 1.5 Scope of This Work .......................................................................................... 10 2. NEO POPULATION AND TAXONOMY ............................................................ 11 2.1 Introduction....................................................................................................... 11 2.2 NEA Orbit Classifications ................................................................................ 11 2.3 NEA Composition Classifications .................................................................... 11 2.4 Observed and Predicted NEA Orbital Characteristics...................................... 12 2.5 Orbital Characteristics of Earth-Impacting NEAs ............................................ 13 2.6 Structural Classifications of NEOs ................................................................... 14 2.6.1 Strength, Coherence, and Porosity............................................................. 14 2.6.2 Ground-Based Observations ...................................................................... 16 3. NEO SCIENCE OPERATIONS............................................................................. 21 3.1 Introduction....................................................................................................... 21 3.2 NEO Properties of Interest................................................................................ 22 3.2.1 Mass ........................................................................................................... 23 3.2.2 Importance of Mass Determination ........................................................... 28 3.2.3 Volume....................................................................................................... 29 3.2.3 Importance of Volume Determination....................................................... 30 3.2.4 Density ....................................................................................................... 30 3.2.5 Importance of Density Determination ....................................................... 31 3.2.6 Determining Internal Structure and Composition...................................... 32 3.2.7 Scientific Determination of Other Quantities ............................................ 33 3.3 NEO Proximity Operations............................................................................... 34 3.3.1 Constraints and Requirements ................................................................... 43 4. NEO IMPACT HAZARDS AND COLLISION MECHANICS............................ 45 4.1 Introduction....................................................................................................... 45 4.2 The Torino Scale and Palermo Technical Scale ............................................... 45 4.3 Earth’s Collision History .................................................................................. 50 4.4 NEO-Earth Collision Mechanics ...................................................................... 53 4.4.1 Collision Geometry.................................................................................... 54 4.4.2 Minimum Orbital Intersection Distance (MOID)...................................... 55 4.4.3 MOID Geometry and Definition................................................................ 56 4.4.4 Orbital Dynamics Considerations.............................................................. 58 4.4.5 Keyholes and Resonant Returns ................................................................ 59 5. THREATENING NEO MITIGATION METHODS.............................................. 61 5.1 Introduction....................................................................................................... 61 5.2 Mitigation Modes.............................................................................................. 61 viii 5.2.1 Annihilation ............................................................................................... 62 5.2.2 Fragmentation ............................................................................................ 62 5.2.3 Deflection................................................................................................... 63 5.3 Types of Deflection Techniques ....................................................................... 64 5.3.1 Non-Impulsive Methods ............................................................................ 68 5.3.2 Low-Thrust Attached Thrusters................................................................. 68 5.3.3 Utilization of the Yarkovsky Effect........................................................... 69 5.3.4 Solar Concentrators.................................................................................... 70 5.3.5 Attached Solar Sails................................................................................... 72 5.3.6 Impulsive Methods..................................................................................... 72 5.3.7 High-Thrust Attached Thrusters ................................................................ 73 5.3.8 Nuclear Fission/Fusion Devices ................................................................ 74 5.4 Nuclear Device Application Methods............................................................... 75 5.4.1 Standoff Nuclear Detonation Theory......................................................... 75 5.4.2 Standoff Nuclear Device Mechanics ......................................................... 76 5.4.3 Standoff Nuclear Detonation Results Scaling............................................ 77 5.5 Antimatter Devices ........................................................................................... 82 5.6 Conclusions....................................................................................................... 86 6. NEO DEFLECTION MECHANICS ...................................................................... 88 6.1 Introduction....................................................................................................... 88 6.2 Deflection Principles......................................................................................... 88 6.3 Deflection Results............................................................................................. 89 6.4 Deflection Application...................................................................................... 91 6.4.1 Point of Deflection Application Along NEO Orbit ................................... 94 6.4.2 Conditions on Deflection Orientation........................................................ 96 6.4.3 Deflection Optimization............................................................................. 96 6.4.4 Deflection Optimization Techniques ......................................................... 98 6.4.5 Current Optimization Approach ................................................................ 99 6.4.6 Design Space Search Methods................................................................
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