Mission Design for Safe Traverse of Planetary Hoppers by Babak E. Cohanim B.S., Iowa State University (2002) S.M., Massachusetts Institute of Technology (2004) Submitted to the Department of Aeronautics & Astronautics in Partial Fulfillment of the Requirements for the Degree of Doctor of Science in Aeronautics & Astronautics at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY June 2013 © 2013 Babak E. Cohanim. All rights reserved Signature of Author......................................................................................... Certified by..................................................................................................... Thesis Committee Chairman: Jeffrey A. Hoffman Professor of the Practice, Aeronautics & Astronautics Certified by..................................................................................................... Thesis Committee Member: Olivier L. de Weck Associate Professor, Aeronautics & Astronautics and Engineering Systems Certified by..................................................................................................... Thesis Committee Member: David W. Miller Professor, Aeronautics & Astronautics Certified by..................................................................................................... Thesis Committee Member: Tye M. Brady Space Systems Group Leader, Draper Laboratory Accepted by.................................................................................................... Aeronautics & Astronautics Graduate Chairman: Eytan H. Modiano Professor, Aeronautics & Astronautics 1 2 Mission Design for Safe Traverse of Planetary Hoppers by Babak E. Cohanim Submitted to the Department of Aeronautics & Astronautics on May 2013 in Partial Fulfillment of the Requirements for the Degree of Doctor of Science in Aeronautics & Astronautics ABSTRACT Planetary hoppers are a new class of vehicle being developed that will provide planetary surface mobility by reusing the landing platform and its actuators to propulsively ascend, translate, and descend to new landing points on the surface of a planetary body. Hoppers enhance regional exploration, with the capability of rapid traverse over hundreds to thousands of meters, traverse over hazardous terrain, and exploration of cliffs and craters. These planetary mobility vehicles are fuel limited and as a result are enabled by carrying sensor payloads that require low mass, low volume, and low onboard computational resources. This thesis describes methods for hoppers to traverse and land safely in this constrained environment. The key questions of this research are: - What types of missions will hoppers perform and how does a hopper traverse as part of these missions? - How does a hopper traverse from its current location to a new landing site safely? This thesis: - describes various hopper mission scenarios and considerations for their mission designs - creates an operational concept for safe landing for the traverse hop mission scenario - develops a method that can be used to rapidly and safely detect landing areas at long ranges and low path angles - develops a method to do fine detection of hazards once at the landing area Thesis Supervisor: Jeffrey A. Hoffman Title: Professor of the Practice of Aerospace Engineering Keywords: hopper, hopping, planetary hopper, planetary hopping, lunar hopper, propulsive hopper, planetary mobility, Talaris hopper, hazard detection, hazard detection and avoidance, optical hazard detection, LIDAR, size density method, sparse slope and roughness 3 Table of Contents Acronyms ...................................................................................................................................................... 8 Mathematical Symbols ................................................................................................................................. 9 1 Introduction ........................................................................................................................................ 10 1.1 Motivation ................................................................................................................................... 11 1.2 Literature Review ........................................................................................................................ 15 1.3 Thesis Objectives ......................................................................................................................... 18 1.4 Thesis Overview .......................................................................................................................... 19 2 Current Methods for Landing and Traverse ........................................................................................ 20 2.1 Hoppers as an Extension of Landers ........................................................................................... 20 2.2 Techniques leveraged from Landers and Rovers ........................................................................ 23 3 Hopper Mission Scenarios................................................................................................................... 31 3.1 Traverse Hop Scenarios ............................................................................................................... 31 3.2 Steep Slope Exploration .............................................................................................................. 35 3.3 Crater Exploration ....................................................................................................................... 36 3.4 Chapter 3 Summary .................................................................................................................... 38 4 Landing Area Selection ........................................................................................................................ 39 4.1 Landing Area Selection Operational Concept for Traversing Spacecraft .................................... 40 4.2 Size Density Method ................................................................................................................... 43 4.3 Size Density Method Algorithm Description ............................................................................... 45 4.4 Size Density Method Simulations and Results ............................................................................ 56 4.5 Chapter 4 Summary .................................................................................................................... 87 5 Landing Aim Point Selection ............................................................................................................... 89 5.1 Sparse Slope & Roughness Operational Concept ....................................................................... 90 5.2 Sparse Slope & Roughness Detection Method Description ........................................................ 93 5.3 Simulation Environment ............................................................................................................. 96 5.4 Performance and Timing Analysis ............................................................................................. 102 5.5 Combined SDM and SSR Analysis .............................................................................................. 104 5.6 Chapter 5 Summary .................................................................................................................. 109 6 Conclusions ....................................................................................................................................... 111 6.1 Summary of Contributions ........................................................................................................ 111 6.2 Future Work .............................................................................................................................. 112 4 6.3 Final Remarks ............................................................................................................................ 114 6.4 Acknowledgements ................................................................................................................... 115 Bibliography .............................................................................................................................................. 116 Appendix A – Surface Image Rendering .................................................................................................... 126 Tables in Thesis Table 1 – Comparison of Planetary Exploration Systems ........................................................................... 12 Table 2 – Navigation and Hazard Detection Architectures Past and Current ............................................. 24 Table 3 – Sensors to Measurements ........................................................................................................... 27 Table 4 – Relative Statistically Safety for Landing Area Selection .............................................................. 40 Table 5 – Cost Comparison for SDM vs. MDM ............................................................................................ 71 Table 6 – Timing analysis between DEM-based and Size Density Methods ............................................... 73 Table 7 – View and Sun Angle Tradespace ................................................................................................. 75 Table 8 – Laser Range Sensors ...................................................................................................................