Study of a Crew Transfer Vehicle Using Aerocapture for Cycler Based Exploration of Mars by Larissa Balestrero Machado A thesis submitted to the College of Engineering and Science of Florida Institute of Technology in partial fulfillment of the requirements for the degree of Master of Science in Aerospace Engineering Melbourne, Florida May, 2019 © Copyright 2019 Larissa Balestrero Machado. All Rights Reserved The author grants permission to make single copies ____________________ We the undersigned committee hereby approve the attached thesis, “Study of a Crew Transfer Vehicle Using Aerocapture for Cycler Based Exploration of Mars,” by Larissa Balestrero Machado. _________________________________________________ Markus Wilde, PhD Assistant Professor Department of Aerospace, Physics and Space Sciences _________________________________________________ Andrew Aldrin, PhD Associate Professor School of Arts and Communication _________________________________________________ Brian Kaplinger, PhD Assistant Professor Department of Aerospace, Physics and Space Sciences _________________________________________________ Daniel Batcheldor Professor and Head Department of Aerospace, Physics and Space Sciences Abstract Title: Study of a Crew Transfer Vehicle Using Aerocapture for Cycler Based Exploration of Mars Author: Larissa Balestrero Machado Advisor: Markus Wilde, PhD This thesis presents the results of a conceptual design and aerocapture analysis for a Crew Transfer Vehicle (CTV) designed to carry humans between Earth or Mars and a spacecraft on an Earth-Mars cycler trajectory. The thesis outlines a parametric design model for the Crew Transfer Vehicle and presents concepts for the integration of aerocapture maneuvers within a sustainable cycler architecture. The parametric design study is focused on reducing propellant demand and thus the overall mass of the system and cost of the mission. This is accomplished by using a combination of propulsive and aerodynamic braking for insertion into a low Mars orbit and into a low Earth orbit. The requirements for propulsive and aerodynamic braking are given by the hyperbolic excess arrival speed and altitude of closest approach at the encounter with both planets, thus driving the overall design requirements for the vehicle. The thesis describes a study performed to determine the applicability of aerocapture for both Mars and Earth orbit insertion from existing cycler orbits. Furthermore, the thesis presents details on the optimal control method used to guide the spacecraft through the planet’s atmosphere and the sliding mode controller used to track the optimal trajectory. The Hermite-Simpson direct collocation is used to optimize the trajectory by targeting the atmospheric exit conditions necessary for the vehicle to reach the desired post-aerocapture orbit apoapsis and to minimize the Δ푣 necessary to circularize the post aerocapture orbit. Additional constraints are imposed on the trajectory such that the maximum load factor, dynamic pressure and heating rate tolerable by the crew and vehicle are not exceeded. iii Table of Contents Table of Contents ..................................................................................................... iv List of Figures .......................................................................................................... vi List of Tables.......................................................................................................... viii Acknowledgement.................................................................................................... ix Chapter 1 Introduction ............................................................................................... 1 1.1 Thesis Objectives ................................................................................................. 1 1.2 Background and Motivation ................................................................................. 2 1.2.1 Earth-Mars Cyclers .......................................................................................... 3 1.2.2 Aerocapture ...................................................................................................... 4 1.3 Thesis Outline ...................................................................................................... 7 Chapter 2 The Crew Transfer Vehicle ....................................................................... 8 2.1 Concept of Operations .......................................................................................... 8 2.1.1 Earth to Mars Transfer ..................................................................................... 8 2.1.2 Mars to Earth Transfer ................................................................................... 10 2.2 CTV Functional System Requirements .............................................................. 11 2.3 CTV Parametric Design Model .......................................................................... 11 2.4 Crew Module, Crew and Consumables .............................................................. 13 2.5 Impulsive Maneuvers and Δv Calculations ........................................................ 14 2.5.1 Departure Maneuver and Cycler Rendezvous................................................ 15 2.5.1.1 Hyperbolic Transfer Orbit ................................................................................ 15 2.5.1.2 Hohmann Transfer............................................................................................ 20 2.5.1.3 Highly Elliptic Transfer ................................................................................... 21 2.5.1.4 Rendezvous Approaches Comparison .............................................................. 27 2.5.2 Planetary Approach ........................................................................................ 29 2.5.3 Post Aerocapture Orbit Circularization .......................................................... 34 2.5.4 Total CTV Maneuver Demand ...................................................................... 35 iv 2.6 Propellant Mass and Boost Stage ....................................................................... 35 2.7 CTV Mass Estimation for the S1L1 Earth-Mars Cycler .................................... 40 Chapter 3 Aerocapture Maneuver ............................................................................ 46 3.1 Vehicle Dynamics .............................................................................................. 47 3.2 Entry Corridor .................................................................................................... 50 3.3 Trajectory Optimization ..................................................................................... 51 3.3.1 Hermite-Simpson Direct Collocation Method ............................................... 55 3.4 Sliding Mode Controller Design ........................................................................ 62 3.5 Aerocapture Set-Up and Results ........................................................................ 67 3.5.1 Entry Corridor Results ................................................................................... 68 3.5.2 Optimal Trajectory and Controller Results .................................................... 74 Chapter 4 Conclusion ............................................................................................... 89 4.1 Future Work ....................................................................................................... 90 References ................................................................................................................ 92 v List of Figures Figure 1. Ballistic S1L1 Cycler [12] ...................................................................................... 4 Figure 2. Aerobraking vs. Aerocapture ................................................................................. 5 Figure 3. Earth to Mars Transfer [23] .................................................................................... 9 Figure 4. Mars to Earth Transfer [23] .................................................................................. 10 Figure 5. CTV Parametric Model ........................................................................................ 12 Figure 6. Cycler Rendezvous – Hyperbolic Transfer Orbit ................................................. 15 Figure 7. Relationship between Δv and Δω and transfer time for hyperbolic transfer orbit 19 Figure 8. Cycler rendezvous with hyperbolic transfer orbit for several apoapsis rotation angles .......................................................................................................................... 19 Figure 9. Cycler Hohmann Transfer .................................................................................... 20 Figure 10. Cycler Rendezvous – Elliptic Transfer Orbit ..................................................... 22 Figure 11. Δv vs. apse line rotation and eccentricity for highly elliptic transfer ................. 25 Figure 12. Relationship between Δv, Δω and transfer time for elliptic transfer orbit ......... 26 Figure 13. Cycler rendezvous with elliptic transfer orbit for several apoapsis rotation angles .......................................................................................................................... 27 Figure 14. Cycler to hyperbolic Mars/Earth approach setting up aerocapture .................... 30 Figure 15. Relationship between Δv, Δω and transfer time for hyperbolic approach