POLITECNICO DI TORINO Corso di Laurea Magistrale in Ingegneria Aerospaziale Tesi di Laurea Magistrale Spacecraft – Plasma Interactions for a LEO – GEO Mission Tug with Direct Drive Hall Effect Thruster Relatore Candidato Prof.ssa Sabrina Corpino Francesco Secchia Correlatore Dott. Tommaso Andreussi Anno Accademico 2017/2018 I have whirl’d with the earth at the dawning, When the sky was a vaporous flame; I have seen the dark universe yawning, Where the black planets roll without aim; Where they roll in their horror unheeded, without knowledge or lustre or name. Ho vorticato con la terra all'alba, Quando il cielo era una fiamma vaporosa; Ho visto l'universo oscuro che sbadiglia, Dove i pianeti neri rotolano senza scopo; Dove rotolano nel loro orrore inascoltati, senza conoscenza, lustro o nome. H.P. Lovecraft, Nemesis. Index Index .................................................................................................................................... I Premessa............................................................................................................................. V Abstract ............................................................................................................................ VII List of Figures ................................................................................................................... IX List of Tables ................................................................................................................. XIII List of Acronyms and Abbreviations .............................................................................. XV 1 Chapter 1 .................................................................................................................... 1 Space Propulsion ................................................................................................. 1 Electric Propulsion .............................................................................................. 4 Electrostatic Propulsion ...................................................................................... 8 1.3.1 Electron Bombardment ............................................................................... 9 1.3.2 Neutralization .............................................................................................. 9 1.3.3 Hall Current ................................................................................................. 9 2 Chapter 2 .................................................................................................................. 11 Development History of Hall Thrusters ............................................................ 11 Application and Present Capabilities ................................................................ 12 Particle Motion and Hall Parameter .................................................................. 13 General Scheme and Acceleration Process ....................................................... 15 2.4.1 Generation of the Thrust ........................................................................... 18 2.4.2 Internal Currents........................................................................................ 19 HT20k Performance .......................................................................................... 21 3 Chapter 3 .................................................................................................................. 25 Space Tug Surroundings ................................................................................... 25 Tug Properties ................................................................................................... 26 Electric Orbit Raising ........................................................................................ 28 GTO – GEO ...................................................................................................... 29 3.4.1 GTO to GEO Tug ...................................................................................... 34 Spiral LEO – GEO ............................................................................................ 34 3.5.1 STK Study ................................................................................................. 36 I 3.5.2 STK Results .............................................................................................. 41 3.5.3 Eclipses Considerations ............................................................................ 42 4 Chapter 4 .................................................................................................................. 43 Mission Concept ............................................................................................... 43 System Design ................................................................................................... 43 4.2.1 Electric Propulsion Subsystem (EP) ......................................................... 45 4.2.2 Electrical Power System EPS .................................................................... 46 4.2.3 Solar Array ................................................................................................ 47 Structural Design ............................................................................................... 48 Introduction to Direct Drive .............................................................................. 49 4.4.1 Differences ................................................................................................ 50 Direct-Drive Mass Benefits ............................................................................... 52 Direct Advantages ............................................................................................. 53 4.6.1 PPU Reduction .......................................................................................... 53 4.6.2 Thermal Control System ........................................................................... 54 Indirect Advantages .......................................................................................... 54 4.7.1 Solar Array Active Area Reduction .......................................................... 55 4.7.2 Shunt Regulator ......................................................................................... 55 4.7.3 PMAD ....................................................................................................... 55 4.7.4 Battery ....................................................................................................... 56 4.7.5 Further Mass Reductions ........................................................................... 56 Mass evaluation ................................................................................................. 56 5 Chapter 5 .................................................................................................................. 58 Sheath Theory ................................................................................................... 58 5.1.1 Plasma between two Walls ........................................................................ 59 5.1.2 Pre – Sheath............................................................................................... 60 5.1.3 Collisionless Sheath .................................................................................. 61 5.1.4 The Bohm Sheath Criterion ...................................................................... 62 5.1.5 Collisional Plasmas ................................................................................... 64 Langmuir Probe ................................................................................................. 64 A Couple of Probes ........................................................................................... 67 II 6 Chapter 6 .................................................................................................................. 69 Plume Interactions ............................................................................................. 69 Spacecraft charging ........................................................................................... 70 6.2.1 Arc-Discharge ........................................................................................... 72 6.2.2 Avoid Spacecraft Charging Effects ........................................................... 72 Schematic Model Introduction .......................................................................... 74 Cathode ............................................................................................................. 75 Spacecraft Chassis and Theory of the Floating Potential .................................. 77 Spacecraft and Solar Array ............................................................................... 78 6.6.1 Linear Load Panel ..................................................................................... 82 6.6.2 Interconnects ............................................................................................. 83 6.6.3 Saturation Region ...................................................................................... 84 Thruster Body ................................................................................................... 85 Non-Linear Equations System .......................................................................... 87 7 Chapter 7 .................................................................................................................. 90 First step ...........................................................................................................