Fundamentals of Electric Propulsion Ion and Hall Thrusters by Dan M. Goebel and Ira Katz

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Fundamentals of Electric Propulsion Ion and Hall Thrusters by Dan M. Goebel and Ira Katz

Fundamentals of Electric Propulsion Ion and Hall Thrusters by Dan M. Goebel and Ira Katz is available for free download in PDF format


Electric propulsion was first envisioned  100 years ago, and throughout most of the 20th century was considered the technology of the future for spacecraft propulsion. With literally hundreds of electric thrusters now operating in orbit on communica- tions satellites,  and ion and Hall thrusters both having been successfully used for primary propulsion in deep-space scientific missions, the future for electric propul- sion has arrived.

The literature contains several books from the  1960s and numerous journal arti- cles and conference papers published over the years discussing electric thruster con- cepts, benefits, physics,  and technological developments. Much of this work has been based on empirical investigations and laboratory-based development programs of different thruster types. As such, the fundamental understanding of how these thrusters work has generally lagged behind the technological achievements and ap- plications of electric thrusters in space.

The quest over the past  10 years to improve often technically mature thruster per- performance and significantly extend thruster life for applications in deep-space propulsion and satellite station-keeping requires a  much deeper understanding of the physics of electric thrusters. The purpose of this book is to discuss and explain how modem ion and Hall thrusters work by describing the fundamental physics of these devices.  This is a  challenging task requiring a  basic knowledge of plasma physics,  ion accelerators,  cathodes, electrical discharges,  high voltage, gas dynam- ics, and many other technologies. As such, we rely heavily on physics-based models that are often greatly simplified compared to the complex two-dimensional and three-dimensional codes required to accurately predict the plasma dynamics that drive thruster performance and ultimately determine their life. Work in this field is still progressing, and we hope this book will lead to further research and advances in our understanding of these surprisingly complex devices.

While this effort encompasses a large body of literature in the area of ion and Hall thrusters,  it is based largely on the research and development performed at the Jet Propulsion  Laboratory (JPL). Therefore, this book should not be considered an all-inclusive treatise on the subject of electric thrusters or a review of their develop- ment history, but rather one that delves into the basics of two of the more modern electric engines that are finding increasingly more applications, specifically ion and Hall thrusters,  in an attempt to provide a better understanding of their principles.

Fundamentals of Electric Propulsion Ion and Hall Thrusters Contents

Note from the Series Editorix
Chapter 1: Introduction1
1.1 Electric Propulsion Background2
1.2 Electric Thruster Types3
1.3 Ion Thruster Geometry6
1.4 Hall Thruster Geometry6
1.5 Beadplume Characteristics9
Chapter 2: Thruster Principles15
2.1 The Rocket Equation15
2.3 Thrust18
2.4 Specific Impulse21
2.5 Thruster Efficiency25
2.6 Power Dissipation27
Force Transfer in Ion and Hall Thrusters34
Neutral Densities and Ingestion in Electric Thrusters35
Chapter 3: Basic Plasma Physics37
3.1 Introduction37
3.2 Maxwell’s Equations38
3.3 Single Particle Motions39
3.4 Particle Energies and Velocities43
3.5 Plasma as a Fluid46
3.5.1 Momentum Conservation46
3.5.2 Particle Conservation48
3.5.3 Energy Conservation51
Diffusion in Partially Ionized Gases54
3.6.1 Collisions55
3.6.3 Diffusion Across Magnetic Fields60
Dif’iusion and Mobility Without a Magnetic Field66
3.7 Sheaths at the Boundaries of Plasmas71
3.7.1 Debye Sheaths73
3.7.2 Pre-Sheaths76
3.7.3 Child-Langmuir Sheaths79
3.7.4 Generalized Sheath Solution81
3.7.5 Double Sheaths84
3.7.6 Summary of Sheath Effects86
Chapter 4: Ion Thruster Plasma Generators91
4.1 Introduction91
4.2 Idealized Ion Thruster Plasma Generator93
4.3 DC Discharge Ion Thruster100
4.3.2 Magnetic Multipole Boundaries102
4.3.3 Electron Confinement105
4.3.8 Discharge Loss108
4.3.9 Discharge Stability110
4.3.10 Recycling Behavior117
4.3.11 Limitations of a 0-D Model120
Generalized 0-D Ring-Cusp Ion Thruster Model124
Ion Confinement at the Anode Wall126
Ion and Excited Neutral Production133
Neutral and Primary Densities in the Discharge Chamber137
Power and Energy Balance in the Discharge Chamber141
4.4 Kaufman Ion Thrusters142
4.5 rf Ion Thrusters148
4.6 Microwave Ion Thrusters158
4.7 2-D Computer Models of the Ion Thruster Discharge Chamber171
4.7.1 Neutral Atom Model172
4.7.2 Primary Electron Motion and Ionization Model176
4.7.3 Discharge Chamber Model Results179
Chapter 5: Ion Thruster Accelerator Grids189
5.1 Grid Configurations190
5.2 Ion Accelerator Basics196
5.3 Ion Optics200
5.3.1 Ion Trajectories200
5.3.2 Perveance Limits204
5.3.3 Grid Expansion and Alignment206
5.4 Electron Backstreaming208
5.5 High-Voltage Considerations216
5.5.1 Electrode Breakdown217
5.5.2 Molybdenum Electrodes218
5.5.3 Carbon-Carbon Composite Materials22 1
5.5.4 Pyrolytic Graphite223
5.6 Ion Accelerator Grid Life224
5.6.1 Grid Models225
5.6.2 Barrel Erosion227
5.6.3 Pits-and-Grooves Erosion230
Hold-off and Conditioning in Ion Thrusters232
Chapter 6: Hollow Cathodes243
6.1 Introduction243
6.2 Cathode Configurations248
6.3 Thermionic Electron Emitter Characteristics25 1
6.4 Insert Region Plasma256
6.5 Orifice Region Plasma270
6.6 Hollow Cathode Thermal Models28 1
6.7 Cathode Plume-Region Plasma283
6.8 Hollow Cathode Life292
6.8.2 Cathode Insert Temperature293
6.8.3 Barium Depletion Model296
6.8.4 Bulk-Material Insert Life298
6.8.5 Cathode Poisoning302
6.9 Keeper Wear and Life304
6.10 Hollow Cathode Operation306
Dispenser Cathodes in Insert Plasmas32 1
Chapter 7: Hall Thrusters325
7.1 Introduction325
7.2 Thruster Operating Principles and Scaling329
7.2.2 Ionization Length and Scaling330
7.2.3 Potential and Current Distributions334
7.3.1 Hall Thruster Efficiency337
7.3.2 Multiply Charged Ion Correction34 1
7.3.3 Dominant Power Loss Mechanisms34 1
7.3.4 Plasma Electron Temperature345
7.3.5 Hall Thruster Efficiency (Dielectric Walls)347
7.3.6 TAL Hall Thruster Efficiency (Metallic Walls)357
7.3.7 Dielectric-Wall Versus Metallic-Wall Comparison359
Channel Physics and Numerical Modeling363
Crossed-Field Structure and the Hall Current3 64
7.3 Hall Thruster Performance Models365
7.4.1 Hybrid Hall Thruster Models366
7.4.2 Steady-State Modeling Results372
7.4.3 Oscillations in Hall Thrusters376
7.5 Hall Thruster Life379
Chapter 8 Ion and Hall Thruster Plumes393
8.1 Introduction393
8.2 Plume Physics395
8.2.1 Plume Measurements395
8.2.2 Flight Data,396
8.2.3 Laboratory Plume Measurements398
8.3.1 Primary Beam Expansion400
8.3.2 Neutral Gas Plumes400
8.3.3 Secondary-Ion Generation407
8.4.2 Sputtering and Contamination408
8.5.1 Microwave Phase Shift410
8.5.2 Plume Plasma Optical Emission412
8.3 Plume Models413
8.4 Spacecraft Interactions415
Momentum of the Plume Particles418
Plasma Interactions with Solar Arrays418
8.5 Interactions with Payloads419
Chapter 9: Flight Ion and Hall Thrusters429
9.1 Introduction429
9.2 Ion Thrusters429
9.3 Hall Thrusters440
A: Nomenclature447
B: Gas Flow Unit Conversions and Cathode Pressure Estimates463
C: Energy Loss by Electrons467
D: Ionization and Excitation Cross Sections for Xenon47 1
E: Ionization and Excitation Reaction Rates for Xenon in
F: Electron Relaxation and Thermalization Times475
G: Clausing Factor Monte Carlo Calculation479
Maxwellian Plasmas483

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