Fundamentals of Electric Propulsion

Understand the fundamental basis of spaceflight with this cutting-edge guide

As spacecraft engineering continues to advance, so too do the propulsion methods by which human beings can seek out the stars. Ion thrusters and Hall thrusters have been the subject of considerable innovation in recent years, and spacecraft propulsion has never been more efficient. For professionals within and adjacent to spacecraft engineering, this is critical knowledge that can alter the future of space flight.

Fundamentals of Electric Propulsion offers a thorough grounding in electric propulsion for spacecraft, particularly the features and mechanisms underlying Ion and Hall thrusters. Updated in the light of rapidly expanding knowledge, the second edition of this essential guide detailed coverage of thruster principles, plasma physics, and more. It reflects the historic output of the legendary Jet Propulsion Laboratory and promises to continue as a must-own volume for spacecraft engineering professionals.

Readers of the second edition of Fundamentals of Electric Propulsion readers will also find:

• Extensive updates to chapters covering hollow cathodes and Hall thrusters, based on vigorous recent research
• New sections covering magnetic shielding, cathode plume instabilities, and more
• Figures and homework problems in each chapter to facilitate learning and retention

Fundamentals of Electric Propulsion is an essential work for spacecraft engineers and researchers working in spacecraft propulsion and related fields, as well as graduate students in electric propulsion, aerospace science, and space science courses.

Dan M. Goebel, PhD, is a Fellow and Senior Research Scientist at the Jet Propulsion Laboratory, and Adjunct Professor of Aerospace Engineering and Electrical Engineeringat UCLA. He is a Member of the National Academy of Engineering, and also a Fellow of the National Academy of Inventors , the IEEE, the AIAA, and the American Physical Society. He is presently the Chief Engineer of the NASA Psyche Mission and also develops advanced electric propulsion thrusters, cathodes and other spacecraft technologies.

Ira Katz, PhD, is an aerospace consultant specializing in electric propulsion and spacecraft charging. He retired from the Jet Propulsion Laboratory after leading the Electric Propulsion group and researching electric propulsion physics. Previously, he worked in industry investigating spacecraft charging and headed the team that developed the NASA Charging Analyzer Program, NASCAP.

Ioannis G. Mikellides, PhD, is a Senior Research Scientist at the Jet Propulsion Laboratory and a Fellow of the AIAA. In the last three decades his research on the theory and numerical simulation of plasmas has spanned a wide range of applications, both in and beyond electric propulsion. He is also the main author of the scientific plasma codes OrCa2D and Hall2De, which have been supporting NASA’s space flight qualification of hollow cathodes and Hall thrusters for years.

Foreword           

Preface

Acknowledgments         

Chapter 1:           Introduction      

1.1          Electric Propulsion Background 

1.2          Electric Thruster Types 

1.3          Electrostatic Thrusters  

1.3.1      Ion Thrusters    

1.3.2      Hall Thrusters   

1.4          Electromagnetic Thrusters          

1.4.1      Magnetoplasmadynamic Thrusters         

1.4.2      Pulsed Plasma Thrusters              

1.4.3      Pulsed Inductive Thrusters          

1.5          Beam/Plume Characteristics      

References        

Chapter 2:           Thruster Principles          

2.1          The Rocket Equation      

2.2          Force Transfer in Electric Thrusters         

2.2.1      Ion Thrusters    

2.2.2      Hall Thrusters   

2.2.3      Electromagnetic Thrusters          

2.3          Thrust  

2.4          Specific Impulse              

2.5          Thruster Efficiency          

2.6          Power Dissipation           

2.7          Neutral Densities and Ingestion

Problems            

References        

Chapter 3:           Basic Plasma Physics      

3.1          Introduction      

3.2          Maxwell’s Equations      

3.3          Single Particle Motions 

3.4          Particle Energies and Velocities 

3.5          Plasma as a Fluid             

3.5.1      Momentum Conservation           

3.5.2      Particle Conservation    

3.5.3      Energy Conservation     

3.6          Diffusion in Partially Ionized Plasma        

3.6.1      Collisions            

3.6.2      Diffusion and Mobility Without a Magnetic Field

3.6.3      Diffusion Across Magnetic Fields              

3.7          Sheaths at the Boundaries of Plasmas    

3.7.1      Debye Sheaths 

3.7.2      Pre-Sheaths      

3.7.3      Child–Langmuir Sheath

3.7.4      Generalized Sheath Solution      

3.7.5      Double Sheaths

3.7.6      Summary of Sheath Effects         

Problems            

References        

Chapter 4: Hollow Cathodes       

4.1          Introduction      

4.2          Cathode Configurations

4.3          Thermionic Electron Emitters     

4.4          Insert Region    

4.5          Orifice Region   

4.6          Cathode Plume Region 

4.7          Heating and Thermal Models     

4.7.1      Hollow Cathode Heaters              

4.7.2      Heaterless Hollow Cathodes      

4.7.3      Hollow Cathode Thermal Models             

4.8          Hollow Cathode Life       

4.8.1      Dispenser Cathode Insert-Region Plasmas            

4.8.2      BaO Cathode Insert Temperature            

4.8.3      Barium Depletion Model              

4.8.4      Bulk-Material Insert Life

4.8.5      Cathode Poisoning         

4.9          Keeper Wear and Life    

4.10        Discharge Behavior and Instabilities       

4.10.1    Discharge Modes            

4.10.2    Suppression of Instabilities and Energetic Ion Production              

4.10.3    Hollow Cathode Discharge Characteristics            

Problems            

References        

Chapter 5:           Ion Thruster Plasma Generators

5.1          Introduction      

5.2          Idealized Ion Thruster Plasma Generator              

5.3          DC Discharge Ion Thrusters         

5.3.1      Generalized 0-D Ring-Cusp Ion Thruster Model  

5.3.2      Magnetic Multipole Boundaries

5.3.3      Electron Confinement  

5.3.4      Ion Confinement at the Anode Wall         

5.3.5      Neutral and Primary Densities in the Discharge Chamber                              

5.3.6      Ion and Excited Neutral Production         

5.3.7      Electron Temperature  

5.3.8      Primary Electron Density             

5.3.9      Power and Energy Balance in the Discharge Chamber     

5.3.10    Discharge Loss  

5.3.11    Discharge Stability          

5.3.12    Recycling Behavior         

5.3.13    Limitations of a 0-D Model          

5.4          Kaufman Ion Thrusters 

5.5          rf Ion Thrusters

5.6          Microwave Ion Thrusters             

5.7          2-D Computer Models of the Ion Thruster 

Discharge Chamber        

5.7.1      Neutral Atom Model     

5.7.2      Primary Electron Motion and Ionization Model  

5.7.3      Discharge Chamber Model Results          

Problems            

References        

Chapter 6:           Ion Thruster Accelerator Grids   

6.1          Grid Configurations        

6.2          Ion Accelerator Basics   

6.3          Ion Optics           

6.3.1      Ion Trajectories

6.3.2      Perveance Limits             

6.3.3      Grid Expansion and Alignment  

6.4          Electron Backstreaming

6.5          High Voltage Considerations      

6.5.1      Electrode Breakdown    

6.5.2      Molybdenum Electrodes             

6.5.3      Carbon–Carbon Composite Materials     

6.5.4      Pyrolytic Graphite           

6.5.5      Voltage Hold-off and Conditioning in Ion Accelerators    

6.6          Ion Accelerator Grid Life              

6.6.1      Grid Models      

6.6.2      Barrel Erosion   

6.6.3      Pits-and-Grooves Erosion            

Problems            

References        

Chapter 7:           Conventional Hall Thrusters       

7.1          Introduction      

7.1.1      Discharge Channel with Dielectric Walls (SPT)     

7.1.2      Discharge Channel with Metallic Walls (TAL)       

7.2          Operating Principles and Scaling

7.2.1      Crossed-Field Structure and the Hall Current       

7.2.2      Ionization Length and Scaling     

7.2.3      Plasma Potential and Current Distributions          

7.3          Performance Models    

7.3.1      Thruster Efficiency Definitions   

7.3.2      Multiply-Charged Ion Correction              

7.3.3      Dominant Power Loss Mechanisms         

7.3.4      Electron Temperature  

7.3.5      Efficiency of Thrusters with Dielectric Walls         

7.3.6      Efficiency of TAL Thrusters Metallic Walls              

7.3.7      Comparison of Thrusters with Dielectric and Metallic Walls           

7.4          Discharge Dynamics and Oscillations       

7.5          Channel Physics and Numerical Modeling             

7.5.1      Basic Model Equations  

7.5.2      Numerical Modeling and Simulations     

7.6          Operational Life of Conventional Hall Thrusters 

Problems            

References        

Chapter 8:           Magnetically Shielded Hall Thrusters      

8.1          Introduction      

8.2          First Principles of Magnetic Shielding      

8.3          The Protective Capabilties of Magnetic Shielding               

8.3.1      Numerical Simulations  

8.3.2      Laboratory Experiments and Model Validation   

8.4          Magnetically Shielded Hall Thrusters with

                Electrically Conducting Walls      

8.5          Magnetic Shielding Low Power Hall Thrusters     

8.4          Remarks on Magnetic Shielding in Hall Thrusters              

References        

Chapter 9:           Electromagnetic Thrusters          

9.1          Introduction      

9.2          Magnetoplasmadynamic (MPD) Thrusters           

9.2.1      Self Field MPD Thrusts  

9.2.2      Applied-Field MPD Thrusters     

9.2.3      Onset Phenomenon      

9.2.4      MPD Thruster Performance Parameters

9.3          Ablative Pulsed Plasma Thrusters             

9.3.1      Thruster Configurations and Performance           

9.3.2      Physics and Modeling    

9.4          Pulsed Inductive Thrusters          

9.4.1      Thruster Performance  

9.4.2      Physics and Modeling    

References        

Chapter 10:         Future Directions in Electric Propulsion 

10.1        Hall Thruster Developments      

10.1.1    Alternative Propellants 

10.1.2    Nested Channel Hall Thrusters for Higher Power

10.1.3    Double Stage Ionization and Acceleration Regions            

10.1.4    Multipole Magnetic Fields in Hall Thrusters         

10.2        Ion Thruster Developments        

10.2.1    Alternative Propellants 

10.2.2    Grid Systems for High Specific Impulse  

10.3        Helicon Thruster Development 

10.4        Magnetic Field Dependent Thrusters     

10.4.1    Rotating Magnetic Field (RMF) Thrusters              

10.4.2    Magnetic Induction Plasma Thrusters     

10.4.3    Magnetic Reconnection Thrusters           

10.5        Laser-Based Propulsion

10.6        Solar Sails           

10.7        Hollow Cathode Discharge Thrusters      

References        

Chapter 11:         Thruster Plumes and Spacecraft Interactions      

1.1          Introduction      

11.2        Plume Physics in Ion and Hall Thrusters 

11.2.1    Plume Measurements  

11.2.2    Flight Data          

11.2.3    Laboratory Plume Measurements           

11.3        Plume Models for Ion and Hall Thrusters              

11.3.1    Primary Beam Expansion             

11.3.2    Neutral Gas Plumes       

11.3.3    Secondary-Ion Generation          

11.3.4    Combined Models and Numerical Simulations    

11.4        Spacecraft Interactions 

11.4.1    Momentum of the Plume Particles          

11.4.2    Sputtering and Contamination  

11.4.3    Plasma Interactions with Solar Arrays     

11.5        Interactions with Payloads          

11.5.1    Microwave Phase Shift 

11.5.2    Plume Plasma Optical Emission 

Problems            

References        

Chapter 12:         Flight Electric Thrusters

12.1        Introduction      

12.2        Ion Thrusters    

12.3        Hall Thrusters   

12.4        Electromagnetic Thrusters          

References        

Appendices

A:            Nomenclature  

B:            Gas Flow Unit Conversions and Cathode

                Pressure Estimates         

C:            Energy Loss by Electrons              

D:            Ionization and Excitation Cross Sections for

                Xenon and Krypton        

E:            Ionization and Excitation Reaction Rates in

                Maxwellian Plasmas       

F:            Electron Relaxation and Thermalization Times    

G:           Clausing Factor Monte Carlo Calculation

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