NASA CR-134886 ER75-4368 MICROWAVE POWER TRANSMISSION SYSTEM STUDIES VOLUME II INTRODUCTION, ORGANIZATION, ENVIRONMENTAL AND SPACEBORNE SYSTEMS ANALYSES RAYTHEON COMPANY EQUIPMENT DIVISION ADVANCED DEVELOPMENT LABORATORY SUDBURY, MASS. 01776 prepared for NATIONAL AERONAUTICS AND SPACE ADMINISTRATION NASA Lewis Research Center Contract NAS 3-17835
1. Report No. NASA CR-134886 2. Government Accession No. 3. Recipient's Catalog No. 4. Title and Subtitle MICROWAVE POWER TRANSMISSION SYSTEM STUDIES Volume II - Introduction, Organization, Environmental and Space- borne Systems Analysis (Sections 1 through 7) 5. Report Date December 1975 6. Performing Organization Code 7. Author(s) O. E. Maynard, W.C. Brown, A. Edwards, J. T. Haley, G. Meltz, J. M. Howell - Raytheon Co. ; A. Nathan - Grumman Aerospace Corp. 8. Performing Organization Report No. ER75-4368 10. Work Unit No. 9. Performing Organization Name and Address Raytheon Company Equipment Division 528 Boston Post Road Sudbury, Massachusetts 01776 11. Contract or Grant No. NAS 3-17835 13. Type of Report and Period Covered Contractor Report 12. Sponsoring Agency Name and Address National Aeronautics and Space Administration Washington, D. C. 20546 14. Sponsoring Agency Code 15. Supplementary Notes Mr. Richard M. Schuh NASA Lewis Research Center Cleveland, Ohio 44135 16. Abstract -- A study of microwave power generation, transmission, reception and control was conducted as a part of the NASA Office of Applications’ joint Lewis Research Center/Jet Propulsion Laboratory five-year program to demonstrate feasibility of power transmission from geosynchronous orbit. This volume (2 of 4) is comprised of Sections 1 through 7 which present introduction, organization, analyses, conclusions and recommendations for each of the spaceborne subsystems. Section 1 presents the Introduction, task definitions, conclusions and recommendations, with discussion of the associated subsystems technologies. It is concluded with a discussion of the report approach and organization. Section 2 presents the organization and approach to the study. Section 3 presents the environmental effects - propagation analyses with appendices covering radio wave diffraction by random ionospheric irregularities, self-focusing plasma instabilities and ohmic heating of the D-region. Section 4 presents the analyses of de to rf conversion subsystems and system considerations for both the amplitron and the klystron with appendices for the klystron covering cavity circuit calculations, output power of the solenoid-focused klystron, thermal control system, and confined flow focusing of a relativistic beam. Section 5 presents the photovoltaic power source characteristics as they apply to interfacing with the power distribution flow paths, magnetic field interaction, de to rf converter protection, power distribution including estimates for the power budget, weights and costs. Section 6 presents analyses for the transmitting anteir considering aperture illumination and size, with associated efficiencies and ground power distributions. Analyses of subarray types and dimensions, attitude error, flatness, phase error, subarray layout, frequency tolerance, attenuation, waveguide dimensional tolerances, mechanical including thermal considerations are included. Implications associated with transportation, assembly and packaging, attitude control and alignment are discussed. Section 7 presents analyses for the phase front control subsystem, including both ground based pilot signal driven adaptive and ground command approaches with their associated phase errors. 17. Key Words (Suggested by Author (s)) Microwave power transmission; power from space; satellite power transmission; phased array power transmission; rectifying antenna (rectenna). 18. Distribution Statement Unclassified - Unlimited 19. Security Oassif. (of this report) Unclassified 20. Security Classif. (of this page) Unclassified 21. No. of Pages 26J 22. Price* $3. 00
TABLE OF CONTENTS VOLUME I - EXECUTIVE SUMMARY Section Page 1. Introduction 2 2. DC to RF Conversion 4 3. Transmitting Antenna and Phase Front Control 9 4. Mechanical Systems 16 5. Flight Operations 22 6. Receiving Antenna 25 7. Systems Analysis and Evaluation 28 8. Critical Technology 34 9. Critical Technology and Test Program 37 10. Recommendations for Additional Studies 42 VOLUME II - Sections 1 through 7 with Appendices A through G 1. INTRODUCTION, CONCLUSIONS AND RECOMMENDATIONS 1.1 Introduction 1-1 1.2 Conclusions and Recommendations 1-3 1.2.1 General 1-3 1.2.2 Subsystems and Technology 1.2.2.1 Environmental Effects - Propagation 1-5 1.2.2.2 DC-RF Conversion 1-5 1.2.2.3 Power Interface and Distribution (Orbital) 1-7 1.2.2.4 Transmitting Antenna 1-7 1.2.2.5 Phase Front Control 1-8 1.2.2.6 Mechanical Systems and Flight Operations 1-9 1.2.2.7 Receiving Antenna 1-10 1.2.2.8 Radio Frequency Interference and Allocation 1-11 1.2.2.9 Risk Assessment 1-12 1.2.3 System Analysis and Evaluation 1-15
TABLE OF CONTENTS -- Continued Page 1.2.4 Technology Development and Test Programs 1-16 1.2.4.1 Technology Development and Ground Test Program 1-16 1.2.4.2 Technology Development and Orbital Test Program 1-16 1.2.5 Additional Studies 1-17 1.3 Report Approach and Organization 1-17 2. ORGANIZATION AND APPROACH 2.1 Organization 2-1 2.2 Approach 2-3 3. ENVIRONMENTAL EFFECTS - PROPAGATION 3.1 Introduction 3-1 3. 2 Atmospheric Attenuation and Scattering 3-2 3.2.1 Molecular Absorption 3-2 3.2.2 Scattering and Absorption by Hydrometeors 3-4 3.3 Ionosphere Propagation 3-12 3.3.1 Ambient Refraction 3-12 3.3.2 Scintillations Due to Ambient Fluctuations and Self-Focusing Instabilities 3-13 3.4 Ionospheric Modification By High Power Irradiation 3-19 3.5 Faraday Rotation Effects 3-21 3.5.1 Introduction 3-21 3.5.2 Diurnal and Seasonal Changes 3-21 3.5. Midlatitude Geomagnetic Storms 3-22 3.6 Conclusions and Recommendations 3-24 4. DC-RF CONVERSION 4.1 Amplitron 4-1 4.1.1 RF Circuit 4-2 4.1.2 Pyrolytic Graphite Radiator 4-4 4.1.3 Magnetic Circuit 4-4 4.1.4 Controlling the Output of Amplitrons 4-5 4.1.5 Weight 4-5
TABLE OF CONTENTS -- Continued Page. 4.1.6 Cost 4-7 4.1.7 Noise and Harmonics 4-7 4.1.8 Parameters Versus Frequency 4-9 4.1.9 Parameters Versus Power Level 4-15 4.2 Klystron 4-16 4.2.1 Periodic Permanent Magnetic Focusing 4-17 4.2.2 Circuit Efficiency 4-20 4.2.3 Klystron Efficiency With Solenoidal Focusing 4-25 4.2.4 Heat Dissipation and Beam Collection 4-27 4.2.5 Variations of Supply Voltages 4-34 4.2.6 Noise, Gain and Harmonic Characteristics 4-37 4.2.7 Tube Designs 4-40 4.2.8 Tube Lifetime 4-43 4.2.9 Weight and Cost 4-43 4.2.10 Conclusions 4-46 4.3 System Considerations 4-48 4.3.1 Amplitron Gain and Efficiency 4-48 4.3.2 Cascaded Vs Parallel Configurations 4-50 4.3.3 Cascaded Amplitron Gain 4-56 4.3.4 Amplifier Noise 4-56 4.3.5 Klystron Power Level 4-61 4.3.6 Converter Filter Requirements 4-64 4.4 Conclusions and Recommendations 4-69 5. POWER SOURCE INTERFACE AND DISTRIBUTION 5.1 Power Source Characteristics 5-1 5.2 Power Source-Converter Interface 5-3 5.3 Power Distribution Flow Paths 5-6 5.4 Magnetic Interaction 5-12 5.5 DC to RF Converter Protection 5-15 5.6 Power Distribution System 5-19 5.7 Power Distribution Cost and Weight 5-23 5.8 Power Budget 5-24 5.9 Conclusions and Recommendations 5-24
TABLE OF CONTENTS -- Continued Page 6. TRANSMITTING ANTENNA 6.1 Aperture Illumination and Size 6-1 6.2 Array Types 6-10 6.3 Subarray Types 6-16 6.4 Subarray Dimensions 6-16 6.5 Subarray Layout 6-20 6.6 Tolerance and Attenuation 6-26 6.6.1 Frequency Tolerance 6-26 6.6.2 Waveguide Dimensional Tolerances 6-27 6.6.3 Waveguide Attenuation 6-28 6. 7 Mechanical Design and Analysis 6-29 6.7.1 Thermal Analysis and Configuration 6-29 6.7.2 Materials 6-38 6.7.3 Transportation, Assembly and Packaging 6-43 6.8 Attitude Control and Alignment 6-47 6.9 Conclusions and Recommendations 6-49 7. PHASE FRONT CONTROL 7.1 Adaptive Phase Front Control 7-4 7.2 Command Phase Front Control 7-10 7.2.1 Phase Estimation 7-10 7.2.2 Bit Wiggle 7-14 7.3 Conclusions and Recommendations 7-14 APPENDIX A - RADIO WAVE DIFFRACTION BY RANDOM IONOSPHERIC IRREGULARITIES A. 1 Introduction A-1 A. 2 Model for Electron Density Irregularities A-2 A. 3 Phase Fluctuations and Their Spatial Correlation at the Diffracting Screen A-3 A. 4 Phase and Amplitude Fluctuations and Their Spatial and Temporal Correlation Functions on an Observational Plane A-4
TABLE OF CONTENTS -- Continued Page. APPENDIX B - SELF-FOCUSING PLASMA INSTABILITIES B-1 APPENDIX C - OHMIC HEATING OF THE D-REGION C-1 APPENDIX D - CAVITY CIRCUIT CALCULATIONS D.1 Input Impedance D-1 D.2 Input Power and Gain at Saturation D-2 D.3 Intermediate- and Output-Gap Voltages D-3 D.4 Cavity Tunings D-3 D.5 Output Cavity and Circuit Efficiency D-4 APPENDIX E - OUTPUT POWER OF THE SOLENOID-FOCUSED KLYSTRON E-l APPENDIX F - KLYSTRON THERMAL CONTROL SYSTEM F. 1 Heat Conduction F-1 F. 2 Temperature, Area and Weight of Radiators F-2 F.2.1 Collector F-3 F.2.2 Collector Reflector and Heat Shield F-4 F.2.3 Body Radiator F-4 F.2.4 Body Reflector and Heat Shield F-5 F. 3 Weight of Heat Pipes F-5 APPENDIX G - CONFINED-FLOW FOCUSING OF A RELATIVISTIC BEAM G-1 VOLUME III - MECHANICAL SYSTEMS AND FLIGHT OPERATIONS (Section 8) Page 1. INTRODUCTION 1-1 2. SUMMARY 2.1 Task 1 - Preliminary Design 2-1 2.1.1 Control Analysis 2-1 2.1.2 Thermal/Structural Analysis 2-1 2.1.3 Design Options and Groundrules for Task 2 Concept Definition 2-5
TABLE OF CONTENTS -- Continued Page 2.2 Task 2 - Concept Definition 2-9 2.2.1 Mission Analysis 2-9 2.2.2 Antenna Structural Definition 2-9 2.2.3 Configuration Analysis 2- 14 2.2.4 Assembly 2-21 2.2.5 Cost 2-31 2.3 Recommendations 2-33 3. TECHNICAL DISCUSSION 3.1 Mission Analysis 3. 1-1 3.1.1 SSPS Configuration and Flight Mode Descriptions 3. 1-1 3.1.2 Transportation System Performance 3. 1-1 3.1.3 Altitude Selection 3. 1-8 3.1.4 SEPS (Ion Engine) Sizing 3. 1-14 32. Antenna Structural Concept 3. 2-1 3.2.1 General Arrangement 3. 2- 1 3.2.2 Rotary Joint 3.2-1 32. 3 Primary/Secondary Antenna Structure 3. 2-15 32.4 Structure/Waveguide Interface 3.2-15 3.2.5 Antenna Weight and Mass Properties 3. 2-18 3.3 Configuration Analysis 3. 3- 7 3.3.1 Control Analysis 3. 3-1 3.3.2 Thermal Evaluation 3. 3-9 3.3.3 Structural Analysis 3. 3-41 3.4 Assembly and Packaging 3.4-1 3.4.1 Detail Parts 3.4-1 3.4.2 Structural Assembly 3.4-9 3. Cost 3. 5. 1 3.5.1 Task 1 - Preliminary Design Results 3.5-1 3.5.2 Task 2 - Concept Definition Results 3. 5-5 3.5.3 MPTS Structural Costs 3. 5-19
TABLE OF CONTENTS -- Continued 4. TECHNOLOGY ISSUES 4.1 Control System 4-1 4.1.1 Evaluation of Alternate Power Transfer and Drive Devices 4-1 4.1.2 Detailed Control System Analysis 4-2 4.2 Structural System 4-3 4.2.1 Composite Structures and Assembly Techniques 4-3 4.2. 2 Tension Brace Antenna Feasibility Assessment 4-4 4.2.3 Local Crippling Stress Evaluation 4-4 4.2.4 Design Environments 4-5 4.2.5 Optimum Antenna Structures 4-5 4.2.6 Finite Element Model Development 4-6 4.2.7 Composite Waveguide 4-6 4.3 Thermal System 4-7 4.3.1 Maximum Temperature 4-7 4.3.2 Transient Analysis 4-8 4.4 Assembly 4-9 4.4.1 Assembly Cost 4-9 4.4.2 Man’s Role in Assembly and Maintenance 4-10 5. REFERENCES 5-1 VOLUME IV - Sections 9 through 14 with Appendices H through K 9. RECEIVING ANTENNA 9.1 Microwave Rectifier Technology 9-1 9.2 Antenna Approaches 9-9 9.3 Topology of Rectenna Circuits 9-14 9.4 Assembly and Construction 9-21 9.5 ROM Cost Estimates 9-21 9.6 Power Interface Estimates 9-25 9.6.1 Inverter System 9-30 9.6.2 Power Distribution Costs 9-30 9.6.3 System Cost 9-31 9.7 Conclusions and Recommendations 9-31
TABLE OF CONTENTS -- Continued Page 10. FREQUENCY INTERFERENCE AND ALLOCATION 10-1 10.1 Noise Considerations 10-3 10.1. 1 Amplitron 10-3 10.1.2 Klystron 10-4 10.1.3 Interference Limits and Evaluation 10-6 10.2 Harmonic Considerations 10-6 10.3 Conclusions and Recommendations 10-12 11. RISK ASSESSMENT 11.1 Technology Risk Rating and Ranking 11-1 11.2 Technology Assessment Conclusions and Recommendations 11-16 12. SYSTEM ANALYSIS AND EVALUATION 12- 1 12.1 System Geometry 12-1 12.2 Parametric Studies 12-3 12,2.1 System Relationships 12-3 12,2.2 Efficiency, Weight and Cost 12-8 12.2.3 Converter Packing 12-12 12.2.4 Capital Cost Vs Power and Frequency Results 12-13 12. 2.5 Ground Power Density and Power Level Selection 12-19 12.2.6 Frequency Selection 12-22 12.2. 7 Characteristics of 5 GW and 10 GW Systems 12-22 12.2.8 Energy Cost 12-36 12.3 Final System Estimates 12-41 12.3.1 Cost and Weight 12-41 12.3.2 Efficiency Budget 12-43 12.3.3 Capital Cost and Sizing Analyses 12-45 12.4 Conclusions and Recommendations 12-45 13. CRITICAL TECHNOLOGY AND GROUND TEST PROGRAM 13.1 General Objectives 13-1 13.2 Detailed Ground Test Objectives 13-2 13.3 Implementation - Ground Test 13-3 13.3.1 Summary 13-3
TABLE OF CONTENTS -- Continued Page 13.3. 2 Phase I 13-5 13.3.3 Phase II 13-5 13.3.4 Phase III 13-9 13.3. 5 Alternate Phase I Converter Implementation 13-11 13.4 Critical Technology Development 13-14 13.4.1 Amplitron 13-14 13.4.2 Klystron 13-14 13.4.3 Phase Control 13-14 13.5 Schedule and Cost 13-15 13.6 Conclusions and Recommendations 13-17 14. CRITICAL TECHNOLOGY AND ORBITAL TEST PROGRAM 14.1 Orbital Test Objectives 14-1 14.2 Implementation 14-3 14.2. 1 Geosatellite (Mission 1) 14-4 14.2.2 Shuttle Sorties (Missions 2 through 11) 14-4 14.2.3 Orbital Test Facility 14-23 14.3 Cost and Schedule 14-25 14.4 Conclusions and Recommendations 14-30 APPENDIX H - ESTIMATED ANNUAL OPERATIONS AND MAINTENANCE COST (5 GW System) H-1 APPENDIX I - ANNUAL OPERATIONS AND MAINTENANCE COST (10 GW System) I-1 APPENDIX J - SYSTEM ANALYSIS EXAMPLES J.1 Introductory Analysis of Initial Operational System With Minimum Size Transmitting Antenna J-1 J.2 Analysis of the Final Operational System and Their Goals J-10 J.3 Analysis of the Initial Operational System Based On the Final System Configuration J-21 J.4 Weight and Cost Analysis for the Initial and Final Operational Systems J-25 J.5 Energy Cost J-27
TABLE OF CONTENTS -- Continued Page APPENDIX K - DETAILS OF GROUND AND ORBITAL TEST PROGRAM K.1 Introduction K-1 K.2 Objectives Implementation Equipment and Characteristics K-1 K.3 Implementation of Objectives Hl, H2, DI and D2 Using Low Earth Orbit Sortie Missions K-3 K.4 Defining an MPTS Orbital Test Facility Program K-13 K.4.1 Assumptions K-13 K.4.2 Sizing the Phased Array Antennas K-14
LIST OF ILLUSTRATIONS Figure Page 2-1 Microwave Power Transmission Systems Study Program Organization 2 2 2-2 Work Breakdown Structure 2-4 2-3 MPTS Schedule 2-5 3-1 Atmospheric Absorption by the 1. 35-cm Line of Water Vapor for a Mean Absolute Humidity of 7. 75 g/m3 and by the 0.5 cm Line of Oxygen at a Temperature of 20°C and a Pressure of One Atmosphere 3-3 3-2 Zenith Attenuation Versus Frequency 3-4 3-3 Comparison of Gaseous Absorption and Rain Attenuation 3-5 3-4 Transmission Efficiency - Molecular Absorption and Rain 3-8 3-5 Rainfall Rate in a Thunderstorm, North-South Section 3-9 3-6 Rainfall Rate in a Thunderstorm, East-West Section 3-10 3-7 Transmission Through Very Heavy Rain (Elevation 40 Degree Angle) 3-10 3-8 Phase Scintillations 3-14 3-9 Typical Gaussian Model Results of Density Correlation 3-15 3-10 Path of a Straight Line Ray from a Geostationary Satellite to a Midlatitude Receiving Site 3-22 3-11 Diurnal and Seasonal Variation in Faraday Rotation and Polarization Mismatch "Loss" 3-23 3-12 Variation in Total Electron Content During a Magnetic Storm 3-25 4-1 Amplitron Assembly 4-3 4-2 5 kW Amplitron Parameters 4-3 4-3 Amplitron Current and Voltage Levels for Various Magnetic Field Levels 4-6 4-4 Power Level Versus Frequency 4-10 4-5 Amplitron Weight/Cost/Efficiency Versus Frequency 4-10 4-6 Anode Radiator Diameter Versus Frequency 4-11 4-7 Anode Radiator Weight Versus Frequency 4-12 4-8 Tube Dimensions Versus Frequency 4-12 4-9 Magnetic Field Intensity Versus Frequency 4-13 4-10 Dissipated Power Density Versus Frequency 4-13
LIST OF ILLUSTRATIONS -- Continued Figure Page 4-11 Temperature Drop Across Vanes Versus Frequency 4-14 4-12 DC Current Versus Frequency 4-14 4-13 Amplitron Weight and Cost Versus Power 4-15 4-17 Klystron Bunching with PPM Focusing 4-18 4-18 Radial Beam Spreading with PPM Focusing 4-18 4-19 Klystron Output Gap with PPM Focusing 4-19 4-20 Klystron Bunching with PPM Focusing, Shorter Magnet Period and Increased Voltage at Gap 1 4-21 4-21 Graphical Analysis of the Collector Depression 4-22 4-22 Klystron Power Summary 4-23 4-2 3 Effect of Temperature on Output-Circuit Efficiency 4-24 4-24 Effect of Temperature on in the Klystron Output Cavity 4-24 4-2 5 Efficiency Vs Output Power for Solenoid-Focused Klystron 4-26 4-2 6 Body Heat Versus Saturated Output Power 4-29 4-2 7 Output Cavity of 43 kW Klystron (Longitudinal Cross Section) 4-31 4-2 8a Outline of the PPM Klystron 4-32 4-28b Outline of the 48 kW Solenoid Klystron 4-33 4-29 Klystron Voltage Control 4-36 4-30 Gain and Noise in PPM-Focused Klystron 4-39 4-31 Computed Noise Characteristic of the PPM Klystron 4-40 4-32 Summary of Design Parameters 4-41 4-33 Weight and Cost Analysis of the PPM Klystron with 5.57 kW Output 4-44 4-34 Weight and Cost Analysis of an EM Klystron with 16 kW Output 4-45 4-35 Weight and Cost Analysis of an EM Klystron with 48 kW Output 4-46 4-36 Comparison of Tube Types 4-47 4-37 Amplitron Gain and Efficiency 4-49 4-38 Cascaded Amplifier Configuration Phase Characteristics 4-52 4-39 Parallel Feed Amplifier Considerations Phase Characteristics 4-53 4-40 Cascaded Amplifier Chain 4-54 4-41 Parallel Amplifier Chain 4-55 4-42 Amplitrons in Cascade 4-57 4-43 Amplifier Noise 4-58
LIST OF ILLUSTRATIONS -- Continued Figure Page 4-44 Noise Output of Preamplifier Stages 4-59 4-45 Amplifier - Noise Power Output 4-60 4-46 Klystron Parameters for 60 kW Beam 4-62 4-47 Waveguide Losses Vs RF Power Per Tube 4-63 4-48 Power Divider 4-64 4-49 Klystron Parameters (Electronic Efficiency = 84%) 4-65 4-50 Total Efficiency with Waveguide Losses 4-66 4-51 Klystron System Efficiency Including Waveguide Losses 4-67 4-52 Klystron Equivalent Filter Characteristic 4-68 4-53 Amplitron Equivalent Filter Characteristics 4-70 5-1 Typical Solar Cell Characteristics Based on 1985 Cell With No Concentrators 5-2 5-2 Source Voltage Characteristics Solar Cell 5-4 5-3 Total Source Characteristics 5-4 5-4 Klystron-Solar Cell Interface 5-5 5-5 Klystron Operation Available Power Usage 5-6 5-6 Amplitron-Solar Cell Interface 5-7 5-7 Quadrant of Microwave Platform Divided Into Areas of Equal Power 5-8 5-8 Circular Power Flow 5-9 5-9 Power Distribution Lateral Power Flow 5-10 5-10 Distribution System Weight Estimate (15 GW Input Power) 5-12 5-11 Microwave Array - Magnetic Torque - Lateral Power Flow 5-13 5-12 Microwave Array - Magnetic Torque - Radial Power Flow 5-14 5-13 Amplitron Failure Modes and Probable Results 5-16 5-14 Klystron Failures and Probable Results 5-17 5-15 Concept for Converter/Crowbar Interface 5-18 5-16 Crowbar and Switchgear Distribution 5-21 5-17 Power Distribution System Short Circuit Currents 5-22 5-18 Simplified Diagram - HVDC Interrupter 5-24 5-19 Power Distribution Cost Summary (9 GW Power Source) 5-26 5-20 Power Distribution Weight Summary (9 GW Power Source) 5-26 5-21 Typical Microwave Array, Power Usage 5-27
LIST OF ILLUSTRATIONS -- Continued Figure 6-1 Fraction of Total Power in Sectors of Prescribed Radii 6-2 6-2 Sidelobe Level and Beamwidths 6-3 6-3 Pattern Efficiency for Uniform Illumination (0 dB Taper) 6-5 6-4 Pattern Efficiency for Uniform Illumination (5 dB Taper) 6-5 6-5 Pattern Efficiency for Uniform Illumination (10 dB Taper) 6-6 6-6 Pattern Efficiency for Uniform Illumination (15 dB Taper) 6-6 6-7 Taper Effect on Pattern and Efficiency 6-7 6-8 First Sidelobe Level Vs Truncated Gaussian Taper 6-8 6-9 Antenna Sizes for Truncated Gaussian Tapers 6-9 6-10 Array-Subarray Organization 6-10 6-11 Beam Efficiency - Truncated Gaussian Distribution (5 dB Edge Taper) 6-11 6-12 Beam Efficiency - Truncated Gaussian Distribution (10 dB Edge Taper) 6-11 6-13 Relative Sidelobes - Truncated Gaussian Distribution (5 dB Edge Taper) 6-12 6-14 Relative Sidelobes - Truncated Gaussian Distribution (10 dB Edge Taper) 6-12 6-15 Outage of a Single DC Filter 6-13 6-16 MPTS Concept 6-13 6-17 Alternative Array Types 6-14 6-18 Space Fed Array 6-15 6-19 Feed Illumination (Array Focused at Feed) 6-15 6-20 Subarray Types 6-17 6-21 Subarray Types 6-17 6-22 Subarray Size Considerations 6-18 6-23 SPS Incremental Cost Vs Subarray Size 6-20 6-24 Three Subarray Layout Approaches 6-21 6-25 Subarray Right End Termination Approaches 6-23 6-26 Two Slotted Waveguide Designs 6-25 6-27 Amplitron Thermal Model 6-30 6-28 Amplitron Thermal Analysis 6-31 6-29 6 kW Klystron Configuration 6-33
LIST OF ILLUSTRATIONS -- Continued Figure Page 6-30 Klystron Configuration Temperature Distribution 6-34 6-31 Subarray Deflection Vs Size 6-36 6-32 Subarray Deflection Vs Size 6-36 6-33 Subarray Configuration (Using 6061-T6 Al. Waveguide) 6-37 6-34 Subarray Layout 6-39 6-35 Thermal Stability at 260°C of Various Adhesives 6-40 6-36 Thermal Stability at 177°C of Epoxy and Epoxy-Phenolic Adhesives 6-41 6-37 Comparison of High Temperature Strength of Various Types of Adhesives 6-42 6-38 Transportation Alternative A 6-44 6-39 Transportation Alternative B 6-45 6-40 Transportation Alternative C 6-46 6-41 Waveguide Weight and Packaging Density 6-47 7-1 Effect of rms Phase Errors on Beam Efficiency 7-2 7-2 Command and Adaptive Phase Front Control Concepts 7-3 7-3 MPTS Phase Front Control Approaches 7-3 7-4 Phase Front Control Approach Comparison 7-4 7-5 Reference Distribution Systems 7-5 7-6 Ground Pilot and Phase Distribution 7-6 7-7 Subarray Phase Control Block Diagram 7-8 7-8 Quadratic Phase Error Example 7-12 7-9 Curved Array Example 7-12 7-10 Phase Estimation Example 7-13 7-11 Bit Wiggle Approach 7-15 A-1 The Geometry Used in the Diffraction Calculations A-5 B-l Self-Focusing Instability B-2 B-2 Self-Focusing Instability Threshold Power Density B-6 B-3 Growth Rate Versus Transverse Wavelength (Night Time Conditions) B-7 B-4 Growth Rate Versus Transverse Wavelength (Daytime Conditions) B-8
LIST OF NON-STANDARD TERMS AFCRL Air Force Cambridge Research Laboratory ATC Air Traffic Control ATS Applications Technology Satellite CFA Crossed Field Amplifier CPU Central Processor Unit GaAs Gallium Arsenide HLLV Heavy Lift Launch Vehicle Met Meteorological MPTS Microwave Power Transmission System MW Microwave N. F. noise factor PPM periodic permanent magnet ROM Rough Order of Magnitude SCR Silicon Controlled Rectifier SEPS Solar Electric Propulsion Stage Sm-Co(SMCO) Samarium Cobalt SPS Satellite Power System SSPS Satellite Solar Power Station TDRS Tracking and Data Relay Satellite TEC Total Electron Content
SECTION 1 INTRODUCTION, CONCLUSIONS, AND RECOMMENDATIONS 1.1 INTRODUCTION The concept of an orbiting electric power generating station that transmits power through space to earth leads to a potential source of comparatively pollution-free power. The basic elements of the concept are an extraterrestrial power source, e. g. , a nuclear reactor or a solar-powered device, and a transmission system to condition the power, transmit it to earth, and again condition it for distribution. This study concerned the use of microwave technology for the transmission system, an approach which has the potential for high efficiency, large power handling capability and controllability. The transmitting antenna would be in geosynchronous equatorial orbit on a fixed line of sight to the ground receiving and rectifying antenna (rectenna). Microwaves can traverse the atmosphere with low attenuation, and advances in microwave power technology have been considerable since the first demonstration of appreciable microwave power transfer by Brown(1). The combination of a solar photovoltaic power source in geosynchronous orbit with microwave trans- mission to earth was first proposed by Glaser(2). This Satellite Solar Power Station (SSPS) concept received increasing attention(3,4) and led to a feasibility study conducted by a team consisting of Arthur D. Little, Inc. , Grumman Aero- space Corp. , Raytheon Co. , and Textron, Inc. under NASA sponsorship(5)Results were sufficiently promising to warrant support of more detailed studies in the technologies involved. The National Aeronautics and Space Administration (NASA), Office of Applications, as part of a joint Lewis Research Center/Jet Propulsion Laboratory five- year program to demonstrate feasibility of power transmission from space, has included a Microwave Power Transmission System Study. The Lewis Research Center, under a competitive procurement, awarded a cost plus fixed fee contract to the Raytheon Company’s Advanced Development Laboratory to undertake the program tasks as follows:
Task I - Preliminary Analysis: To identify potential high efficiency, low cost and low weight in orbit system configurations. Task II - Conceptual Design: To estimate in greater detail and accuracy than in Task I selected systems cost, weight and performance. Task III - Technical and Economic Evaluation of Systems: To compare the conceptual designs on the basis of such considerations as cost, weight, reliability, development risk, and to select one concept for further study. Task IV - Development of Ground Test Program: To define a ground test program with its associated technology development and to estimate the cost of the program. Task V - Development of Orbital Test Program: To develop a program for a series of orbital tests associated with technology development and to scope the schedule and cost of the program. Task VI - Reporting: To provide periodic technical, financial and schedule reporting and to provide a final report. The study concentrated on the microwave power transmission system (MPTS) for transmitting power from space to earth, and as such the results are independent of the power source selected. For example, a solar thermal converter or a nuclear reactor in orbit could be considered in place of a solar photovoltaic power source. Nevertheless, the solar photovoltaic source remains the best known and studied of alternatives, and so was used for purposes of illustration where required. The study examined system performance, including efficiency and cost and component size and weights as a function of ranges of variables for the Microwave Power Transmission System (MPTS) which included: Ground Power Output Operating Frequency DC-RF Converter Power Level DC-RF Converter Type - Amplitron Klystron Transmitting Antenna Subarray Size Transmitting Antenna Subarray Power Levels
Technique for Cooling Transmitter Tubes Beam Control Techniques Transmitting Antenna Illumination Pattern Peak Receiving Antenna Power Density A broad range of Satellite Power System (SPS) considerations were investigated to ascertain their impact on the MPTS. These included the following: Socio-Economic Considerations Power Source Operations and Maintenance Flight Operations Transportation System Re-Supply SPS Flight Mechanics Orbital Assembly System Assurance Technologies Reliability Safety Environmental Impact The study did not evaluate resource utilization and energy payback. These were addressed in reference 5, however they should be further investigated in the course of maturing the detail design features. 1.2 CONCLUSIONS AND RECOMMENDATIONS 1.2.1 GENERAL The recommended transmitting antenna is a planar phased array about 1 km in diameter constructed of aluminum or composites and weighing about 6 x 106 kg. It consists of 18M x 18M slotted waveguide subarrays which are electronically controlled to direct the power beam at the ground receiving antenna which results in an rms error of about 10M. The subarrays use groups either of 5 kW amplitrons in series or 50 kW klystrons in parallel to convert input dc power to microwave power. The receiving antenna is an array about 10 km in diameter consisting of dipole elements each integrated with a solid state diode and filters which convert microwave power back to dc power.
The recommended operating frequency of 2.45 GHz in the USA industrial band results in near optimum efficiency, avoids brownouts in rain and should have minimal problems in radio frequency interference and allocation. A recommended 5 GW ground power output level provides economy of scale while limiting the peak microwave power density in the center of the beam at earth to about 20 mW/ cm2. Microwave system transmission efficiency is about 60% and cost is about 500 $/kW including orbital assembly and transport of the transmitting antenna from the ground to geosynchronous orbit at 200 $/kg. The orbital transportation and assembly cost should not exceed about 200 $/kg if a satellite power system is to have energy costs comparable with projections for ground based nuclear plants. The recommended flight plan is transport to low earth orbit using a reusable heavy lift launch vehicle, assembly in low earth orbit and then transport to synchronous orbit using a solar electric propulsion stage. Emphasis should be placed on orbital manufacture and assembly to achieve favorable launch vehicle packaging densities. The critical technology items of the MPTS needing early development are the de to microwave converters, materials, electronic phase control subsystems, transmitting antenna waveguide including its interface with the microwave converters, and structures. A six-year, three-phase critical technology development and ground test program is recommended at a rough order of magnitude cost of $27M. The ground test involves transmitting and receiving antennas to obtain data on beam controllability and radio frequency interference, which will provide design confidence for orbital tests. The planned orbital test program implements defined objectives and relies on the Shuttle transportation system to develop and demonstrate orbital assembly techniques and to establish learning for cost and schedule projections. In order to accomplish all defined objectives it culminates in an orbital test facility which could be the nucleus for a pilot plant in geosynchronous orbit. The objectives and their implementation are subject to change and should be reassessed periodically as further in-depth studies are completed and technology developments are matured. The rough order of magnitude cost for the currently indicated flight test and associated technology development is $3500M.
1.2. 2 SUBSYSTEMS AND TECHNOLOGY A summary set of conclusions and recommendations in each of the major technical areas is provided at the end of each of the Sections 3 through 14. These are collected in the following paragraphs. 1.2. 2. 1 Environmental Effects - Propagation For the atmosphere at frequencies below 3 GHz: a. Absorption and scattering effects are small except for wet hail. b. Refraction changes and gradients cause negligible displacement or dispersion of the high power beam and do not degrade significantly a ground based pilot beam phase front as seen at the transmitting antenna. For the ionosphere at frequencies above 1 GHz: c. Refraction changes and gradients cause negligible displacement or dispersion of the high power beam, and do not degrade significantly a ground based pilot beam phase front as seen at the transmitting antenna. d. Absorption and scattering effects are negligible. e. Faraday rotation has only a small effect for a linearly polarized receiving antenna. f. Changes in electron density caused by power densities of 20 mW/ cm2 and above at 2.45 GHz need to be investigated for possible effects on other ionosphere users. g. Possibility of harmonic radiation from the ionosphere (radio frequency interference effects) should be investigated. 12.2.2 DC-RF Conversion For the amplitron concept: a. Cold pure metal cathode (platinum) for long life. b. Pyrolytic graphite radiator for cathode and anode for light, efficient waste heat radiation. c. Samarium cobalt permanent magnet for light weight and low cost.
d. Operating frequency 1. 5 GHz to 3. 0 GHz; 2. 45 GHz preferred. e. Power added 5 kW to 10 kW per tube; 5 kW preferred. f. Efficiency with rf noise and harmonic filters is conservative 85%; improvement to 90% is a realistic goal. g. Cascade configuration because of low gain characteristics. h. Regulation of constant current or constant phase by movable pole piece or impulse magnet technique for high efficiency. i. Open tube construction, possibly with contaminant baffle, for higher reliability, simple thermal control and lower weight. For the klystron concept: j . Hot cathode design used in study, but a cold cathode development desirable for longer life. k. Pyrolytic graphite radiators for efficient heat radiation. 1. Heat pipes needed for transfer of heat to the radiator surface; study and development required. m. Operating frequency can be 1 GHz - 30 GHz; 2. 45 GHz is good. n. Solenoid focusing and power outputs of 48 kW or greater, with output power dividers to the waveguide. o. Collector depression needed for highest efficiency; requires further study to determine practicality of reaching 80%. p. Five-stage design including a second harmonic bunching cavity to reduce noise bandwidth. q. Open tube construction, possibly with contaminant baffle, for higher reliability, simple thermal control and lower weight. r. Parallel configuration.
1.2.2.3 Power Interface and Distribution (Orbital) a. Lateral power flow for minimum weight, b. Recycling switchgear (crowbar) needed for protection against tube arcing. c. Power source and slip rings to be sectored into a minimum of eight independent units to permit a practical switchgear design by limiting maximum short circuit current. d. Cost and weight can be scaled by the square root of input power for system tradeoff studies. e. Magnetic interaction effects are negligible in attitude control system design. For the amplitron: f. Constant current regulation at the converter to maximize power output and minimize phase shift variations with voltage changes. g. Cascade configuration because of low gain characteristic. h. Power source voltage should be 20 kVdc. For the klystron: i. Unregulated operation to maximize power output. j . Parallel operation to minimize failure effects and simplify compensation for phase shift variations with voltage changes. k. Power source voltage should be 40 kVdc. 1.2.2.4 Transmitting Antenna a. The transmitting antenna will be a circular, planar, active phased array on the order of 1 km in diameter. b. Antenna illumination will be truncated Gaussian with tapers of 5 dB to 10 dB, which can be quantized into about five regions of uniform power. c. The antenna will be sectored into subarrays of nominal dimensions 18M x 18M.
d. Subarrays consist of slotted waveguide radiators providing a high overall beam formation and interception efficiency of at least 95 percent for a contiguous rectenna within the main lobe. e. Waveguide wall thickness nominally is 0. 5 mm, but additional investigation may show this can be reduced; width is 12 cm and depth is 6 cm. Cross sections other than rectangular should be included in future detailed investigations. f. Aluminum, graphite epoxy, and graphite polyimide are candidate materials for the slotted array waveguides. g. Aluminum configurations require structural segmenting of the subarrays and variation of operating frequency to compensate for longitudinal thermal distortions. h. Graphite polyimide configurations offer the highest temperature margin with minimal distortion, but all composites must be evaluated for stability and outgassing properties. i. Waveguide manufacture and subarray assembly on orbit is recommended to achieve favorable launch vehicle packaging density. j . Microwave interferometers are recommended for MPTS and SPS attitude control, and for initial and periodic alignment of subarrays using screwjack actuators on each subarray. 1.2.2. 5 Phase Front Control a. Adaptive (retrodirective) approach needed for maximum efficiency. b. Command approach needed for safety and back-up. c. Calibrated transmission line and/or subarray-to-subarray transfer of reference phase data for adaptive phase control mechanization. d. Phase estimation for command mechanization. e. Investigate bit wiggle technique as diagnostic tool. f. Detailed investigations should be conducted to minimize phase control electronics costs, weight, and blockage for each subarray.
12. 2. 6 Mechanical Systems and Flight Operations The following summarizes significant conclusions for the mechanical systems and flight operations. a. Rectangular grid structural arrangement with triangular hat section is recommended for basic members of the transmitting antenna structure. b. Aluminum, graphite epoxy, and graphite polyimide are recommended candidate materials. c. Aluminum materials result in the probable lowest cost and development risk program with thermal limits being their most critical area. d. Composites are attractive for low thermal distortion and high temperature operation (polyimide), but ultra-violet compatibility, and outgassing leading to rf generator contamination need investigation. e. Assuming the Shuttle as the transportation system, low altitude assembly is recommended. The associated transportation and assembly cost for $10. 5M/launch is estimated to be near 600 $/kg. f. Advanced transportation system needed for low cost of large payloads to low earth orbit at relatively low launch packaging densities for the payload. Low cost advanced transportation system required to transport assembled or partially assembled systems from low earth orbit to geosynchronous equatorial orbit. g. Orbital assembly requires remote controlled manipulators. h. Maximum on orbit manufacturing and assembly will be necessary when using the Shuttle transportation or other options with small volume capacity requiring high launch packaging densities to achieve payload performance. Technology issues for mechanical systems are listed and discussed in Section 4 of Section 8 (Mechanical Systems and Flight Operations). This listing identifies areas in technology where more work needs to be done and suggests approaches for accomplishing these tasks. The following simplified list is incorporated here as recommendations for further detailed investigation.
i. Evaluate alternate power transfer and drive devices for the rotary joint. j . Conduct detailed control system analysis. k. Conduct detailed investigations of composite structures and assembly techniques. 1. Investigate tension-brace concepts and compare them with the built-up section approach. m. Evaluate the local crippling stress characteristics of the basic thin material elements of the structure. n. Establish the design environments for launch into low earth orbit, transfer to synchronous orbit as well as those associated with fabrication and assembly. o. Continue investigation of near optimum antenna structural design approaches as environments, geometry, and characteristics with respect to manufacturing, assembly, maintenance, and life are matured. p. Investigate techniques to limit the maximum temperature experienced by the structural elements at the same time achieving high power output for the transmitting antenna. q. Conduct detailed investigation of transient thermal effects. r. Continue detailed investigation of approaches to establish and limit cost of assembly. s. Continue detailed investigation of transport, assembly, positioning, and maintenance operations to define man’s role and to define the equipment needed for effective support. 1.2.2.7 Receiving Antenna a. An array of small independent elements able to collect and rectify incident microwave power is required for low cost and high efficiency. b. A linearly polarized dipole with GaAs Schottky barrier diode is recommended.
c. Development of rectifying antenna elements including diodes for low power density is needed. d. Rectenna collection and conversion efficiency is 84% and a realistic development goal is 90%. e. Support structure is major cost item requiring further in-depth study as types of terrain, soils mechanics, and environments are established. f. Power interface to the user network needs development to reach 92% and greater efficiency. 1.2. 2. 8 Radio Frequency Interference and Allocation For both amplitron and klystron: a. 2.45 GHz is recommended as the operating frequency. b. Harmonic filters at the rf generators are needed to meet commercial service regulations. c. Radio astronomy and similar sensitive receiving systems will need notch filters to protect against MPTS harmonics. d. Multiple SPS installations require further in-depth investigation. For the amplitron: e. A bandpass filter is needed to improve performance relative to radio astronomy noise regulations. f. Noise level with filter added is estimated to exceed radio astronomy isotropic regulations between 2. 3 GHz and 2. 7 GHz, and to exceed radio astronomy 60 dB antenna regulations above 1. 9 GHz. Early development of the amplitron and filters is required to establish noise characteristics. For the klystron: g. Noise level exceeds radio astronomy isotropic regulations only in USA industrial band of 2. 4 GHz to 2. 5 GHz. h. Noise level exceeds radio astronomy 60 dB antenna regulations between 2. 1 GHz and 2. 85 GHz.
1.2.2.9 Risk Assessment The highest risk items in an SPS were identified and ranked according to their relative importance in impacting MPTS equipment design, development and operation. They were ranked as follows: 1. DC-RF Converters and Filters 2. Materials 3. Phase Control Subsystems 4. Waveguide 5. Structure 6. Manufacturing Modules 7- Remote Manipulators 8. Biological 9. Attitude Control 10. Ionosphere 11. Power Transfer 12. Switchgear 13. Radio Frequency Interference and Allocation 14. Support Modules 15. Orbital Assembly Operations 16. Reliability 17. Solar Electric Propulsion System (SEPS) 18. Transportation Operations 19. SPS Flight Mechanics (Stationkeeping) 20. Operations and Maintenance 21. Power Source 22. Heavy Lift Launch Vehicle (HLLV) 23. Socio-Economic Considerations 24. Re-Supply The following are recommended as considerations for risk assessment in developing the system concept, technology development, ground test and flight test.
a. The microwave power transmission system can be configured in such a manner as to not require invention or technology breakthrough, however, continuing efforts should be made to take advantage of applicable breakthroughs as they might be developed over the years. b. There are 24 items having significant technology risk for the MPTS which require agressive development programs before high confidence can be established in their implementation. c. The first five most critical items needing technology development in order of priority are: DC-RF Converters and Filters, Materials, Phase Control Subsystems, Waveguides, and Structures. d. Although Manufacturing Modules and Remote Manipulators are in the critical technology category, significant advancement cannot be undertaken until certain characteristics associated with the technology of the first five items are established. e. General existing developments leading to the understanding of biological effects of low and high microwave power densities are important. In addition, specific investigations must be undertaken which are site dependent to a large extent. These should be undertaken as the development and operational sites are identified. f. Attitude control technologies for the operational system interact with beam efficiency, safety and depending on the approach they may result in dynamic loads and materials that will impact the microwave system and components. For flight test systems operating at low orbital altitudes, high angular rates and accelerations lead to significantly more complex implementation than is required for the operational system. These require further in-depth investigation as flight test objectives and their implementation are progressively and more firmly established. g. Ionospheric effects on the microwave power transmitting system will probably be small. Effects of the system on the ionosphere and on its other users may be significant. The flight test system, in particular the size of the system, may be established by ionospheric effects demonstration test requirements. Further in-depth analysis and tests are required before establishing the requirements firmly.
h. Power transfer at high power levels across flexing and rotary- joints constitute a large scale technology development problem. i . Switchgear including protective elements must be developed for the high power spaceborne application. j 0 When it has been established that power from space can be a significant part of the solution to national and international power needs, detailed radio frequency interference investigations must be undertaken and frequency allocations must be established. Radio astronomy users must be major participants in this activity. k. Support modules and orbital assembly techniques for space flight operations must be developed as the requirements are established in detail. 1. Reliability as well as operations and maintenance considerations to assure long life in space and on the ground will be critical to the operational acceptability of the system. Both mechanically passive and active elements are involved . The maintenance equipment may well be more complex than the functional equipment and a thorough tradeoff of competitive approaches is required. m. Solar electric propulsion stages, transportation operations, heavy lift launch vehicles, SPS flight mechanics and the power source will have characteristics that impact the design of the microwave power transmission system and its equipments. Thorough understanding of these characteristics and perhaps associated constraints must be established as technology development and concept formulation progresses. n. Socio-economic considerations will become most important as the total concept formulation is established. How the considerations of environmental impact (favorable and unfavorable) interact with design, operations and economics are yet to be established in the required detail. o. Re-supply of the space station, particularly of gases and fluids, will impact the system and equipment design. Operations must be established such as to assure an acceptable level of contamination of sensitive components such as the open elements of the many rf generators.
p. Progressive technology risk assessments and rankings must be established as the technology developments mature and the system concept is established. This will play an important part in technology development, ground test and flight test program definition and re-definition as well as in the details of the overall concept. 1.2.3 SYSTEM ANALYSIS AND EVALUATION The system analysis and evaluation section incorporates and reflects the subsystem and technology study results in arriving at the following: a. Capital specific cost decreases as ground power output increases. b. At higher power levels, cost is lowest near 2 GHz. c. Frequency of 2.45 GHz in the industrial band is the recommended choice. d. System configurations having ground bus power levels above 5 GW 2 exceed 20 mW/cm peak ground power density which is beginning to affect the ionosphere and so 5 GW is currently recommended as the maximum for planning purposes. Further in-depth analysis and testing is required to understand these effects more thoroughly and perhaps relax the constraint. e. Overall MPTS efficiency is expected to be about 54%-56% initially with improvement potential to about 63%-67% for amplitron configurations; klystron configurations would be 49%-52% to 56%-59%. f . Amplitrons result in lower cost systems than do klystrons. g. Aluminum results in potentially lower cost but more complex systems than do graphite composites. h. Dominant cost factors for SPS are the power source and transportation. i. As a guide, the power source parameters should not exceed the combination of 350 $/kW with 1. 0 kg/kW or possibly 250 $/kW with 1. 5 kg/kW where the power is as delivered to the transmitting antenna. j . As a guide, transportation and orbital assembly should not exceed 200 $/kg.
k. As a guide, build and deploy cycle for SPS should not exceed 3 years to limit interest charges. 1. For the aluminum-amplitron configuration, near optimum transmitting antenna and receiving antenna sizes are 0. 9 km and 10 km respectively, and transmitting antenna weight is about 6 x 10kg. 1. 2. 4 TECHNOLOGY DEVELOPMENT AND TEST PROGRAMS The recommended critical technology developments in support of both the integrated ground test program and the orbital test program are as proposed in Sections 13 and 14. The integrated ground test program and orbital test programs are based on the level of detail established to date in studies including the current status of technology development. It is recommended that they be re-evaluated in terms of both the objectives and their implementation as further detail study is conducted and technology developments are matured. 1. 2. 4. 1 Technology Development and Ground Test Program a. Initial technology development is needed for dc-rf converter, materials, and phase control subsystem. b. Test program will provide data on controllability and radio frequency interference. c. Transmitting antenna phased array and rectenna are required for integrated ground testing. d. Rough order of magnitude costs are $4M for technology and $23M for the integrated ground test. 1. 2. 4. 2 Technology Development and Orbital Test Program a. Orbital test is needed to develop and demonstrate dc-rf converter startup and operation, zero 'g' assembly and operations, and learning with respect to projected costs and schedule. b. Requirements are satisfied by a geosychronous test satellite and by a series of Shuttle sortie missions that lead to an orbital test facility. c. A low earth orbital test facility can be sized to determine the effects on the upper ionosphere of high microwave power densities.
d/ Modified ground based facilities such as at Arecibo are best suited to determine the effects on the lower ionosphere of high microwave power densities. e. Technology development is needed in not only the ’’critical” areas but in essentially all MPTS areas in order to support a progressive program to demonstrate readiness to proceed to significant scale for a pilot plant or prototype. f. Rough order of magnitude costs are $318M for critical technology development, and $96M for the geosatellite, and to accomplish all identified objectives $3052M for the sorties and orbital test facility. 1. 2. 5 ADDITIONAL STUDIES Recommendations for early further in-depth studies complementing the technology development programs are: a. Analyze transient thermal effects on the transmitting antenna structure, waveguide and electronics as it passes in and out of eclipse to determine impact on controllability and materials selection. b. Analyze power beam ionospheric effects to estimate impact on other users and provide a detail model for phase front control simulation. c. Model closed loop phase front control to better estimate error budget and performance under transient conditions. d. Determine special requirements for multiple ( 100) stations relating to spacing in orbit and on the ground, control, frequency selection and interference. e. Detail alternate uses and intermediate benefits of MPTS and potential impact on its design and development. f . Investigate ways of reducing transportation and assembly costs by a better (higher level of detail) synthesis of launch vehicle, assembly and equipment technologies. 1. 3 REPORT APPROACH AND ORGANIZATION This report presents the final results and the techniques leading to those results that evolved through the course of the study. There is no deliberate attempt to present a chronological record or documentation of the evolution through intermediate steps, except where it might serve a useful tutorial function.
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