Systems Definition Space Based Power Conversion

Cover	1
Title Page	2
Table of Contents	4
1.0 Introduction and Background	10
1.1 Introduction	10
1.1.1 The Study Effort	10
1.1.2 Contributers	10
1.1.3 Related Efforts	10
1.2 Background	10
1.2.1 The Space Power Concept	10
1.2.2 Auxiliary Systems	11
1.2.3 Energy Overview and the SPS	13
2.0 Programmatics	16
2.1 Dreivation of Satellite Energy System Program Definition	16
2.2 Requirements	18
3.0 Alternative Power Generation Approaches	20
3.1 Concepts Investigated	20
3.2 Solar Thermionic, Direct Radaition Coold (Concpet 1)	20
3.3 Solar Thermionic, Liquid Cooled (Concept 2)	20
3.4 Solar Closed Brayton Cycle (Concept 3)	21
3.5 Solar Thermionic/Brayton Cycle Cascade (Concept 4)	21
3.6 Silicon Photovoltaic (Concept 5)	21
3.7 Gallium Arsenide Photovoltaic (Concept 6)	22
3.8 Nuclear Thermionic (Concept 7)	22
3.9 Nuclear Closed Brayton Cycle (Concept 8)	23
3.10 Power Trnsfer System (Concept 9)	23
3.11 Emphasized Concepts	23
4.0 Subsystems	24
4.1 Materials	24
4.2 Solar Concentrators	25
4.2.1 High Concentration Ratio (Over 1000)	25
4.2.2 Low Concentration Ratio (Under 10)	27
4.3 Structure	27
4.4 Cavity Solar Absorber	28
4.5 Concentrator / Absorber Optimization	29
4.6 Thermionics	29
4.6.1 Background	29
4.6.2 Converter Characteristics	30
4.6.3 Radiator	32
4.6.4 Busbar Design	35
4.6.5 Weight Analysis	37
4.6.6 Conclusions	37
4.7 Solar Cells	38
4.7.1 Requirements	38
4.7.2 Cell Performance Prediction	39
4.7.2.1 Efficiency	39
4.7.2.3 Radiation	41
4.8 Turbomachines and Associted Heat Exchangers	41
4.8.1 Brayton Cycle	41
4.8.2 Brayton Cycle Design Equations	42
4.8.3 Brayton System Parametrics	43
4.8.3.1 Working Fluid Selection	43
4.8.3.2 Parametrics	43
4.9 Nuclear Reactors	45
4.9.1 Necessity for Breeder as SPS Reactor	45
4.9.2 Breeder Reactor Program Concept	45
4.9.2.1 Example Program Concept (Molten Salt Breeder Reactor - MSBR)	46
4.9.3 Reactor Selection	46
References	50
4.10 Radiators	50
4.10.1 Meteoroid Environment	50
4.10.2 Tube/Fin Radiator	52
4.10.2.1 Panel Design Analysis and Modeling	52
4.10.3 Radiator Configuration	56
4.10.4 Radiator System Optimization	59
4.10.5 Occultation Effects	61
4.10.6 Heat Pipe/Fin Radiator	62
4.10.6.1 Panel Design Analysis and Modeling	62
4.10.6.2 Heat Pipe Concept	62
4.10.6.3 Heat Pipe Working Fluids	63
4.10.6.4 Heat Pipe Performance	64
4.10.6.5 Candidate Materials: Heat Pipe/Fin Radiator	64
4.10.6.6 Heat Pipe Radiator Configuration	64
4.10.6.7 Occultation Effects: Heat Pipe/Fin Radiator	65
4.10.6.8 Mass Optimization: Heat Pipe/Fin Radiation For Brayton Systems	65
4.10.7 Radiators For Solar Cells	68
References	69
4.11 Power Distribution	69
4 11.1 The Problem	69
4.11.2 Conductors	69
4.11.3 AC Versus DC Trade	70
5.0 System Optimization and Configuration Description	72
5.1 System Optimization	72
5.1.1 Approach	72
5.1.2 Iteration	72
5.1.3 Alternative Systems	72
5.2 Solar Direct Radiation Cooled Thermionic (Concept 1)	72
5.3 Solar Liquid Cooled Thermionic (Concept 2)	75
5.4 Solar Closed Cycle Brayton (Concept 3)	77
5.5 Thermionic Brayton Cascade (Concept 4)	79
5.6 Solar Silicon Photovoltaic (Concept 5)	79
5.7 Solar Gallium Arsenide Photovoltaic (Concept 6)	82
5.8 Nuclear Thermionic (Concept 7)	83
5.9 Nuclear Closed Brayton Cycle (Concept 8)	84
5.10 Solar Power Transfer (Concept 9)	86
6.0 Cost	88
6.1 Baselined Auxiliary Systems	88
7.0 Comparison of Concepts	94
7.1 Approach	94
7.2 Configuration and Mass Comparison	94
7.3 Environmental Impact	95
7.3.1 Exhaust Emissions	95
7.3.2 Energy Balance	95
7.4 Overview	97
References	97
8.0 SPS Development	98
8.1 Developmental Goals	98
8.2 Recommended Development Plan	98
8.3 Expanded Analysis and Ground Experiments (Part 1)	98
8.4 Shuttle Based Demonstrations (Part 2)	98
8.5 Precursor System Development and Demonstration (Part 3)	99
8.6 Operational System Development & Demonstration (Part 4)	99
List of Illustrations	6
Fig. 1-1. Satellite Power Stations	10
Fig. 1-2. Receiving Antenna	11
Fig. 1-3. Solar Turbomachine Power Satellite Option	12
Fig. 1-4. "Space Freighter" Lands	12
Fig. 1-5. Orbital Construction Facility	13
Fig. 2-1. Electricity/Labor Cost Ratio	16
Fig. 2-2. Growth in U.S. Installed Capacity	16
Fig. 2-3. U.S. Capacity Margin	17
Fig. 2-4. Annual Additions to Installed Capacity	18
Fig. 3-1. Solar Thermionic Direct Radiation Cooled System	21
Fig. 3-2. Solar Thermionic, Liquid-Cooled System	21
Fig. 3-3. Solar Brayton Cycle System	21
Fig. 3-4. Cascaded Solar Thermionic/Brayton Cycle System	21
Fig. 3-5. Silicon Photovoltaic System	22
Fig. 3-6. Gallium Arsenide Photovoltaic System	22
Fig. 3-7. Nuclear Thermionic System	22
Fig. 3-8. Nuclear Thermionic System	23
Fig. 4-1. Material Selection Approach	24
Fig. 4-2. Materia! Technology Trend	25
Fig. 4-3. Faceted Concentrator (Individual Steerable Facets Direct Solar Impages Onto Solar Array or Into Cavity Absorber)	25
Fig. 4-4. Typical Reflective Facet	25
Fig. 4-5. Variables in Solar Concentrator Analysis	25
Fig. 4-6. Solar Concentrator Performance	26
Fig. 4-7. Influences on Concentrator Efficiency (Solar Off-Axis Locations and Light Spread From Reflector Facets)	26
Fig. 4-8. Reflectivity Performance of Plastic Films	26
Fig. 4-9. Compound Parabolic Concentrator	27
Fig. 4-10. Derivation of Ideal Beam Dimensions	28
Fig 4-11. Typical Power Satellite Conducting Primary Structure (Example, Size Varies)	28
Fig. 4-12. Cavity Solar Absorber	28
Fig. 4-13. Model for Concentrator/Absorber Optimization	29
Fig. 4-14. Characteristics of Mass-Optimized Concentrator/Absorber Combinations	29
Fig. 4-15. Thermionic Efficiency Versus Emitter Temperature	30
Fig. 4-16. Molybdenum Work Function Plot	30
Fig. 4-17. Thermionic Diode Characteristics as a Function of Emitter Temperature for a Molybdenum Emitter and a Nickel (Molybdenum Coated) Collector	31
Fig. 4-18. Increase in Efficiency and Output Voltage with Decreasing Plasma Drop for Constant I of 1290 A	31
Fig. 4-19. Heat Rejection as a Function of Converter Efficiency (Modified From Ref. 8)	32
Fig. 4-20. Thermal Conductivity Data	33
Fig. 4-21. SPS Thermionic Converter Design	33
Fig. 4-22. Isometric Cutaway of SPS Thermionic Converter	33
Fig. 4-23 Multifoil Thermal Insulation	34
Fig. 4-24. Thermal Conductivity Comparison	35
Fig. 4-25. Multifoil Thermal Insulation Temperature Profile for Brush-Coated ThO2 on Tungsten	35
Fig. 4-26. Electrical Resistivity of Metals	36
Fig. 4-27 SPS Electrical Pane! Design	36
Fig. 4-28. Solar Cell Performance Predictions	39
Fig. 4-29. Fundamental Limitations May Enforce Performance Plateau	39
Fig. 4-32. Closed Brayton Cycle Schematic	41
Fig 4-33. Cycle State Diagram	42
Fig. 4-34. Xenon-Helium Mixture Results in Lighter and Smaller Turbomachine	43
Fig. 4-35. Specific Mass Variation With Temperature (Example Influence Coefficient)	43
Fig. 4-36. United States Energy Resources	45
Fig. 4-37. Breeder Reactor Program Concept	46
Fig. 4-38. Particle Bed Reactor Concept	47
Fig. 4-39. Sporadic and Stream Average TotalMeteroid Environment (Omnidirectional)	51
Fig. 4-40. Meteoroid Motion	51
Fig. 4-41. Resultant Interaction With Object in Earth's Orbit	51
Fig. 4-42. SPS Radiators Can be Preferentially Oriented	51
Fig. 4-43. Flux Seen by Radiator	51
Fig. 4-44. Meteroid Shielding Philosophy	53
Fig. 4-45. Radiator Configurations	53
Fig. 4-46. Minimum Weight Two-Sheet Aluminum Barrier	53
Fig. 4-47. Beta Program Solves Thermal Network Modeling of Radiator Structure	53
Fig. 4-48. Radiator Thermal Mode	54
Fig. 4-49. Baseline Radiators	54
Fig. 4-50. Optimum Radiator Panel Dimensions — Low Temperature Helium Radiator	54
Fig. 4-51. Radiator Heat Rejection Helium Fluid	55
Fig. 4-52. Radiator Pane! Mass Helium Fluid	55
Fig. 4-53. Radiator Mass Distribution (Helium)	55
Fig. 4-54. Use of Liquid Radiator With Brayton Cycle Requires Additional Heat Exchanger	56
Fig. 4-55. Optimum Radiator Panel Dimensions Low Temperature NaK Radiator	56
Fig. 4-56. Radiator Panel Arrangement — Concept No. 1	57
Fig. 4-57. Radiator Panel Arrangement — Concept No. 2	57
Fig. 4-58. Radiator Panel Arrangement — Concept No. 3	57
Fig 4-59. Radiator Configuration Concept	57
Fig. 4-60. Original and New Radiator Configurations	58
Fig. 4-61. Original Panel Arrangement Showing Typical Feeder Path to Center-Fed Headers	58
Fig. 4-62. "Halo" Radiator Configuration	58
Fig. 4-63. Radiator System, Solar Thermionic SPS	58
Fig. 4-64. Liquid Metal (NaK) Loop	59
Fig. 4-65. Stress Versus Creep — Haynes 188	59
Fig. 4-66. Header or Feeder Volume Versus Creep	59
Fig. 4-67. Radiator System Modeling	60
Fig. 4-68. Radiator	61
Fig. 4-69. Effect of Significant Radiator Parameters on Total Mass	61
Fig. 4-70. Effect of Power Level on Radiator System Specific Mass (Optimum LT)	61
Fig. 4-71. Radiator Fluid Temperature During Occulation	62
Fig. 4-72. Radiator Welds Performed in Orbit	62
Fig. 4-73. Heat Pipe Concept	62
Fig. 4-74. Heat Pipe Options	63
Fig. 4-75. Heat Pipe Fluids: Latent Heat of Vaporization	63
Fig. 4-76. Heat Pipe Fluids: Surface Tension	63
Fig. 4-77. Heat Pipe Fluids: Absolute Viscosity	63
Fig. 4-78. Heat Pipe Fluids: Vapor Pressure	63
Fig. 4-79. Heat Pipe Fluids: Heat Transport Capability and Temperature Range	64
Fig. 4-80. Heat Rejection Area and Capability is Limited by Heat Pipe Length Unless Pumped Manifolds are Used	65
Fig. 4-81. Radiator: Pumped Manifolds/Heat Pipe/ Fin	65
Fig. 4-82. Heat Pipe/Fin Radiator Panel Concept	65
Fig. 4-83. Occultation Effects: Heat Pipe/Fin Radiatormasses for fluid inlet temperatures	66
Fig. 4-84. Radiator Mass Comparison: Heat Pipe (Constant Section Manifolds) and Tube/ Fin (Tapered Manifolds)	67
Fig. 4-85. Effect of Manifold Taper on Radiator Mass	67
Fig. 4-86. Heat Pipe Radiator With Tapered Manifolds	67
Fig. 4-87. Radiator Mass Comparison: Heat Pipe and Tube/Fin (Both With Tapered Manifolds)	68
Fig. 4-88. Radiators for Solar Cells	68
Fig. 4-89. Microwave Power Transmission Efficiency Chain	69
Fig. 4-90. Moving Large D.C. Currents	70
Fig. 4-91. A.C. Versus D.C. Distribution	70
Fig. 5-1. Diode Panel (Heat Pipe Side)	73
Fig 5.2. Power Converter Panel (For Diode Panels)	73
Fig. 5-3. Busbar Circuit	73
Fig. 5-4. Panel Masses	74
Fig. 5-5. Cavity Absorber is Formed From Panels	74
Fig. 5-6. Thermionic SPS Module	74
Fig. 5-7. Thermionic SPS Configuration	74
Fig. 5-8. Reduction of Interelectrode Busbar Mass	75
Fig. 5-9. Diode/Radiator Interface	75
Fig. 5-10. Radiator Concept	76
Fig. 5-11. Liquid Cooled Thermionics ISAIAH Model	76
Fig. 5-12. Brayton Module	77
Fig. 5-13. Module Quantity Optimization	78
Fig. 5-14. Brayton SPS Configuration	78
Fig. 5-15. Optimization Model, Photovoltaic SPS	80
Fig. 5-16. Derivation at Optimum Concentration Ratios	80
Fig. 5-17. Cost and Mass Minima are not Coincident	81
Fig. 5-18. Silicon SPS Efficiency Chain	81
Fig. 5-19. Approaches to SPS Maintenance	81
Fig. 5-20. Silicon SPS End-of-Life Configuration	81
Fig. 5-21. Main Frame, Silicon SPS	81
Fig. 5-22. Silicon SPS Power Module	82
Figure 5-23. Photovoltaic Array	82
Fig. 5-24. Compound Parabolic Concentrators	83
Fig. 5-25. GaAs SPS Configuration	83
Fig. 5-26. MSBR Nuclear Thermionic System	83
Fig. 5-27. Nuclear Brayton Cycle SPS	84
Fig. 5-28. Reactor Module	84
Fig. 5-29. RPBR Approaches	85
Fig. 5-30. Simplified RPBR Configuration	85
Fig. 5-31. Cone Angle of Solar Image is Equal to the Cone Angle to the Sun	86
Fig. 5-32. Mirror Attitude Changes Around Orbit	86
Fig. 5-33. Combined Mirror and Solar Output	86
Fig. 5-34. Shows the Low Latitude Target Area for the Power Relay System	87
Fig. 6-1. Heavy Lift Launch Vehicle	88
Fig. 6-2. Chemical OTV Maintenance Freighter	88
Fig. 6-3. Self Power Requirements	88
Fig. 6-4. Thermal Engine SPS Assembly Stat	88
Fig. 6-5. Thermionic SPS Assembly Station	88
Fig. 6-6. MSBR (Nuclear) SPS Assembly Station	89
Fig. 6-7. Photovoltaic SPS Main Frame Assembly Station	89
Fig. 6-8. Photovoltaic SPS Module Assembly Station	89
Fig. 6-9. SPS Transmitter Assembly Station	89
Fig. 6-10. SPS Geosynchronous Orbit Assembly Station	89
Fig. 6-11. Silicon Photovoltaic SPS Program	89
Fig. 6-12. Gallium Arsenide Photovoltaic SPS Program	90
Fig. 6-13. Brayton Thermal Engine SPS Program	90
Fig. 6-14. Thermionic SPS Program	91
Fig. 6-15. SPS Program Costs	93
Fig. 6-16. Required Busbar Costs	93
Fig. 7-1. Concepts to Same Scale (10 GW Ground Output)	94
Fig. 7-2. Mass Comparison of Concepts	94
Fig. 7-3. System Life Cycle Costs	94
Fig. 7-4. Required Busbar Charges	95

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