Low Earth Orbit Satellite Design (eBook)

The principal author, Dr. George Sebestyen, has an extensive background helping to design 34 different spacecraft. He founded and was President of Defense Systems, Inc. (now part of ATKOrbital). Steve Fujikawa is a spacecraft attitude determination and control system (ADACS) specialist, and the President of Maryland Aerospace Inc.Mr. Alex Chuchra is a spacecraft thermal design specialist with extensive NASA experience.Mr. Nick Galassi is a spacecraft structural analyst with NASA and other private spacecraft programs.The combined expertise of this group has resulted in this brief but comprehensive engineering design handbook to aid the practical LEO spacecraft designer.

Preface 6
Book Overview 16
Contents 7
About the Authors 14
Chapter 1: The Space Environment 19
1.1 The Environment 19
1.1.1 The Earth Magnetic Field 19
1.1.2 Solar Energy 21
1.1.3 Residual Atmosphere 21
1.1.4 Gravity and Gravity Gradient 23
1.2 The Earth and Spacecraft Coordinate System 23
1.3 Other Space Environmental Matters 25
Chapter 2: Satellite Missions 26
2.1 Satellite Orbits 26
2.2 Satellites Today 27
2.3 Satellite Imaging 30
2.3.1 Imaging Payload Fundamentals 32
2.3.2 The Telescope 33
2.3.3 Image Quality 35
2.3.4 Adequacy of the Light Input 36
2.3.5 Image Integration (Exposure) Time 38
2.3.6 Pointing to a Target on the Ground 40
2.3.7 Swath Width 43
2.3.8 Spacecraft Agility and Targeting 45
2.3.9 Imaging Spacecraft Attitude Sensing, Control Requirements 45
2.3.10 Data Quantity and Downlink Data Rate 46
2.3.11 An Imaging Scenario 47
2.4 Satellite Constellations 48
2.4.1 Present Constellations 48
2.4.2 Coverage and Gaps 50
2.4.3 Other Satellite Constellation Considerations 54
Chapter 3: Orbits and Spacecraft-Related Geometry 55
3.1 Acceleration of Gravity, Velocity, Period 55
3.2 Position of Spacecraft as a Function of Time 56
3.3 Spacecraft Elevation, Slant Range, CPA, Ground Range 58
3.4 Pointing to a Target on the Ground From the Spacecraft 63
3.5 Ballistic Coefficient and On-Orbit Life 65
3.6 Computing the Projection of the Sun on Planes on the Spacecraft 67
Chapter 4: Electric Power Subsystem Design 71
4.1 Required Orbit Average Power (OAP) 72
4.2 Battery Capacity and Battery System Design 73
4.2.1 Battery Capacity 73
4.2.2 Battery Choice 75
4.3 Solar Arrays Configuration 76
4.4 Beta Angle Vs. Time 81
4.5 Solar Cells and Cell Laydown 81
4.6 EPS Block Diagram 82
Chapter 5: Spacecraft Communications 85
5.1 Frequency Allocation 85
5.2 Modulation Types 87
5.3 Bit Error Rate (BER) and Forward Error Correction (FEC) 88
5.4 Link Equations 89
5.5 Spacecraft Antennas 92
5.5.1 The N-Turn Helix Antenna 92
5.5.2 Half Wave Quadrifilar Helix Antenna 93
5.5.3 The Turnstile Antenna 94
5.5.4 The Patch Antenna 94
5.5.5 Horn Antennas 95
5.5.6 Dish Antennas 96
5.5.7 Intersatellite Links and Steerable Antennas 97
5.5.8 Phased Arrays 98
5.5.9 Deployable Antennas 98
5.6 Increasing Throughput by Varying Bit Rate or Switching Antennas 98
5.7 Geometrical Constraints on Space-to-Ground Communication 100
5.8 RF Subsystem Block Diagram 101
Chapter 6: Spacecraft Digital Hardware 103
6.1 Computer Architecture 103
6.2 Computer Characteristics and Selection 105
6.3 Spacecraft Computers Available Today 105
Chapter 7: Attitude Determination and Control System (ADACS) 107
7.1 ADACS Performance Requirements Flowdown 107
7.2 Description of the Most Common ADACS Systems 109
7.2.1 Gravity Gradient Stabilization 109
7.2.2 Pitch Bias Momentum Stabilization 111
7.2.3 3-Axis Zero Momentum Stabilization 113
7.2.4 Magnetic Spin Stabilization 114
7.3 The ADACS Components 115
7.3.1 Reaction Wheels and Sizing the Wheels 115
7.3.2 Torque Coils or Rods: Momentum Unloading 116
7.3.3 Star Trackers 118
7.3.4 GPS Receivers 121
7.3.5 Other ADACS Components 122
7.3.6 The ADACS Computer and Algorithms 122
7.3.7 ADACS Modes 123
7.4 Attitude Control System Design Methodologies 124
7.5 Integration and Test 128
7.6 On Orbit Checkout 130
Chapter 8: Spacecraft Software 131
8.1 Functions and Software Architecture 132
8.2 Performing Each Function or Module 134
8.2.1 Initialization of the CDH Processor, Hardware, and Operating System 134
8.2.2 Executing Scheduled Events 134
8.2.3 Stored Command Execution 135
8.2.4 Housekeeping 136
8.2.5 Management of the On-Board Electric Power System 136
8.2.6 Management of the On-Board Thermal Control System 137
8.2.7 Telemetry Data Collection 137
8.2.8 Communications Software 138
8.2.9 Attitude Control System Software 139
8.2.10 Uploadable Software 139
8.2.11 Propulsion Control System Software 140
8.3 Software Development 140
Chapter 9: Spacecraft Structure 142
9.1 Introduction 142
9.2 Requirements Flow-Down and the Structure Design Process 143
9.3 Structure Options, Their Advantages and Disadvantages 145
9.4 Structure Materials and Properties 151
9.5 Fasteners 152
9.6 Factors of Safety 153
9.7 Structural Analyses 154
9.7.1 Structural Analysis Overview 154
9.7.2 Structural Analysis Steps in Detail 155
9.8 Weight Estimate 169
Chapter 10: Deployment Mechanisms 175
10.1 Deployment Devices 176
10.1.1 Hinges 176
10.1.2 Deployable Booms 176
10.1.3 Large Deployable Antennas 178
10.2 Restraint Devices 179
10.2.1 The Explosive Bolt Cutter 179
10.2.2 Electric Burn Wires 180
10.2.3 Solenoid Pin Pullers 181
10.2.4 Paraffin Pin Pushers 182
10.2.5 Motorized Cams or Doors 182
10.2.6 Separation System 182
10.2.7 Dampers 183
10.2.8 Fluid Dampers 183
10.2.9 Magnetic Dampers 184
10.2.10 Constant Speed Governor Dampers 184
10.3 Choosing the Right Mechanism 184
10.4 Testing Deployables 185
Chapter 11: Propulsion 186
11.1 The Basics 186
11.2 Propulsion Systems 189
11.2.1 Cold Gas Propulsion System 189
11.2.2 Hydrazine Propulsion System 191
11.2.3 Other Propulsion Systems 192
11.3 Propulsion System Hardware 192
11.4 Propulsion Maneuvers 194
11.4.1 Maneuvers for Spacecraft in a Constellation, Maintaining and Getting to Station 194
11.4.1.1 Station Keeping 194
11.4.1.2 Getting on Station 196
11.4.1.3 Thrust Duration 198
11.4.1.4 Hohmann Transfer Orbit Maneuver 198
11.5 Other Propulsion Requirements 198
Chapter 12: Thermal Design 200
12.1 The Thermal Environment 201
12.2 Heat Absorption 204
12.3 Heat Rejection 205
12.4 Heat Generated by the Spacecraft Electronics 205
12.5 Tools Available for Altering Spacecraft Thermal Performance 206
12.5.1 The Impact of Surface Finishes 206
12.5.2 Thermal Conduction 207
12.5.3 Conducting Heat across Screwed Plates or Bolt Boundaries 208
12.5.4 Heat Pipes 208
12.5.5 Louvers 209
12.5.6 Heaters 209
12.6 Constructing a Thermal Model of the Spacecraft 210
12.7 A Point Design Example 210
12.8 Thermal and Thermal Vacuum Testing 212
12.9 Model Correlation to Conform to Thermal Test Data 213
12.10 Final Flight Temperature Predictions 213
Chapter 13: Radiation Hardening, Reliability and Redundancy 215
13.1 Radiation Hardening 215
13.1.1 Total Dose 215
13.2 Reliability 218
13.3 Redundancy 220
Chapter 14: Integration and Test 221
14.1 Component Level Testing 221
14.1.1 The “Flat-Sat” 223
14.2 Spacecraft Level Tests 223
14.3 Environmental Testing 224
14.3.1 Vibration Tests 224
14.3.2 Thermal Test 230
14.3.3 Bakeout 231
14.3.4 Thermal Vacuum Test 232
Chapter 15: Launch Vehicles and Payload Interfaces 234
15.1 Present Launch Vehicles 234
15.2 Launch Vehicle Secondary Payload Interfaces 236
15.3 Secondary Payload Environment 240
15.3.1 Vibration Levels 240
15.3.2 Mass Properties 242
15.3.3 Insertion, Separation and Recontact 242
15.3.4 RF Environment 242
15.3.5 Acoustic Environment 243
15.3.6 Shock Environment 243
15.3.7 Additional Spacecraft Environmental and Other Factors 244
15.4 Analyses, Documentation and Other Factors 244
Chapter 16: Ground Stations and Ground Support Equipment 246
16.1 Ground Stations 246
16.2 Ground Support Equipment 249
16.3 Ground Station Manual and Operator Training 249
16.4 Other Ground Station Matters 250
Chapter 17: Spacecraft Operations 251
17.1 Ground Station Functions for Spacecraft/Payload Operation 251
17.1.1 The Map and Access Time Interval Display 252
17.1.2 Telemetry Monitoring 253
17.1.3 Spacecraft Command Generation 255
17.1.4 Anomaly Discovery and Resolution 255
17.1.5 Archiving TTM and Data 256
17.2 Data and Data Rate Limitations 256
17.3 Other Ground Station Operations 256
17.3.1 Post Launch and Checkout 256
17.3.2 Test Plans and Reports 257
17.3.3 Manning the Ground Station 257
17.3.4 Cost of Spacecraft Operations 257
17.3.5 Operator Training and the Spacecraft Simulator 258
17.3.6 Mission Life Termination 258
17.3.7 Ground Station Development Schedule 258
Chapter 18: Low Cost Design and Development 259
18.1 Approach to Low Cost 259
18.2 The Contract Should Focuses on Functional Rather than Technical Specifications 260
18.3 Experienced, Small Project Team 260
18.4 Vertical Integration 261
18.5 Short Schedules and Concurrency of Development and Manufacturing 261
18.6 Make Major Technical and Cost Trade-Offs Rapidly and Decisively 262
18.7 Production Coordinator to Expedite Manufacturing 262
18.8 Do Not Try to Save Money in Testing 263
18.9 Holding Program Budget Responsibility Tightly 263
18.10 Conclusion 264
Chapter 19: Systems Engineering and Program Management 265
19.1 Introduction 265
19.2 Top Level Requirements 265
19.3 Requirements Flowdown 266
19.4 Multiple Approaches 267
19.5 Trade Studies 267
19.6 Selection of a Point Design 268
19.7 Concept of Operations 268
19.8 Preliminary Design Review (PDR) 268
19.9 Interface Control Documents (ICDs) 269
19.10 Detail Design 269
19.11 Critical Design Review (CDR) 269
19.12 System and Mission Simulations 270
19.13 Test Bed and “Flatsat” 270
19.14 Statement of Work 270
19.15 The Work Breakdown Structure 270
19.16 Cost 283
19.17 Scheduling 284
19.18 Critical Path 284
19.19 Schedule Slack 285
19.20 Earned Cost 285
19.21 Cost to Complete Calculation 285
19.22 Requirements Creep and Engineering Change Proposal. 286
19.23 Reallocating Budgets, Cost Management 286
19.24 Documentation 286
19.25 Test Plans and Test Reports 287
Chapter 20: A Spacecraft Design Example 288
20.1 The Spacecraft Mission Requirements 288
20.2 Derived Technical Requirements 288
20.3 Preliminary Design 291
20.4 Design Steps 292
Chapter 21: Downloadable Spreadsheets 293
Appendix 1: Tensile Strengths of SS Small Screws 295
Appendix 2: NASA Structural Design Documents Accessible at http://standards.nasa.gov 296
Appendix 3: Temperature Coefficients of Materials 297
Appendix 4: Hohmann Transfer Orbit 299
Appendix 5: Elevation and Azimuth from Spacecraft to Ground Target for Various CPA Distances 301
Appendix 6: Beta as a Function of Time (Date) 303
Appendix 7: Eclipse Duration 304
Glossary 306
References 313
Index 316