Design, assembly, integration, and testing of a power processing unit for a cylindrical Hall thruster, the NORSAT-2 flatsat, and the Vector Gravimeter for Asteroids instrument computer by Adam Ladislav Svatos A thesis submitted in conformity with the requirements for the degree of Master of Applied Science University of Toronto Institute for Aerospace Studies University of Toronto c Copyright 2017 by Adam Ladislav Svatos Abstract Design, assembly, integration, and testing of a power processing unit for a cylindrical Hall thruster, the NORSAT-2 flatsat, and the Vector Gravimeter for Asteroids instrument computer Adam Ladislav Svatos Master of Applied Science Graduate Department of University of Toronto Institute for Aerospace Studies University of Toronto 2017 This thesis describes the author's contributions to three separate projects. The bus of the NORSAT-2 satellite was developed by the Space Flight Laboratory (SFL) for the Norwegian Space Centre (NSC) and Space Norway. The author's contributions to the mission were performing unit tests for the components of all the spacecraft subsystems as well as designing and assembling the flatsat from flight spares. Gedex's Vector Gravimeter for Asteroids (VEGA) is an accelerometer for spacecraft. The author's contributions to this payload were modifying the instrument computer board schematic, designing the printed circuit board, developing and applying test software, and performing thermal acceptance testing of two instrument computer boards. The SFL's cylindrical Hall effect thruster combines the cylindrical configuration for a Hall thruster and uses permanent magnets to achieve miniaturization and low power consumption, respectively. The author's contributions were to design, build, and test an engineering model power processing unit. ii Acknowledgements I would like to extend my thanks to Dr. Robert Zee, Director of the Space Flight Laboratory (SFL) at the University of Toronto, for bringing me into that organization and for allowing me to flourish as an independent researcher. Students at the SFL carry exceptional responsibility in developing space hardware, and I am grateful for the opportunity to carry on in that tradition. Also, I would like to thank Bryan Johnston-Lemke, Payam Mehradnia, Rodrigo Cornejo, Jakob Lifshits, and Dr. Simon Grocott for advising me on the design of the Cylindrical Hall thruster power system. I would be remiss if I did not make special mention of the SFL class of 2017: Damon, Mehdi, Mike, Rob, and Simon. Our year-long project of designing the impossible spacecraft is over, but our bonds still remain. I am proud of what we accomplished and maybe someday we will see our design take shape and explore an asteroid. It was an honour to work with all of you and I look forward to crossing paths again. Throughout my time at the SFL, my family has supported me unwaveringly. I would like to thank my parents, my brother Nicholas, and my grandparents. I would also like to thank Alison, for her kindness, for her love, and for her willingness to listen to and to discuss my research challenges. This work was financially supported by the Ontario Graduate Scholarship. iii Contents Acknowledgements iii Contents iv List of Tables vii List of Figures viii 1 Introduction 1 1.1 NORSAT-2 . .1 1.2 Vector Gravimeter for Asteroids . .2 1.3 Electric propulsion for microsatellites . .2 2 NORSAT-2 FlatSat design, manufacturing, and unit testing 4 2.1 Introduction . .4 2.2 Structure . .4 2.3 Power ...............................................5 2.4 Command and Data Handling . .7 2.5 Very High Frequency Data Exchange payload . .7 2.6 Cameras . 13 2.7 High speed radio receiver . 14 2.8 Command radio downlink . 14 2.9 Command uplink . 15 2.10 Attitude determination and control system . 16 2.11 Global positioning system . 16 3 Design and layout of the VEGA instrument on-board computer 18 3.1 Introduction . 18 3.1.1 Electronics architecture . 18 3.1.2 Data architecture . 19 3.2 Objective . 20 3.3 Requirements . 20 3.4 Methodology . 22 3.5 Results . 23 iv 4 Unit testing of the VEGA instrument on-board computer 24 4.1 Introduction . 24 4.2 Objective . 24 4.3 Requirements . 24 4.4 Software development . 25 4.4.1 I2C . 25 4.4.2 SPI . 26 4.4.3 GPIO . 26 4.5 Thermal acceptance . 27 4.6 Results . 28 5 Power processing unit for a cylindrical Hall thruster 29 5.1 Introduction . 29 5.1.1 Abbreviations . 29 5.1.2 Motivation . 29 5.1.3 Mechanism of operation of an annular Hall thruster . 30 5.1.4 Development of cylindrical Hall thrusters . 31 5.1.5 Comparison between cylindrical and annular Hall thrusters . 32 5.1.6 Plasmadynamics of a Hall thruster modelled using the predator-prey model . 33 5.1.7 Insights from the model . 35 5.1.8 Realizing performance improvements in a Hall thruster . 36 5.2 Requirements . 37 5.2.1 Difference between an engineering model and a flight model . 37 5.2.2 Customer requirements . 38 5.2.3 Functional requirements . 38 5.3 Methodology . 39 5.3.1 Electrical . 39 5.3.2 Derating parts for space . 40 5.3.3 Thermal . 40 5.4 Electrical design . 42 5.4.1 Architecture . 42 5.4.2 Selecting an isolated switching-mode power supply topology . 43 5.4.3 Current- and voltage-fed push-pull converters . 45 5.4.4 Boost chopper . 50 5.4.5 Circuit simulation using numerical methods . 50 5.4.6 Supporting components . 54 5.4.7 Effect of layout on electromagnetic interference . 55 5.4.8 Printed circuit board layers . 56 5.4.9 Power stage component layout . 56 5.5 Controller design . 57 5.6 Thermal design . 57 5.6.1 Evaluating the junction temperature of critical components . 57 5.6.2 Evaluating the steady-state temperature of critical traces on the push-pull converter 58 5.6.3 Effect of layout on component thermal stress . 59 v 5.7 Results . 60 5.7.1 Power . 61 5.7.2 Control and data . 63 5.7.3 Thermal . 63 5.8 Testing . 63 5.8.1 Anode driving . 63 5.8.2 Load bank . 64 5.9 Future Work . 65 6 Hall thruster power processing unit control 66 6.1 Introduction . 66 6.1.1 Overview of basic control theory . 66 6.1.2 Overview of feedback loop stability . 68 6.2 Requirements . 70 6.3 Design Methodology . 71 6.3.1 Controlling the current-fed push-pull converter . 71 6.3.2 Boost chopper . 71 6.3.3 Low voltage rails . ..