THERMAL ANALYSIS AND DESIGN OF THE PHOTOVOLTAIC INVESTIGATION ON LUNAR SURFACE (PILS) PAYLOAD GREETA JOSE THAIKATTIL Bachelor of Science in Mechanical Engineering University of Dayton December 2016 submitted in partial fulfillment of requirements for the degree MASTER OF SCIENCE IN MECHANICAL ENGINEERING at the CLEVELAND STATE UNIVERSITY DECEMBER 2020 We hereby approve this thesis for GREETA JOSE THAIKATTIL Candidate for the Master of Science in Mechanical Engineering degree for the Department of Mechanical Engineering And CLEVELAND STATE UNIVERSITY’S College of Graduate Studies by _______________________________________________________ Thesis Committee Chairman, Dr. Maryam Younessi Sinaki _______________________ Department/Date _______________________________________________________ Thesis Committee Member, Dr. Tushar Borkar _______________________ Department/Date _______________________________________________________ Thesis Committee Member, Dr. Brian Motil _______________________ Department/Date Student’s Date of Defense: December 15, 2020 ACKNOWLEDGEMENTS I was supported through every step of my journey at Cleveland State by many incredible people. Firstly, I would like to thank Dr. Maryam Younessi for her guidance in not only my thesis, but also in pushing me to think beyond my current work and to my future. I would also like to thank the committee members, Dr. Brian Motil and Dr. Tushar Borkar, for their time and support. I also want to thank the Project Investigators of PILS, Tim Peshek and Jeremiah McNatt, for letting me use PILS as a platform to combine my education and work at NASA Glenn. I am also incredibly grateful to my mentors, Susan Jansen and Malcolm Robbie, who have always worked to provide me an environment to grow in all aspects of my career. And of course, thank you to my colleagues and supervisors at Vantage Partners and HX5 for accommodating my schedule and needs these past three years- even letting me leave work in the middle of the day on many occasions to attend classes. Finally, I would like to thank my parents, fiancé, and siblings for their immeasurable support. THERMAL ANALYSIS AND DESIGN OF THE PHOTOVOLTAIC INVESTIGATION ON LUNAR SURFACE (PILS) PAYLOAD GREETA JOSE THAIKATTIL ABSTRACT Solar power has been identified as key technology required for extensive exploration of the moon and space. However, solar cell design so far has been based on earth and earth orbit environments, which is vastly different from the lunar surface. The Photovoltaic Investigation on the Lunar Surface (PILS) is a small payload carrying a set of solar cells of the latest technology to the moon in order to test the cells’ feasibility and viability in the lunar environment. The objective of this thesis is to analyze the PILS payload design in its mission environments and optimize the thermal design to ensure that the critical components remain within their survival limits throughout transit and within operational temperature limits during lunar surface operations. The thermal analysis software Thermal Desktop was used to create a thermal model of the PILS payload which was analyzed in transit, three lunar orbits, descent and lunar surface operations in order to optimize the payload’s active and thermal design. This thesis discusses the thermal model in detail which includes the geometry, conduction through the assembly, environmental conditions, and orbital definitions. The thermal model was then analyzed to investigate the temperature change in each component in all environments with the critical electronic components. The active thermal protection, heaters, were optimized for a “0 sink” case where the PILS payload was assumed to be in deep space – with no view to the sun or the moon for solar, albedo or planetshine heating. The passive thermal protection design was optimized for the hottest scenario in this iv mission: lunar noon during surface operations on the moon. Finally, the effects on the PILS payload from landing off-nominally on the lunar surface was also analyzed. The results show that the overall thermal design is successful in keeping all critical components within their operational temperature range throughout the entire mission. v TABLE OF CONTENTS Page ABSTRACT……………………………………………………………………… iv LIST OF TABLES……………………………………………………………….. viii LIST OF FIGURES…………………………………………………………….... ix NOMENCLATURE……………………………………………………………... xi ABBREVIATIONS……………………………………………………………… xii CHAPTER I. INTRODUCTION……………………………………………………….. 1 1.1 Overview……………………………………………………..….. 1 1.2 Literature Review………………………………………………... 6 1.3 Thesis Objective…………………………………………………. 10 II. MODEL DEVELOPMENT……………………………………………… 11 2.1 Fundamental Equations…………………………………………... 11 2.2 Properties………………………………………………………… 14 III. MODEL…………………………………………………………………. 19 3.1 Thermal Model Assumptions…………………………………….. 19 3.2 Thermal Desktop Model…………………………………………. 21 3.2.1 Graphical Model…………………………………………. 21 3.2.2 Thermal Protection………………………………………. 23 3.3 Orbital Definition………………………………………………… 25 3.4 Sensitivity Analysis on Uncertain Properties……………………. 29 3.4.1 Contactors for Adhesives………………………………… 30 3.4.2 Material for Internal PCBs………………………………. 31 3.4.3 Contact Conductivity…………………………………….. 32 3.5 Cases Analysis…………………………………………………… 35 3.5.1 Zero Sink Case…………………………………………… 35 3.5.2 Nominal Orbits Hot Case………………………………… 35 vi 3.5.3 Off-Nominal Landing on Lunar Surface Case…………… 36 IV. RESULTS………………………………………………………………... 38 4.1 General Temperature Trends for Nominal Orbits……………….. 38 4.1.1 Transit……………………………………………………. 39 4.1.2 Lunar Orbit 1…………………………………………….. 40 4.1.3 Lunar Orbit 2……………………………………………... 41 4.1.4 Lunar Orbit 3……………………………………………... 42 4.1.5 Descent…………………………………………………… 43 4.1.6 Lunar Surface…………………………………………….. 44 4.1.7 Summary…………………………………………………. 45 4.2 Heater Sizing…………………………………………………….. 50 4.3 Effects of Landing Accuracy on Lunar Surface…………………. 52 4.4 Testing…………………………………………………………… 55 V. CONCLUSIONS………………………………………………………… 56 REFERENCES………………………………………………………………….. 57 APPENDICES A. Spectrolab XTE-SF Datasheet…………………………………………….. 59 B. Spectrolab XTJ Datasheet………………………………………………… 60 C. Dunmore Aluminum Tape Datasheet……………………………………... 62 vii LIST OF TABLES Table Page 2-1: Summary of Solar and Albedo Heating Values .........................................................12 2-2: Summary of Optical Properties ..................................................................................14 2-3: Thermophysical Properties .........................................................................................16 2-4: Summary of Thermophysical Properties of Adhesives ..............................................18 3-1: Orbital Definition .......................................................................................................26 3-2: Printed Circuit Board Materials..................................................................................31 4-1: Temperature Results for Nominal Orbits Without Heat Generated by Internal PCBs ...................................................................................................................................48 4-2: Temperature Results for Nominal Orbits With the Heat Generated by Internal PCBs. ...................................................................................................................................49 4-3: Heater Sizing for Zero Sink Case ...............................................................................50 4-4: Lunar Surface with 4.75 W on Internal PCBs, Initialized with No Heat during Descent ......................................................................................................................51 viii LIST OF FIGURES Figure Page 1-1: Sheet and Solar Cells Assembly .................................................................................. 3 1-2: Overall PILS Assembly ............................................................................................... 4 1-3: Internal Printed Circuit Boards (PCBs) ....................................................................... 5 3-1: View from the Sun's perspective in Transit ............................................................... 20 3-2: Payload attitude during Lunar Surface Operations ................................................... 20 3-3: Overall Graphical Representation of the PILS thermal model .................................. 21 3-4: Thermal Model of PILS assembly, Front View ........................................................ 22 3-5: Thermal Model of PILS Assembly, Back View ........................................................ 22 3-6: Thermal Model of the Internal PCBs ........................................................................ 23 3-7: MLI and Silver Teflon on the PILS assembly ........................................................... 24 3-8: Transit Orbit .............................................................................................................. 25 3-9: Lunar Orbit 1 ............................................................................................................. 26 3-10: Lunar Orbit 2 ........................................................................................................... 27 3-11: Lunar Orbit 3 ........................................................................................................... 27 3-12: Descent .................................................................................................................... 28 3-13: Lunar Surface .........................................................................................................