THERMAL FREETOP A FREE OPEN-SOURCE SPACECRAFT THERMAL ANALYSIS SOFTWARE PACKAGE __________________________ A Thesis Presented to the Faculty of the College of Science Morehead State University _________________________ In Partial Fulfillment of the Requirements for the Degree Master of Science _________________________ by Yu Tso April 30, 2018 ProQuest Number:10816661 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. ProQuest 10816661 Published by ProQuest LLC ( 2018). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, MI 48106 - 1346 Accepted by the faculty of the College of Science, Morehead State University, in partial fulfillment of the requirements for the Master of Science degree. ____________________________ Jeffrey A. Kruth Director of Thesis Master’s Committee: ________________________________, Chair Dr. Charles D. Conner _________________________________ Dr. Benjamin K. Malphrus _________________________________ Kevin Z. Brown ________________________ Date THERMAL FREETOP A FREE OPEN-SOURCE SPACECRAFT THERMAL ANALYSIS SOFTWARE PACKAGE Yu Tso Morehead State University, 2018 Director of Thesis: __________________________________________________ Jeffrey A. Kruth Thermal management is crucial to spacecraft design in that most of the subsystems are electronic devices, and electronic devices need to work in a specific temperature range to assure the performance. To meet the requirements of spacecraft thermal management, the engineers always need a convenient and useful tool to assist with the design process. Thermal Freetop is an outstanding fit for this purpose. Thermal Freetop is a finite element thermal analysis package with the similar interfaces and same functions as those of Thermal Desktop[1], a commercial spacecraft thermal management software tool,and Thermal Freetop is based on the open source software such as FreeCAD, Salome, Paraview, 42, GMAT, ElmerSolver and ElmerGrid. Accepted by: ______________________________, Chair Dr. Charles D. Conner ______________________________ Dr. Benjamin K. Malphrus ______________________________ Kevin Z. Brown To my families and my friends. Contents 1 Executive Summary 1 2 Introduction 2 3 Relevant Technical Issues 4 4 Design Tradeoffs 5 5 Design Implementations 6 5.1 FreeCAD: The Main Frame of Thermal Freetop and the CAD Software . .6 5.2 GMAT and 42: The Trajectory Simulation Software . .7 5.3 Salome: The Preprocessor . .9 5.4 ElmerSolver: The Finite Elment Solver . 11 5.5 Paraview: The Postprocessor . 16 6 Results 19 7 Conclusion and Recommendations 20 8 Partial Differential Equation Form of Heat Conduction in Cartesian Co- ordinate System 21 8.1 Purposes of Finite Element Method (FEM) . 21 8.2 Derivation of Heat Conduction Equations . 21 8.3 The One-Dimensional and Steady-State Heat Conduction Equation without Heat Generated . 23 vii 8.4 An Example of Solving One-Dimensional and Steady-State Heat Conduction 24 8.5 Example 01: A Single Bar with Heat Flux on the Bottom Side and Fixed Temperature on the Top Side as Boundary Conditions(BCs) . 26 8.5.1 Solving Example 01 with Thermal Freetop . 28 8.5.2 Discussion . 33 8.6 Example 02: A Bar Consisting of Two Materials with Heat Flux on the Bot- tom Side and Fixed Temperature on the Top Side as Boundary Conditions(BCs) 34 8.6.1 Solving Example 02 with Thermal Freetop . 36 8.6.2 Discussion . 38 8.7 Example 03: A Bar Consisting of Three Materials with Heat Flux on the Bot- tom Side and Fixed Temperature on the Top Side as Boundary Conditions(BCs) 39 8.7.1 Solving Example 03 with Thermal Freetop . 40 8.7.2 Discussion . 44 9 Thermal Radiation 45 9.1 Blackbody Radiation . 45 9.1.1 Stefan-Boltzmann Law . 45 9.1.2 Planck's Law . 45 9.1.3 Wien's Displacement . 46 9.1.4 From Planck's Law to Stefan-Boltzmann Law . 46 9.2 Emissivity . 46 9.3 Solving the One-Dimensional and Steady-State Heat Conduction Equation with Heat Flux and an Emitting Surface as Boundary Conditions(BCs) . 47 9.4 Example 01: A Plate with Heat Flux on the Bottom Side and Emitting Surface on the Top Side as Boundary Conditions(BCs) . 48 9.4.1 Solving Example 01 with Thermal Freetop . 49 9.4.2 Discussion . 54 9.5 Example 02: A Thicker Plate with Heat Flux on the Bottom Side and Emit- ting Surface on the Top Side as Boundary Conditions(BCs) . 55 9.5.1 Solving Example 02 with Thermal Freetop . 56 viii 9.5.2 Discussion . 61 9.6 Example 03: A Smaller Plate with Heat Flux on the Bottom Side and Emitting Surface on the Top Side as Boundary Conditions(BCs) . 62 9.6.1 Solving Example 03 with Thermal Freetop . 63 9.6.2 Discussion . 68 References 70 ix Chapter 1 Executive Summary The objective of Thermal Freetop is to relieve the pain in the process of constructing thermal model, so eventually it will be a integral finite element simulation software with the necessary characteristics. The users don't need to switch from one package to another, since everything is included. 1 Chapter 2 Introduction Thermal management is extremely complicated since all subsystems are required to work in a specific temperature range. If the temperature exceeds the operating temperature ranges then the performace of the devices drop. Even worse is that if the temperature is outside the survival temperature range, the devices just crash and the whole mission may fail. The main task of thermal management is to keep the temperature where the subsystems work in the appropriate range. To achieve this many factors have to be taken in to account: 1. The geometry of the spacecraft. 2. The material properties of the structure. 3. The connections (fasteners) between all subsystems. 4. The waste heat generated by the subsystems. 5. The heat path to absorb or dissipate heat. The thermal design involves so many aspects that it is very difficult to complete it totally by solving the partial differential equations with the complex boundary conditions by hands. The engineers always need the assistance of computer numerical analysis. Thermal Desktop is a well-known commercial one in this area. Thermal Desktop is a powerful spacecraft thermal analysis software in the sense that it is able to simulate the heat transfer behaviour incluing that in the space radiation environment. However, it requires license, and there are many details to be careful of in the process of building the model. Users always spend most of their time learning the software rather than doing thermal analysis. The objective of this project is to develop a user-friendly, intuitive and reliable free open source spacecraft thermal analysis package which is open to individuals who are interested in spacecraft thermal analysis. The newly-developed thermal simulation software is named as Thermal Freetop. 2 Figure 2.1: The developer information of Thermal Freetop. 3 Chapter 3 Relevant Technical Issues To develope Thermal Freetop, the basic knowledge of the areas listed below are needed: 1. Heat transfer: without understanding the physics of heat transfer, it is likely that the developers can't spot the wrong solution from their simulation software. 2. Astrodynamics: thermal management of spacecraft involves the dynamics of spacecraft since the developers need the relative position and orientation between the components and the radiating source to define the boundary conditions. 3. Partial differential equations (PDEs): with the knowledge of PDEs, the developers can figure out the necessary characterics of the simulation software. 4. Numerical analysis: with the knowledge of numerical analysis, the developers can have a big picture of what should be added to the software package. 5. Python programming: FreeCAD is the main frame of Thermal Freetop, and it is open for 3rd party developer to extend its functionalities. FreeCAD is mainly based on Python language, so it is a must that the developers have the skills of python programming. 6. Graphical user interface design: with the skill the developers can produce user-friendly and intuitive interface. The main challenges are that the developers need many skills and enough time to get things done. 4 Chapter 4 Design Tradeoffs Developing software is a long-term run and it always takes much more time than that expected in the first place. Also it is not pragmatic to expect things could be done from the scratch by only one person. Thus, instead of creating everything on my own, Thermal Freetop works on the top of other great works from different groups of developers: 1. CAD software (main frame): FreeCAD. 2. Finite element solver: ElmerSolver, ElmerGrid. 3. Mesher and preprocessor: Salome-platform. 4. Visualization of data: Paraview. 5. Astrodyanmics simulation software: GMAT, 42. 5 Chapter 5 Design Implementations As what is mentioned in the previous chapters, Thermal Freetop works on the top of many fantastic and useful open-source, free software packages from other groups. The main contribution of this project is in that it combines different software packages and tries to integrate them to make a new one. Thermal Freetop is expected to be useful and able to relieve the pain of switching from one software to another to get thermal analysis done. Thermal Freetop is mainly programmed with PyQt4, a graphical user interface design library linked with Python, and it is able to call other packages to perform specific functions. Figure-5.1 is an example of the PyQt4 code used to show the information of the developer.