NASW-4435 THERMION: VERIFICATION OF A THERMIONIC HEAT PIPE IN MICROGRAVITY UTAH STATE UNIVERSITY 1990- 1991 (_4ASA-CC'-I-JOCIO) THERMI!J*I: _/FRIF[CAT[ON OF N9Z-Z479_ A [;_L_'T.j_![C _-_U_,[ PTPF IN MTCROGRAV[TY Findl r',ep_rr., 1o9 "_ - 1"_9L (Utih State Univ.} 2_i _ CSCL 20M 0J/77 FORWARD This final report describes the verification of a thermionic heat pipe in microgravity. This project consists of two design scenarios: THERMION-I andTHERMION-II. The design was done entirely by a team of Utah State University (USU) students. The project has been completed under the sponsorship of NASA through the Universities Space Research Association (USRA) and in cooperation with the Idaho National Engineering Laboratory (INEL). We at Utah State University are very pleased with the results of this design effort. We are proud of the product, and we are excited about the achievement of all our learning objectives. The systems design process is one that cannot be taught, it must be experienced. The opportunity to use our maturing engineering and scientific skills in producing the THERMION final design has been both challenging and rewarding. We are proud of the skills we have developed in identifying system requirements, spreading them into specifications, communicating with each other in all kinds of technical environments, conducting parametric and trade-off studies, learning to compose for the good of the system, and selecting actual hardware to be used. The critical design review (CDR), conducted in May of this year at USU, was presented to INEL, Phillips Laboratory, JPL, and Space Dynamics Laboratory/USU personnel as well as other distinguished members of the engineering community. A revision of the paper will be presented at the AIAA/USU Conference on Small Satellites in August of this year. INEL and Phillips Laboratory, in collaboration with the Space Dynamics Laboratory/USU, are considering further development and testing of the THERMION project. We would like to express our appreciation and thanks to the following people who have helped us with this design project: Frank J. Redd, class professor, MAE Department Head, USU Michael Jacox, INEL, SEHPTR Project Manager Kevin Horner-Richardson, Thermacore, Inc. James Burke, Jet Propulsion Laboratory John Garvey, McDonnell Douglas J. Clair Batty, professor, MAE Department, USU Ralph Haycock, professor, MAE Department, USU Ed Vendell, professor, MAE Department, USU Kay D. Baker, professor, EE Department, USU Robert Gunderson, professor, EE Department, USU John Kemp, professor, EE Department, USU Pete Brunson, artist, Space Dynamics Lab/USU David Widauf, professor, ITE Department, USU R. Gilbert Moore, Physics Department, USU Shelly Wegener, technical writer, Space Dynamics Lab/USU Frank J. Redd, PhD George E. Powell Professor, MAE Teaching Assistant THERMION: VERIFICATiON OF A THERMIONIC HEAT PIPE IN MICROGRA WTY ABS TRA C T The Idaho National Engineering Laboratory (INEL) is conducting intensive research in the design and development of a small, excore heat-pipe-thermionic space nuclear reactor power system (SEHPTR). Progress in this research effort has identified the need for an in-space flight demonstration of a solar-powered, thermionic heat-pipe element. The proposed demonstration will examine the performance of such a device and verify its operation in microgravity. The Utah State University space system design project for 1990-1991 focuses on the design of a microsatellite-based technology demonstration experiment to measure the effects of microgravity on the performance of an integrated thermionic-heat-pipe device in low-earth orbit. The specific objectives are to verify the operation of the liquid-metal heat pipe and the cesium reservoir in the space environment. The scope of the project includes the design of the flight test vehicle, the solar collection subsystem, the satellite attitude control subsystem, test instrumentation, data collection/processing and the telemetry subsystem. Interfaces with various launch systems are examined with emphasis on flight as secondary payload on the McDonnell Douglas Delta II. This report describes two design configurations, THERMION-I and THERMION-II, which meet the requirements specified above. THERMION-I is designed for a long- lifetime (greater than one year) investigation of the operations of the thermionic heat pipe element in low earth orbit. Heat input to the element is furnished by a large mirror which collects solar energy and focuses it into a cavity containing the heat pipe device. THERMION-II is a much simpler design which is utilized for short-term (approximately one day) operation. This experiment remains attached to the Delta II second stage and utilizes energy from 500 Ib of alkaline batteries to supply heat energy to the heat pipe device. The cost for fabrication, integration and flight are estimated at almost $3 million. CLA SS PAR TICIPA N TS THERMION I GEORGE POWELL System Engineering WALTER HOLEMANS System Engineering SCOTT BLADEN Payload EDWIN ROWSELL Payload RUSSELL FERGUSON Payload RICHARD WEATHERSTON Payload GLEN PETERSON Attitude Determination & Control BART EWER Attitude Determination & Control PAUL WHEELWRIGHT Attitude Determination & Control RICK BJORN Structure MIKE OLSEN Structure GEORGE POWELL Data Management & Storage RUSSELL MIKESELL Communications WALTER HOLEMANS Power System SHAUN ANDERSON Launch Vehicle Interface & Deployment MARK RAWLINGS Launch Vehicle Interface & Deployment GREG FERNEY Thermal Management JEFF HIRASUNA Thermal Management RUSSELL MIKESELL Test & Evaluation THERMION II WALTER HOLEMANS System Engineering GEORGE POWELL System Engineering WALTER HOLEMANS Power System JONATHON BLOTTER Launch Vehicle Interface & Payload VAL MOSER Launch Vehicle Interface & Payload GEORGE POWELL Data Management & Communications TABLE OF CONTENTS 1.0 INTRODUCTION 1.1 DESIGN PROJECT 1.1.1 THERMION-I 1.1.2 THERMION-II 1.2 DESIGN CONSTRAINTS 1.3 DESIGN EVOLUTION OF THERMION-I 1.3.1 Heat Pipe Testing System 1.3.2 Solar Collection System 1.3.3 Attitude Control and Determination System 1.3.4 Satellite Structure and Configuration System 1.3.5 Data Management System 1.3.6 Communications System 1.3.7 Power System 1.3.8 Launch Vehicle Interface and Deployment System 1.3.9 Thermal Management System 1.3.1 0 Test and Evaluation System 1.3.1 1 Conclusions 2.0 PA YLOAD 2.1 THERMIONIC HEAT PIPE DEVICE 2.2 INSULATING CAVITY 2.2.1 Design Evolution 2.2.2 Insulating Cavity 2.2.3 Isulation 2.3 SOLAR COLLECTION 2.3.1 Solar Design Constraints 2.3.1.1 FresnelLens 2.3.1.2 Inflatable Collector 2.3.1.3 Reflecting Mirror 2.3.2 Solar Concentrating Mirror 2.3.2.1 Mirror's Configuration and Operation 2.3.2.2 Mirror's Reflective Surface 2.3.2.3 Structure and Strength of the Mirror 2.3.3 Secondary Concentrator 2.4 POWER MEASURING DEVICE 2.4.1 Conceptual Operation 2.4.2 Governing Equations 2.5 TEMPERATURE MEASUREMENT 2.5.1 Sensor Configuration 2.6 CONCLUSIONS 2.6.1 Conceptual Design 2.6.2 Options and Concerns 3.0 A TTITUDE DETERMINA T/ON AND CONTROL 3.1 DESIGN REQUIREMENTS 3.2 DESIGN EVOLUTION 3.3 ATTITUDE DETERMINATION SENSORS 3.3.1 Sun Sensors 3.3.2 Horizon Crossing Sensor 3.4 ATTITUDE CONTROL ACTUATORS 3.4.1 Torque Rods 3.4.2 Momentum Wheel 3.5 ENVIRONMENTAL TORQUES 3.6 EQUATIONS OF MOTION AND CONTROL LOGIC 3.6.1 Control Simulation 3.7 FUTURE DESIGN WORK 4.0 STRUC TURES 4.1 SYSTEM REQUIREMENTS 4.2 STRUCTURE 4.2.1 Design Phases 4.2.2 Final Design 4.3 DEPLOYMENT 4.4 MATERIALS 4.4.1 Subsystem Housing 4.4.2 Attachment Bracket and Hinge 4.4.3 Payload Arm 4.4.4 Shielding and Mounts 4.5 SUBSYSTEM LAYOUT 4.6 MASS PROPERTIES 4.7 CONCLUSIONS 5.O DATA MANAGEMENT 5.1 DATA MANAGEMENT REQUIREMENTS 5.2 SYSTEM COMPONENTS 5.2.1 CPU 5.2.2 Expanded Memory 5.2.3 Data Acquisition 5.2.3.1 Cavity Temperature 5.2.3.2 Data Rates 5.2.4 Housekeeping 5.2.5 Storage Container 5.3 RADIATION DAMAGE PREVENTION 5.4 CONCLUSIONS 6.0 COMMUNICATIONS 6.1 REQUIREMENTS 6.2 COMMUNICATION SYSTEM 6.2.1 THERMION-I Satellite Antenna 6.2.2 Ground Station Antenna 6.2.3 Spacecraft Transmitter and Receiver