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Produced by the NASA Center for Aerospace Information (CASI) i i i i 1 i CARA CORPORATION i 0 i (ACCESSIpN iJN^^ O _ ` 9 (T U i PS) y (NASA CR OR TMX OR A'D^ (C D ' V+ NUMBER) ^ i (CA TE i GOR y) r17 i k4731,lc22 ' i i i i i The Relation Between Solar Cell Flight Performance Data and Materials and Manufacturing Data Final Report Contract No. NA.SW-1732 3 nii }J i': a ABSTRACT The purpose of this study was to examine the flight performance data for solar cell power systems in satel- lites, and to try to relate the differences in performance to the materials and manufacturing factors of the solar cell system. Because of difficulties encounterd in the retrieval of existing data, a second purpose evolved towards the end of this study. This was to develop methods of data gathering during a satellite project that would simplify data retrieval for a posteriori studies. The two major conclusions of this work are: 1. Solar cell studies of past flights based on available data are impossible to perform without great expenditures of time and money. 2. A data gathering and storage system can be designed which, if implemented on future flights, would make such a posteriori studies straightforward and fruitful. As a result of these conclusions, we make the following two recommendations: 1. No a posteriori studies based on flight data and solar cell components information should be funded. Such studies will probably fail because of the difficulties of data retrieval. This recommendation can probably be extended •1 to vehicle components other than solar cells, although our experience is based on the solar cell problem. 2. The implementation of a data gathering and retrieval system to be used for each mission should be investigated. Currently, a greiat deal of valuable information is lost forever once a mission is completed. i r _Y } ._. _, 010 .. Y a } TABLE OF CONTENTS PAGE I. INTRODUCTION AND SUMMARY . 1 A. Purpose and Methods . 0 . 1 B. Summary of Results .. 3 C. Conclusions and Recommendations . 4 II. THE SELECTION OF FLIGHTS . 0 . 8 A. Preliminary Screening . 8 a B. Environmental Factors . 0 15 C. Final Flight Selection . a 0 a . 0 . 18 III. INFORMATION AND DATA GATHERING . 20 A. Initial Steps . 20 B. Computer Search of Literature . 20 C. DOD Flight Documentation . 22 D. NASA Flight Documentation . 23 E. Radiation Environment Data . 0 . 24 F. Thermal Environment Data . 26 G. Personal Contacts . 28 H. Results of Data Gathering Process . 29 3(. Ykk i 3n ^t f a¢ ti ip. Al s ssX j VII. FABRICATION OF A SILICON SOLAR ARRAY 43, i H A. Fabrication Process . 43 ax B. Growth of the Silicon Ingot . 43 C. Slicing and Preparation of the Silicon s Blank . 45 t°E D. Formation of the Appropriate Junction 46 E. Attachment of Contacts . 46 F. Deposition of Anti-reflecting Coating 46 G. Fabrication of the Solar Array . 47 VIII. FORMS FOR THE PROPOSED DATA COLLECTION PROCESS' TO ACCOMPANY SATELLITE FLIGHTS . 48 11 IX. MANAGEMENT RECOMMENDATIONS FOR THE PROPOSED DATA COLLECTION PROCESS T6 ACCOMPANY SATELLITE FLIGHTS . 50 X. CONCLUSIONS . 53 APPENDIX: COMPLETED DATA OUTLINES FOR SOME SPECIFIC FLIGHTS 54 m • iii f jf 31 I' t 1(] LIST OF FIGURES t: r PAGE Figure 1. Perigee vs. Apogee for Class 1 Flights . 79 ar. Figure 2. Angle of Inclination vs. Period for 1(55) and 1(32) Flights . 80 f Figure 3. Angle of Inclination vs. Period for I (70) y 1(80) and 1(90) Flights . '. , 81 3 I Figure 4. Angle of Inclination vs. Period for B Flights 82 Figure 5. Angle of Inclination vs. Period for ll S Flights . 83 Figure 6. Angle of Inclination vs. Period for 0 Flights . a . 84 y iv ; I LIST OF TABLES PAGE Table I. Log of 1958 - 68 Space Projects Class # 1 . 85 r Table II. "Inside" Orbits (I) - 760 Miles . 92 Table III. "First Belt" Orbits (B) 1500 - 2500 Miles . 95 t Table IV. Geostationary Orbits (S) . 96 E Table V. "Deep" Orbits (0) - 60,000 - 70,000 Miles 97 Table VI. Specific Flights to be Studied - Selection Criteria 98 Table VII. Citations Obtained From Computer Literature Searches . 108 Table VIII. Specific Flights with Individual Contact . 109 Table IX. Specific Flights with Solar Cell Vendor . 113 Table X. Form C -01 - Data Availability Code . 114 Table XI. Form C-02 - Master Chart: Dictionary for Form C-01 . 115 Table XII. Form C-03 - Outline for Recording Pertinent Data . ... 116 Table XIII. Form A of Proposed Data Collection Process to Accompany Satellite Flights 119 Table XIV. Form B of Proposed Data Collection Process to Accompany Satellite Flights . 122 Table XV. Form C of Proposed Data Collection Process to Accompany Satellite Flights . 125 V t y ^` I. INTRODUCTION AND SUMMARY A. Purpose and Methods The purpose of this study was to examine the flight per- formance data for solar cell power systems in satellites, and to try to relate the differences in performance to the materials and manufacturing factors of the solar cell system. Because of difficulties encountered in the retrieval of ex- isting data, a second purpose evolved towards the end of this study. This was to develop methods of data gathering during a satellite project that would simplify data retrieval for a posteriori studies. The method of approach in the solar cell study consisted I ^^ of trying . to select a group of flights whose space environ- ments are all similar, for which sufficient flight performance data exist, and for which information on the materials and manufacturing factors is available. For the selected group of flights, an attempt was to be made to relate the differ- ences in performance to specific-materials or manufacturing r parameters that may be expected to affect performance. The work was divided into four general phases defined by the following outline Phase I a. Classify all flights from 1957 through 1967 according to their space environ- ment, so that groups of flights with similar environments can be`identified. b. Ascertain availability of performance data and materials and manufacturing L parameters •s..s:ssssAC -rs.`...n3- a [; ..^ _ _ - _ emu. ^ __ :_v-_:cm^_YU^-.a'z da'x-i&'s^..t ,^,-^ - _ .- e.._ .-,,..>: .;.' _ c o Generate a coding procedure to facilitate the recording and use of information gathered relative to performance and ma- terials and manufacturing factors. 1 Phase Its Select a group of flights based on the work in Phase I. a Phase III: Acquire and systematize the actual data needed for the flights selected ire Phase II. is Phase IV: Perform analysis to relate materials and manufacturing factors to flight performance of the selected flights. ^s ^t A space environment classification scheme was devised which permitted the 611 flights examined to be separated into x¢ groups of similar environments and preliminary decisions to be made on the suitability of these groups for the purposes of this study. An initial selection of 77 flights with similar space environments was made for purposes of further study. These flights have orbital parameters below 760 miles, are below the maxima in the first radiation belt, and have appreciable thermal cycles. The final selection was based on the availa- bility of flight performance data. The criterion for this } selection was that the telemetry data transmitted by the satel- lite had to include solar array output voltage, array current and array temperature. It was found that nine flights satis- fied this criterion. They were the Pegasus series, numbers 1 9 2, and 3; the OSO series, numbers 1, 2, 3, and 4; OGO 4; and Nimbus 2. These were the nine flights for which a detailed search for materials and manufacturing information was made. 2 The classification of flights according to similarity of environment was done by analyzing the orbital parameters and grouping the flights into classes of similar perigee, apogee, angle of inclination, and period. The gathering of performance data and materials and manufacturing factors was performed by using computerized literature searches, examining existing document;, visiting manufacturers and government installations, and from corre- spondence and personal discussions with individuals who had responsibilities for the solar cell. systems. To facilitate the recording and use of the data gathered in this study, a coding procedure and form was designed. When it became apparent that the data needed to perform i a correlation analysis could not be retriwred, consideration was given to the methods of capturing and storing the data at i the time of the flight mission. This was done in agreement with the Technical Monitor. Within the time available (the last quarter of this contract), an initial approach to this. problem was successfully developed. B. Summary of Results The most important result of this study is that it is not possible to perform a posteriori materials studies on solar cell systems without an inordinate expenditure of time and money.