Master Thesis - OUFTI-1

University of Liège
Faculty of Applied Sciences
Aerospace and Mechanical Engineering Department
Master Thesis
Dynamic Analysis and Launch Qualication of OUFTI-1
Nanosatellite
Nicolas FRANCOIS
Thesis submitted in partial fulllment of the requirements for the degree of
Master in Aerospace Engineering
Advisor : Prof. Gaëtan KERSCHEN
Academic Year 2009 - 2010

Acknowledgments
I wish to acknowledge all the people who helped me, during the whole year, to carry
out this master thesis.
First of all, I would like to express my gratitude to my advisor Professor Gaëtan KER-
SCHEN for his precious advice and support, and for giving me the opportunity to take
one's rst steps in the fascinating world of space industries.
I am deeply indebted to Professor Jean-Claude GOLINVAL who opened me the doors
of his laboratory and gave me his condence to use his precious material.
I would like to thank Professors Jean-Claude GOLINVAL and Pierre ROCHUS, but
also Daniel SIMON and Amandine DENIS for accepting to serve on the examination commitee
of this master thesis.
I am pleased to acknowledge all the members of the OUFTI team, who created a pleasant
working atmosphere. This year will remain a wonderful experience for me that I will
never forget.
Last but not least, I thank my family for encouraging and supporting me, not only
during this academic year, but during my entire studies.
1

Abstract
OUFTI-1, standing for "Orbital Utility For Telecommunication Innovation ", is the rst
nanosatellite developed by the University of Liège as well as the rst one which was ever
developed in Belgium. This name, which is a typical expression from the city of Liège
showing surprise or amazement, was chosen to point up the origin of the satellite. The
project takes place within the framework of a long-term program called LEODIUM (which
means Liège in Latin). The main goal of this program is to open a new window on scientic
careers and space-related activities.
OUFTI-1 will be equipped of three payloads:
• A D-STAR repeater. OUFTI-1 will be the rst satellite to use this new digital
amateur radio communication protocol in space.
• A digitally-controlled electrical power system developed in collaboration with Thales
Alenia Space ETCA.
• High-eciency solar cells from Azur Space.
OUFTI-1 will be launched on board the new european launcher: Vega.
This present thesis focuses on the structural design and dynamic analysis of OUFTI-
1. The design part covers essentially the creation of a reliable support for the batteries
in accordance with several requirements. It includes also some changes in the general
conguration of the satellite. The analysis part is based on the creation of an accurate
nite element modeling procedure for electronic cards. Then, this procedure is applied
to each electronic card and several FE analysis are performed to ensure the structural
integrity of the satellite. Finally, a random vibration analysis is presented. The goal of
this analysis is to demonstrate the ability of OUFTI-1 to survive at the launch phase.
2

Contents
1 Introduction 13
1.1 The CubeSat program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.1.1 The concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.1.2 The Pumpkin's CubeSat kit . . . . . . . . . . . . . . . . . . . . . . 14
1.1.3 The P-POD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1.2 OUFTI-1 project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.2.1 Genesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.2.2 The launch opportunity . . . . . . . . . . . . . . . . . . . . . . . . 16
1.2.3 Mission objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.2.4 OUFTI team . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2 OUFTI-1: Flight system conguration and general properties 20
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.2 Reference frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.3 Flight system conguration . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.3.1 Skeleton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.3.2 Solar panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.3.3 Antenna support . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.3.4 Permanent magnet and hysteretic bars . . . . . . . . . . . . . . . . 27
2.3.5 Electronic cards and battery support . . . . . . . . . . . . . . . . . 32
2.4 Physical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.4.1 Catia modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.4.2 Center of gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.4.3 Inertia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.5 Mass budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3 Design of a new support for the batteries 44
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.2 Problems encountered with the last year's design . . . . . . . . . . . . . . 44
3.3 Available mass budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3

3.4 Initial idea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.5 Battery selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.6 Material selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.6.1 Denition of the requirements . . . . . . . . . . . . . . . . . . . . . 51
3.6.2 Objective function and CES software . . . . . . . . . . . . . . . . . 53
3.7 Thermal control's devices selection . . . . . . . . . . . . . . . . . . . . . . 55
3.7.1 Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.7.2 Heaters' control system . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.7.3 Thermal insulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
3.8 Final design of the support . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.9 Validation of the design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.9.1 Mass budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.9.2 Static loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
3.9.3 Dynamic behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
3.10 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4 Electronic cards dynamic modeling 72
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.2 State-of-the-art . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.2.1 Accuracy of the model . . . . . . . . . . . . . . . . . . . . . . . . . 73
4.2.2 Creating FE models of PCBs . . . . . . . . . . . . . . . . . . . . . 74
4.2.3 Determination of the PCB properties . . . . . . . . . . . . . . . . . 74
4.2.4 Choice of mesh element . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.2.5 Recognition of components eects . . . . . . . . . . . . . . . . . . . 79
4.2.6 Modeling of the chassis . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.2.7 Denition of the boundary conditions . . . . . . . . . . . . . . . . . 82
4.2.8 Introduction of damping . . . . . . . . . . . . . . . . . . . . . . . . 82
4.2.9 Dynamic response computation . . . . . . . . . . . . . . . . . . . . 84
4.3 Application to the homemade on-board computer of OUFTI-1 . . . . . . . 85
4.3.1 Denition of the PCB properties . . . . . . . . . . . . . . . . . . . 85
4.3.2 Recognition of the components eects . . . . . . . . . . . . . . . . . 86
4.3.3 Experimental test of the OBC 2 card . . . . . . . . . . . . . . . . . 88
4.3.4 Application of the simple method . . . . . . . . . . . . . . . . . . . 91
4.3.5 Application of the global mass smearing method . . . . . . . . . . . 93
4.3.6 Application of the local mass smearing method . . . . . . . . . . . 94
4.3.7 Application of a homemade method . . . . . . . . . . . . . . . . . . 95
4.3.8 Sensitivity analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
4.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
4

5 Complete FE analysis of OUFTI-1: Static, modal and random vibration101
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.2 Modeling strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.2.1 Materials properties . . . . . . . . . . . . . . . . . . . . . . . . . . 102
5.2.2 Main structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
5.2.3 Solar panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.2.4 Antenna support . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
5.2.5 Electronic cards and battery support . . . . . . . . . . . . . . . . . 104
5.2.6 The endless screws . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
5.2.7 ADCS and THER components . . . . . . . . . . . . . . . . . . . . . 109
5.3 Static analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
5.3.1 Loads denition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
5.3.2 Boundary conditions . . . . . . . . . . . . . . . . . . . . . . . . . . 112
5.3.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
5.4 Modal analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
5.4.1 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
5.5 Random vibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
5.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
6 Conclusions 120
6.1 Summary of the accomplished work . . . . . . . . . . . . . . . . . . . . . . 120
6.2 Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
6.3 Parallel activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
5

List of Figures
1.1 The Pumpkin's CubeSat family . . . . . . . . . . . . . . . . . . . . . . . . 15
1.2 Poly-Picosatellite Orbital Deployer (P-POD) . . . . . . . . . . . . . . . . . 15
1.3 The new European launcher: Vega . . . . . . . . . . . . . . . . . . . . . . 16
1.4 Main stage of Vega [20] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.5 The three payloads of OUFTI-1 . . . . . . . . . . . . . . . . . . . . . . . . 18
2.1 Reference frame of OUFTI-1 . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.2 Product tree of OUFTI-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.3 CSK structure with the FM 430 . . . . . . . . . . . . . . . . . . . . . . . . 23
2.4 Dose depth curve for OUFTI-1 orbit [6] . . . . . . . . . . . . . . . . . . . . 24
2.5 One fully-integrated solar panel of OUFTI-1 . . . . . . . . . . . . . . . . . 25
2.6 Available holes on the CSK structure for cabling path [15] . . . . . . . . . 25
2.7 Interference between solar panel clips and OUFTI-1 solar cells [15] . . . . . 26
2.8 Conguration and dimensions of the antenna support . . . . . . . . . . . . 27
2.9 Description of the port obstructed by the antenna support . . . . . . . . . 27
2.10 Principle of the OUFTI-1 ADCS subsystem [25] . . . . . . . . . . . . . . . 28
2.11 Last year's conguration of the ADCS . . . . . . . . . . . . . . . . . . . . 28
2.12 Ideal positioning of the hysteretic bars . . . . . . . . . . . . . . . . . . . . 29
2.13 Magnetic eld obtained in the hysteretic bars for the rst conguration [25] 30
2.14 Magnetic eld obtained in the hysteretic bars for the second conguration
[25] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.15 Final conguration of the ADCS . . . . . . . . . . . . . . . . . . . . . . . . 31
2.16 Magnetic eld obtained in the hysteretic bars for the nal conguration [25] 31
2.17 Pictures of the ADCS components [25] . . . . . . . . . . . . . . . . . . . . 32
2.18 Conguration of OUFTI-1 electronic cards . . . . . . . . . . . . . . . . . . 33
2.19 Pictures of the engineering models of OUFTI-1 electronic cards . . . . . . 34
2.20 Exploded view of OUFTI-1 . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.1 Last year's design of the battery assembly . . . . . . . . . . . . . . . . . . 44
3.2 Available space under and above the batteries . . . . . . . . . . . . . . . . 45
3.3 Batteries during and after the vacuum test [15] . . . . . . . . . . . . . . . 46
3.4 Initial idea for the new design . . . . . . . . . . . . . . . . . . . . . . . . . 48
6

3.5 Adaptation of the base idea to the OUFTI-1 dimensions . . . . . . . . . . 49
3.6 Available space for including the batteries . . . . . . . . . . . . . . . . . . 49
3.7 Battery Kokam SLB 603870H . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.8 Classication by density and Young's modulus . . . . . . . . . . . . . . . . 53
3.9 Classication by density and yield stress . . . . . . . . . . . . . . . . . . . 54
3.10 Polyimide thermofoil heater . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.11 Thermostat Klixon 4BT − 2 . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.12 Connection with four thermostats . . . . . . . . . . . . . . . . . . . . . . . 57
3.13 Thermal insulator: Polyester netting . . . . . . . . . . . . . . . . . . . . . 58
3.14 Thickness of the box's "base plate" . . . . . . . . . . . . . . . . . . . . . . 59
3.15 P C 104 connector's hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.16 Reinforcers and connection holes . . . . . . . . . . . . . . . . . . . . . . . . 60
3.17 Final design of the box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
3.18 Schematics of the box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3.19 Reinforcements around the connection holes . . . . . . . . . . . . . . . . . 61
3.20 Notches for the thermostats . . . . . . . . . . . . . . . . . . . . . . . . . . 62
3.21 End stops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
3.22 Final design of the cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.23 Schematics of the cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
3.24 Maximal Von Mises stress inside the support . . . . . . . . . . . . . . . . . 67
3.25 The two most signicant modes of the battery support . . . . . . . . . . . 69
3.26 A rst rough shape of the battery support . . . . . . . . . . . . . . . . . . 70
4.1 Example of manufacturing variation [44] . . . . . . . . . . . . . . . . . . . 74
4.2 Example of dierences between the values provided by manufacturers and
the values determined by experimental tests [44] . . . . . . . . . . . . . . . 75
4.3 Illustration of the experimental set-up for a static bend test . . . . . . . . 75
4.4 Illustration of the experimental set-up for a torsion test [44] . . . . . . . . 76
4.5 MAC between the two models . . . . . . . . . . . . . . . . . . . . . . . . . 78
4.6 Symmetrical modes of the steel plate . . . . . . . . . . . . . . . . . . . . . 78
4.7 Detailed model of a component [45] . . . . . . . . . . . . . . . . . . . . . . 79
4.8 Illustration of the dierent simplication methods [45] . . . . . . . . . . . . 80
4.9 Illustration of the dierent categories of components [45] . . . . . . . . . . 81
4.10 Illustration of the peak-amplitude method [53] . . . . . . . . . . . . . . . . 83
4.11 Location of the OBC 2 card in OUFTI-1 . . . . . . . . . . . . . . . . . . . 85
4.12 Components classication of the OBC 2 card . . . . . . . . . . . . . . . . . 86
4.13 Catia modeling of the OBC 2 card . . . . . . . . . . . . . . . . . . . . . . 87
4.14 Example of spacecraft stiness requirements for dierent launchers . . . . . 88
4.15 Location of measurement and excitation points . . . . . . . . . . . . . . . . 90
4.16 Experimental set-up for the test of the OBC 2 card . . . . . . . . . . . . . 90
4.17 Global FRF of the OBC 2 card . . . . . . . . . . . . . . . . . . . . . . . . 91
7

4.18 MAC matrix using the simple method . . . . . . . . . . . . . . . . . . . . 92
4.19 MAC matrix using the global mass smearing method . . . . . . . . . . . . 93
4.20 MAC matrix using the local mass smearing method . . . . . . . . . . . . . 95
4.21 MAC matrix using the homemade method . . . . . . . . . . . . . . . . . . 96
4.22 Initial shape of the OBC 2 card's fourth mode . . . . . . . . . . . . . . . . 97
4.23 Mode shapes obtained by adding sensors of several mass to the FE model . 98
4.24 Inuence of a change of modeling strategy for the P C 104 connector on the
OBC 2 card's fourth mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
5.1 Illustration of a "glue" assembly [56] . . . . . . . . . . . . . . . . . . . . . 103
5.2 The FM 430 card from Pumpkin . . . . . . . . . . . . . . . . . . . . . . . 105
5.3 The OBC 2 card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.4 The EPS card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.5 The xEPS card developed in collaboration with Thales Alenia Space ETCA 107
5.6 Modeling of the midplane standos . . . . . . . . . . . . . . . . . . . . . . 109
5.7 Illustration of the worst case conguration . . . . . . . . . . . . . . . . . . 110
5.8 Frame rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
5.9 Illustration of the complete quasi-static loading state of OUFTI-1 . . . . . 112
5.10 Displacements of OUFTI-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
5.11 Maximal Von Mises stress inside OUFTI-1 . . . . . . . . . . . . . . . . . . 114
5.12 First mode of OUFTI-1 (325.51 Hz) . . . . . . . . . . . . . . . . . . . . . 116
5.13 Second mode of OUFTI-1 (333.92 Hz) . . . . . . . . . . . . . . . . . . . . 116
5.14 PSD of several LVs at qualication level [60] . . . . . . . . . . . . . . . . . 117
5.15 Precise PSD of Vega [57] . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
6.1 Schemas of solar panels +X and +/ − Y [15] . . . . . . . . . . . . . . . . . 130
6.2 Schemas of the solar panel +Z [15] . . . . . . . . . . . . . . . . . . . . . . 131
6.3 Schemas of the solar panel −Z [15] . . . . . . . . . . . . . . . . . . . . . . 131
6.4 Schemas of electronic cards [15] . . . . . . . . . . . . . . . . . . . . . . . . 132
6.5 Available volume for each electronic card [62] . . . . . . . . . . . . . . . . . 133
6.6 Fixations of endless screws on the base plate [62] . . . . . . . . . . . . . . 134
6.7 Picture of the xation between one midplane stando and the chassis [33] . 135
6.8 Disposition of midplane standos inside the CubeSat [30] . . . . . . . . . . 135
6.9 Datasheet of the battery Kokam SLB 603870H . . . . . . . . . . . . . . . 137
8

List of Tables
2.1 Coordinates of the OUFTI-1 CoG . . . . . . . . . . . . . . . . . . . . . . . 37
2.2 Mass budget of OUFTI-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.1 Available mass budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.2 Important corrections in the mass budget . . . . . . . . . . . . . . . . . . . 47
3.3 Properties of several batteries from Kokam [36] . . . . . . . . . . . . . . . 50
3.4 Materials properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.5 Dierent available congurations and problems for thermostats . . . . . . . 58
3.6 Necessary mass budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
3.7 First natural frequencies of the battery support . . . . . . . . . . . . . . . 68
4.1 Frequency deviations between the two models . . . . . . . . . . . . . . . . 77
4.2 Properties of the FR 4 material . . . . . . . . . . . . . . . . . . . . . . . . 85
4.3 Frequency deviations between corresponding modes using the simple method 91
4.4 Frequency deviations between corresponding modes using the global mass
smearing method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
4.5 Increases of density due to each component of the OBC 2 card . . . . . . . 94
4.6 Frequency deviations between corresponding modes using the local mass
smearing method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
4.7 Frequency deviations between corresponding modes using the homemade
method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
4.8 Natural frequencies obtained by adding sensors of several mass to the FE
model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.1 Properties of the materials used in OUFTI-1 . . . . . . . . . . . . . . . . . 102
5.2 Properties of the FM 430 card . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.3 Properties of the OBC 2 card . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.4 Properties of the EPS card . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.5 Properties of the xEPS card . . . . . . . . . . . . . . . . . . . . . . . . . . 107
5.6 Properties of the COM card . . . . . . . . . . . . . . . . . . . . . . . . . . 108
5.7 Results of the static analysis . . . . . . . . . . . . . . . . . . . . . . . . . . 112
5.8 Five rst natural frequencies of OUFTI-1 in hard-mounted conguration . 115
9

List of Acronyms
ADCS
Al
AlNiCo
ASI
BGA
CAD
CalPoly
CDS
CFRP
CoG
COM
COTS
CSL
CSK
CTE
CVCM
D-STAR
DAR
DoF
EPS
ESA
ESTEC
FE
FM
FR
FRF
GaAs
GFRP
GPS
ICD
IRM
Attitude Determination and Control System
Aluminum
Aluminum-Nickel-Cobalt
Italian Space Agency
Ball Grid Array
Computer-Aided Design
California Polytechnic State University
CubeSat Design Specication
Carbon Fiber Reinforced Plastic
Center of Gravity
Telecommunication
Commercial-O-The-Shelf
Liège Space Center
CubeSat Kit
Coecient of Thermal Expansion
Collected Volatile Condensable Material
Digital Smart Technology for Amateur Radio
Deviation Waiver Approval Request
Degree of Freedom
Electrical Power Supply
European Space Agency
European Space Research and Technology Center
Finite Element
Flight Module
Flame Resistant
Frequency Response Function
Gallium-Arsenide
Glass Fiber Reinforced Plastic
Global Positioning System
Interface Control Document
Royal Meteorological Institute
10

ITD Ibrahim Time Domain
ITR Interface Technical Review
JARL Japan Amateur Radio League
KISS Keep It Simple, Stupid (and Short)
LEODIUM Low Earth Orbit Demonstration In University Mode
Li Lithium
LV Launch Vehicle
MAC Modal Assurance Criterion
MECH Mechanism
MLI Multilayer Insulation
MoS Margin of Safety
OBC On-Board Computer
OBC 1 Pumpkin's On-Board computer (FM 430)
OBC 2 Homemade On-Board Computer
OUFTI Orbital Utility For Telecommunication Innovation
P-POD Poly-Picosatellite Orbital Deployer
PCB Printed Circuit Board
PGA Pin Grid Array
PSD Power Spectral Density
QFP Quad Flat Pack
RBF Remove Before Flight
RF Radio Frequency
SDR Software-Dened Radio
SF Safety Factor
SMT Surface Mount Technology
SSI Stochastic Subspace Identication
STRU Structure & Conguration
THER Thermal Control
T i Titanium
TID Total Irradiation Dose
TML Total Mass Loss
UCL Catholic University of Louvain-la-Neuve
UHF Ultra High Frequency
UHMWPE Ultra High Molecular Weight Polyethylene
ULg University of Liège
VCD Verication Control Document
VHF Very High Frequency
xEPS Experimental Electrical Power Supply
11

Thesis outline
This thesis focuses on the structural design of a new support for the batteries and dynamic
analysis of the nanosatellite OUFTI-1, developed at the University of Liège (ULg).
This work will be divided into 6 parts:
• Firstly, a brief introduction about the project and its history will be presented.
• Then, the general conguration of the satellite will be discussed. The requirements
and constraints which led to the nal conguration, will be introduced subsystem by
subsystem to bring an overall view of the project.
• In the third chapter, the design of a new support for the batteries will be studied.
The reasons that led to change the support created last year, will be exposed and
the development phase will be discussed step by step.
• After this structural design part, we will focus on dynamic analysis. The rst step
will be to create a dynamic modeling procedure for the electronic cards. The dierent
methods that already exist to realize an accurate Finite Element (FE) model will be
discussed. Then, the best one will be applied to the Homemade On-Board Computer
(OBC 2) of OUFTI-1.
• Applying this procedure to each electronic card of OUFTI-1, complete static and
dynamic analysis will be performed. Random vibration analysis will also be presented
to demonstrate the structural integrity of the satellite during the launch phase.
• Finally, the conclusions of this thesis will be drawn and perspectives for future works
will be highlighted.
12

Chapter 1
Introduction
1.1 The CubeSat program
1.1.1 The concept
The OUFTI-1 project takes place in the CubeSat program initiated approximately 10
years ago jointly by California Polytechnic State University (CalPoly) and Stanford University.
This program aims to provide an easier access to space by creating a standard based
on the following features:
• The mass of the satellite must be less than 1 kg (1.33 kg in the last version of the
CubeSat Design Specication (CDS) [1], but this version stands not for the Vega
Maiden Flight on board which OUFTI-1 will be launched).
• The shape of the satellite must be a cube of 10 × 10 × 10 cm.
This standard allows to create satellites in a short development time. In addition, owing
to their small size, CubeSats can take place in a space launcher as secondary payloads,
which is less expensive. For all of this reasons, the CubeSat program meets a great success
with universities and industries.
At the moment, the project involves more than 100 universities, high schools or private
rms all over the world developing CubeSats containing scientic, private and governments
payloads. All these developers are linked together by a great community spirit, and each
one benets from the sharing of information between the several teams [1].
However, it is important to note that, owing to constraints listed above, the development
of a CubeSat is a technical challenge, even if it is faster and cheaper than the development
13

of larger satellites. So, the CubeSat philosophy is quite dierent. Indeed, the leitmotiv of
several CubeSat teams is KISS: "Keep It Simple, Stupid (and Short)".
This philosophy is based on the fact that, if two dierent solutions are available to
realize the same task with the same eciency, the best one is the simplest one.
This explains that CubeSats projects use Commercial-O-The-Shelf (COTS) components
instead of space-qualied ones. It is a particularity of these projects and, for this
reason, the ocial requirements must be lightened for this type of mission.
The denition provided here is a general one. All the technical requirements that a
nanosatellite has to respect to be validated as a CubeSat are available in reference [1].
1.1.2 The Pumpkin's CubeSat kit
In order to answer to the request which grows incessantly, some industries have decided
to develop structures that respect these requirements. Among all these commercial structures,
the most popular remains the CubeSat Kit (CSK) from Pumpkin [2]. This structure
is available in three dierent formats (as shown in Figure 1.1).
For OUFTI-1, the goal was to create a 1 unit CubeSat. So, after a long hesitation
between the Pumpkin's structure and an other one provided by ISIS, it was decided to buy
the 1 unit skeleton from Pumpkin.
The decision of buying a commercial structure was chosen because the development
of a space structure is a complicated problem. Indeed, requirements imposed to spacequalied
devices are so restrictive that the development of a space-qualied structure is
too ambitious for ULg, which had absolutely no experience in satellite development before
this project.
14

1.1.3 The P-POD
Figure 1.1: The Pumpkin's CubeSat family
The P-POD, which stands for "Poly-Picosatellite Orbital Deployer ", is the standardized
CubeSat deployment system developed by CalPoly (shown in Figure 1.2). It is a rectangular
box with a door (situated on the right side in Figure 1.2). It serves as the interface between
CubeSats and the Launch Vehicle (LV). Three CubeSats can be placed within one P-POD.
When the launcher is in orbit, the P-PODs deploy the CubeSats using a spring mechanism
to push CubeSats along a series of rails and eject them into orbit. Further detail can be
found in reference [3].
Figure 1.2: Poly-Picosatellite Orbital Deployer (P-POD)
15

1.2 OUFTI-1 project
1.2.1 Genesis
OUFTI-1, standing for "Orbital Utility For Telecommunication Innovation ", is the rst
nanosatellite developed by the University of Liège (ULg) as well as the rst one which was
ever developed in Belgium. This name, which is a typical expression from the city of Liège
showing surprise or amazement, was chosen to point up the origin of the satellite.
The project started in 2007 when Mr. Luc HALBACH, an engineer of Spacebel, suggests
the idea of testing a new amateur radio digital technology in space on board a CubeSat: the
D-STAR protocol. This idea has catched the attention of several academic members from
ULg and, within a few weeks, a team was created to work on the project: OUFTI-1 was
born. This team includes two students from ULg, Stefania GALLI and Jonathan PISANE,
who realized the mission design of OUFTI-1 [4] and the design and implementation of the
rst telecommunication elements of OUFTI-1 [5] respectively. Last year, it was a great
team composed of 13 students coming from three dierent schools (University of Liège,
Gramme Institute and ISIL Institute), who developed the project to the state at which
this thesis starts (references [6] to [18]).
1.2.2 The launch opportunity
OUFTI-1 will be launched on board the new european launcher: Vega (shown in Figure
1.3) for free, which is an incredible opportunity. This launcher was developed by Arianespace
jointly to the Italian Space Agency (ASI) and European Space Agency (ESA). Further
detail can be found in reference [19]. The main payload of the Vega Maiden Flight is the
LARES system (an articial satellite provided by ASI with a spherical body and covered
by corner cube reectors). The secondary payloads includes 9 CubeSats, plus the satellite
ALMASat-1 from the University of Bologna.
Figure 1.3: The new European launcher: Vega
16

Figure 1.4 shows the main stage of Vega during a vibration test. The LARES system
is situated on the top of the stage and, on the left of this picture, one P-POD can be seen.
Last year, the P-PODs were theoretically placed horizontally inside the launcher. However,
in order to facilitate the access to them (e.g., for recharging the batteries), it was decided
to right them at an angle of 10 ◦ from the vertical. This fact is really important to note
because this modication will change signicantly the loads apply on the CubeSat.
Figure 1.4: Main stage of Vega [20]
This opportunity results from an initiative of ESA that, in January 2008, published a
call to oer a free launch for nine CubeSats on the Vega Maiden Flight after presenting the
project at the Vega Maiden Flight CubeSat Workshop at the European Space Research
and Technology Center (ESTEC). The OUFTI-1 team has submitted its own proposal in
March 2008 and, in June 2008, received the conrmation that OUFTI-1 will take part in
the Vega Maiden Flight. The eight other selected CubeSats and their specic missions,
are:
• Robusta (Montpellier - France): Study of radiation eects on bipolar transistors
• UWE-3 (Würzburg - Germany): Development of an active attitude control system
• AtmoCube (Trieste - Italy): Space weather measurements
• E-St@r (Torino - Italy): Test of an active 3-axis attitude control system
• UNICubeSat (Roma - Italy): Atmospheric neutral density measurements
• PW-Sat (Warsaw - Poland): Test of a deployable drag augmentation device
• Goliat (Bucharest - Romania): Earth imaging and space environment measurements
17

• XatCobeo (Vigo - Spain): Development of a Software-Dened Radio (SDR) and solar
panel deployment system
The Vega Maiden Flight will deploy these CubeSats into an orbit of 354 × 1447 km
altitude with 71 ◦ inclination.
1.2.3 Mission objectives
The primary goal of the OUFTI-1 project is to provide hands-on satellite experience to
students. For the OUFTI-1 project, there are three main payloads (illustrated in Figure
1.5).
Figure 1.5: The three payloads of OUFTI-1
The rst one is the setting up of a functional D-STAR repeater in space. D-STAR,
which stands for "Digital Smart Technology for Amateur Radio ", is a ham radio protocol
recently developed by the Japan Amateur Radio League (JARL). The overall system
provides a lot of new built-in features including digital communication (i.e., the quality
of the data received is better than an analog signal at the same strength), simultaneous
voice and data transmission (e.g., Global Positioning System (GPS) data and computer
les), complete routing over the Internet and callsign-based roaming on a worldwide basis
[21]. Therefore, the D-STAR system provides a new capability and functionality to the
ham radio world and increases the eciency of emergency communications (e.g., during
the hurricane Katrina, the whole telecommunications were out of order and it is amateur
radio that allowed people to communicate with the rescue teams). This payload allows to
test the performances of this protocol in space environment.
18

The second one is an Experimental Electrical Power Supply (xEPS) developed in collaboration
with Thales Alenia Space ETCA. xEPS is based on a digitally-controlled yback
converter [17]. This type of electrical power system was never tested in space environment
so, to avoid any problem, this system is redundant with an analogical one (which is commonly
used in space applications).
The third payload is high-eciency solar cells provided by Azur Space. This new generation
of solar cells is triple-junction Gallium-Arsenide (GaAs) cells with an eciency of
30%.
These two last payloads result from the fact that nanosatellites are ideal low-cost solutions
for testing new technologies in space environment. So, industries present a real
interest for these missions and could provide some funds or equipments just to prove that
their technology is ecient.
1.2.4 OUFTI team
This year, the team is composed of two project managers, a system engineering team
composed of three graduate students, most of them being involved in the project last
year, several professors and 14 second master students from dierent institutions (ULg,
Gramme Institute, ISIL Institute and Catholic University of Louvain-la-Neuve (UCL)).
Most of these students are directly involved in the OUFTI-1 project but some of them
alredy work on the future projects.
19

Chapter 2
OUFTI-1: Flight system conguration
and general properties
2.1 Introduction
In consequence of the restricted dimensions of a CubeSat, the management of the available
space to integrate all the components of each subsystem is a real challenge.
Through this chapter, we will focus on the organization of subsystems inside the satellite.
For each of them, the requirements that led to this particular choice, and the progression
from the starting point [15] to the nal conguration, will be presented.
An other objective is to bring an overall view of the satellite, which will allow to have
a better understanding of the following chapters.
2.2 Reference frame
First of all, a reference frame must be dened. Its origin is located at the CubeSat
geometric center. The frame is oriented using the right-hand rule (as shown in Figure 2.1).
This particular frame presents 3 major advantages:
• It is the same frame as the one given in the ocial documents [1].
• The distance, that separates the Center of Gravity (CoG) from the geometric center,
can be directly evaluated.
• It allows to locate each component of the satellite in an easy way. For example,
the faces are identied using the name of the axis which is perpendicular to them
20

Figure 2.1: Reference frame of OUFTI-1
preceded by the direction of this axis (e.g., the face where the access port area is
located, is referred as face −X).
2.3 Flight system conguration
Through this section, the general conguration of the satellite will be discussed. Each
component will be reviewed in a global understanding approach. Further detail on each of
them can be found in reference [15].
First of all, the product tree of the entire satellite is presented in Figure 2.2. This
one allows to have an overall view of how the several components can be sorted. Indeed,
OUFTI-1 can be divided into three main categories:
• The main structure, including all CSK structural parts, and components which are
connected to external faces of the OUFTI-1 skeleton.
• The internal equipments, including all electronic cards and structural devices which
are located inside the satellite.
• The xations, including all screws and other xing means which allow to connect all
OUFTI-1 components together.
21

Figure 2.2: Product tree of OUFTI-1
22

2.3.1 Skeleton
The skeleton of OUFTI-1 corresponds to the 1U structure of Pumpkin's CSK. This
structure comprises three main parts:
• A chassis, with a thickness of 1.27 mm.
• A base plate, with a thickness of 1.52 mm, that is screwed on the chassis with 6
M3 × 4 mm stainless steel screws. It supports one normal foot, two spring plunger
feet and one deployment switch foot. These special feet are used to deploy the
CubeSats from the P-PODs when they are placed in orbit.
• An end plate, with a thickness of 1.52 mm, that is screwed on the chassis with 4
M3 × 4 mm stainless steel screws. It supports four normal feet.
The skeleton is made of Aluminum (Al) 5052 H32 and the feet are made of Al−6061 T 6.
A surface treatment is also performed on the structure. The rails (situated on the corners
of the chassis) and the feet are hard-anodized to prevent galling when they are in contact
with the P-POD. The rest of the structure is alodined, which is an electrically-conductive
surface nish [22]. This last fact is very important because the structure will be used as
the reference electrical mass for the CubeSat.
The kit also includes a Flight Module (FM) 430 (used as main On-Board Computer
(OBC) in OUFTI-1: OBC 1). It is important to note that all the functions available on
this card are not used for OUFTI-1 (e.g., the MHX transceiver). This fact will turn out to
be a crucial information for the nal conguration (see section 2.3.3).
Figure 2.3 shows the devices of the CubeSat kit bought by ULg.
Figure 2.3: CSK structure with the FM 430
23

2.3.2 Solar panels
The armor panels of OUFTI-1 are made of Al − 7075 T 73. Their role is to protect
all the equipments of the satellite against the harsh space environment: cosmic radiations,
debris, thermal variations, ...
Last year, a simulation of the OUFTI-1 orbit was performed to obtain the Total Irradiation
Dose (TID) at which the satellite is submitted during one year [6]. The TID is
the addition of the eects of the trapped electrons and protons within the radiation belts,
the solar protons and the Bremsstrahlung eect. The results are presented in Figure 2.4,
where the TID is considered as a function of equivalent aluminum shielding thickness.
Figure 2.4: Dose depth curve for OUFTI-1 orbit [6]
In the case of OUFTI-1, the thickness of these panels was chosen to 1.5 mm, which corresponds
to an equivalent aluminum shielding thickness of 1.95 mm for the entire satellite.
The complete study that led to this particular choice is available in reference [15]. There
are ve panels mounted on the OUFTI-1 skeleton:
• Two panels, one on the base plate and the other on the end plate, with external
dimensions of 90 × 96 mm 2 .
• Three panels placed on the faces +X and +/ − Y of the chassis, with external
dimensions of 82 × 96 mm 2 24

There is no solar panel on the face −X because the access port area can not be obstructed.
The solar cells were mounted on these panels at the rate of two per panel. Their integration
was performed by EADS Astrium. A picture of a fully-integrated panel is available
in Figure 2.5. Schematics and exact dimensions of each of these panels are available in
appendix A.
Figure 2.5: One fully-integrated solar panel of OUFTI-1
One of the problem encountered is that these panels cover integrally the holes of the
faces on which they are placed. So, to provide a way for the cabling path, some of them
are drilled of several holes with a diameter of 3 mm. The available holes for the cabling
path are presented in Figure 2.6.
Figure 2.6: Available holes on the CSK structure for cabling path [15]
Finally, it should be noted that these panels will be glued on the OUFTI-1 skeleton
using a specic glue: epoxy Stycast 2850 (with catalyst 24 LV), chosen following an advice
of Mr. Pierre ROCHUS, an engineer from Liège Space Center (CSL). For example, this
glue was already used for the Planck satellite thermal test at CSL. The reasons that led
us to choose the glue, are:
25

• We do not want to drill or manufacture the CSK structure in any way. Indeed, any
modication of this structure involves that new space qualication tests must be
performed to validate it, which is not desired in our case.
• Pumpkin has also developed solar panel clips to facilitate the integration of solar
panels on the CSK structure [23]. However, in our case, these clips interfere with
some solar cells (as shown in Figure 2.7) and then, they can not be used to attach
our solar panels to the CSK structure.
Figure 2.7: Interference between solar panel clips and OUFTI-1 solar cells [15]
2.3.3 Antenna support
OUFTI-1 uses two antennas, one for the downlink transmission in the Very High Frequency
(VHF) band (145 MHz) and the other for the uplink transmission in the Ultra
High Frequency (UHF) band (435 MHz). These antennas are made of a cupro-beryllium
alloy.
The antenna deployment mechanism is managed by the Mechanism (MECH) subsystem
[24]. The antenna support is made of Al − 5754 and it is also hard-anodized, as the
rails and feet of the skeleton, to ensure the electrical insulation of the antennas.
The principle of the deployment mechanism is the following one: each antenna is rolled
around the guide rails and is attached to it thanks to a wire of "Dyneema", which is
an Ultra High Molecular Weight Polyethylene (UHMWPE) ber. Thirthy minutes after
the deployment from the P-POD (which is a general requirement to avoid any collision
between the CubeSats), the Electrical Power Supply (EPS) subsystem will deliver some
electrical current to a thermal knife composed of a Titanium (T i) wire. When a current
goes through this wire, it heats by Joule's eect: P = U I. This wire heats until it reaches
the "Dyneema" melting point. At this moment, the antennas are released and deploy.
26

This support is mounted on the face −X. This conguration is possible thanks to the
restricted dimensions of the support (as shown in Figure 2.8).
Figure 2.8: Conguration and dimensions of the antenna support
Indeed, as already mentioned, the CubeSat standard requires that the access port area
will not be obstructed. However, in our case, the only port which would be obstructed is
the port used for the MHX transceiver (as shown in Figure 2.9). And, as it was already
mentioned, OUFTI-1 does not use this function of the FM 430. So, there is no problem to
put the antenna support at this place.
Figure 2.9: Description of the port obstructed by the antenna support
The xing method is the same as for the solar panels. The support will be glued on
the skeleton using epoxy Stycast 2850 (with catalyst 24 LV).
2.3.4 Permanent magnet and hysteretic bars
To maintain the attitude of OUFTI-1, a control system is needed. This one is managed
by the Attitude Determination and Control System (ADCS) subsystem [25].
27

In our case, because of the limited available power and the fact that the payloads do
not require a precise attitude control, it was decided to use a passive control system. This
system comprises one permanent magnet, with dimensions of 20 × 4 × 4 mm, made of
AlNiCo 5 (an Aluminum-Nickel-Cobalt alloy) and four hysteretic bars, with dimensions
of 80 × 1 × 1 mm, made of P ermenorm 5000 H2. The principle is the following one: the
permanent magnet tends to align its magnetization axis with the local Earth's magnetic
eld (as shown in Figure 2.10). The hysteretic bars allow to limit, by hysteretic damping,
the rotation rate of the satellite to an acceptable value (which will have to be determined
by tests).
Figure 2.10: Principle of the OUFTI-1 ADCS subsystem [25]
Last year, a solution with only two hysteretic bars was implemented (the conguration
is available in Figure 2.11).
Figure 2.11: Last year's conguration of the ADCS
28

However, in this conguration, a critical point that was not taken into account, is
the saturation of the hysteretic bars by the permanent magnet. Indeed, this phenomenon
limits the magnetic moment of the magnet, which presents a problem because this magnetic
moment is essential to maintain the satellite attitude so, stronger it is, better is the solution.
In accordance with these observations, the conguration with the greatest distance between
the magnet and the hysteretic bars seems to be preferable. This situation is particularly
tricky in nanosatellites because the available space is strongly restricted. Moreover, the
principal axis of each hysteretic bar should be as close as possible of the plane perpendicular
to the magnetization axis of the magnet. Any displacement from this plane leads to the
apparition of an undesired component of the magnetic eld H magnet directed along the bar.
This component results in a displacement of the working point on the hysteresis cycle, and
it therefore aects the damping eciency of the hysteretic bar. An other problem is that
the magnetic eld inside the hysteretic bars should be less than 30 A/m, which is a typical
value of the Earth's magnetic eld on OUFTI-1 orbit. This suggests that the bars should
ideally be placed as depicted in Figure 2.12.
Figure 2.12: Ideal positioning of the hysteretic bars
First conguration
Firstly, it was decided to place the magnet on the battery support, close to the center
of face −X. Its orientation was chosen in accordance with the requirement of the Radio
Frequency (RF) subsystem: "The magnetization axis of the magnet must be parallel to
the antennas' plane". The hysteretic bars were then placed as far as possible from the
permanent magnet. Unfortunately, this conguration has showed an important inuence
of the magnet on the hysteretic bars, which reduces the damping eciency. Figure 2.13
shows the magnetic eld due to the magnet in the vicinity of the hysteretic materials.
Therefore, a new conguration with a greater distance between hysteretic bars and the
permanent magnet must be found.
29

Figure 2.13: Magnetic eld obtained in the hysteretic bars for the rst conguration [25]
Second conguration
Then, it was decided to shift the magnet and to place it in the corner between faces −X,
+Y and +Z. This new arrangement ensures the lowest possible inuence of the magnet
on the hysteretic bars (as shown in Figure 2.14).
Figure 2.14: Magnetic eld obtained in the hysteretic bars for the second conguration
[25]
Final conguration
The critical point of the elongation of the hysteretic bars was not studied yet, and it
appeared that it was crucial to have a high elongation. So, in order to satisfy this necessity,
a new design was imagined. This one considers the possibility of using two parallel bars
in each direction perpendicular to the magnet, for a total of four bars placed on corners
between faces +X/ + Y , +X/ − Y , +Y/ − Z and −Y/ − Z respectively. So, to obtain
the greatest distance between the magnet and the hysteretic bars, this one is placed in the
middle of the corner between faces −X and +Y (as shown in Figure 2.15).
30

Figure 2.15: Final conguration of the ADCS
This improves the overall system eciency and leads to an optimal solution (the magnetic
eld inside each hysteretic bar is represented in Figure 2.16).
Figure 2.16: Magnetic eld obtained in the hysteretic bars for the nal conguration [25]
Pictures of the permanent magnet and hysteretic bars (these ones are not yet manufactured
to the good dimensions) are shown in Figure 2.17.
31

Figure 2.17: Pictures of the ADCS components [25]
2.3.5 Electronic cards and battery support
OUFTI-1 disposes of ve electronic cards. These cards are all based on the P C 104
standard [26]. The particularity of this standard is the P C 104 connector. This device,
with 104 pins welded on it, allows a direct connection between all the cards of OUFTI-1.
The PCBs are all made of Flame Resistant (FR) 4 that belongs to the class of Glass Fiber
Reinforced Plastic (GFRP) material.
The conguration for these cards, shown in Figure 2.18, is based on the following
requirements:
• The FM 430 card is placed in the bottom of the satellite, because it is on this card
that the access ports are placed. So, these ports have to be placed in front of the
holes of the chassis provided for this purpose, which are situated on the base plate.
• The OBC 2 card is placed just above the FM 430 card. The reason is that these two
cards have to communicate continuously so, to avoid a complicate cabling path, they
are placed as close as possible one from the other. These two cards are managed by
the student in charge of the OBC subsystem [27].
• Then, we choose to integrate the EPS card, because it is on this card that there
is most components and, consequently, it is the card with the greatest mass. So,
its location aects seriously the position of the CoG and, to respect the CubeSat
standard requirement on the CoG location, it is better to place it as close as possible
from the CubeSat geometric center.
• For the same reason, the battery support comes next. Further detail will be available
on chapter 3.
• The fourth card is the xEPS one. The reason is the same that one for the two OBC
cards (these cards have to be linked by several wires). However, in addition, we
32

Figure 2.18: Conguration of OUFTI-1 electronic cards
33

consider the possibility of oshoring the protection circuit of the batteries on one
electronic card and, in this case, the card with least components is the xEPS. The
last two cards are managed by the student in charge of EPS and xEPS subsystems.
• Finally, the Telecommunication (COM) card is placed on the top of the satellite, close
to the end plate. This card is managed by students in charge of the COM subsystem
([28] and [29]).
Schematics and exact dimensions of each of these cards are available in appendix B,
such as the available volume for each of them.
Each of the components presented in this section, is separated from the others by spacers,
made of Al − 6061 T 6, with variable dimensions (4 mm, 15 mm and 19 mm). The
whole is xed to the main structure with the help of 4 M3 × 8 cm stainless steel endless
screws, which are screwed on the base plate. On the other end of these screws, there are
four midplane standos [30], made of Al −6061 T 6, that allow to connect the screws to the
chassis. These midplane standos are also xed using M3 nuts. Schematics and pictures
of these xations are available in appendix C.
Pictures of the engineering models of each of these cards are available in Figure 2.19.
Figure 2.19: Pictures of the engineering models of OUFTI-1 electronic cards
34

2.4 Physical properties
The physical properties (including CoG and inertia) are of primary importance for the
denition of a 3-dimensional body. In addition, other students, like the ones in charge of
ADCS [25] or MECH [24] subsystems, need them to perform their simulations.
In this section, the Catia software will be used to determine theCoG location and
inertia properties of OUFTI-1. When a complete engineering model of the satellite will be
available, these values can be veried experimentally [31].
2.4.1 Catia modeling
Last year, a detailed model of the satellite was carried out using the Catia software [32].
During this year, this model was rened to obtain the nal conguration of the satellite.
This conguration is shown in Figure 2.20.
This type of modeling, which is widely used in mechanical industries, presents several
advantages:
• Firstly, it allows to have an overall view of each component's location within the
CubeSat. This is very helpful to verify that a given component could be placed at
a specic location or to create an appropriate integration procedure for the satellite
[33]. In addition, Catia les are compatible with the Samcef software [34], which is
used to perform the FE analysis. So, the two can be combined to take the best of the
two worlds (Catia for Computer-Aided Design (CAD) modeling and Samcef for FE
analysis) and to facilitate the task of the engineer who is in charge of the structural
subsystem.
• Then, Catia can calculate several physical properties such as the location of the CoG
(which is really helpful in our case considering the reference frame that we use) or
the inertia properties. However, to be accurate, Catia requires the denition of each
material used to manufacture the several components of the satellite.
• Finally, Catia facilitates the creation of technical drawings.
2.4.2 Center of gravity
An other requirement imposed by the CubeSat standard is: "The CubeSat center of
gravity shall be located within a sphere of 2 cm from its geometric center ". This requirement
allows to ensure that each P-POD CoG remains located inside a specic volume.
35

Figure 2.20: Exploded view of OUFTI-1
36

In our case, this requirement can be easily veried considering our particular reference
frame. The results obtained for OUFTI-1 in its nal conguration are listed in Table 2.1.
Axes Coordinates (in mm)
X -0.139
Y -2.558
Z 0.691
Table 2.1: Coordinates of the OUFTI-1 CoG
So, the distance between the geometric center of OUFTI-1 and its CoG can be calculated
using Equation (2.4.1).
√
d = x 2 CoG + y2 CoG + z2 CoG
= 2.6533 mm (2.4.1)
Therefore, the requirement is respected.
2.4.3 Inertia
For a continuous rigid body, the inertia tensor is given by Equation (2.4.2).
⎛
⎞
I xx I xy I xz
I = ⎝I yx I yy I yz
⎠ (2.4.2)
I zx I zy I zz
where:
I xx =
∫ (y 2 + z 2) dm (2.4.3)
I yy =
∫ (x 2 + z 2) dm (2.4.4)
I zz =
∫ (x 2 + y 2) dm (2.4.5)
∫
I xy = I yx = −
∫
I xz = I zx = −
∫
I yz = I zy = −
(x y) dm (2.4.6)
(x z) dm (2.4.7)
(y z) dm (2.4.8)
37

I xx , I yy and I zz are called the moments of inertia while the other elements are called
the products of inertia.
This tensor can be calculated from any point of the structure. However, to facilitate
its calculation, it is preferable to dene it from the CoG. Thus, the inertia tensor linked to
our reference frame is given in Equation (2.4.9).
⎛
2.104 6.025 10 −2 1.69 10 −2 ⎞
I CoG = ⎝6.025 10 −2 1.757 −9.641 10 −2 ⎠ × 10 6 g mm 2 (2.4.9)
1.69 10 −2 −9.641 10 −2 2.019
In addition, the principal moments of inertia can be calculated, as well as the principal
axes, to completely dene the inertia properties of OUFTI-1. They are given in Equations
(2.4.10) to (2.4.12) and (2.4.13) to (2.4.15) respectively.
M 1 = 1.715 × 10 6 g mm 2 (2.4.10)
M 2 = 2.05 × 10 6 g mm 2 (2.4.11)
2.5 Mass budget
M 3 = 2.114 × 10 6 g mm 2 (2.4.12)
⎛ ⎞
−0.159
A 1 = ⎝ 0.938 ⎠ (2.4.13)
0.307
⎛ ⎞
−0.042
A 2 = ⎝ 0.305 ⎠ (2.4.14)
−0.952
⎛ ⎞
0.986
A 3 = ⎝0.164⎠ (2.4.15)
0.009
As already mentioned on chapter 1, one of the general constraints for a CubeSat is:
"Each single CubeSat shall not exceed 1 kg mass ".
To ensure that OUFTI-1 respects this requirement, each component of the CubeSat
was weighted. However, at the end of this year, some of them are not yet nished. For
38

these ones, an estimation of the mass was presented in a "best case/worst case" philosophy.
The mass budget nally obtained is presented in Table 2.2. It is rstly divided between
the several subsystems in order to focus on the weight of each component to identify the
main mass consuming ones. Then, a general table is presented and the total mass of
OUFTI-1 is calculated. It should be noted that each mass was rounded to upper 0.01 g,
which brings some safety to the measurements. However, to obtain a reliable nal result,
a Safety Factor (SF) of 2% was applied to the total mass of OUFTI-1.
2.6 Summary
Through this chapter, the general conguration of OUFTI-1 was discussed.
First, a reference frame was dened to allow to locate precisely each component of the
CubeSat. The advantages of the selected frame were also highlighted.
Then, the organization of the several subsystems was exposed. For each of them, a
detailed description of the location, xing methods and general physical and mechanical
properties was presented. These descriptions allow to bring an overall view of the satellite
to the profane.
Finally, the physical properties of OUFTI-1 were determined, and their fulllments of
the ESA requirements were veried.
39

Subsystem: Structure & Conguration
Parts Components Number Best case (g) Worst case (g)
Base plate 1 35.72
Foot 1 1.32
Grower washer M3 1 0.06
Screw M3 × 4 mm 1 0.37
Drilled foot 3 3.63
Base plate
Spring plunger 2 1.2
Nut M3 2 1.1
Plastic stem 1 0.15
Deployment switch 1 2.44
Screw M1 × 1 cm 2 0.44
Nut M1 1 0.18
Shym 4 0.62
Subtotal 47.23
End plate 1 26.29
Foot 4 5.27
End plate Shym 4 0.62
Grower washer M3 4 0.21
Screw M3 × 4 mm 4 1.48
Subtotal 33.87
Chassis
Chassis 1 63.39
Screw M3 × 4 mm 10 3.19
Subtotal 66.58
Base panel 1 38.5
Solar cell 2
Base panel Kapton lm /
Adhesive /
10.5
Coverglass /
Subtotal 49
End panel 1 33
Solar cell 2
End panel Kapton lm /
Adhesive /
8.9
Coverglass /
Subtotal 41.9
40

Parts Components Number Best case (g) Worst case (g)
Chassis's panel 3 94
Solar cell 6
Chassis's panels Kapton lm /
Adhesive /
31.3
Coverglass /
Subtotal 125.3
Box 1 27.33
Battery support
Cover 1 19.24
Screw M3 × 8 mm 4 1.86
Subtotal 48.43
Endless screw 4 14.6
Spacer 4 mm 4 0.31
Spacer 15 mm 12 3.39
Fixations
Spacer 19 mm 4 1.43
Midplane stando 4 3.03
Washer 4 0.38
Screw M3 × 4 mm 4 1.28
Nut M3 4 1.31
Subtotal 25.73
Total 438.04
Subsystem: Mechanism
Parts Components Number Best case (g) Worst case (g)
Antennas
435 MHz 1 1.25
145 MHz 1 3.46
Subtotal 4.71
Antenna support
Support 1 26
Deployment mechanism 1 1
Subtotal 27
Thermal knife Thermal knife 1 0.5
Subtotal 0.5
Total 32.21
Subsystem: Attitude & Determination Control System
Parts Components Number Best case (g) Worst case (g)
Permanent magnet Permanent magnet 1 2 3
Subtotal 2 3
Hysteretic bars Hysteretic bar 4 2 3
Subtotal 2 3
Total 4 6
41

Subsystem: Thermal Control
Parts Components Number Best case (g) Worst case (g)
General Heat sensor 3 3 6
Subtotal 3 6
Heater 2 2 3
Batteries
Thermostat 4 0.75 0.85
Wire 8 8 10
Thermal insulation 1 0.02 0.08
Subtotal 10.77 13.93
Cu strap 1 5 10
EPS
Bolt M3 3 9 18
Resistance 2 2 3
Subtotal 16 31
Total 29.77 50.93
Subsystem: Electrical Power Supply
Parts Components Number Best case (g) Worst case (g)
EPS Card 1 64.67
Subtotal 64.67
xEPS Card 1 58.7
Subtotal 58.7
Battery Kokam
Batteries SLB 603870H
2 62 66
Wire 4 4 8
Subtotal 66 74
Total 189.37 197.37
Subsystem: On-Board Computer
Parts Components Number Best case (g) Worst case (g)
FM 430 Card 1 66.85
Subtotal 66.85
OBC 2 Card 1 50.47
Subtotal 50.47
Total 117.32
Subsystem: Telecommunication
Parts Components Number Best case (g) Worst case (g)
COM Card 1 50 65
Total 50 65
42

OUFTI-1
Subsystems Best case (g) Worst case (g)
Structure & Conguration 438.04
Mechanism 32.21
Attitude & Determination Control System 4 6
Thermal Control 29.77 50.93
Electrical Power Supply 189.37 197.37
On-Board Computer 117.32
Telecommunication 50 65
Adhesive 20 40
Cabling 15 30
Subtotal 895.71 976.87
Safety coecient 1.02 1.02
OUFTI-1 mass 913.63 996.41
Table 2.2: Mass budget of OUFTI-1
43

Chapter 3
Design of a new support for the
batteries
3.1 Introduction
Through this chapter, the design of a new support for the batteries will be studied.
Firstly, the reasons that led to change the support created last year, will be exposed.
Then, the entire development phase, from the initial idea to the manufacturing of the
new support, will be discussed step by step. This phase was realized in accordance with
the requirements of EPS and Thermal Control (THER) subsystems.
3.2 Problems encountered with the last year's design
The design that was imagined last year [15], is presented in Figure 3.1.
Figure 3.1: Last year's design of the battery assembly
44

In this design, the battery Printed Circuit Board (PCB) was suspended to the xEPS
card, using four T i screws. The two PCBs are separated by four T i spacers and thermal
washers are placed at the level of the battery PCB to isolate it thermally.
The main problem of this design was the available space between the batteries and the
electronic cards situated under and above them, as it is shown in Figure 3.2.
Figure 3.2: Available space under and above the batteries
The available space between the lower battery and the highest component above the
EPS card is given in Equation (3.2.1) and the distance between the upper battery and the
highest component under the xEPS card is given in Equation (3.2.2).
d Battery - EPS = 5.57 − 4.8 = 0.77 mm (3.2.1)
d Battery - xEPS = 4.83 − 1.5 = 3.33 mm (3.2.2)
So, it can already be noted that the position of the batteries inside the satellite is not
optimal. In addition, due to the restricted value of the distances which separate these
components, several problems can occured, especially concerning the vibrations. Indeed,
the batteries could collide one of the two electronic cards and cause important damages on
it.
In addition to this restricted available space, it appeared, after a test under vacuum
conditions, that the batteries bulged (as shown in Figure 3.3). This increase the problem of
the available space and, moreover, can aect the electrical performance of the batteries. To
avoid this problem, the solution which was investigated, was to encapsulate the batteries
inside a box.
45

Figure 3.3: Batteries during and after the vacuum test [15]
However, the problem for the design of this box is double:
• Firstly, the restricted available space (2.05 mm on each side in the optimal conguration)
does not allow to design a reliable box. Indeed, the vibrations generated
during the launch phase might reach amplitudes that rise above this value. So, the
box might damage the electronic cards situated close to it.
• Then, the mass budget of the satellite in the last year's nal conguration is already
higher than the 1 kg mass allowed by the CubeSat standard (the total mass of
OUFTI-1 in this conguration was 1.032 kg).
Thus, we had to give up this solution and to create a new design, including a box, to
encapsulate the batteries.
3.3 Available mass budget
The rst step to realize, when a new design is created, is to calculate the available
mass budget. To obtain this budget, we have to substract the mass of the components
that composed the old design from the total mass of OUFTI-1 obtained for the last year's
conguration. Then, the result must be substracted from the maximum acceptable mass
of 1 kg to obtain the available mass for the new support. This calculation is performed in
Table 3.1 and Equation 3.3.1.
m available = m max, acceptable
−
SF
= 1000 ( 1031.4148
1.02 − 1.02
= 103.79 g
( mtot, last year
− m last year
SF
′ s design
)
− 134.58
)
(3.3.1)
46

Components
Mass (g)
4 spacers 25 mm 4 × 0.475 = 1.9
4 T i screws 4 × 0.86 = 3.44
4 T i spacers 4 × 0.29 = 1.16
4 T i nuts 4 × 2.32 = 9.28
2 heaters 2 × 1.5 = 3
Heaters' control system 10
Radiative insulation 15
16 thermal washers 16 × 0.08125 = 1.3
Battery PCB 15.5
2 batteries Kokam SLB 603870H 2 × 33 = 66
4 wires 4 × 2 = 8
Total 134.58
Table 3.1: Available mass budget
To this result, some important corrections must be added. These corrections, which
came from revisions or improvements of designs, are related in Table 3.2.
Components Last year's mass (g) This year's mass (g) Dierences (g)
Thermal knife 19 0.5 + 18.5
Permanent magnet 13 3 + 10
Hysteretic bars 14 3 + 11
COM card 75 65 + 10
Total 121 71.5 + 49.5
Table 3.2: Important corrections in the mass budget
So, the total available mass budget for the new support is: 103.79 + 49.5 = 153.29 g.
3.4 Initial idea
The base idea of the new support was imagined by Jean-Philippe NOEL, who is in
charge of the THER subsystem [35]. The idea is the following one: instead of placing the
batteries one on the other, it was a better idea to place them one next to the other. This
new conguration allows to release more space between the batteries and the electronic
cards for integrating the box. An illustration of this new design is available in Figure 3.4.
47

The concept is the following one:
Figure 3.4: Initial idea for the new design
• The support is composed of two dierent parts: one box, in which the batteries will
be placed, and one cover, which will prevent the batteries' bulge. These two parts
will be connected together by several screws.
• The assembly will be supported by the four endless screws, just like all the electronic
cards. So, new spacers will have to be designed to replace the 25 mm ones that previously
separated the EPS card from the xEPS card. Their length will be determined
later.
• The box is composed of a "base plate" with reinforcers. The holes situated at the
level of the batteries' width are there to allow the wires to come out of the box.
Starting from this idea, the support was adapted to the OUFTI-1 dimensions. It was
decided to place it with the box on the side of the xEPS card. This detail has to be noted
because the four endless screws are not placed symmetrically inside the CubeSat so, the
direction in which the support will be integrated, takes on all its importance. This choice
is based on the CubeSat standard requirement about the CoG location already mentioned
in section 2.4.2. The result obtained is given in Figure 3.5.
48

Figure 3.5: Adaptation of the base idea to the OUFTI-1 dimensions
3.5 Battery selection
Once the four holes for the endless screws are drilled, the available space for the batteries
is restricted to the dimensions shown in Figure 3.6.
Figure 3.6: Available space for including the batteries
With these dimensions in mind, the battery selection can start.
Last year, it was decided to use Lithium (Li) batteries for their compact form and their
high specic capacity. Two dierent types of batteries were considered: Varta and Kokam.
49

A test under vacuum conditions was performed on these batteries and it appeared that
the Kokam bulged and not the Varta. However, it should be noted that batteries from
Varta presented several uncertainties in relation to their electrical capacity evolution in
time. In addition, these batteries were no longer provided by the industry and, for the
remaining ones, the storage conditions were not known. So, it was decided to use batteries
from Kokam.
The main selection criteria are: dimensions, mass, electrical capacity and, last but
not least, reliability. Accounting for these restrictions, three batteries were selected. Their
properties are available in Table 3.3. It should be noted that the electrical capacity of these
batteries is given for standard conditions (T = 25 ◦ C, V = 2.7 − 4.2 V and q = 0.5 C).
Batteries
Length Width Thickness Mass Electrical capacity
(mm) (mm) (mm) (g) (Ah)
SLP B 554374H 73.5 ± 0.5 42.5 ± 0.5 5.4 ± 0.2 32 ± 1 1.25
SLB 603870H 69.5 ± 0.5 37.5 ± 0.5 6.5 ± 0.2 32 ± 1 1.5
SLP B 723870H4 70 ± 0.5 37.5 ± 0.5 7.2 ± 0.2 37 ± 1.5 1.5
Table 3.3: Properties of several batteries from Kokam [36]
Considering the electrical capacity, OUFTI-1 needs 1.2 Ah. So, the rst battery can not
be selected because the Margin of Safety (MoS) is too small in this case. In addition, this
battery has dimensions that do not allow to include it in the available space described in
Figure 3.6. Now, if the physical properties are also taken into account, the better solution
is to use the battery Kokam SLB 603870H, which is lighter and smaller than the other
one. A picture of this battery is presented in Figure 3.7. Its datasheet is available in
appendix D.
Figure 3.7: Battery Kokam SLB 603870H
This choice, which fullls all the requirements of Structure & Conguration (STRU)
50

subsystem, was validated by the EPS team. So, the mass and dimensions of the batteries
are now known and a rst guess of how arrange the reinforcers can be realized.
3.6 Material selection
An other important step for realizing the design of the support, is the selection of the
material that will be used to manufacture it. Indeed, the thickness of the dierent parts
that must prevent the batteries' bulge, was determined in relation to the properties of the
selected material.
3.6.1 Denition of the requirements
Firstly, the requirements imposed to the material must be dened precisely.
Structural requirements
The rst feature of the battery support is its structural integrity during the launch.
Indeed, it will have to support the harsh vibration environment without causing damages
to the other components of the satellite. So, the strength is an important property that
will ensure the structural integrity of the support. The toughness is also an important
property to sustain the stage ignition/separation, fairing jettisoning and POGO eects
during launch. Then, the structural requirements can be expressed as:
• The material shall be rigid (high Young's modulus).
• The material shall have a good resistance in traction/compression.
• The material shall have a toughness of at least 25 MP a m 0.5 (which is a value typically
used in the space applications).
Thermal requirements
Firstly, the material shall resist to the operating temperature range of the batteries
([0 ◦ C − 40 ◦ C]). Then, thermal variations inside the CubeSat can disturb the batteries'
performances. These variations can be limited by using a material with a high thermal
inertia. In addition, the heat produced by the heaters must only serve to maintain the
batteries' temperature in an acceptable range. Any waste of energy could cause important
problems on the power distribution inside the satellite. So, a material with a low thermal
conductivity is preferable to keep the heat inside the support. Finally, thermal cycling can
also induce deformations of the support. However, in this case, the support could not play
its role of preventing the batteries' bulge. This eect can be limited if the Coecient of
51

Thermal Expansion (CTE) of the material is not too high (e.g, CTE of the CSK structure
is: 20 − 25 µstrain/K). Then, the thermal requirements can be expressed as:
• The material shall resist to temperature range [−10 ◦ C − 50 ◦ C] (by taking a security
margin of 10 ◦ C).
• The material shall shield batteries against thermal variations.
• The material shall have a low thermal conductivity (however, if this requirement is
not respected, it is possible to use some thermal insulators between the batteries and
their support).
• The material shall have a low CTE.
Outgassing requirements
These requirements are imposed by the ESA [37]:
• Total Mass Loss (TML) of the material shall be ≤ 1%.
• Collected Volatile Condensable Material (CVCM) of the material shall be ≤ 0.1%.
Presetting
In accordance with all these requirements, four materials were selected: Al alloys,
Carbon Fiber Reinforced Plastic (CFRP), GFRP and T i alloys. All of these materials
fulll all the requirements and they are all typically used in space applications. Their
general properties are available in Table 3.4.
Materials Densities (kg/m 3 ) Young's moduli (GP a) Yield stresses (MP a)
Al alloys 2500 − 2900 68 − 80 95 − 610
CFRP 1500 − 1600 69 − 150 550 − 1050
GFRP 1750 − 1970 15 − 28 110 − 192
T i alloys 4400 − 4800 110 − 120 750 − 1200
Table 3.4: Materials properties
52

3.6.2 Objective function and CES software
Selecting particular materials and manufacturing process is a complex task that needs
several iterations to be carried through. The procedure used here is based on references
[38] and [39].
The rst step consists in dening one or several objective functions that allow to classify
the materials. In our case, the objective is to obtain a reliable support with a minimal
weight. So, two objective functions can be dened (see Equations 3.6.1 and 3.6.2).
M 1 = E1/2
ρ
(3.6.1)
M 2 = σ2/3 y
(3.6.2)
ρ
where M 1 and M 2 are the performance index to maximize, E is the Young's modulus of
the material, ρ is its density and σ y is its yield stress.
According to these functions, it is possible to use the CES software to realize the material
selection. This powerful software, developed by the Prof. M. ASHBY, includes a
complete material database coupled with a program that classies material with regard to
predined properties.
In our case, the four materials listed in section 3.6.1 were classied using the CES
software. The graphs obtained are presented in Figures 3.8 and 3.9.
Figure 3.8: Classication by density and Young's modulus
53

Figure 3.9: Classication by density and yield stress
So, the nal classication of these materials is:
1. CFRP
2. Al alloys
3. GFRP
4. T i alloys
However, an other important criterion to take into account is the cost. Indeed, each of
these materials has a given cost, which is not the same for each of them. Moreover, the
cost is also closely linked to the manufacturing process which can be used to modeled the
material into the desired form.
For this reason, Al alloys become more attractive than CFRP. In addition, the choice
of Al alloys allows to create a support with more restricted dimensions, which is really
important considering the available space between EPS and xEPS cards.
The selection of a particular alloy was then based on an ESA requirement which stipulates
that: "Aluminum 7075 or 6061 shall be used for both the main CubeSat structure
and the rails. If other materials are used the developer shall submit a Deviation Waiver
Approval Request (DAR) and adhere to the waiver process ".
In this requirement, the denition for a "CubeSat main structure" is the following one:
a main structure is a structure which supports, in addition to its own weight, the weight
54

of other signicant components of the satellite, which is precisely the case of the battery
support.
For availability reasons, the Al − 7075 T 6 alloy was selected [40].
3.7 Thermal control's devices selection
Now, the selection of the dierent devices that perform the thermal control of the
batteries, will be discussed. It should be noted that this selection was realized by the
THER team. Further detail on each of these devices can then be found in reference [35].
In this section, we will only draw a list of these components and, for each of them, the
advantages that led to this particular choice.
3.7.1 Heaters
To maintain the batteries' temperature range in acceptable values, the use of heaters is
necessary. In our case, the heaters are polyimide thermofoil heaters from Minco industry
(illustrated in Figure 3.10) [41].
Figure 3.10: Polyimide thermofoil heater
These heaters present several advantages:
• They are available in a lot of dierent forms and dimensions. In our case, we chose
heaters that had the dimensions closest to the batteries' ones.
• They are lightweight.
• They can be glued directly on the batteries. This particularity is widely used in space
applications.
• They are space-qualied.
55

The last property to determine is the value of the resistance. Thermal simulations
performed last year [12] allow to determine that the power necessary to heat the batteries, is
250 mW . Assuming that heaters are supplied by a tension of 2.5 V (which is a conservative
approach because the tension of the batteries can not pass under 2.7 V ), the resistance
can be easily calculated (see Equation 3.7.1).
P = U I = U 2
R ⇒ R = U 2
P = 2.52 = 25 Ω (3.7.1)
0.25
The available heater that is closest to this value is a heater with a resistance of 23.7 Ω,
which is again a conservative approach because the power generated will be higher than
250 mW .
The heaters will be glued, as already mentioned, directly on the batteries, on their face
+Z (which corresponds to the side of the box).
3.7.2 Heaters' control system
Two solutions were investigated to realize the heaters' control system:
• Creation of an electrical circuit that used heat sensors to decide when the heaters
have to be supplied.
• A thermostat that is self-ecient.
In accordance with the KISS philosophy, the second solution was preferred because it
is more reliable.
The selected thermostats are Klixon 4BT − 2 [42], illustrated in Figure 3.11 (the dimensions
are given in inches).
Figure 3.11: Thermostat Klixon 4BT − 2
56

These thermostats were chosen because:
• They have very small dimensions (diameter = 6.68 mm and thickness = 2.04 mm).
• They are lightweight (mass = 0.2 g).
• They are space-qualied (conform to qualication MIL-S-24236/13).
In our case, the selected thermostat is an open-on-rise one. The mechanism of these
thermostats is the following one:
• When the temperature of the batteries passes under 7.2 ◦ C, the thermostats supply
the heaters. This particular value was chosen by the THER subsystem to avoid that
the temperature of the batteries becomes negative. Indeed, the tolerance guaranteed
by the manufacturer is 4.4 ◦ C, and the rst available value above this one is
7.2 ◦ C (4.4 ◦ C is also available but, in this case, the non-negativity of the batteries'
temperature could not be assured at each time).
• They continue until the temperature of the batteries pass above 23.9 ◦ C (± 4.4 ◦ C).
At this moment, the thermostats open the circuit and the heaters are no longer
supplied.
Now, the problem is to determine how many thermostats are necessary to obtain a
reliable control system. Dierent solutions were investigated:
• The rst idea was to use four thermostats per battery. These ones will be connected
2 by 2 in series, and the two parts will be connected in parallel. This solution is
illustrated in Figure 3.12 (where the B stands for Battery, H for Heater and T for
Thermostat).
Figure 3.12: Connection with four thermostats
This solution had to be given up because it is too expensive for this particular application.
57

• So, it was decided to use two thermostats per battery (to prevent a non-uniform
distribution from the temperature inside the battery). These ones will be placed on
the face −Z of the batteries (which corresponds to the side of the cover). So, a notch
must be manufactured on the cover. Now, it must be decided how these thermostats
will be connected together. The Table 3.5 summarizes the dierent types of available
congurations and problems that can occured.
Thermostat breaks open Thermostat breaks closed
Connection Heater will never be supplied so, The second thermostat will work
in series the battery will freeze as if it was alone
Connection The second thermostat will work Heater will be continuously supplied so,
in parallel as if it was alone the battery will burn out
Table 3.5: Dierent available congurations and problems for thermostats
In accordance with these observations, it was decided to connect them in series.
Indeed, for the connection in parallel, the second problem causes a constant supply
of the heater. In this case, all the power available inside the satellite would be used
to supply this heater, and the entire satellite would be lost. With the connection in
series, in the worst case, one battery freezes but the rest of the satellite is safe.
3.7.3 Thermal insulator
Aluminum, which is the material chosen to manufacture the battery support, is a thermal
conductor. So, to avoid all waste of energy during the batteries' heating, a thermal
insulator must be placed between the batteries and their support.
The selected insulator is a polyester netting, illustrated in Figure 3.13.
Figure 3.13: Thermal insulator: Polyester netting
This type of insulator is typically used as a spacer material to minimize conductive
heat transfer between Multilayer Insulation (MLI) blanket layers. The netting material
is chosen for its low outgassing characteristics and is specially cleaned to assure that it is
residue free [43].
One layer of insulator will be placed on each side of the batteries (the layer on the cover
side will surround the thermostats).
58

3.8 Final design of the support
Now that all the components to include inside the support are dened and the material
used to manufacture it is selected, the nal design of this one must be initiated.
The dierent steps of the box's design are summarized here:
• Firstly, the thickness of the box's "base plate" was xed to 1 mm. This restricted
thickness can be obtained thanks to the selected material (Al − 7075 T 6). Indeed,
this material allows to create proles with very low thickness (that is not the case
of the CFRP for which the manufacturing process is much more complicated). This
thickness of 1 mm was applied everywhere, except around the xations with the
endless screws because it was these parts of the box that sustain the entire weight of
the support. So, to avoid stress concentration that would lead to a fracture of the
support, the thickness of these parts was increased to 2 mm. This step is illustrated
in Figure 3.14.
Figure 3.14: Thickness of the box's "base plate"
• Then, a hole must be added on the side of face −Y to allow the P C 104 connector
from the EPS card to pass next to the support and to reach the connector from the
xEPS card. A set must also be taken into account to avoid any collision between the
support and the connector due to vibrations. This set has a value of 0.5 mm on each
side in our case. This step is illustrated in Figure 3.15.
Figure 3.15: P C 104 connector's hole
• The next step concerns the reinforcers. Their thickness was also xed to 1 mm. The
reinforcers were designed at the upper dimensions of the batteries (in order to be
able to include them inside the box in every case), except for the thickness, for which
they were designed at their lower dimensions. Indeed, the main goal of this support
59

is to prevent the batteries' bulge. So, this one has to constrain the batteries in every
case to prevent this bulge. However, this particular thickness does not allow to x
the screws that realize the connection between the box and the cover of the support.
For this reason, the thickness of the reinforcement was increased to 6 mm around
the connection holes. This step is illustrated in Figure 3.16.
Figure 3.16: Reinforcers and connection holes
• Finally, useless material was removed from several places (the two side of the support
and the side reinforcers) to lighten the box. Some weld toes were also added to obtain
the nal design of the box presented in Figure 3.17. It should be noted that the weld
toes situated at the level of the two parts around the hole for the P C 104 connector,
are bigger than the others. This choice was made to avoid any stress concentration
inside the support's legs, which would lead to the fracture of this one.
Figure 3.17: Final design of the box
This nal design leads to a volume of 9.76 × 10 −6 m 3 , which corresponds to a mass of
27.33 g. Schematics with exact dimensions are presented in Figure 3.18.
60

Figure 3.18: Schematics of the box
The dierent steps of the cover's design are summarized here:
• Firstly, just as for the "base plate" and the reinforcers of the box, the thickness of
the cover was xed to 1 mm. To avoid a waste of mass, the cover's dimensions were
restricted to their minimal value. However, some reinforcements have to be added
around the holes of the connection screws to avoid any stress concentration. These
reinforcements allow to obtain a lighter design. This step is illustrated in Figure 3.19.
Figure 3.19: Reinforcements around the connection holes
61

• Then, the thermostats, that will be placed on the cover side, have to be in direct
contact with the batteries. However, the role of the support, which is to prevent the
batteries' bulge, must not to be forgotten. This fact does not allow to increase the
height of the entire cover. So, some notches have to be manufacture in the cover to
allow the thermostats' integration. This step is illustrated in Figure 3.20.
Figure 3.20: Notches for the thermostats
• An important fact that must be noted is that the thickness of the batteries is not
constant. Indeed, there is a small part, including an electrical insulator, which is of
negligible thickness. So, to avoid any bulge of the thicker part, some end stops must
be added under the cover. This step is illustrated in Figure 3.21.
Figure 3.21: End stops
• Finally, as for the box, some weld toes are added to obtain the nal design of the
cover presented in Figure 3.22.
62

Figure 3.22: Final design of the cover
This nal design leads to a volume of 6.869 × 10 −6 m 3 , which corresponds to a mass of
19.24 g. Schematics with exact dimensions are presented in Figure 3.23.
3.9 Validation of the design
Now, the design which was nally obtained, must be validated.
3.9.1 Mass budget
Firstly, the necessary mass budget must be lower than the available mass budget estimated
in section 3.3. This one is calculated in Table 3.6.
63

Figure 3.23: Schematics of the cover
64

Components
Mass (g)
Box 27.33
Cover 19.24
4 screws M3 × 8 mm 4 × 0.465 = 1.86
4 spacers 4 mm 4 × 0.0775 = 0.31
4 spacers 19 mm 4 × 0.3575 = 1.43
2 batteries KOKAM SLB 603870H 2 × 33 = 66
4 wires 4 × 2 = 8
2 heaters 2 × 1.5 = 3
4 thermostats 4 × 0.2125 = 0.85
8 wires 8 × 1.25 = 10
Thermal insulator 0.08
Total 138.1
Table 3.6: Necessary mass budget
This budget is well lower than the available mass budget, which is of 153.29 g. So, our
design is valid with regard to the mass.
3.9.2 Static loads
Then, the structural integrity of the support under static loads at which it will be
submitted during the launch phase, must be veried.
For this, some FE analysis have to be performed. To limit the modeling eorts, only
the relevant structural parts will be considered. The modeling strategy for each part of
the support is:
• The box and the cover of the support are exible volumes made of Al − 7075 T 6.
The properties of this material are:
Young's modulus: E = 72.5 GP a
Poisson ratio: ν = 0.33
Density: ρ = 2800 kg/m 3
• The batteries, which are also exible volumes, weight 32 g and have a volume of
1.482 × 10 −5 m 3 in nominal conditions, which lead to a density of 2159.25 kg/m 3 .
However, their Young's modulus can not be estimated and is not provided in the
datasheets. To determine it, some static bench tests would be necessary but, in our
case, these components will be represented by increasing the density of the support
inside the area normally occuped by the batteries.
65

• Other components, including thermostats, heaters and thermal insulator, are less
important and do not aect signicantly the global dynamic behavior of the support.
So, they will be ignored in this model.
At this level, the precise acceleration at which the support is submitted, is not known
(because a model of the entire satellite is not available). In addition, the boundary conditions
can not be determined exactly. So, it was decided to follow a conservative approach
using the following approximations:
• The connections with the endless screws are supposed to be perfectly rigid in the 3
spatial directions. This approximation is pretty good because the spacers between
the electronic cards and the support can be considered as extremely rigid in their
longitudinal axis. In addition, the endless screws, which are xed at each of their
extremities, can also be considered as rigid xations. However, for the rotational
Degrees of Freedom (DoF), there is a certain exibility, due to the little set between
the screws and the support's holes, that can not be measured accurately without
having a complete engineering model of the satellite. So, these ones are let free,
which lead to an overestimation of the structural deections and an underestimation
of the natural frequencies.
• The acceleration applied to the support is not known. However, a known value is the
maximal acceleration of the launcher along its longitudinal axis, which is the more
constraining one and rates 6.3 g. So, using a SF of 2, this acceleration reaches a
value of 12.6 g that will be applied to our model.
The results obtained are presented in Figure 3.24. It can be directly noted that the
maximum Von Mises stress inside the support is situated, as predicted before, at the level
of the legs. However, even with our approximations and the conservative approach applied
here, the value of this stress (1.53 MP a) is strongly lower than the yield stress of the
Al − 7075 T 6, which has a value of 444.5 MP a.
66

Figure 3.24: Maximal Von Mises stress inside the support
67

3.9.3 Dynamic behavior
Finally, it is also important to verify that the dynamic behavior of the support could
not cause trouble for the satellite.
The modeling of the support is the same as the one described in the previous section.
The 5 rst natural frequencies obtained are available in Table 3.7.
Frequency (Hz)
1 2869.53
2 3219.66
3 5978.78
4 6022.2
5 6192.42
Table 3.7: First natural frequencies of the battery support
The two most signicant modes are represented in Figure 3.25 to illustrate the general
dynamic behavior of the assembly.
From these results, it can be deduced that the dynamic behavior of the support will
not aect the global behavior of the satellite in a critical way. It can also be noted that the
second vibration mode of the support is a bending mode of the legs. This fact consolidates
our idea that the principal stress concentration will be situated at this particular place,
and validates our choice to increase the thickness of these legs.
To conclude, these results demonstrate that our design is valid with regard to the
dynamic behavior.
68

Figure 3.25: The two most signicant modes of the battery support
69

3.10 Summary
Through this chapter, the design of a new support for the batteries was discussed.
First, the problems encountered with the last year's design were exposed to explain
why this particular design had to be given up.
Then, the available mass budget to realize this support was calculated, which is a crucial
step when a new design had to be created.
The selection of the several components which have to be included inside the support,
was also exposed. In addition, the material selection, which has to be in accordance with
several requirements that were listed, was studied.
Finally, the design procedure was presented step by step, just like it progressed during
the whole year. This design was then validated by several analysis and calculations.
At the moment where this thesis ends, the plans are provided to the support's manufacturers
(a rst rough shape of the box is presented in Figure 3.26).
Figure 3.26: A rst rough shape of the battery support
70

Thermal tests under vacuum conditions and structural ones of this support are planned
for June 2010. For the STRU subsystem, the following verications will have to be performed:
• A visual inspection of the support to detect potential failures.
• A sinusoidal test before and after the thermal tests. This particular test allows to
compare the natural frequencies of the support before and after it is submitted to
vacuum conditions. If there is any dierence between these two sets of frequencies, it
means that the support suers some failures (which could not be detected visually)
and that its structural integrity is not guaranteed in the harsh space environment.
It should be noted that, between these two sinusoidal tests, the support must not be
modied in any way.
• A verication of the tting torques applied to the screws.
71

Chapter 4
Electronic cards dynamic modeling
4.1 Introduction
One of the most vulnerable part of a satellite is its electronic cards. During launch,
the electronic components are subjected to harsh random vibration environment and some
failures can occured. The probability of these failures is strongly inuenced by the local
PCB response. To prevent from this undesirable phenomenon and to avoid it, it is a current
practice to create FE models of electronic cards to predict their local vibration response.
Throughout this chapter, the problem of how to model the dynamic behavior of an
electronic card, will be discussed.
Firstly, we will go around the state-of-the-art in this domain. Multiple methods will be
presented and their accuracy will be briey discussed.
Then, these methods will be applied to a practical example: the homemade OBC (OBC
2) of OUFTI-1.
Finally, an experimental test will be performed and the results will be correlated with
the ones obtained by the FE model. The inuence of various parameters on the PCB
response will also be studied through some sensitivity analysis.
4.2 State-of-the-art
It should be noted that the information incorporated in this section come from references
[44] to [49] (especially from references [44] and [45]).
72

4.2.1 Accuracy of the model
First and foremost, it is important to note that the accuracy of the FE model which
will be created, is strongly related to the decision-making. Indeed, if the results required
are the component internal stresses, a detailed FE model is necessary. However, the long
time required to build and solve this type of model can not be justied when only the
PCB response is required. In this case, it is possible to greatly simplify the model by using
several methods which will be discussed later.
In addition, the accuracy of a FE model will be mainly dependent on various sources
of error, including:
• Manufacturing variability, which will cause deviations in the vibration response of
supposedly identical PCBs. This variability includes not only material and assembly
properties, but also dimensional tolerances applied during the manufacturing
procedure.
• Inaccuracies in the denition of the model input parameters. They can result from
the modeling assumptions used or the impossibility to obtain reliable values of these
parameters (no prototype available, ...).
• Errors in the solution process (e.g., linear solutions in non-linear situations).
The major diculties encountered during the creation of a PCB FE model are so:
• To specify the input parameters, namely: stiness, density, boundary conditions and
damping. The accuracy with which these parameters are specied, will determine
the accuracy of the predicted response. So, experimental tests must be performed
to determine reliable values of these parameters in order to obtain an accurate FE
model.
• Variation of these parameters due to manufacturing, assembly, wear, ...
An example of manufacturing variation is shown in Figure 4.1, where the same test is
performed on supposedly identical PCBs. It can be directly seen than the responses
obtained are really dierent one from the other.
73

Figure 4.1: Example of manufacturing variation [44]
• Limitations due to parameters and variation sources which can not be easily specied,
such as non-linear eects, limitations of the FE mesh, physical eects that are too
complicated to be easily included in the model (i.e., air or acoustic inuences), ...
Most often, these diculties are overcome by including appropriate SF in the model.
4.2.2 Creating FE models of PCBs
The procedure to follow for creating FE models of PCBs, can be divided into 5 parts:
• Determination of the PCB properties
• Recognition of components eects
• Modeling of the chassis
• Denition of the boundary conditions
• Introduction of damping
4.2.3 Determination of the PCB properties
The PCB properties include: Young's modulus, Poisson ratio, density, thickness, ...
The specication of these properties represents the most dicult step in creating a PCB
FE model. In general, their values may be provided by manufacturers. However, these
values are not always exact (as shown in Figure 4.2). So, it is better to determine them
by ourselves.
74

Figure 4.2: Example of dierences between the values provided by manufacturers and the
values determined by experimental tests [44]
The Young's modulus can be determined using a static bend test. However, it is important
to note that most PCBs are laminated and so, their properties may vary depending
on the direction of loading. Thus, the determination of the Young's modulus necessitates
three dierent tests, one according to each axis of the PCB. Figure 4.3 shows an example
of this type of test.
Figure 4.3: Illustration of the experimental set-up for a static bend test
The shear modulus of a PCB may most conveniently be determined through a torsion
test, as shown in Figure 4.4.
So, the shear modulus can be calculated using Equation 4.2.1:
G xy = 3 K t a b
4 t 3 (4.2.1)
where K t is the slope of the load displacement curve, a and b are the dimensions of the
specimen edges and t is its thickness.
75

Figure 4.4: Illustration of the experimental set-up for a torsion test [44]
If the PCB mass and dimensions are known, the density of the PCB is easily found
using Equation 4.2.2.
ρ P CB = m P CB
V P CB
(4.2.2)
where m P CB is the mass of the PCB and V P CB is its volume. It is important to note that
this equation is based on the implicit assumption that the thickness is constant over the
entire PCB (which it is not always the case as it can be observed in Figure 4.2).
An other important fact to keep in mind is that all the tests must be performed on the
etched PCB because, as it was already mentioned, manufacturing will induce changes in
the PCB properties, like loss of mass or stiness.
4.2.4 Choice of mesh element
After the denition of the PCB properties, it remains to choose the type of mesh
elements which will be used to mesh the PCB. In accordance with the particular geometry
of this type of structure, two possibilities can be pointed up:
• Volume elements
• Shell elements
In this particular case, the shell elements are the best solution because a PCB can be
linked to a thin structure. Indeed, these elements allow to obtain results as accurate as if
volume elements were used, but they require less computation time and memory, which is
a great advantage in the current world of industry.
To convince ourselves of this fact, let us use the two solutions on a simple example.
Consider a steel plate with an area of 10×10 cm. The properties of this particular material
are well known:
76

• Young's modulus: E = 205 GP a
• Poisson ratio: ν = 0.3
• Density: ρ = 7850 kg/m 3
Consider also that the plate has a constant thickness of 1.6 mm (which is the given
thickness of OUFTI-1 PCBs). This plate was meshed once with volume elements and
once with shell elements. Then, the two sets of results are correlated. The most popular
correlation techniques make use of natural frequencies ω and mode shapes φ. And, the
most popular indicators of the correlation between two sets of data are:
• The frequency deviation, that can be calculated using Equation 4.2.3.
This indicator is generally expressed in %.
∆f (ω 1 , ω 2 ) = |ω 1 − ω 2 |
ω 1
(4.2.3)
• The Modal Assurance Criterion (MAC), that can be calculated using Equation 4.2.4.
MAC (φ 1 , φ 2 ) =
(
φ
T
1 φ 2
) 2
(φ T 1 φ 1 ) (φ T 2 φ 2 )
(4.2.4)
MAC values oscillate between 0 and 1, a unitary value meaning perfect correlation.
The results obtained by using these two indicators in our particular case, are presented
in Table 4.1 and in Figure 4.5.
Natural frequencies obtained Natural frequencies obtained Frequency
using volume elements (Hz) using shell elements (Hz) deviations (%)
1 528.2 527.8 0.08
2 771 770.2 0.1
3 954.8 953.8 0.1
4 1364.1 1361.9 0.16
5 1364.1 1361.9 0.16
Table 4.1: Frequency deviations between the two models
77

Figure 4.5: MAC between the two models
According to these results, it can be armed that the shell elements allow to obtain
results as accurate as the ones obtained using volume elements. The slight dierence in
the MAC matrix is only due to the fact that the fourth and fth modes of the plate are
symmetrical ones, as it is shown in Figure 4.6.
Figure 4.6: Symmetrical modes of the steel plate
So, from this point, the shell elements will be used to mesh the electronic cards during
FE analysis until the end of this thesis.
78

4.2.5 Recognition of components eects
When components are soldered to a PCB, they locally increase the mass and stiness of
this PCB. So, to be accurate, especially when a large number of components are present,
the FE model of the PCB must include these eects.
Theoretically, this problem can be solved by creating a detailed FE model of each
individual component present on the card, as illustrated in Figure 4.7. However, as already
mentioned in section 4.2.1, this solution, which brings a high level of detail in the model,
is not justied if only the PCB response is required. Indeed, in this type of model, each
lead of the component must be modeled using three rotational stiness elements, for which
the stiness must be determined by a trial/error approach. This requires too much time
and eorts for the expected results and so, this type of modeling is generally less favorable
than simplied methods.
Figure 4.7: Detailed model of a component [45]
Dierent levels of simplication are possible. They are summarized here:
• Simple method: The components eects are completely neglected. The reasoning
behind this method is the following one: ignoring the stiness increases the PCB
response and decreases the natural frequencies, whilst ignoring the mass decreases the
PCB response and increases the natural frequencies. So, each eect "compensates"
the other. This method is useful when no data about the components properties and
location are available.
• Global mass smearing method: The mass of each component is spread out over
the entire area of the PCB. The stiness contributions are completely neglected. This
method, which could be appeared not accurate, is based on the fact that neglecting
the stiness is a conservative approach (for the reasons exposed in the previous point).
To apply this method to a particular model, the card must be weighted and then,
its mass must be divided by the volume of its PCB to obtain the global density to
apply on this one.
79

• Global mass/stiness smearing method: Both mass and stiness of each component
are spread out over the entire area of the PCB. To apply this method to a
particular model, the same calculation than in the previous point, must be performed
to obtain the global density. The global stiness is achieved using an area weighted
average of the locally smeared Young's moduli as shown in Equation 4.2.5.
E global =
∑
Ei A i
A total
(4.2.5)
where E i is the Young's modulus at the location i on the PCB, A i is the surface area
of this location and A total is the total surface area of the PCB.
• Local smearing method: This method is the same as the previous one, except
that, instead of smearing the components properties over the entire PCB, they are
spread out over local regions of the PCB, where the local regions can be dened as
the projection of the components area on the PCB.
These methods are illustrated in Figure 4.8.
Figure 4.8: Illustration of the dierent simplication methods [45]
80

Now, the question is: When each method can be applied and why
To answer to this question, it should be noted that electronic components can be divided
into three categories:
• Light components: This category includes small discrete components, such as
resistors or transistors. The mass and stiness of these particular components are so
small than they can be neglected. So, in general, the simple method is applied to
these components.
• Surface Mount Technology (SMT) components: This category symbolizes
components such as Quad Flat Pack (QFP) Ball Grid Array (BGA) and Pin Grid
Array (PGA), which are generally about 10 − 30 mm square. The mass and stiness
increases of these particular components are proportional to their length and inversely
proportional to the thickness of the PCB on which they are soldered. So, in general,
the global or local smearing methods are applied to these components.
• Heavy components: This category includes large components, such as transformers,
large power capacitors and resistors. Due to their important mass and stiness,
these components are generally modeled using a local smearing method or, more
rarely, a detailed FE model.
These categories are illustrated in Figure 4.9.
Figure 4.9: Illustration of the dierent categories of components [45]
81

4.2.6 Modeling of the chassis
A general rule of thumb when a FE model is created, is to always model the next level
up from the structure. In the case of PCBs modeling, this level is the chassis.
If the chassis is not included in the model, it may severely aect the accuracy of this one,
unless the chassis will be extremely rigid in comparison to the PCB. Indeed, in reality, the
PCB is xed on the chassis. So, to obtain accurate results, it is a current practice to attach
the PCB on this structure during experimental tests. Thus, the boundary conditions are
identical to the ones encountered during the lifetime of the PCB and the obtained dynamic
response is more accurate.
4.2.7 Denition of the boundary conditions
Once the FE models of the PCB and the chassis are created, the next step is to
combine them together. To achieve this, rigid and/or exible FE assembly methods are
used, depending on the studied case:
• In terms of translational displacement, most xing methods are very sti. So, they
can be modeled using rigid assembly methods.
• In terms of rotational displacement, all xing methods display some exibility. So,
the use of rotational local stiness assembly methods, is required.
In this last case, the main diculty is to determine the value of the rotational stiness.
Two situations are possible:
• No prototype of the PCB is available. In this case, the options are very limited: the
value of this stiness can be estimated basing on subjective experience, or a detailed
FE model of the joint must be created (which takes, as already mentioned, too much
time in several cases).
• A prototype of the PCB is available. In this case, tests can be performed and the
value of the stiness can be determined using a trial/error approach. However, it
is important to note that methods developed in some works [50], were originally
intended for use with card-lock style xing mechanisms, which provide clamping
force along the entire edge of a PCB. So, these methods should be used with caution
in the case of locally xed PCBs (e.g., bolted, ...).
4.2.8 Introduction of damping
Several methods exist to measure experimentally the damping of a given structure (see
references [51] to [53]):
82

• The logarithmic decrement method: This method is a time domain approach.
It calculates damping based on the free decay of oscillations in the structure using
Equation 4.2.6.
( )
xn
∆ = ln = 2 π ζ
x n+1
√ ⇒ ζ = 1
√
1 − ζ
2
1 + ( 2 π
∆
) 2
(4.2.6)
where ∆ is the logarithmic decrement between times n and n + 1, x i is the response
of the structure at a given time i and ζ is the damping factor.
If the assumption of low damping can be applied, this equation is greatly simplied.
This simplication is presented in Equation 4.2.7.
∆ ≈ 2 π ζ ⇒ ζ = 2 π
∆
(4.2.7)
• The peak-amplitude method: This method is a frequency domain approach. It
calculates damping based on the Frequency Response Function (FRF) of the structure.
Once the FRF is obtained, the response at the half-power points (illustrated in
Figure 4.10) is measured and the damping can be calculated as shown in Equation
4.2.8.
Figure 4.10: Illustration of the peak-amplitude method [53]
83

Q =
ω k
= 1
ω b − ω a 2 ζ ⇒ ζ = 1 ω b − ω a
(4.2.8)
2 ω k
where Q is the quality factor, ω r is the natural frequency, ω a and ω b are the frequencies
of half-power points and ζ is the damping factor.
• The Steinberg's equation: This method is an analytical one [54]. It states that
the transmissibility at resonance of a PCB is equal to several times (depending of
the natural frequency considered) the square root of the natural frequency, as shown
in Equation 4.2.9.
Q = a √ ω r
with
⎧
⎪⎨
⎪⎩
a = 0.5
ω r ≤ 100 Hz
a = 0.75 100 Hz < ω r ≤ 200 Hz
(4.2.9)
a = 1 200 Hz < ω r ≤ 400 Hz
a = 2 400 Hz < ω r
where Q is the transmissibility at resonance and a is the tting factor based on ω r ,
which is the natural frequency. Unfortunately, the data on which the Steinberg's
method is based, are unavailable and therefore, the method is unveriable. For this
reason, it will not be used in this thesis.
• And a lot of other methods: Circle tting, Stochastic Subspace Identication (SSI),
Ibrahim Time Domain (ITD), ...
It is important to note that, in case of low damping, the frequency domain methods are
pretty poor because the curves on which they are based, are dicult to measure accurately
due to the high rate of change of the frequency response curve. So, in case of low damping,
time domain methods will be preferred.
An other important remark is that damping may vary with the excitation level. So,
several tests must be performed at several levels of excitation to determine an accurate
value of the damping factor.
4.2.9 Dynamic response computation
To avoid large errors when computing the dynamic response of a PCB, two points
should be considered:
• Enough modes should be computed in the modal solution to excite a signicant
fraction (at least 90%) of the total mass of the structure.
• If the deection of the PCB is comparable to its thickness, a non-linear analysis will
be preferred.
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4.3 Application to the homemade on-board computer of
OUFTI-1
Now, the several methods discussed through section 4.2 will be applied to the particular
case of the homemade OBC of OUFTI-1. This electronic card is located just above the
FM 430 card from Pumpkin (as shown in Figure 4.11).
Figure 4.11: Location of the OBC 2 card in OUFTI-1
4.3.1 Denition of the PCB properties
Each electronic card of OUFTI-1 was manufactured by Deltatec [55], a very high-level
design house specialized in advanced technologies. They provided us the properties of the
FR 4 material they used to manufacture the PCB of the OUFTI-1 electronic cards. These
properties are presented in Table 4.2.
Properties Values
Young's modulus 20 GP a
Poisson ratio 0.3
Density 2200 kg/m 3
Ultimate stress 423 MP a
Table 4.2: Properties of the FR 4 material
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Their study was based on the fact that the material is isotropic. They did not determine
the anisotropic values because, owing to the PCB assembly (which is a piling up of several
layers of FR 4 and copper), these values are too complicated to obtain. So, anisotropic FE
model of the PCB can not be performed in this thesis.
Finally, they give us a value of 1.6 mm for the PCB thickness. But, measuring it by
ourselves, the values obtained are included in a range of: [1.65 − 1.75 mm]. So, the value
which will be imposed to our FE models, is 1.7 mm.
The mesh elements that will be used to mesh the PCB of the OBC 2 card, as already
mentioned in section 4.2.4, are shell elements.
Finally, for the damping, according to reference [49], a modal damping of 2% is a quite
representative value for a PCB because there is a great friction between the dierent layers
which constitute it. In our case, a value of 1% will be applied to the model to keep a
security margin of 1%.
4.3.2 Recognition of the components eects
First of all, we have to decide which type of components will be taken into account
in the FE model of the OBC 2. As already mentioned, these components can be divided
into three dierent categories: light, SMT and heavy components. The classication of
components soldered to this card, is presented in Figure 4.12.
Figure 4.12: Components classication of the OBC 2 card
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In our case, only the SMT and heavy components will be included in the FE model of
the OBC 2 card. The light components, due to their negligible eect on the stiness and
mass properties of the PCB, will not be modeled in any application. The Catia modeling
of the OBC 2 card is presented in Figure 4.13.
Figure 4.13: Catia modeling of the OBC 2 card
To take into account the mass contributions of these components on the OBC 2 response,
the methods exposed in section 4.2.5 will be applied one by one. Thus, the accuracy
of each of them will be discussed, based on experimental results obtained through the
test that will be presented in section 4.3.3.
The stiness contributions will not be included in FE models for several reasons:
• First, the datasheets provided with most electronic components, do not contain this
information.
• Then, realizing a static bend test on each component is too expensive with regard to
the expected results.
• Finally, as already mentioned, ignoring the stiness is a conservative approach. So,
the natural frequencies that will be obtained, will be lower than the real ones. This
fact is not critical in our case because, in general, LV manuals specify minimum
values for the payload natural (fundamental) frequency of vibration in order to avoid
dynamic coupling between low frequency dynamics of the LV and payload modes.
So, if the natural frequencies obtained using this method fulll the requirements, the
real ones will automatically fulll these requirements. An example of this type of
requirement is presented in Figure 4.14.
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Figure 4.14: Example of spacecraft stiness requirements for dierent launchers
4.3.3 Experimental test of the OBC 2 card
In this section, the description of the experimental test performed on the OBC 2 card,
will be explained. Three main parameters have to be dened for a vibration test: the
boundary conditions (the support), the type of excitation and the acquisition system.
Each of these parameters has a great inuence on the results obtained and so, they have
to be chosen carefully.
Boundary conditions
The choice of the support used during a test is strongly related to the type of excitation
and to the acquisition system. Indeed, some system (e.g., laser transducers) needs an
accurate pointing and so, a rigid support to maintain the tested structure. So, this choice
has to be made in compliance with the other requirements of the test.
In our case, the test was realized in "free-free" boundary conditions. This particular
conguration was chosen in order to avoid the apparition of additional unknowns concerning
the xing method. In addition, it gives rigid body modes at low frequencies, which
allow to distinguish them from the real modes of the OBC 2 card. To simulate these conditions,
the card was suspended by four elastics attached to the four endless screws' holes
of the card.
Type of excitation
Then, the type of excitation that will be used, must be dened. The selection criteria
are generally: simplicity and reliability.
In our case, the hammer excitation was chosen. Indeed, owing to the restricted dimensions
of the electronic card, this type of excitation is the most practical one. The
hammer used is the smallest available in the laboratory. It was equipped with a tip made
of vinyl, which allow to obtain an acceptable Power Spectral Density (PSD) in the range
of: [0 − 2000 Hz]. A better choice, with regard to the PSD, is to use the stainless steel
88

tip, but this one is subject to the "bounce" eect, which can cause perturbations on the
vibration response of the structure. No additional mass was used to increase the hammer
impact. Note that an exponential window was applied to the excitation signal. This is a
current practice when a hammer is used to perform the test.
It should also be noted that no impact averaging was performed. Indeed, to apply this
method, impacts include in a series must be the same and, any dierence in the impact
location or intensity has a signicant eect on the results. Now, the OBC 2 card is so
small that the reproduction of the same impact several time can not be assured. In our
case, the excitation point was chosen on a corner of the card (see Figure 4.15).
Acquisition system
Finally, the acquisition system, which takes measurements on the structure, has to be
chosen. An important requirement, that will be discussed in section 4.3.8, is that this
acquisition system does not interfere with the dynamic response of the structure.
In our case, it was decided to use an accelerometer. This type of sensor is currently
used when the signal to measure is a high-frequency one (e.g., a shock), which is the case
here. Once again, owing to the restricted dimensions and mass of the electronic card, this
accelerometer has to be as lightweight and small as possible, to avoid any interference with
the OBC 2 dynamic response. In our case, the accelerometer used weights only 0.2 g and
is enough small for being placed everywhere on the electronic card.
It was chosen to realize 22 measurements on the card. According to this particular
choice, the best solution to attach the accelerometer is the beeswax, which allows a good
grip without interfering with the dynamic response, and an easy handling. The measurement
points are presented in Figure 4.15.
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Figure 4.15: Location of measurement and excitation points
The acquisition parameters applied to the measured signal, are:
• A frequency sampling of 512 Hz
• A resolution of 2.5 Hz
The complete set-up is presented in Figure 4.16.
Figure 4.16: Experimental set-up for the test of the OBC 2 card
90

The global FRF of the OBC 2 card is presented in Figure 4.17.
Figure 4.17: Global FRF of the OBC 2 card
Now that everything was dened, the dierent simplication methods can be applied
to the OBC 2 card and compared to experimental results. This comparison will be realized
using the two indicators introduced in section 4.2.4, namely the frequency deviation and
the MAC.
4.3.4 Application of the simple method
The rst method to be applied is the simple method. So, all the components eects are
completely neglected and only the PCB remains. These properties being already dened,
the results can be directly computed. They are presented in Table 4.3 and in Figure 4.18.
Corresponding modes Frequency deviations (%)
1 1.01
2 11.37
Table 4.3: Frequency deviations between corresponding modes using the simple method
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Figure 4.18: MAC matrix using the simple method
It can be immediately noted that these results are not good because only two modes
of the card are found by the model.
This great dierence between the results from the model and the ones obtained by
experimental test, can be explained by several facts:
• Firstly, the boundary conditions are not fully "free-free" in the experimental set-up
(this type of boundary conditions is impossible to reproduce in reality owing to the
gravity). This could bring some unknowns about these boundary conditions which
are not taken into account in the FE model. This fact could lead to dierent dynamic
responses of the PCB.
• Then, the choice of hammer and/or tip could be not appropriate to our case. And, if
the structure is not well excited, its dynamic response can not be measured accurately.
• Finally, owing to the restricted dimensions of the studied structure, the exact location
of measurement points is uncertain. Any error in this location could lead to a
comparison between two points (the measurement point and its "equivalent" from
the FE model) that have fundamentally dierent displacements.
But, for our study, the results obtained are sucient and so, an other test will not be
performed.
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4.3.5 Application of the global mass smearing method
The second method to be applied is the global mass smearing method. In this method,
the mass of each component is spread out over the entire area of the PCB. So, the global
density is obtained by dividing the mass of the complete electronic card by the volume of
the PCB. This calculation is realized in Equation 4.3.1.
ρ global = m OBC 2 50.4607 × 10−3
= = 3536.1388 kg/m 3 (4.3.1)
V P CB 1.427 × 10 −5
The results are presented in Table 4.4 and in Figure 4.19.
Corresponding modes Frequency deviations (%)
1 21.89
2 30.07
Table 4.4: Frequency deviations between corresponding modes using the global mass smearing
method
Figure 4.19: MAC matrix using the global mass smearing method
It can be remarked that the results are better than the ones obtained using the simple
method. So, this method is more accurate than the preceding one (which is in accordance
with the theory).
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4.3.6 Application of the local mass smearing method
The third method to be applied is the local mass smearing method. In this method,
the mass of each component is spread out over local regions of the PCB. So, the density
of the PCB is locally increased. The value of this increase can be calculated by dividing
the mass of each component by the product between the base area of the component and
the thickness of the PCB. The increase of density caused by each component is presented
in Table 4.5.
Components Equivalent densities (kg/m 3 )
P C 104 connector 15308.5
I 2 C − EEP ROM 2717.2
MAX 890 2335.3
MSP 430 2068.2
Crystal 32.768 kHz 3816.4
JT AG connector 4275.9
Table 4.5: Increases of density due to each component of the OBC 2 card
The results are presented in Table 4.6 and in Figure 4.20.
Corresponding modes Frequency deviations (%)
1 21.46
2 25.98
Table 4.6: Frequency deviations between corresponding modes using the local mass smearing
method
Once again, it can be remarked that the results are better than the ones obtained using
the global mass smearing method. So, this method is more accurate than the preceding
one (which is in accordance with the theory).
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Figure 4.20: MAC matrix using the local mass smearing method
4.3.7 Application of a homemade method
Generally, the methods used in the previous sections, are applied to the entire PCB.
However, as already mentioned in section 4.2.5, these methods can be particularized to the
dierent categories of components and several methods can be applied on the same PCB.
The homemade method described here is based on this concept. It considers the following
simplications:
• The light components are completely neglected.
• The SMT components, including: the I 2 C − EEP ROM, the two MAX 890, the
MSP 430, the Crystal 32.768 kHz and the JT AG connector, are modeled using the
global mass smearing method. This solution was chosen because it is easier to apply
than the local mass smearing method and, with regard to the mass contributions of
these components, it brings the same level of accuracy.
• The heavy components, including only the P C 104 connector, are modeled using a
detailed FE model. This solution was chosen because, owing to its dimensions and
its properties, the P C 104 connector plays an important role in the PCB dynamic
response. So, it is better to model it entirely. To be able to create this particular
model, the properties of this connector are necessary. Its mass is easily obtained
by weighting it and has a value of 10.12 g, which leads to a density calculated in
Equation 4.3.2
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ρ P C 104 connector =
10.12 × 10−3
7.193 × 10 −6 = 1406.9234 kg/m3 (4.3.2)
For its stiness, no static bend test was possible to perform. So, its value was xed
based on reference [49], where the Young's modulus of an equivalent component was
determined by test. So, the Young's modulus used in our FE model is 846 MP a.
Applying this simplications on the FE model, the results obtained are presented in
Table 4.7 and in Figure 4.21.
Corresponding modes Frequency deviations (%)
1 15.29
2 17.33
Table 4.7:
method
Frequency deviations between corresponding modes using the homemade
Figure 4.21: MAC matrix using the homemade method
It can be remarked that this particular method is the one which gives the best results
according to the MAC and the frequency deviations. For these last ones, the great
dierences between the values obtained by the model and the ones resulting from the experimental
test, can be easily explained. They are due to the fact that the stiness is
ignored, and that ignoring the stiness is a conservative approach which underestimates
the values of the natural frequencies. So, in the following chapter, this particular method
will be applied to each electronic card of OUFTI-1 to obtain its complete FE model.
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4.3.8 Sensitivity analysis
During the description of the modeling strategy, it was highlighted that several parameters
play an important role on the accuracy of the obtained FE model. In this section, the
eect that a variation of some of these parameters causes on the PCB dynamic response,
will be studied.
Mass of the sensor used during the experimental test
The rst analysis concerns the mass of the sensor used to realize the measurements
during the test. Indeed, this sensor brings a local increase of mass and stiness on the
PCB, just as each electronic component. To obtain accurate results, this fact has normally
to be taken into account in our model, which is never the case when a FE model is realized.
So, the question is: what is the real eect of the sensor on the PCB dynamic response
To try to answer to this question, a sensitivity analysis will be performed by integrating
sensors of several mass in our model. Then, the shape of the fourth mode of the OBC 2
card will be studied for 3 cases: a sensor of 0.2 g (as the sensor used in our case), one of
1 g and the last of 2 g.
To realize this, a concentrate mass is added to the model. However, this mass has to
be placed at a strategic point to obtain results which highlight its inuence on the mode
shape. Indeed, if this mass was placed on a vibration node, nothing could be observed
because it would not be excited. So, to realize this choice, the initial shape of the fourth
mode is necessary. This one is given in Figure 4.22.
Figure 4.22: Initial shape of the OBC 2 card's fourth mode
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According to this particular shape, it was chosen to place the sensor at the level of the
measurement point 1 (see Figure 4.15), which is situated in one of the two corners on the
opposite side of the P C 104 connector, because it is this part of the electronic card which
presents the greatest deformations and so, which participates the most to this mode. Table
4.8 presents the natural frequencies obtained in each case and their deviations with regard
to the initial one, and Figure 4.23 shows the eect on the mode shape.
Cases Natural frequencies (Hz) Frequency deviations (%)
Initial 907.68 /
Sensor of 0.2 g 893.81 1.53
Sensor of 1 g 862.66 4.96
Sensor of 2 g 847.62 6.62
Table 4.8: Natural frequencies obtained by adding sensors of several mass to the FE model
Figure 4.23: Mode shapes obtained by adding sensors of several mass to the FE model
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Thanks to these results, the following conclusions can be drawn:
• The increase of mass brought by the sensor has an important eect on the value of
the natural frequencies. Indeed, it can be seen that, even with a sensor of 0.2 g,
the shift in frequency reaches a value of 13.87 Hz, which is not negligible. And this
eect becomes more important when the mass of the sensor increases. This problem
is essentially due to the fact that the studied structure has very restricted dimensions
and mass. So, any increase of mass, so small it is, involves interferences with the
PCB dynamic response.
• This eect can also be highlighted with the mode shape. Indeed, it can be seen that
the amplitude of the PCB deformation at the sensor location decreases when the
mass of the sensor increases.
So, in this particular case, it will be better to use a sensor which does not need to
touch the structure to perform the measurements (e.g., laser transducers, ...). This allows
to avoid any interference with the dynamic response of this structure.
Modeling of the P C 104 connector
The second analysis concerns the modeling of the P C 104 connector. It was choose to
represent it using a detailed FE model, for reasons exposed previously. But, the question
is: what does this particular choice involve on the PCB dynamic response To answer to
this question, the fourth mode of the OBC 2 card for the two dierent type of modeling,
is shown in Figure 4.24.
Figure 4.24: Inuence of a change of modeling strategy for the P C 104 connector on the
OBC 2 card's fourth mode
Thanks to these results, it can be seen that the inuence of the P C 104 connector on
the PCB dynamic response is stronger using the detailed FE model (the deformation of the
card is less important at the connector location and more important on the opposite side).
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This is due to the fact that this connector brings a non-negligible increase of stiness to
the PCB, and that this particular increase is not taken into account using the local mass
smearing method. So, the best solution is well to use the detailed FE model for the P C 104
connector.
4.4 Summary
Through this chapter, the electronic cards dynamic modeling was discussed.
First, we took a turn of the several existing methods to realize this particular modeling.
The accuracy of each method was studied and the critical parameters on which this
accuracy is mainly dependent, were highlighted.
Then, these methods were applied to the homemade OBC of OUFTI-1. The results
obtained were correlated with ones measured during an experimental test.
Finally, some sensitivity analysis were undertaken to study the eect of several parameters
on the dynamic behavior of the OBC 2.
After this chapter, the following conclusions have to be kept in mind:
• The most accurate method developed in this chapter is the homemade method, which
combines several general methods to create an accurate FE model of the electronic
card. So, it is this method that will be applied in the following chapter.
• The experimental results could be better. So, if an other test is performed next year,
the following facts have to be taken into account:
To come closer to the "free-free" boundary conditions, the card could be xed
by only one hole, using one elastic. The set-up will be more unstable, but the
additional modes that will be excited, are rigid body modes so, there is no
problem.
The hammer excitation is the best solution to excite the structure in "free-free"
boundary conditions. However, it could be better to realize the test using a
stainless steel tip, which will bring a stronger PSD. Note that it will need to
bring attention to the "bounce" eect.
It could be interesting to give up the "free-free" boundary conditions and to
realize a chassis which allows to x the electronic card on a shaker. Thus, the
real boundary conditions of the electronic card's lifetime will be more accurately
reproduced and the results will be better. Note that the chassis have so to be
included in the FE model.
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Chapter 5
Complete FE analysis of OUFTI-1:
Static, modal and random vibration
5.1 Introduction
Through this chapter, a complete FE analysis of OUFTI-1 will be performed.
Firstly, the modeling strategy for each of its components will be exposed. A selection
will be realized between these components to choose which of them have a critical inuence
on the global behavior of the entire satellite and so, have to be taken into account in the
FE model, and which can be neglected to limit the modeling eorts.
Then, three dierent analysis will be carried out:
• A static analysis, where the satellite will be submitted to the static loads encountered
during the launch phase.
• A modal analysis, which will allow to obtain the natural frequencies of the satellite
and to verify their fulllment of the ESA requirements.
• A random vibration analysis, where the satellite will be submitted to a random
vibration. This analysis is essential because the decision to accept the satellite on
board Vega (or any other space launcher), is strongly based on its results.
5.2 Modeling strategy
Through this section, the modeling strategy for the relevant components of the satellite
will be exposed. It should be noted that this modeling is performed using the Samcef
software. Firstly, the Catia model presented in chapter 2, is uploaded in the Samcef
101

environment. Then, this model is exploded in several parts to isolate each component.
Finally, a behavior and a material are assigned to each of them and they are linked together
using the assembly methods available in Samcef (the methods used must be as close as
possible from the real connection between the two components to obtain accurate results).
5.2.1 Materials properties
Firstly, the properties of the materials used for manufacturing the several components,
are presented in a single table (see Table 5.1). This allows to avoid multiple repeatings of
tables including these properties through this section. Afterwards, these materials will be
just mentioned and their properties will not be reminded. It should be noted that these
properties were found using the CES software.
Materials Young's moduli (GP a) Poisson ratios Densities (kg/m 3 )
Al − 5052 H32 71.795 0.33675 2685
Al − 5754 69 0.33 2700
Al − 7075 T 6 72.5 0.33 2800
Al − 7075 T 73 71 0.33 2800
FR 4 20 0.3 2200
Stainless steel 205 0.3 7850
Table 5.1: Properties of the materials used in OUFTI-1
5.2.2 Main structure
The main structure of OUFTI-1, which corresponds to the CSK structural parts,
was modeled using shell components. Indeed, the thickness of the base and end plates
(1.52 mm) and the one of the chassis (1.27 mm) are negligible with regard to their other
dimensions (100 mm), which allows to use this type of modeling. All these components
are made of Al − 5052 H32.
The base and end plates are connected to the chassis by several M3 × 4 mm stainless
steel screws. To model this type of connection in Samcef, the procedure is the following
one:
• A point (vertex) is placed at the center of the two holes (one on the considered plate
and the other on the chassis).
• These vertex are linked to the wire of their respecting hole using a "mean" assembly.
This type of assembly determines the mean rotation and displacement of the nodes
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concerned. This particularity allows to model the fact that the screw is not rigidly
xed to the structural parts, and that a set can occured. It is important to note that
the denition of this type of assembly must be realized carefully. Indeed, one vertex
is used as the reference point for the determination of the "mean" assembly. It is
important that this point is selected rst and therefore, is dened as support 1. The
vertex must be dened in the "Modeler" module as "not a datum point". The group
of master nodes will be placed on support 2. No other parameters are required [56].
• Finally, the two vertex are linked together using a "xed" assembly, which allows to
model the screw. This type of assembly joins the two parts rigidly together.
The other components, such as the feet (normal and special ones), the deployment
switch, ... were not taken into account because they do not aect signicantly the global
behavior of the satellite.
5.2.3 Solar panels
The solar panels, made of Al − 7075 T 73, were also modeled using shell components
with a thickness of 1.5 mm.
These solar panels will be connected to the dierent faces (+X, +Y , −Y , +Z and −Z)
of the satellite using a specic glue: epoxy Stycast 2850 (with catalyst 24 LV), as alredy
mentioned. To model this type of connection in Samcef, a "glue" assembly is used. This
assembly is currently used when a glue is involved in a connection between two components.
It establishes a linear relation between the nodes on support 1 and the faces of the elements
on support 2 (as shown in Figure 5.1). The mesh is automatically adapted [56].
Figure 5.1: Illustration of a "glue" assembly [56]
The solar cells and the electronic pads were not included in the model for the same
reasons than before (negligible eect).
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5.2.4 Antenna support
For the antenna support, it was chosen to only model the support itself (made of
Al − 5754). Indeed, due to their negligible mass, the antennas do not play an important
role in the global behavior of the support, as well as the thermal knife and the "Dyneema"
wire. However, owing to its complex geometry, this support can not be modeled using shell
components. So, in this case, volume elements are used (in Samcef, it corresponds to apply
the behavior of "exible volume" on the support).
The xing method is the same as the one used for the solar panels. The support is
connected to the face −X of the chassis using a "glue" assembly.
5.2.5 Electronic cards and battery support
The modeling procedure for the electronic cards was discussed in chapter 4. In this
chapter, it was noted that the best method to realize an accurate FE model of an electronic
card is the homemade method, which uses the following simplications:
• The light components are completely neglected.
• The SMT components are modeled using the global mass smearing method.
• The heavy components, such as the P C 104 connectors, are modeled using a detailed
FE model.
It was also noted that the electronic cards, due to their low thickness (1.7 mm), can be
modeled using shell elements.
So, this method will now be applied to each electronic card individually.
The FM 430 card
This card is presented in Figure 5.2.
Applying the homemade method to this card is not so easy. Indeed, it can be seen that
several heavy components are present on this card. Unfortunately, the properties of these
components are not known so, a detailed FE model of these ones can not be realized. For
this reason, it was decided that the P C 104 connector would be modeled using a detailed
FE model, and the other components would be modeled using the global mass smearing
method. The properties nally obtained for this card, are presented in Table 5.2.
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Figure 5.2: The FM 430 card from Pumpkin
Components Young's moduli (GP a) Poisson ratios Densities (kg/m 3 )
P C 104 connector 0.846 0.3 1406.923
PCB 20 0.3 3975.473
Table 5.2: Properties of the FM 430 card
The OBC 2 card
This card is presented in Figure 5.3.
Figure 5.3: The OBC 2 card
The application of the homemade method to this particular electronic card, was already
presented in section 4.3.7. The results nally obtained are reminded in Table 5.3.
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Components Young's moduli (GP a) Poisson ratios Densities (kg/m 3 )
P C 104 connector 0.846 0.3 1406.923
PCB 20 0.3 2822.705
Table 5.3: Properties of the OBC 2 card
The EPS card
This card is presented in Figure 5.4.
Figure 5.4: The EPS card
This electronic card is the one with the greatest number of components. For the most,
these components belong to the SMT category (introduced in section 4.2.5) so, they can be
modeled using the global mass smearing method. The P C 104 connector is still modeled
using a detailed FE approach. The properties nally obtained for this card are presented
in Table 5.4.
Components Young's moduli (GP a) Poisson ratios Densities (kg/m 3 )
P C 104 connector 0.846 0.3 1406.923
PCB 20 0.3 3186.405
Table 5.4: Properties of the EPS card
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The xEPS card
This card is presented in Figure 5.5.
Figure 5.5: The xEPS card developed in collaboration with Thales Alenia Space ETCA
Except for one (situated at the top of the image, on the left), all the components of
this card belong to the SMT category. So, once again, all the components will be modeled
using the global mass smearing method. The P C 104 connector will still be modeled using
the same method that in the previous cases. The properties nally obtained for this card,
are presented in Table 5.5.
Components Young's moduli (GP a) Poisson ratios Densities (kg/m 3 )
P C 104 connector 0.846 0.3 1406.923
PCB 20 0.3 3404.345
Table 5.5: Properties of the xEPS card
The COM card
Unfortunately, at the moment when this thesis ends, this card is not yet manufactured.
So, no picture of it can be presented. In addition, no accurate information are available
for this card (e.g., concerning its mass). Its nal mass was estimated to maximum 65 g by
the COM subsystem. So, like for the other electronic cards, the P C 104 connector will be
model accurately and the mass of the other components will be spread out over the entire
PCB. The properties nally obtained for this card, are presented in Table 5.6.
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Components Young's moduli (GP a) Poisson ratios Densities (kg/m 3 )
P C 104 connector 0.846 0.3 1406.923
PCB 20 0.3 4046.952
Table 5.6: Properties of the COM card
Battery support
The battery support is more dicult to model. Indeed, its two parts (the box and the
cover), made of Al − 7075 T 6, have specic geometries which do not allow to model them
using shell elements. So, to be as accurate as possible, it was decided to model these two
parts using volume elements. For the batteries, the problem is quite dierent. These ones
do not have a constant thickness, and their Young's modulus is not known. So, it was
decided to represent them using a local mass smearing method (the mass of the batteries
can be obtained by weighting them or by consulting their datasheet). As remind, the
density of the battery is 2159.25 kg/m 3 . Then, the batteries are xed to their support
using a "glue" assembly.
Assembly
These ve electronic cards and the battery support are all xed on the endless screws.
To realize these connections, some vertex were added to each endless screws, at the level
of each of these components. These vertex are used to create the endless screws and so,
are rigidly xed to them. Then, a "mean" assembly is applied between each vertex and
the wire of its corresponding hole on the considered component.
5.2.6 The endless screws
The endless screws, due to their higher dimensions and to the fact that they are involved
in a lot of connections (as explained in section 5.2.5), will be modeled more accurately than
the screws which connect the CSK structural parts together. These screws are M3 × 8 cm
stainless steel screws. So, to model them accurately, a circular beam behavior was used,
with a diameter of 2.459 mm, which corresponds to the M3 standard.
In reality, these screws are connected to the base plate at one extremity, and to the
chassis at the other, thanks to the midplane standos. For the rst connection, the same
assembly method as the one used for the electronic cards and the battery support, is
applied. For the second one, an homemade method was imagined. The midplane standos
were replaced by two vertex connected together using a "xed" assembly. To clarify the
following explication, Figure 5.6 shows this particular modeling. One of these vertex (1) is
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located at the extremity of the considered endless screw, and the other (2) is situated at
the same level, but in front of the hole of the chassis which allows to connect this one with
the considered midplane stando. Then, the screw which realizes the connection between
the chassis and the considered midplane stando, is modeled using the same method that
for the connection between the base and end plates, and the chassis (by using two vertex
(2 and 3), xed rigidly one to the other).
Figure 5.6: Modeling of the midplane standos
5.2.7 ADCS and THER components
The ADCS components, including the permanent magnet and the four hysteretic bars,
are not modeled. The same decision was taken for the THER components, including
heaters, thermostats and thermal insulation. This choice was made for several reasons:
• First, due to their restricted dimensions and mass, they do not play a signicant role
in the global behavior of the satellite.
• In addition, they are all made of materials which present special properties so, these
ones are dicult to obtain.
• Finally, even if these properties can be obtained, they will be modify during the
manufacturing of these elements (in the case of the permanent magnet and hysteretic
bars) and so, the results obtained with and without these components, will not be
more accurate one compared to the other.
Now that the modeling of each part of the satellite is dened, the analysis can start.
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5.3 Static analysis
As described in reference [57], Vega, and so, its payloads, is subjected to quasi-static
loads during ight. So, the aim of this study is to ensure the structural integrity of each
part of the satellite when it is submitted to these steady state acceleration.
5.3.1 Loads denition
The rst step is to clearly dene the quasi-static loads which will be applied on our
CubeSat. For this, the worst case will be considered. This particular case occures if
OUFTI-1 is placed in third position inside the P-POD because, in this conguration, it
has to support the weight of two CubeSats in addition of the quasi-static loads imposed
by the launcher. This conguration is illustrated in Figure 5.7. As remind, the P-POD
will be placed at an angle of 10 ◦ from the vertical.
Figure 5.7: Illustration of the worst case conguration
The maximal steady state acceleration given in reference [57], is the one along the
launcher's longitudinal axis. This acceleration has a value of 6.3 g. In our case, it was
decided to apply a SF of 2 on each acceleration. So, the acceleration along the Z axis of
the Vega frame is 12.6 g. The lateral accelerations, due to the dynamic pressure inside the
launcher, have a maximal value of 1.2 g. So, an acceleration of 2.4 g will be applied along
X and Y axes of the Vega frame.
However, due to the particular conguration of the P-POD, a rotation matrix must be
applied to these accelerations to bring them back in the CubeSat frame (as illustrated in
Figure 5.8).
Note that the CubeSat are placed with their base plate (face −Z) on the side +Z inside
the P-POD (as it can be seen in Figure 5.8). This conguration is the one given in the
ocial documents [58].
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Figure 5.8: Frame rotation
The calculation of the steady state accelerations in the CubeSat frame is presented in
Equation 5.3.1.
⎛ ⎞ ⎛
⎞ ⎛ ⎞ ⎛ ⎞
a X, CubeSat 1 0 0
2.4 2.4
⎝a Y, CubeSat
⎠ = ⎝0 cos (10 ◦ ) −sin (10 ◦ ) ⎠ × ⎝ 2.4 ⎠ = ⎝ −0.1756 ⎠ (5.3.1)
a Z, CubeSat 0 sin (10 ◦ ) cos (10 ◦ ) 12.6 −12.8253
Owing to the particular case which is considered, the weight of the two other CubeSats
placed inside the P-POD must be added to these acceleration. The maximal acceptable
mass for one CubeSat is 1 kg. So, the forces acting on the four feet of OUFTI-1 base plate,
due to the two CubeSats placed above it, are calculated in Equation 5.3.2.
F = m × g × a quasi−static = 2 × 9.81 × 12.8253 = 251.64 N ≈ 252 N (5.3.2)
which lead to a force of 63 N on each foot along the Z axis of the CubeSat frame.
It is important to note that the accelerations considered in this analysis occured at
dierent phases of the ight (the maximal longitudinal acceleration is reached at the third
stage's maximal acceleration and maximal lateral accelerations are reached during the lifto
and under the ight maximal dynamic pressure). So, the resulting model is conservative,
which brings an additional security with regard to the results.
An illustration of the complete loading state (in the CubeSat frame) is given in Figure
5.9.
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Figure 5.9: Illustration of the complete quasi-static loading state of OUFTI-1
5.3.2 Boundary conditions
To determine the boundary conditions to apply to our CubeSat, its mounting within
the P-POD must be known. This one is available in reference [58]. Then, these conditions
must be dened as follow:
• The CubeSat is placed inside the P-POD with its base plate on the +Z side. So,
in the worst case considered here, the end plate's feet are in direct contact with the
P-POD. For this reason, these feet will be clamped to simulate this perfectly rigid
contact.
• In addition, the rails situated in the corners of the CubeSat are in contact with the
rails of the P-POD. So, some lockings (along X and Y axes) will be applied on the
rails of the CubeSat to represent this linear contact.
5.3.3 Results
The results nally obtained are presented in Table 5.7 and in Figures 5.10 and 5.11.
Maximal displacement (mm) Maximal Von Mises stress (MP a)
0.0909 101.97
Table 5.7: Results of the static analysis
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Figure 5.10: Displacements of OUFTI-1
In Figure 5.10, it can be seen that the maximal displacements of OUFTI-1 are along
the Z axis, which is the longitudinal direction of the P-POD. More particularly, it is the
center of electronic cards which presents the greatest displacement. This is in complete
accordance with the loading state. Indeed, the structure supports the greatest acceleration
along this particular axis.
In addition, it can be noted that the base and end plates present some deformations
at the feet location, which are due to the boundary conditions and to the loads applied to
them.
In Figure 5.11, it can be seen that the maximal Von Mises stress appears around the feet
of the end plate. This is, once again, in accordance with the conditions applied. Indeed,
these feet are clamped, which is a the strongest restrictive constraint.
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Figure 5.11: Maximal Von Mises stress inside OUFTI-1
According to the reference [59], it is possible to dene a MoS for the entire satellite.
This calculation is performed in Equation 5.3.3.
where:
MoS =
allowable load
(applied load) − SF − 1 (5.3.3)
• allowable load: Allowable load under specied functional conditions (e.g., yield,
buckling, ultimate)
• applied load: Computed or measured load under dened load condition (design loads)
• SF : Safety factor applicable to the specied functional conditions including the
specied load conditions (e.g., yield, buckling, ultimate)
For OUFTI-1, the maximal Von Mises stress appears in the end plate, which is made
of Al − 5052 H32. This material has a yield stress of 162 MP a, the maximal applied stress
is 101.97 MP a and the SF used for this study is 2. So, the value nally obtained for the
MoS is 0.5887. It means that OUFTI-1 can support a loading case 58.87% higher than
the one used during this analysis. It also means that our CubeSat fullls well the ESA
requirement, which stipulates that all MoS must be positive.
This last result marks the end of our static analysis. Now, a modal analysis will be
performed to estimate the global dynamic response of OUFTI-1.
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5.4 Modal analysis
This analysis will allow to predict the global dynamic behavior of OUFTI-1.
In this analysis, the CubeSat is modeled using exactly the same strategy as in section
5.2. Only the static loads and the boundary conditions are removed to obtain the behavior
of OUFTI-1 in "free-free" boundary conditions. This type of study allows to obtain a rst
idea of its behavior in real life conditions in a simple way. In addition, the results can
be used to realize a model updating. Indeed, this conguration has the advantage that
it does not introduce additional unknowns about the boundary conditions. So, the model
updating can be performed more accurately. However, these conditions are really dicult
to simulate during an experimental test and some approximations must be done (but it is
not the topic that we want to develop here).
5.4.1 Results
It was decided to compute the ve rst modes of OUFTI-1. Their natural frequencies
are listed in Table 5.8.
Modes (mm) Natural frequencies (Hz)
1 325.51
2 333.92
3 343.27
4 368.63
5 377.29
Table 5.8: Five rst natural frequencies of OUFTI-1 in hard-mounted conguration
It can be noted that all these frequencies turn around a value of 350 Hz. This is due to
the fact that each of these modes excites only the electronic cards of OUFTI-1 (and their
xations).
These results prove that OUFTI-1 respects the ESA requirement on the natural frequencies:
"The Cubesats shall not have structural modes at frequencies lower than 120 Hz
in hard-mounted conguration".
Now, the rst two modes will be described (the following ones present the same behavior
and so, it does not have a great interest to analyze them):
• The rst mode of OUFTI-1, which corresponds to a natural frequency of 325.51 Hz,
is presented in Figure 5.12.
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Figure 5.12: First mode of OUFTI-1 (325.51 Hz)
This mode is characterized by a vibration, in phase opposition, of the two extreme
electronic cards (the FM 430 on the side −Z and the COM on the side +Z). The
other electronic cards, the main structure and the external panels are not excited by
this mode.
• The second mode of OUFTI-1, which corresponds to a natural frequency of 333.92 Hz,
is presented in Figure 5.13.
Figure 5.13: Second mode of OUFTI-1 (333.92 Hz)
This mode is characterized by a vibration of most electronic cards. Indeed, the FM
430 and the COM present oscillations in phase, just like the EPS and xEPS. These
two groups of cards vibrate in phase opposition one from each other. It can also be
seen that the endless screws are more involved in this mode than in the rst one.
The OBC 2 card, the main structure and the external panels are not excited by this
mode.
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Next year, several tests will have to be performed to validate this model and to verify
the exact fulllment of the ESA requirements.
Now, the last analysis which must be performed on OUFTI-1, concerns random vibrations.
5.5 Random vibration
This analysis is based on the characteristics of the LV which is selected. Indeed, this
study needs several information about the vibration environment that the satellite has to
withstand during launch, and these information are specic to each launcher.
For CubeSats, this analysis is generally limited to random vibration. These vibrations
are generated by the propulsion system of the launcher and by the vibration-acoustic
response of adjacent structures. Maximum excitation levels occured during the principal
stage ignition. To characterize these vibrations, each launcher possesses its own PSD. The
typical PSDs of several LVs, at qualication level, are given in Figure 5.14. The last version
of the Vega PSD is given in Figure 5.15.
Figure 5.14: PSD of several LVs at qualication level [60]
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Figure 5.15: Precise PSD of Vega [57]
The model used for this analysis is the same as the one used to perform the modal
analysis. To be more accurate, this model would have to integrate the P-POD FE model,
to represent accurately the boundary conditions really imposed to the CubeSat during the
launch phase.
To realize a random vibration analysis, the FE model of the satellite must be excited
at the level imposed by the selected launcher. In the case of Vega, for qualication level
(which is the most restrictive level), the PSD can be decomposed as follow:
• 0.07 g 2 /Hz in the frequency range: [20 − 60 Hz]
• From 0.07 g 2 /Hz to 0.1 g 2 /Hz in the frequency range: [60 − 70 Hz]
• 0.1 g 2 /Hz in the frequency range: [70 − 200 Hz]
• From 0.1 g 2 /Hz to 0.2 g 2 /Hz in the frequency range: [200 − 300 Hz]
• 0.2 g 2 /Hz in the frequency range: [200 − 600 Hz]
• From 0.2 g 2 /Hz to 0.02 g 2 /Hz in the frequency range: [600 − 2000 Hz]
This particular PSD must be introduced in Samcef software through a ".psd" le.
Unfortunately, due to a problem encountered with Samcef (which is not yet resolved),
this analysis can not be performed this year. However, all the necessary les were created,
and information were collected to facilitate the work of the next year's student.
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5.6 Summary
Through this chapter, a complete FE analysis of OUFTI-1 was performed.
First, the modeling strategy used to represent each component of the satellite in the
FE model, was described accurately.
Then, a static analysis was performed. This analysis allows to conclude that OUFTI-1
withstands the quasi-static loads imposed by Vega in the worst case conguration. So, the
structural integrity of the satellite in static state is ensured.
The modal analysis led to results which satisfy ESA requirements on the dynamic behavior
of the Vega payloads, and showed that the most critical parts of the satellite are
its electronic cards, which are strongly excited in the rst modes. Next year, several tests
will have to be performed to validate this model.
Finally, the procedure to realize a random vibration analysis was drawn. Each step of
this analysis was presented and resolved. However, due to an unsolved problem encountered
with the Samcef software, this analysis could not be realize for this thesis. Once this
analysis will be performed and when a complete engineering model of the satellite will be
availble, qualication tests will have to be performed (strictly following the ESA procedure
[61]) to denitely validate the satellite and to send them to Kourou for its launch.
119

Chapter 6
Conclusions
This master thesis developed the structural design and dynamic analysis of OUFTI-1.
The main objectives were to design a new reliable support for the batteries, which fullls
all the requirements imposed by several subsystems, and to create an accurate FE dynamic
modeling procedure for the electronic cards.
Through this chapter, the results obtained during all the year, will be summarized.
Then, perspectives for future works will be highlighted.
Finally, the parallel activities linked to the project, will be briey exposed.
6.1 Summary of the accomplished work
The rst chapter of this thesis consisted in a general presentation of the project. The
CubeSat concept was introduced to allow to the profane to understand what is a CubeSat
and what are the principal requirements and restrictions which are imposed to this particular
type of satellite. Then, the genesis of the OUFTI-1 project was presented to expose the
guideline of the project from its starting point to the level at which this thesis started. The
launch opportunity oered by the ESA, was also discussed. Finally, the mission payloads
and the OUFTI team were described to nalize this overall view of the OUFTI-1 project.
Chapter 2 presented the general ight system conguration. The reference frame used to
locate precisely each component of the CubeSat, was dened. Then, each part of OUFTI-1
was presented in a global understanding approach. The technical constraints which led to
this particular organization, were highlighted, and the methods which will be used to x
the dierent components together, were exposed. Finally, general physical and mechanical
properties, including: the CoG location, the inertia properties and the mass budget, were
120

calculated, and their fulllment of all requirements imposed by ESA, was veried.
Chapter 3 developed the complete battery support design, from the initial idea to the
manufacturing of this support. The reasons that led to modify the last year's design, were
also presented. This design included:
• The selection of the several components which had to be incorporated inside the
support, including: batteries, thermal control's devices such as thermostats, heaters
and thermal insulator, was performed.
• Then, the material which was used to manufacture the support, was selected. This
material has to fulll several physical, mechanical and thermal requirements. This
step is really important because the thickness of the dierent parts that must prevent
the batteries' bulge, was determined in relation to the properties of the selected
material.
• Once the material and the components were selected, the design phase was presented.
The procedure was introduced step by step, just like it progressed during the whole
year.
• Finally, the design was validated by several calculations, such as the mass budget,
and FE analysis, including static and dynamic analysis.
Chapter 4 exposed a general procedure to create an accurate FE dynamic model of
electronic cards. Firstly, several existing methods were presented and their accuracy was
studied. Then, these methods were applied to the particular case of the homemade OBC
of OUFTI-1. A homemade method, based on the fact that several methods can be applied
to particular categories of components soldered on a same PCB, was also created. This
method is the one which presented the best results and so, it is the one that was applied to
each electronic card of OUFTI-1. Finally, some sensitivity analysis with regard to several
parameters which strongly inuence the PCB dynamic response, were carried out.
Finally, chapter 5 consisted in a complete FE analysis of the satellite. Firstly, the
modeling strategy used to represent each component of the satellite in the FE model, was
described accurately. Then, a static analysis was performed, and the results obtained ensure
that OUFTI-1 withstands well the quasi-static loads which will be applied to it during
the launch phase. The modal analysis led also to results that fulll all ESA requirements.
Finally, the procedure to realize a random vibration analysis was presented and all necessary
les were created.
Throughout this thesis, we have tried to develop a detailed and rigorous description of
the approach followed during all our progression. To realize this, a theoretical basis was
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provided for each method used. We have also tried to express clearly the several reasons
which led us to use these particular methods, as well as the assumptions to respect for
applying them, because we see in these assumptions one of the cornerstones for the success
of a rigorous scientic work.
6.2 Perspectives
This section intends to give some guidelines for the future student who will be in charge
of the structural subsystem. In the summary of each chapter, the problems encountered
were highlighted. This section is here to remind these problems and to highlight them once
again.
Concerning the general ight system conguration, most of the problems were solved.
The order of the electronic cards was conrmed and xed. The radiance diagram of the antennas
was realized by the RF subsystem, which allowed to denitely conrm the location
of the permanent magnet (in accordance with the requirements of the ADCS subsystem).
This allowed also to dened the location of the four hystereric bars inside the CubeSat.
The next problem will be to realize a complete integration procedure for the ight model
of OUFTI-1. A basic procedure for the integration of the engineering model was already
composed this year [33], but it must be completed by several information (how to include
the cables inside the satellite, how to connect the several subsystems together, ...). The
mass budget must also be denitely conrmed by weighting the components which still
present some uncertainties about their mass.
Concerning the battery support, the manufacturing has to be nalized. Then, thermal
and structural tests must be performed to be correlated with the models created this year.
This step will allow to denitely validate this design and to ensure its structural integrity
during all the CubeSat lifetime.
Concerning the electronic cards, an other experimental test will have to be performed,
following advice given in chapter 4, to denitely validate the fact that the homemade
method is the one which gives the best results. The physical properties of all components,
such as the Young's modulus, can also be determined to allow to model them using global
or local smearing methods which include the stiness contributions of these components.
Finally, the experimental modal survey of OUFTI-1 in its hard-mounted version, will
have to be performed and correlated to the FE model presented in the last chapter of this
thesis. In addition, the random vibration analysis and tests for the launch phase must also
be performed to qualify OUFTI-1 for its travel to space.
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6.3 Parallel activities
This project, which is a particular subject for a master thesis, gives to the students the
opportunity to take part in a lot of parallel activities, such as ESA conferences or CubeSat
meetings all over the world. So, the activities, in which I am directly involved, performed
during this academic year, will be presented here:
• The rst activity, which set at Royal Meteorological Institute (IRM) based at Bruxelles
(Belgium), was a general public presentation. During this activity, the goal
was to present the project to people that has no knowledge, or nearly, of the space
activities. It allows us to go one's rst steps inside the project and to familiarize us
with its multidisciplinary aspects.
• The second activity, which set at CSL (Belgium), was a conference with the Del-C 3
team. During this activity, presentations of the two teams' projects were realized. It
allows us to exchange several points of view with them and to move forward in our
understanding of constraints imposed by the space environment.
• The following activity was the Interface Technical Review (ITR), which set at the
EuroSpace Center of Redu (Belgium). At this moment, each student had all the technical
background necessary to accomplish his personal work. Before going to Redu,
each of them had to provide a data package including all the interfaces between his
subsystem and the other ones, and internal interfaces inside his own subsystem [62].
For each of these interfaces, a technical solution was proposed by the students who
are in charge of the concerned subsystems. Then, during the weekend spent to Redu,
several meetings were realized. These meetings concerned the four general categories
of interfaces that exist in a satellite, including: mechanical, thermal, electrical and
data interfaces. They involved the students of the OUFTI team, the system engineering
team, the project managers, the professors and several industrial specialists.
During these meetings, each solution was studied with the help of all this sta, and
was approved or improved to fulll the requirements imposed to it. This activity allowed
to dene precisely all the interfaces present inside the CubeSat and to highlight
them, and brought to each student involved in the project, a better understanding
of the overall satellite. It allowed also to take a big step for the project achievement
by emerging from an Interface Control Document (ICD) for OUFTI-1.
• Finally, the last activity during this year, was the Workshop on the Verication of
the CubeSats for the Vega Maiden Flight, which set at ESTEC (The Netherlands).
During this workshop, the verication concept and the acceptance data package were
introduced. These concepts are really important because they include all the verications
which must be performed on each CubeSat before delivering it to ESA. The
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last versions of the Verication Control Document (VCD) and the ICD were also introduced.
These documents were covered point by point to explain to the CubeSats
teams what ESA expects from them for the qualication of their CubeSats. Several
presentations on the structural verication and collision & contamination analysis
were also performed by ESA experts. Finally, each team had defended its project
through a general presentation about their schedule for the following months. This
activity allows us to meet people coming from all over the world, and to take advantage
of their own experience to learn more and more about this fascinating world
that the space is.
124

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Appendix A
Schemas of solar panels
Figure 6.1: Schemas of solar panels +X and +/ − Y [15]
130

Figure 6.2: Schemas of the solar panel +Z [15]
Figure 6.3: Schemas of the solar panel −Z [15]
131

Appendix B
Schemas of electronic cards and their available volume
Figure 6.4: Schemas of electronic cards [15]
132

Figure 6.5: Available volume for each electronic card [62]
133

Appendix C
Fixations of the endless screws
Figure 6.6: Fixations of endless screws on the base plate [62]
134

Figure 6.7: Picture of the xation between one midplane stando and the chassis [33]
Figure 6.8: Disposition of midplane standos inside the CubeSat [30]
135

Appendix D
Datasheet of the battery Kokam SLB 603870H
136

Figure 6.9: Datasheet of the battery Kokam SLB 603870H
137