MASTER'S THESIS Health Monitoring of Re-entry Vehicles Michael McWinnie Master of Science Space Engineering - Space Master Luleå University of Technology Department of Computer Science, Electrical and Space Engineering Health Monitoring of Re-entry Vehicles Michael McWhinnie Supervisor: Dr. Peter Roberts School of Engineering Cranfield University A thesis submitted for the degree of: MSc Astronautics and Space Engineering 2011 August c Cranfield University, 2011. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder. Abstract The inevitable return of space hardware from low earth orbit via targeted re-entries or naturally decaying orbits, creates a risk to human casualty and property damage. Fragmentation models that are used to assess this risk, however, contain a large degree of uncertainty and lack experimental data for calibration. A recently proven method for a↵ordably recording this crit- ical re-entry data is the use of an automated, compact re-entry health mon- itoring system passively attached to a host spacecraft. The device records a variety of data during the breakup, only to release and transmit its data volume to a commercial satellite constellation for retrieval and analysis. Using the Automated Transfer Vehicle re-entry scenario, this study explores the limitations of such a concept by identifying and analysing system and scenario-related constraints. Although realisable, two major findings were made evident. First, the transmittable data volume, though sufficient in this scenario, is likely to be quickly exceeded in more data-intensive scenarios. Second, power consumption on a passive device is a major constraint for longer duration missions. The data recorded is expected to provide invaluable insights leading to model calibration and spacecraft ‘design-for-demise’ techniques. Given the necessity to mitigate casualty risk and comply with agency guidelines, the aim here is to relieve spacecraft operators of manoeuvring costs and sub- sequent payload reductions. There is also potential to use the device as a ‘black-box’ for reusable re-entry vehicles of the future. Such a device could reduce developmental costs and risk to manned-spaceflight. Acknowledgements To all who have directly or indirectly assisted in the creation of this work: My supervisor Dr. Peter Roberts for his insights and guidance, everyone in Meeting Group 1 for ideas transpired through discussion, SpaceMasters past and present, Tweefontein for their understanding and hospitality, Emily for her love and support, and of course, my family. Thank you. ii Contents List of Figures v List of Tables vii Notation ix Acronyms xi 1 Introduction 1 1.1 Thespacedebrisproblem .......................... 1 1.2 The re-entry health monitoring problem . 2 1.3 Statement of purpose . 3 1.4 Overviewofthestudy ............................ 4 2 Background and Context 5 2.1 Debrishazard................................. 5 2.2 Design-for-demise............................... 7 2.3 Fragmentation models . 8 2.3.1 Object-orientedcodes . 8 2.3.1.1 DAS . 8 2.3.1.2 ORSAT . 9 2.3.1.3 SESAM . 10 2.3.2 Spacecraft-oriented codes . 10 2.3.2.1 SCARAB . 10 2.4 Reentry observation campaigns . 12 2.5 The Automated Transfer Vehicle (ATV) . 12 2.6 TheRe-entryBreakupRecorder(REBR) . 13 iii CONTENTS 2.6.1 Overview ............................... 14 2.6.2 Mission profile . 15 2.6.3 Flight history . 15 3 Research Design 17 3.1 Researchsummary .............................. 17 3.2 Scopeofstudy ................................ 18 4 Mission Concept 21 4.1 Missionobjectives .............................. 21 4.2 MissionConcept ............................... 22 4.2.1 Physical properties . 22 4.2.2 Payload . 22 4.2.3 On-orbit phase . 23 4.2.4 Atmospheric entry phase . 23 4.2.5 Data recovery phase . 24 5SystemRequirements 27 5.1 Systempassivity ............................... 27 5.2 Aerothermalrequirements . 29 5.3 Dynamicrequirements ............................ 30 5.4 Fragmentation requirements . 31 5.5 Communicationrequirements . 32 5.6 Summary ................................... 33 6 Trajectory Modelling 35 6.1 Trajectory model rationale . 35 6.2 Planartrajectorymodel ........................... 36 6.2.1 Formulation of dynamic model and assumptions . 36 6.2.2 Formulation of atmospheric model and assumptions . 40 6.2.3 Initial conditions . 40 6.2.4 Trajectoryresults........................... 42 6.2.5 Discussion............................... 46 6.2.5.1 Maximum transmittable data volume . 46 6.2.5.2 Aeroshell design . 48 iv CONTENTS 6.2.5.3 Thermal protection system . 49 7 Payload 51 7.1 Attitudedetermination. 51 7.1.1 Attitude rates of change . 52 7.1.2 Integration technique . 54 7.2 Temperaturemeasurement. 55 7.2.1 Device housing and thermocouple type . 56 7.2.2 Thermocouple amplifiers . 57 7.3 Heat flux measurement . 57 7.3.1 The lumped system approach to heat transfer . 58 7.3.2 Model Validation . 60 7.3.2.1 Error sources and assumptions . 61 7.3.2.2 Calculated heat flux output for the RAFLEX tempera- tureprofile ......................... 62 7.3.3 Discussion............................... 63 7.3.4 Applicability to the ATV re-entry environment . 65 7.3.5 Conclusion . 66 7.4 Pressuresensor ................................ 66 7.5 Data transceiver and Antenna . 67 7.6 Data generation and transmission . 69 7.6.1 Sampling rate lower-bound . 69 7.6.2 Sampling rate upper-bound . 70 7.6.3 Estimated data volume generated . 70 7.7 Micro-controller and data storage . 71 8 Power 73 8.1 Payload power consumptions . 73 8.2 Payload activation scheduling . 74 8.2.1 Low-power payload schedule . 77 8.2.2 Medium-power payload schedule . 77 8.2.3 High-power payload schedule . 77 8.3 Batteryselectionandsizing . 78 8.4 Discussion................................... 79 v CONTENTS 9 Mass 81 9.1 Payload mass . 81 9.2 Thermal protection system mass . 81 9.3 Housing mass . 82 10 Conclusion 85 10.1 Thesiscontribution.............................. 85 10.2 Looking forward . 87 10.3Futurework.................................. 88 10.4 Final thoughts . 89 References 91 A Additional Trajectory Results 95 B Ariane-5 Performance Envelope 101 vi List of Figures 2.1 Impact of de-orbit timeframe mitigation strategies on manned-mission debris impact flux for objects 1cm (1). 6 ≥ 2.2 Di↵ering heat loads for a full re-entry, and a re-entry exposure starting at a generic altitude (2). 9 2.3 A typical spacecraft model generated in SCARAB (2). 11 2.4 Overview of the ATV design and layout (3). 13 2.5 Exploded view of the REBR with copper housing (4). 14 2.6 REBR mission profile overview as initially conceived in it’s 2005 patent (5)........................................ 16 5.1 Panel shadowing in SCARAB from geometric surface area projections (6) 31 6.1 Inertial coordinate system for re-entry. 37 6.2 Drag coefficient as a function of Knudsen number as calculated by various fragmentation models, for an AA7075 Aluminium sphere of 1m diameter (2)........................................ 38 6.3 ISA density model with an exponential extension above 20km altitude. 41 6.4 Re-entry trajectory profiles. Note unequal axes for presentation purposes. 43 6.5 Velocity profiles versus time over full entry angle range. 43 6.6 Trajectoryaltitude-timehistory. 44 6.7 Mach number profiles, where the intersections with the black line indi- cates the beginning of the subsonic flight region. 44 6.8 G-loadinghistory................................ 45 6.9 Flight path angle evolution during re-entry. 45 vii LIST OF FIGURES 6.10 Altitude profile for lifting body with CL =0.05. Note the inflexion at moderate altitudes, causing an increase in total flight times. 49 7.1 Ariane-5 cryogenic main stage EPC body angular rates during re-entry (7)........................................ 54 7.2 MIR body angular rates during re-entry (8). 55 7.3 Calorimeter design for the RAFLEX air data system (9) . 60 7.4 Specific heat of Copper as a function of temperature (9). 62 7.5 Replication of temperature data generated by a calorimetric probe KFA2 during the RAFLEX II experiment on the MIRCA re-entry capsule (10). 63 7.6 Aerothermal heat flux output from Matlab model, with relevant compo- nents. 64 7.7 Post-processed aerothermal heat flux output from KFA2 calorimeter on- board RAFLEX (10). 65 7.8 Iridium coverage at sea-level using the 48 beams for all 66 satellites. 68 A.1 Drag force versus time over full entry angle range. 95 A.2 Gravitational acceleration profiles over full entry angle range. 96 A.3 Ground track profiles versus time over full entry angle range. 96 A.4 Ground-track in lifting-body scenario for CL =0.05. 97 A.5 Stagnation-point heat flux profiles over full entry angle range. 97 A.6 Stagnation-point temperatures over full entry angle range. 98 A.7 Comparison of exponential and ISA (black) density models. 98 A.8 Lifting body re-entry flight-path history for CL =0.05. 99 A.9 Lift force in lifting-body scenario for CL =0.05. 99 B.1 Ariane-5 sustained launch accelerations (11). 101 B.2 Ariane-5 shock envelope across vibration frequency spectrum (11). 102 viii List of Tables 2.1 SCARAB aerothermal models for various flow regimes (6). 11 4.1 MissionObjectives............................... 21 5.1 Tradeo↵ table comparing fully passive and active RHMS systems. 28 5.2 System requirements summary, with corresponding sections. 33 6.1 Initial conditions for low altitude trajectory . 39 6.2 Initial conditions for RHMS trajectory in ATV re-entry scenario. 41 6.3 Trajectory results for various initial entry angles. Entry and impact angles are relative to local horizontal. 42 6.4 Estimated data transmission times and subsequent maximum transmit- table data volumes, using flight-path angle as the main constraint. Times includea30secondconnectiondelay.. 48 7.1 ADIS16375 Performance specifications (12). 53 7.2 Melting temperature, thermal conductivity and penetration times for some common materials. 56 7.3 Calorimetric head parameters used in RAFLEX II and Matlab validation model(10).