Table Of ContentThe Technology of Discovery
The Technology of Discovery
Radioisotope Thermoelectric Generators and
Thermoelectric Technologies for Space Exploration
Edited by
David Friedrich Woerner
Jet Propulsion Laboratory
California Institute of Technology, USA
This edition first published 2023
© 2023 John Wiley & Sons, Inc.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or
transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise,
except as permitted by law. Advice on how to obtain permission to reuse material from this title is available
at http://www.wiley.com/go/permissions.
The right of David Friedrich Woerner to be identified as the author of the editorial material in this work has
been asserted in accordance with law.
Registered Office
John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA
Editorial Office
9600 Garsington Road, Oxford, OX4 2DQ, UK
For details of our global editorial offices, customer services, and more information about Wiley products visit
us at www.wiley.com.
Wiley also publishes its books in a variety of electronic formats and by print- on- demand. Some content that
appears in standard print versions of this book may not be available in other formats.
Trademarks: Wiley and the Wiley logo are trademarks or registered trademarks of John Wiley & Sons,
Inc. and/or its affiliates in the United States and other countries and may not be used without written
permission. All other trademarks are the property of their respective owners. John Wiley & Sons, Inc. is not
associated with any product or vendor mentioned in this book.
Limit of Liability/Disclaimer of Warranty
While the publisher and authors have used their best efforts in preparing this work, they make no
representations or warranties with respect to the accuracy or completeness of the contents of this work and
specifically disclaim all warranties, including without limitation any implied warranties of merchantability
or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written
sales materials or promotional statements for this work. The fact that an organization, website, or product
is referred to in this work as a citation and/or potential source of further information does not mean that
the publisher and authors endorse the information or services the organization, website, or product may
provide or recommendations it may make. This work is sold with the understanding that the publisher is not
engaged in rendering professional services. The advice and strategies contained herein may not be suitable
for your situation. You should consult with a specialist where appropriate. Further, readers should be aware
that websites listed in this work may have changed or disappeared between when this work was written and
when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial
damages, including but not limited to special, incidental, consequential, or other damages.
Library of Congress Cataloging- in- Publication Data
Names: Woerner, David Friedrich, editor.
Title: The technology of discovery : radioisotope thermoelectric generators
and thermoelectric technologies for space exploration / David Frederich
Woerner.
Description: Hoboken, NJ : Wiley, 2023. | Includes bibliographical
references and index.
Identifiers: LCCN 2022051673 (print) | LCCN 2022051674 (ebook) | ISBN
9781119811367 (hardback) | ISBN 9781119811374 (adobe pdf) | ISBN
9781119811381 (epub)
Subjects: LCSH: Thermoelectric generators. | Radioisotopes in astronautics.
| Thermoelectric apparatus and appliances. | Outer space–Exploration.
Classification: LCC TK2950 .W647 2023 (print) | LCC TK2950 (ebook) | DDC
621.31/243–dc23/eng/20221108
LC record available at https://lccn.loc.gov/2022051673
LC ebook record available at https://lccn.loc.gov/2022051674
Cover Design: Wiley
Cover Images: © NASA/JPL-Caltech/Malin Space Science Systems
Set in 9.5/12.5pt STIXTwoText by Straive, Pondicherry, India
v
Contents
Foreward xi
Note from the Series Editor xiii
Preface xv
Authors xix
Reviewers xxi
Acknowledgments xxiii
Glossary xxv
List of Acronyms and Abbreviations xxxiii
1 The History of the Invention of Radioisotope Thermoelectric
Generators (RTGs) for Space Exploration 1
Chadwick D. Barklay
References 5
2 The History of the United States’s Flight and Terrestrial RTGs 7
Andrew J. Zillmer
2.1 Flight RTGs 7
2.1.1 SNAP Flight Program 7
2.1.1.1 SNAP-3 8
2.1.1.2 SNAP-9 8
2.1.1.3 SNAP-19 9
2.1.1.4 SNAP-27 11
2.1.2 Transit-RTG 13
2.1.3 Multi-Hundred-Watt RTG 13
2.1.4 General Purpose Heat Source RTG 15
2.1.4.1 General Purpose Heat Source 15
2.1.4.2 GPHS-RTG System 16
2.1.5 Multi-Mission Radioisotope Thermoelectric Generator 17
2.1.6 US Flight RTGs 18
vi Contents
2.2 Unflown Flight RTGs 18
2.2.1.1 SNAP-1 18
2.2.1.2 SNAP-11 18
2.2.1.3 SNAP-13 18
2.2.1.4 SNAP-17 22
2.2.1.5 SNAP-29 22
2.2.1.6 Selenide Isotope Generator 23
2.2.1.7 Modular Isotopic Thermoelectric Generator 24
2.2.1.8 Modular RTG 24
2.3 Terrestrial RTGs 25
2.3.1 SNAP Terrestrial RTGs 25
2.3.1.1 SNAP-7 25
2.3.1.2 SNAP-15 26
2.3.1.3 SNAP-21 26
2.3.1.4 SNAP-23 26
2.3.2 Sentinel 25 and 100 Systems 27
2.3.3 Sentry 28
2.3.4 URIPS-P1 28
2.3.5 RG-1 29
2.3.6 BUP-500 30
2.3.7 Millibatt-1000 31
2.4 Conclusion 31
References 31
3 US Space Flights Enabled by RTGs 35
Young H. Lee and Brian K. Bairstow
3.1 SNAP-3B Missions (1961) 35
3.1.1 Transit 4A and Transit 4B 35
3.2 SNAP-9A Missions (1963–1964) 36
3.2.1 Transit 5BN-1, 5BN-2, and 5BN-3 36
3.3 SNAP-19 Missions (1968–1975) 38
3.3.1 Nimbus-B and Nimbus III 38
3.3.2 Pioneer 10 and 11 41
3.3.3 Viking 1 and 2 Landers 43
3.4 SNAP-27 Missions (1969–1972) 45
3.4.1 Apollo 12–17 45
3.5 Transit-RTG Mission (1972) 47
3.5.1 TRIAD 47
3.6 MHW-RTG Missions (1976–1977) 48
3.6.1 Lincoln Experimental Satellites 8 and 9 48
3.6.2 Voyager 1 and 2 50
Contents vii
3.7 GPHS-RTG Missions (1989–2006) 52
3.7.1 Galileo 52
3.7.2 Ulysses 53
3.7.3 Cassini 55
3.7.4 New Horizons 57
3.8 MMRTG Missions: (2011-Present (2021)) 59
3.8.1 Curiosity 59
3.8.2 Perseverance 61
3.8.3 Dragonfly–Scheduled Future Mission 62
3.9 Discussion of Flight Frequency 64
3.10 Summary of US Missions Enabled by RTGs 73
References 74
4 Nuclear Systems Used for Space Exploration by Other Countries 77
Christofer E. Whiting
4.1 Soviet Union 77
4.2 China 81
References 82
5 Nuclear Physics, Radioisotope Fuels, and Protective Components 85
Michael B.R. Smith, Emory D. Collins, David W. DePaoli, Nidia C. Gallego,
Lawrence H. Heilbronn, Chris L. Jensen, Kaara K. Patton, Glenn
R. Romanoski, George B. Ulrich, Robert M. Wham, and Christofer E. Whiting
5.1 Introduction 85
5.2 Introduction to Nuclear Physics 86
5.2.1 The Atom 86
5.2.2 Radioactivity and Decay 88
5.2.3 Emission of Radiation 90
5.2.3.1 Alpha Decay 91
5.2.3.2 Beta Decay 92
5.2.3.3 Photon Emission 92
5.2.3.4 Neutron Emission 93
5.2.3.5 Decay Chains 94
5.2.4 Interactions of Radiation with Matter 94
5.2.4.1 Charged Particle Interactions with Matter 96
5.2.4.2 Neutral Particle Interactions with Matter 97
5.2.4.3 Biological Interactions of Radiation with Matter 100
5.3 Historic Radioisotope Fuels 102
5.3.1 Polonium-210 104
5.3.2 Cerium-144 104
5.3.3 Strontium-90 105
viii Contents
5.3.4 Curium-242 106
5.3.5 Curium-244 106
5.3.6 Cesium-137 107
5.3.7 Promethium-147 107
5.3.8 Thallium-204 108
5.4 Producing Modern PuO 108
2
5.4.1 Cermet Target Design, Fabrication, and Irradiation 110
5.4.2 Improved Target Design 111
5.4.3 Post-Irradiation Chemical Processing 112
5.4.4 Waste Management 113
5.4.5 Conversion to Production Mode of Operation 114
5.5 Fuel, Cladding, and Encapsulations for Modern
Spaceflight RTGs 115
5.5.1 Evolution of Radioisotope Heat Source Protection 115
5.5.2 General Purpose Heat Source 119
5.5.3 Fine Weave Pierced Fabric (FWPF) 120
5.5.4 Carbon-Bonded Carbon Fiber (CBCF) 121
5.5.5 Heat Transfer Considerations 122
5.5.6 Cladding 122
5.6 Summary 125
References 125
6 A Primer on the Underlying Physics in Thermoelectrics 133
Hsin Wang
6.1 Underlying Physics in Thermoelectric Materials 133
6.1.1 Reciprocal Lattice and Brillouin Zone 135
6.1.2 Electronic Band Structure 135
6.1.3 Lattice Vibration and Phonons 138
6.2 Thermoelectric Theories and Limitations 141
6.2.1 Best Thermoelectric Materials 141
6.2.2 Imbalanced Thermoelectric Legs 143
6.3 Thermal Conductivity and Phonon Scattering 144
6.3.1 Highlights of SiGe 145
References 145
7 End-to-End Assembly and Pre-flight Operations for RTGs 151
Shad E. Davis
7.1 GPHS Assembly 151
7.2 RTG Fueling and Testing 159
7.3 RTG Delivery, Spacecraft Checkout, and RTG Integration
for Flight 172
References 181
