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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Serie: JPL Space Science and Technology Series
- Sprache: Englisch
The Technology of Discovery Incisive discussions of a critical mission-enabling technology for deep space missions In The Technology of Discovery: Radioisotope Thermoelectric Generators and Thermoelectric Technologies for Space Exploration, distinguished JPL engineer and manager David Woerner delivers an insightful discussion of how radioisotope thermoelectric generators (RTGs) are used in the exploration of space. It also explores their history, function, their market potential, and the governmental forces that drive their production and design. Finally, it presents key technologies incorporated in RTGs and their potential for future missions and design innovation. The author provides a clear and understandable treatment of the subject, ranging from straightforward overviews of the technology to complex discussions of the field of thermoelectrics. Included is also background on NASA's decision to resurrect the GPHS-RTG and discussion of the future of commercialization of nuclear space missions. Readers will also find: * A thorough introduction to RTGs, as well as their invention, history, and evolution * Comprehensive explorations of the contributions made by RTGs to US space exploration * Practical discussions of the evolution, selection, and production of RPS fuels * In-depth examinations of technologies and generators currently in development, including skutterudite thermoelectrics for an enhanced MMRTG Perfect for space explorers, aerospace engineers, managers, and scientists, The Technology of Discovery will also earn a place in the libraries of NASA archivists and other historians.
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Table of Contents
Cover
Title Page
Copyright Page
Foreward
Note From the Series Editor
Preface
Authors
Reviewers
Acknowledgments
Glossary
List of Acronyms and Abbreviations
1 The History of the Invention of Radioisotope Thermoelectric Generators (RTGs) for Space Exploration
References
2 The History of the United States’s Flight and Terrestrial RTGs
2.1 Flight RTGS
2.2 Unflown Flight RTGs
2.3 Terrestrial RTGs
2.4 Conclusion
References
3 US Space Flights Enabled by RTGs
3.1 SNAP‐3B Missions (1961)
3.2 SNAP‐9A Missions (1963–1964)
3.3 SNAP‐19 Missions (1968–1975)
3.4 SNAP‐27 Missions (1969–1972)
3.5 Transit‐RTG Mission (1972)
3.6 MHW‐RTG Missions (1976–1977)
3.7 GPHS‐RTG Missions (1989–2006)
3.8 MMRTG Missions: (2011‐Present (2021))
3.9 Discussion of Flight Frequency
3.10 Summary of US Missions Enabled by RTGs
References
4 Nuclear Systems Used for Space Exploration by Other Countries
4.1 Soviet Union
1
4.2 China
References
5 Nuclear Physics, Radioisotope Fuels, and Protective Components
5.1 Introduction
5.2 Introduction to Nuclear Physics
5.3 Historic Radioisotope Fuels
5.4 Producing Modern PuO
2
5.5 Fuel, cladding, and encapsulations for modern
5.6 Summary
References
6 A Primer on the Underlying Physics in Thermoelectrics
6.1 Underlying Physics in Thermoelectric Materials
6.2 Thermoelectric Theories and Limitations
6.3 Thermal Conductivity and Phonon Scattering
References
7 End‐to‐End Assembly and Pre‐flight Operations for RTGs
7.1 GPHS Assembly
7.2 RTG Fueling and Testing
7.3 RTG Delivery, Spacecraft Checkout, and RTG Integration for Flight
References
8 Lifetime Performance of Spaceborne RTGs
8.1 Introduction
8.2 History of RTG Performance at a Glance
8.3 RTG Performance by Generator Type
References
9 Modern Analysis Tools and Techniques for RTGs
9.1 Analytical Tools for Evaluating Performance Degradation and Extrapolating Future Power
9.2 Effects of Thermal Inventory on Lifetime Performance
9.3 (Design) Life Performance Prediction
9.4 Radioisotope Power System Dose Estimation Tool (RPS‐DET)
References
10 Advanced US RTG Technologies in Development
10.1 Introduction
10.2 Skutterudite‐based Thermoelectric Converter Technology for a Potential MMRTG Retrofit
10.3 Next Generation RTG Technology Evolution
10.4 Considerations for Emerging Commercial RTG Concepts
References
Index
End User License Agreement
List of Tables
Chapter 2
Table 2.1 A catalog and summarization of general characteristics of US buil...
Chapter 3
Table 3.1 The United States’ historic, current, and scheduled to be launche...
Chapter 5
Table 5.1 High‐level particle characteristics. Data referenced from the Nat...
Table 5.2 Natural decay modes relevant to RTG fuels.
Table 5.3 Nuclear reactions relevant to RTG fuels.
Table 5.4 Cermet target measuring performance.
Chapter 9
Table 9.1 Changes in Mission Power and Thermoelectric Degradation as a Func...
Table 9.2 Brief description of various RPS‐DET and SCALE software applicati...
Table 9.3 RPS‐DET geometry library selections.
List of Illustrations
Preface
Figure 0.1 A schematic of a silicon‐germanium thermoelectric unicouple used ...
Chapter 1
Figure 1.1 An early experimental thermoelectric generator designed by Jordan...
Figure 1.2 One of the latter prototype thermoelectric generators designed by...
Figure 1.3 The public debut of the SNAP‐3 RTG technology demonstration devic...
Chapter 2
Figure 2.1 Cross section of a SNAP‐3 RTG.[5]
Figure 2.2 A fully assembled SNAP‐9 RTG.[6],
Figure 2.3 Cross section of an assembled SNAP‐19 RTG as flown on the Pioneer...
Figure 2.4 Major components of the modified SNAP‐19 RTGs used on the Viking ...
Figure 2.5 Astronaut Alan Bean removing fuel from the lunar lander to insert...
Figure 2.6 Diagram of the SNAP‐27 RTG.
Figure 2.7 An assembled MHW RTG in cutaway.
Figure 2.8 Cutaway view of the MHW‐RTG heat source assembly.
Figure 2.9 Expanded view of a GPHS module.
Figure 2.10 Diagram illustrating several major components of the GPHS‐RTG....
Figure 2.11 The white MMRTG for the Perseverance Rover after fueling and sit...
Figure 2.12 Cross‐section of a SNAP‐13 thermionic generator.[18]
Figure 2.13 Illustration of the SNAP‐29 concept showing integration with a s...
Figure 2.14 Concept of a SNAP‐7D thermoelectric generator powering a US Navy...
Figure 2.15 Model of SNAP‐15 power source in cutaway.[18]
Figure 2.16 Cutaway view of the SNAP‐21 system.[19]
Figure 2.17 Cutaway view of URIPS power supply.[31]
Figure 2.18 Cutaway view of RG‐1 power system.[31]
Chapter 3
Figure 3.1 Transit 4A spacecraft with companion payloads before launch. Tran...
Figure 3.2 Transit 4A (a) and Transit 4B (b) SNAP‐3B telemetry data. Voltage...
Figure 3.3 Transit 5BN‐1 (a) and Transit 5BN‐2 (b) power (W(o)) histories (s...
Figure 3.4 Intact SNAP‐19 fuel capsule from Nimbus B aborted launch, shown i...
Figure 3.5 Nimbus III spacecraft with 2 SNAP‐19 RTGs visible on the left. [1...
Figure 3.6 Nimbus III SNAP‐19 RTGs power output (W(e)) (smoothed data). [3]...
Figure 3.7 Pioneer 10/11, with 2 RTGs visible on each of 2 booms. [1], NASA....
Figure 3.8 Power history of the Pioneer SNAP‐19 RTGs (summed data). [11]
Figure 3.9 Viking lander model—the two RTGs are covered by windscreens and a...
Figure 3.10 Power (W(e)) history of the Viking SNAP‐19 RTGs (summed and smoo...
Figure 3.11 (a) Apollo landing sites where ALSEPs were deployed. Credit: NAS...
Figure 3.12 Power (W(e)) history of the ALSEP SNAP‐27 RTGs (smoothed data). ...
Figure 3.13 Triad spacecraft.
Figure 3.14 LES 8 and 9 deployed in geosynchronous orbit. [2]
Figure 3.15 Daily maximum and minimum RTG output powers (W) for LES‐8 during...
Figure 3.16 A Voyager spacecraft, with three MHW‐RTGs end‐to‐end on the boom...
Figure 3.17 Power (W(e)) history of Voyager MHW‐RTGs, incomplete data circa ...
Figure 3.18 Galileo at Io, with Jupiter in the background. The two GPHS‐RTGs...
Figure 3.19 Galileo Total RTG Power (telemetry and predictions, GE ’90 Estim...
Figure 3.20 Ulysses spacecraft. [20], NASA.
Figure 3.21 Measured and Predicted Power from the Ulysses GPHS‐RTG. F‐3 is t...
Figure 3.22 Cassini‐Huygens at Saturn. Two of the GPHS‐RTGs are visible on t...
Figure 3.23 Cassini recorded RTG power output telemetry data over the entire...
Figure 3.24 Artist’s rendition of New Horizons at Pluto, with GPHS‐RTG in th...
Figure 3.25 New Horizons (NH) Power History.
Figure 3.26 Curiosity took this self‐portrait on 11 May 2016.
Figure 3.27 Mars map showing landing sites of Viking 1, Viking 2, Curiosity,...
Figure 3.28 Curiosity Rover MMRTG monthly averaged power.
Figure 3.29 Artist’s rendition of Perseverance rover, with MMRTG on the left...
Figure 3.30 Perseverance Rover MMRTG Daily Averaged Power.
Figure 3.31 Perseverance MMRTG (F2) power output during surface operations, ...
Figure 3.32 Conceptual art of Dragonfly dual‐quadcopter on Titan, with RTG e...
Figure 3.33 NASA’s launched radioisotope spaceflight missions by destination...
Figure 3.34 Non‐NASA launched radioisotope spaceflight missions.
Figure 3.35 Past, current, and upcoming US RTG missions by decade.
Figure 3.36 RTG power in space from past, current, and upcoming US missions ...
Figure 3.37 The number of RTG units launched by past, current, and upcoming ...
Chapter 4
Figure 4.1 Model of the Lunokhod 1 rover in the Museum of Cosmonautics (Mosc...
Chapter 5
Figure 5.1 Illustration of a helium atom’s fundamental particles, regions, a...
Figure 5.2 Exponential decay behavior of radioisotopes related to first thre...
Figure 5.3 Decay chain of pure
238
Pu. Image permissions: OECD NEA, JANIS and...
Figure 5.4 Illustration of the fields that charged particles experience whil...
Figure 5.5 Total neutron cross sections for
1
H (a) and
238
Pu (b). Cross sect...
Figure 5.6 Production of
238
Pu from
237
Np.
Figure 5.7
238
Pu production process.
Figure 5.8 Chemical processing campaign flowsheet.
Figure 5.9 Potential full‐scale production schedule for chemical processing ...
Figure 5.10 SNAP‐19 heat source.
Figure 5.11 SNAP‐27 heat source.
Figure 5.12 Multi‐hundred watt heat source.
Figure 5.13 Aeroshell materials: fine weave pierced fabric and AXF‐5Q graphi...
Figure 5.14 Microstructure of carbon‐bonded carbon fiber (CBCF) insulation....
Figure 5.15 Clad vent set: shield cup assembly at left with weld shield at t...
Figure 5.16 Clad vent set: shield cup assembly in background with weld shiel...
Chapter 6
Figure 6.1 First Brillouin zones of (a) simple cubic, (b) face‐center cubic,...
Figure 6.2 Energy vs. lattice directions for (a) Free‐electron model and an ...
Figure 6.3 Calculated band structure and DOS of several thermoelectric mater...
Figure 6.4 Phonon dispersion plot within crystalline Si. [19]
Figure 6.5 Crystal structure of skutterudite, with the filler atoms in cyan,...
Chapter 7
Figure 7.1 Lipinski, Ronald J., Hensen, Danielle L. “Criticality Calculation...
Figure 7.2 Cutaway and Exploded View of Step‐0 GPHS Module and Stack.
Figure 7.3 GPHS aeroshell cap with lune form made in upper left corner.
Figure 7.4 GPHS module set‐up on the jig grinder before performing an aerosh...
Figure 7.5 Two GPHS fuel clads retrieved from a cut‐open PC and placed in th...
Figure 7.6 A fueled GIS being lowered into a GPHS cavity using a vacuum lift...
Figure 7.7 An ETG received at INL. This ETG became an RTG once fueled and wa...
Figure 7.8 An MMRTG’s cavity following removal of the electrical heater and ...
Figure 7.9 A fueled GPHS module inside the MRM canister being prepared for f...
Figure 7.10 RTG assembly fixture applying preload to the end of an RTG fueli...
Figure 7.11 INL vibration technician monitoring RTG test date displayed on t...
Figure 7.12 An MMRTG mounted to its vibration test fixture in the vertical t...
Figure 7.13 An RTG being weighed. Note the gold and red rigging for lifting ...
Figure 7.14 An RTG mounted to the custom aluminum fixture for mass propertie...
Figure 7.15 An RTG positioned for magnetics measurements.
Figure 7.16 Thermal Vacuum Atmosphere Chamber to test RTGs.
Figure 7.17 An MMRTG suspended in a Thermal Vacuum Atmosphere Chamber.
Figure 7.18 MMRTG Flight Unit 1 long‐term storage preparation at INL.
Figure 7.19 INL nuclear operators disassemble a 9904 shipping cask. The whit...
Figure 7.20 INL nuclear operators load the MMRTG Flight Unit 2 (F2), for the...
Figure 7.21 MMRTG Flight Unit 2 (F2) for Mars 2020 mission “hot‐fit” checks ...
Figure 7.22 MMRTG Flight Unit 2 (F2) for Mars 2020 mission being hoisted up ...
Chapter 8
Figure 8.1 Compilation of lifetime performance for nearly all missions power...
Figure 8.2 Lifetime performance for RTG missions that predate SNAP‐19 (a) ve...
Figure 8.3 Lifetime performance of the SNAP‐9A flight systems normalized to ...
Figure 8.4 Lifetime performance of the two SNAP‐19B flight systems on the Ni...
Figure 8.5 Lifetime performance of the SNAP‐27 flight systems normalized to ...
Figure 8.6 Lifetime performance of the SNAP‐19 flight systems normalized to ...
Figure 8.7 Lifetime performance of the MHW‐RTG flight systems normalized to ...
Figure 8.8 Lifetime performance of the GPHS‐RTG flight systems normalized to...
Figure 8.9 Lifetime performance of the MMRTG flight system powering Curiosit...
Chapter 9
Figure 9.1 Power generation for Cassini RTGs as a fraction of the beginning‐...
Figure 9.2 Example log‐log plots of RTG data. (a) The first five years of Ca...
Figure 9.3 Rate constant plot for Cassini RTG performance after thermal inve...
Figure 9.4 Plot of residuals for the thermoelectric converter degradation.
Figure 9.5 Power losses originating from decreased BOM power caused by lower...
Figure 9.6 Power losses originating from thermoelectric degradation during M...
Figure 9.7 Radioisotope thermoelectric generator power degradation mechanism...
Figure 9.8 Variations of Seebeck coefficient (a) electrical resistivity, (b)...
Figure 9.9 Comparison of Voyager RTG power output actuals and original DEGRA...
Figure 9.10 Examples of RPS‐DET geometries. (a) Voyager‐like environment, (b...
Figure 9.11 Examples of RPS‐DET 2D cross‐sectional slices of 3D mesh tallies...
Chapter 10
Figure 10.1 Changes under consideration for the potential eMMRTG.
Figure 10.2 Illustration of the MMRTG and eMMRTG thermoelectric couples.
Figure 10.3 Photograph of the SKD couples currently on test at JPL and TESI....
Figure 10.4 The first fabricated SKD 48‐couple module. (a) is the top of the...
Figure 10.5 Cross‐section of a 48‐couple module showing the super‐critically...
Figure 10.6 The normalized peak power of the p‐legs as a function of time an...
Figure 10.7 The normalized peak power of the n‐legs as a function of time an...
Figure 10.8 The normalized peak power of SKD couples as a function of time a...
Figure 10.9 Measured and predicted power for the SKD 48‐couple module is in ...
Figure 10.10 Comparison of current‐best‐estimate of eMMRTG and MMRTG 17‐year...
Figure 10.11 Cutaway diagram of a GPHS‐RTG. Available from: https: //en.wiki...
Figure 10.12 SiGe Unicouple Components. Available from: https://en.wikipedia...
Figure 10.13 GPHS‐RTG Converter Shell and Thermopile Mating Operations. [16]...
Figure 10.14 Illustration Showing NSPM‐20 Tier Factors. [28]
Figure 10.15 Encapsulation and heat source architectures for an
241
Am RTG de...
Guide
Cover Page
Title page
Copyright page
Foreward
Note From the Series Editor
Preface
Authors
Reviewers
Acknowledgments
Glossary
List of Acronyms and Abbreviations
Table of Contents
Begin Reading
Index
Wiley End User License Agreement
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The Technology of Discovery
Radioisotope Thermoelectric Generators and Thermoelectric Technologies for Space Exploration
Edited by
David Friedrich Woerner
Jet Propulsion LaboratoryCalifornia 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.
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Library of Congress Cataloging‐in‐Publication DataNames: 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/20221108LC record available at https://lccn.loc.gov/2022051673LC ebook record available at https://lccn.loc.gov/2022051674
Cover Design: WileyCover Images: © NASA/JPL‐Caltech/Malin Space Science Systems
Foreward
I am pleased to commend the Jet Propulsion Laboratory (JPL) Space Science and Technology Series, and to congratulate and thank the authors for contributing their time to these publications. It is not easy for busy scientists and engineers who face constant launch date and deadline pressures to find the time to tell others clearly and in detail how they solve important and difficult problems. So, I applaud the authors of this series for the time and care they devoted to documenting their contributions to the adventure of space exploration. In writing these books, these authors are truly living up to JPL’s core value of openness.
JPL has been NASA’s primary center for robotic planetary and deep‐space exploration since the Laboratory launched the nation’s first satellite, Explorer 1, in 1958. In the years since this first success, JPL has sent spacecraft to each of the planets, studied our own planet in wavelengths from radar to visible, and observed the universe from radio to cosmic ray frequencies. Even more exciting missions are planned for the next decades in all these planetary and astronomical studies, and these future missions must be enabled by advanced technology that will be reported in this series. The JPL Deep Space Communications and Navigation book series captures the fundamentals and accomplishments of those two related disciplines. This companion Science and Technology Series expands the scope of those earlier publications to include other space science, engineering, and technology fields in which JPL has made important contributions.
I look forward to seeing many important achievements captured in these books.
Laurie Leshin, Director
Jet Propulsion Laboratory
California Institute of Technology
Note From the Series Editor
This title is the latest contribution to the Jet Propulsion Laboratory (JPL) Space Science and Technology Series. This series is a companion series of the ongoing Deep Space Communications and Navigation Systems (DESCANSO) Series and includes disciplines beyond communications and navigation. DESCANSO is a Center of Excellence formed in 1998 by the National Aeronautics and Space Administration (NASA) at JPL, which is managed under contract by the California Institute of Technology.
The JPL Space Science and Technology series, authored by scientists and engineers with many years of experience in their fields, lays a foundation for innovation by sharing state‐of‐the‐art knowledge, fundamental principles and practices, and lessons learned in key technologies and science disciplines. We would like to thank the support of the Interplanetary Network Directorate at JPL for their encouragement and support of this series.
Jon Hamkins, Editor‐in‐Chief
JPL Space Science and and Technology Series
Jet Propulsion Laboratory
California Institute of Technology
Preface
“Far better is it to dare mighty things, to win glorious triumphs, even though checkered by failure … than to rank with those poor spirits who neither enjoy nor suffer much, because they live in a gray twilight that knows not victory nor defeat.”
— Theodore Roosevelt
Radioisotope Thermoelectric Generators (RTGs) have proven to be one of the most creative solutions to the challenge of providing a reliable source of electrical power for deep space missions. RTGs have powered spacecraft that have discovered Ocean Worlds in our solar system, evidence that Mars harbored persistent liquid water in its ancient past, the largest known glacier in the solar system on Pluto, that Enceladus—a moon of Saturn—spouts icy plumes fed from a subterranean ocean, and given us our first taste of interstellar space.
This book is a history, primer, reference book, and partial record of what has become one of the most successful technologies ever fielded for the sake of space science, and an educated look at potential futures for RTGs. This title binds all of this together with an explanation of the basic physics of how RTGs are able to produce power from heat, along with discussions of specific programs, missions, failures, and more.
The history of RTG production has been episodic. The first RTG was invented during the Eisenhower administration in the 1950s and gave rise to frequent RTG‐powered space missions in the 1960s and 1970s. However, in subsequent decades, the pace of missions that required this enabling technology waned to approximately the one to two launches per decade we see today. Production of various types of RTGs was stopped and restarted in concert with demand. This led to a dwindling of the industrial base and expertise required to produce these unique generators, and imprinted an ebb and flow or episodic pattern onto the production rate of RTGs over time.
Today, the US Department of Energy and NASA have formed a strong team using a “constant rate” approach to serve the demand and needs of a power‐hungry community of space explorers. RTGs provide power where the sun does not shine regularly or strongly enough, and, we believe, RTGs will continue to be a vital power and energy source for complex deep space missions for generations to come. They are solid‐state, quiet, extremely reliable, and long‐lived.
The history of RTGs is glorious. That may sound like hyperbole, it is not. Some RTGs have been powering spacecraft in flight for over 45 years. No RTG has ever caused a mission or spacecraft failure. Their performance and lifetimes are unmatched by any other power source for spaceflight that humankind has mastered. They require no periodic maintenance in flight. RTGs are electrical generators that enable humankind to explore our darkest, dustiest, coldest regions of the solar system, and the vastness of the space outside of our sun’s minuscule heliosphere.
RTGs use materials that exhibit the Seebeck effect to convert heat into Direct Current (DC) electrical power. The Seebeck effect was first reported in 1823 by the Baltic German physicist Thomas Johann Seebeck. His discovery is the foundation for the technologies employed in RTGs for space missions using thermoelectric couples.
RTGs convert heat to power by directing heat flow through thermoelectric couples. Heated thermoelectric couples produce a voltage and when a load is applied, current will flow from each couple. Voila, DC electricity. Yet, RTGs are products of chemistry, materials science, nuclear physics, and decades of sophisticated engineering. They are solid‐state, have no moving parts, and each is unitary, needing no ancillary equipment to produce power. Since their creation, extensive and well‐funded research, engineering, and flight experience forged modern RTG designs for space exploration.
RTGs are not simple. They are annular in design and employ rings of thermoelectric couples arrayed around a stack of heat sources to convert heat to electricity. Drawings of them tend to unintentionally mask some of the internal components, some of which can reach temperatures over 1,000 degrees Centigrade or 1,832 degrees Fahrenheit, and are maintained at those temperatures for years. It is difficult to comprehend what happens to materials at those temperatures. Chemical reactions are vastly accelerated over our day‐to‐day experiences. Materials that are solid at room temperature may sublimate when heated to such temperatures. In addition, materials can diffuse into one another.
A schematic of a thermoelectric couple suggests simplicity and masks several phenomena, such as the dramatic temperature reduction between its hot‐ and cold‐side components. For example, Figure 0.1 shows a silicon‐germanium thermoelectric couple (aka unicouple), which comprises five subassemblies that include eighteen separate components. During steady‐state operation in today’s RTGs, the temperature along the length of this type of unicouple drops from 1,035 °C (1,895 °F) at the hot shoe to 290 °C (554 °F) at the heat shunt. That gradient stretches just over one inch and yields a temperature change of ~750 °C (~1,382 °F). This dramatic temperature gradient suggests deep, unobvious complexities tied to thermoelectric technologies and RTGs.
Figure 0.1 A schematic of a silicon‐germanium thermoelectric unicouple used in the GPHS‐RTGs flown on the Cassini mission. Parenthetical letters refer to chemical elements or compounds.
Credit: Lockheed Martin.
Insight into the unobvious is what you will discover in these pages and should provide the reader with enough RTG history to make them conversant, enough flight history to incorporate this knowledge into deep space mission designs, some background to inform policy and funding decisions, and comprehensive insights intended to help sidestep many of the failures of the past. We employed real‐world examples throughout and applied theory to practical situations. We intend this book to bridge the gap between university studies and professional work. Therefore, we provide extensive lists of references to point readers to fundamental and referential sources.
The material herein complements and expands the public history of RTGs, explores the current state‐of‐ the‐art, and attempts to peer forward in time. We intend to provide more historical detail of both successes and failures, discuss advances and setbacks of novel thermoelectric materials and technologies that scientists have investigated and abandoned, and chart possible courses to future RTGs and their technologies.
The reinvigorated search for life beyond Earth and NASA’s drive to install a permanent human presence on the Moon have breathed new life into space exploration, and each thrust will require technologies that operate effectively in cold and dark spaces. RTGs provide hope for these immediate goals and will enable many more important discoveries. It is a marvelous time to be exploring space!
David Friedrich Woerner,
Jet Propulsion Laboratory/California Institute of Technology, Pasadena, California, USA
Authors
Brian K. BairstowJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena California
Chadwick D. BarklayUniversity of Dayton ResearchInstitute, Dayton, Ohio
Russell BennettTeledyne Energy Systems, Inc.Hunt Valley, Maryland
Thierry CaillatJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Ike C. ChiJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Emory D. CollinsOak Ridge National LaboratoryOak Ridge, Tennessee
Shad E. DavisIdaho National LaboratoryIdaho Falls, Idaho
David W. DePaoliOak Ridge National LaboratoryOak Ridge, Tennessee
Patrick E. FryeAerojet RocketdyneCanoga Park, California
Nidia C. GallegoOak Ridge National LaboratoryOak Ridge, Tennessee
Lawrence H. HeilbronnUniversity of TennesseeKnoxville, Tennessee
Tim HolgateJohn Hopkins University AppliedPhysics Laboratory, Laurel, Maryland
Chris L. JensenOak Ridge National LaboratoryOak Ridge, Tennessee
Steve KeyserTeledyne Energy Systems, Inc.Hunt Valley, Maryland
Andrew M. LaneAerojet RocketdyneCanoga Park, California
Young H. LeeJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Jong‐Ah PaikJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Kaara K. PattonOak Ridge National LaboratoryOak Ridge, Tennessee
Brian PhanJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Stan PinkowskiJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Glenn R. RomanoskiOak Ridge National LaboratoryOak Ridge, Tennessee
Kevin L. SmithJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Michael B.R. SmithOak Ridge National LaboratoryOak Ridge, Tennessee
Ying SongTeledyne Energy Systems, Inc.Hunt Valley, Maryland
George B. UlrichOak Ridge National LaboratoryOak Ridge, Tennessee
Joe VanderVeerTeledyne Energy Systems, Inc.Hunt Valley, Maryland
Hsin WangOak Ridge National Laboratory,Oak Ridge, Tennessee
Karl A. WefersAerojet RocketdyneCanoga Park, California
Robert M. WhamOak Ridge National LaboratoryOak Ridge, Tennessee
Christofer E. WhitingUniversity of Dayton Research InstituteDayton, Ohio
David Friedrich WoernerJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Andrew J. ZillmerIdaho National LaboratoryIdaho Falls, Idaho
Reviewers
Chadwick D. BarklayUniversity of Dayton ResearchInstitute, Dayton, Ohio
Charles E. BensonJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Thierry CaillatJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Eric S. ClarkeIdaho National LaboratoryIdaho Falls, Idaho
Joe C. GiglioIdaho National LaboratoryIdaho Falls, Idaho
Terry J. HendricksRetired—Jet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Douglas M. IsbellJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Stephen G. JohnsonIdaho National LaboratoryIdaho Falls, Idaho
Vladimir JovovicJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Emily F. KlonickiJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Christopher S. MatthesJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Lucas T. RichIdaho National LaboratoryIdaho Falls, Idaho
Glenn R. RomanoskiOak Ridge National LaboratoryOak Ridge, Tennessee
Carl E. SandiferNASA Glenn Research CenterCleveland, Ohio
Michael B.R. SmithOak Ridge National LaboratoryOak Ridge, Tennessee
George B. UlrichOak Ridge National LaboratoryOak Ridge, Tennessee
Christofer E. WhitingUniversity of Dayton Research InstituteDayton, Ohio
David Friedrich WoernerJet Propulsion Laboratory/CaliforniaInstitute of TechnologyPasadena, California
Andrew J. ZillmerIdaho National LaboratoryIdaho Falls, Idaho
Acknowledgments
I wish to acknowledge my parents, Robert Woerner and Mary Crow. It is their devotion to me, love, and upbringing that made my participation in this project possible.I want to thank Brett Kurzman and Stacey Woods, our editors, and their colleagues at Wiley.com. They were responsive, dedicated, patient, and extremely helpful in preparing this manuscript.
I want to thank the small army of women and men that made this publication possible, those tireless souls that founded, grew, and built the Radioisotope Power System community into what it is today. The list of their names could fill the pages of this book, and I struggled with who to single out and mention here and concluded I would err on the side of not slighting anyone and just say thank you to the entire RPS community. Thank you. Thank you. You gave me friends, companions, and a career I did not expect.
I am deeply humbled and fascinated by the work and achievements of the RPS community and hope that this manuscript does them at least some small amount of justice. I know the authors have poured their hearts into the book and deserve a round of applause.
I/we are indebted to the reviewers whose clarity of mind and perceptive insights kept us focused and out of the “ditch” of lousy writing.
Lastly, I want to thank those space exploring scientists and engineers who thrill the world with their fabulous discoveries. The draft of the next Planetary Science and Astrobiology Decadal Survey was released less than a handful of days before I typed these words. The draft promises that the search for past and present life in our solar system will continue. It describes new and exciting scientic missions to come in the next decade should Congress and NASA fund them. Several missions to destinations in our solar system are only achievable by RPS powered robots. Expect grand findings.
A portion of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004).
Portions of this work were authored under the support of Oak Ridge National Laboratory managed UT‐ Battelle, LLC, under contract DE‐AC05‐00OR22725 with the US Department of Energy (DOE).
Portions of this work were authored thanks to the generous support of the University of Dayton Research Institute.
A portion of this research was carried out at the Idaho National Laboratory, under a contract with the US
Department of Energy (DE‐AC07‐05ID14517).
List of Acronyms and Abbreviations
3M
Minnesota Mining and Manufacturing Company
AEC
Atomic Energy Commision
ALSEP
Apollo Lunar Surface Experiments Package
APL
Applied Physics Laboratory
AR
Aerojet Rocketdyne
ARC
Ames Research Center
ATLO
Assembly, Test, and Launch Operations
ATR
Advanced Test Reactor
AU
Astronomical Unit
BOL
Beginning of Life
BOM
Beginning of Mission
CBCF
Carbon Bonded Carbon Fiber
CCAFS
Cape Canaveral Air Force Station
CFC
Chlorofluorocarbon
CFR
Code of Federal Regulations
CG
Center of Gravity
CLPS
Commercial Lunar Payload Services
CM
Configuration Manager
CMOS
Complementary Metal Oxide Semiconductor
COC
Certificate of Compliance
COPV
Composite Over‐Wrapped Pressure Vessel
CSCBA
Converter Shipping Container Base Assembly
DARPA
Defense Advanced Research Projects Agency
DC
Direct Current
DoD
Department of Defense
DOE
Department of Energy
DOS
Density of States
DOT
Department of Transportation
DPA
Destructive Physical Analysis
DSA
Design Safety Analysis
ECR
Electrical Contact Resistance
EHS
Electric Heat Source
EM
Electromagnetic
EMI/EMC
Electromagnetic Interference/Electromagnetic Compatibility
eMMRTG
Enhanced Multi‐Mission Radioisotope Thermoelectric Generator
ENDF
Evaluated Nuclear Data File
EODL
End of Design Life
EOM
End of Mission
ESA
European Space Agency
ESD
Electrostatic Discharge
ETG
Electrically Heated Thermoelectric Generator
EU
Engineering Unit
FAA
Federal Aviation Administration
FC
Fuel Clad
FET
Field Effect Transistor
FWPF
TM
Fine Weave Pierced
TM
Fabric
GE
General Electric
GFY
Government Fiscal Year
GIS
Graphite Impact Shell
GLFC
Graphite LM Fuel Cask
GPHS
General Purpose Heat Source
GPHS‐RTG
General Purpose Heat Source Radioisotope Thermoelectric Generator
GPS
Global Positioniong System
GRC
Glenn Research Center, NASA
GSE
Ground Support Equipment
GSFC
Goddard Spaceflight Center, NASA
GUI
Graphical User Interface
HBM
Human‐Body Model
HDBK
Handbook
HEOMD
Human Exploration and Operations Mission Directorate
HEPA
High‐Efficiency‐Air‐Particulate
HFIR
High Flux Isotope Reactor
HRS
Heat Rejection System
HS
Heat Source
I&T
Integration and Test
IAAC
Inert Atmosphere Assembly Chamber
ICV
Inner Containment Vessel
IECEC
International Energy Conversion Engineering Conference
INL
Idaho National Laboratory, DOE
INSRB
Interagency Nuclear Safety Review Board
IRD
Interface Requirements Document
IRHS
Intact Reentry Heat Source
ISPM
International Solar Polar Mission
ISRO
Indian Space Research Organization
JHUAPL
Johns Hopkins University Applied Physics Laboratory
JPL
Jet Propulsion Laboratory/California Institute of Technology
KAERI
Korea Atomic Energy Research Institute
KBO
Kuiper Belt Object
KSC
Kennedy Space Center
LANL
Los Alamos National Laboratory, DOE
LDS
Ling Dynamic System
LES
Lincoln Experimental Satellite
LET
Linear Energy Transfer
Li‐ion
Lithium Ion
LMTO
Linear Muffin‐Tin Orbital
LPPM
Life Performance Prediction Model
LSP
Launch Services Program
LTOF
Lift Turnover Fixture
LV
Launch Vehicle
LWRHU
Lightweight Radioisotope Heater Unit, aka RHU
MACS
Medium Altitude Communications Satellite
MHW
Multi‐Hundred‐Watt
MHW HS
Multi‐Hundred‐Watt Heat Source
MHW‐RTG
Multi‐Hundred‐Watt‐Radioisotope Thermoelectric Generator
MIL
Military
min
minimum; except when min is clearly being used to denote the time unit minute
MIT
Massachusetts Institute of Technology
MITG
Modular Isotopic Thermoelectric Generator
ML
Mission Life
MMAS
Martin Marietta Astro Space
MMLT
Mini‐Modules Life Tester
MMRTG
Multi‐Mission Radioisotope Thermoelectric Generator
MRM
Module Reduction and Monitoring
MSL
Mars Science Laboratory
NASA
National Aeronautics and Space Administration
NEPA
National Environmental Policy Act
NETS
Nuclear and Emerging Technologies for Space Conference
Next Gen RTG
Next Generation Radioisotope Thermoelectric Generator
NGRTG
Next Generation Radioisotope Thermoelectric Generator
NH
New Horizons
NNDC
National Nuclear Data Center
NNL
National Nuclear Laboratory
NOAA
National Oceanic and Atmospheric Administration
NPAS
Nuclear Power Assessment Study
NPS
Nuclear Power System
NRC
Nuclear Regulatory Commission
NSPM
National Security Presidential Memoranda
ORNL
Oak Ridge National Laboratory, DOE
PAWS
Powered Polar Automated Weather Station
PGS
Power Generation and Storage
PHSF
Payload Hazardous Servicing Facility
PMC
Plutonia Molybdenum Cermet
PMP
Portable Monitoring Package
PPO
Pure Plutonium Oxide
PRT
Platinum Resistance Thermometer
PSD
Planetary Science Division, NASA
QU
Qualification Unit
REDC
Radiochemical Engineering Development Center, ORNL
RFP
Request For Proposal
RHU
Radioisotope Heater Unit
RIC
RTG Integration Cart
RPS
Radioisotope Power System
RPS‐DET
Radioisotope Power System Dose Estimation Tool
RSICC
Radiation Safety Information Computational Center
RTG
Radioisotope Thermoelectric Generator
RTGF
Radioisotope Thermoelectric Generator Facility
RTGTS
Radioisotope Thermoelectric Generator Transportation System
SAM
Sample Analysis Mars
SAR
Safety Analysis Report
SARC
Safety Analysis Report Commitment
SEB
Single‐Event Burnout
SEE
Single‐Event Effect
SEFI
Single‐Event Functional Interupt
SEGR
Single‐Event Gate Rupture
SER
Safety Evaluation Report
SET
Single‐Event Transient
SEU
Single‐Event Upset
SIG
Selenide Isotope Generator
SiGe
Silicon germanium
SKD
Skutterudite
SMD
Science Mission Directorate, NASA
SNAP
Systems for Nuclear Auxiliary Power
SNS
Space Nuclear System
SOW
Statement of Work
SPF
Single Point Failure
SRG
Stirling Radioisotope Generator
SRS
Savannah River Site
SSPSF
Space and Security Power Systems Facility
STD
Standard
SUV
Sports Utility Vehicle
SV
Space Vehicle
SwRI
Southwest Research Institute
TAGS
Tellurium antimony germanium silver alloy
TBR
To Be Reviewed
TCR
Thermal Contact Resistance
TE
Thermoelectric
TEC
Thermoelectric Couple
TEG
Thermoelectric Generator
TEM
Thermoelectric Multicouple
TESI
Teledyne Energy Systems, Incorporated
TRN
Terrain Relative Navigation
TSOC
Test and Operations Support Contract
TVAC
Thermal Atmosphere Vacuum Chamber
UDRI
University of Dayton Research Institute
UK
United Kingdom
US
United States
USAF
United States Air Force
USN
United States Navy
VA
Verification Activity
VCE
Voltage, Collector‐Emitter
VDS
Volts, Drain‐Source
VHP
Vaporous Hydrogen Peroxide
VIF
Vertical Integration Facility
wrt
with respect to
1The History of the Invention of Radioisotope Thermoelectric Generators (RTGs) for Space Exploration
Chadwick D. Barklay
University of Dayton Research Institute, Dayton, Ohio
In December of 1903, the Wright Brothers made the first successful powered flight of an airplane. There are significant levels of examination of Orville and Wilbur’s incremental improvements to the original design of their flying machine to build the Wright Flyer II. However, there is not much appreciation of the backstory that inspired the brothers to explore the fundamentals of aerodynamics and pursue the research and development required to make a powered, heavier‐than‐air aircraft. Wilbur Wright indicated in a letter he wrote in 1912 that the pioneering work of Otto Lilienthal in the late 1800s was a precursor to their efforts. But it was a rubber band‐powered toy helicopter their father, Milton Wright, gave them in 1878 that Orville credited as the object that sparked their interest in flight.
As an opening discussion of the history of the radioisotope thermoelectric generator (RTG), it is essential to understand the backstory of the invention that has allowed humankind to explore beyond the solar system’s boundaries. In 1954, Kenneth Jordan and John Birden invented the RTG at the Atomic Energy Commission (AEC) Mound Laboratory. Oral history posits that the two inventors drafted their initial design concept during lunch on a napkin in the Mound Laboratory cafeteria. Their initial research efforts used a small steam‐electric generator to demonstrate that heat utilized from the radioactive decay of polonium‐ 210 could generate electricity. However, more‐efficient methods for producing electricity were required, and Jordan and Birden coupled a polonium‐210 heat source to a thermoelectric material array to generate electricity (Figure 1.1). This early prototype used forty chromel‐constantan thermocouples to generate power from a suspended sphere containing 146 curies of encapsulated polonium‐210. The outside container of the prototype was made of aluminum and used an early form of silica aerogel (Santocel) as insulation. This unit produced 9.4 milliwatts of power for a total efficiency of 0.20%.[1] In 1959, Jordan and Birden received a patent for their invention, which is still the underpinning innovation for all RTGs used by the National Aeronautics and Space Administration (NASA) for planetary and deep‐space exploration.[2]
Figure 1.1 An early experimental thermoelectric generator designed by Jordan and Birden that couples a polonium‐210 heat source with a thermoelectric material array.
Credit: Mound Science and Energy Museum Association.
Similarly, the events leading up to the first powered flight at Kittyhawk, the backdrop of Jordan and Birden’s early efforts, are not widely known. The US Congress established the AEC in the shadows of World War II to establish centralized governmental controls to manage the research and production of atomic weapons in the post‐war era.[3] During the first decade of the AEC, laboratories under the AEC umbrella conducted a broad spectrum of research activities on producing natural and synthetic radioisotopes in reactors and cyclotrons. These early efforts focused on how radioisotopes can influence thermonuclear fusion produced by weapons. In conjunction with research and development activities for weapons programs, research was also ongoing to determine the utility of radioisotopes for particle physics, medicine, geography, and several industrial applications.
Within the same timeframe, the War Department, the predecessor to the Department of Defense, recognized a need for establishing a non‐profit, global policy think tank, and the Douglas Aircraft Company created the RAND Project, later the RAND Corporation, to fulfill this need. In 1946, the RAND Project explored the preliminary design of a satellite vehicle [4], and in 1947, RAND expanded its examination to evaluate the use of radioisotopes to address the electrical power requirements for satellite vehicles.[5] This initial analysis considered the use of polonium‐210 and strontium‐89 as thermal sources for power generation. In 1949, RAND published a study that outlined the use of nuclear power sources for satellites in Earth orbit, and in 1951, the Department of Defense (DOD) requested that the AEC initiate research on nuclear power for spacecraft.[6] As a result, the AEC initiated a series of studies that concluded that both fission and radioisotope power systems were technically feasible for satellites. [7]
In late 1953, President Dwight D. Eisenhower delivered his “Atoms‐for‐Peace” address at the United Nations to promote the peaceful uses of atomic energy. During that same timeframe, Jordan and Birden built two experimental thermal batteries using polonium‐210 and chromel‐constantan thermocouples to validate their thermal battery theory and develop fabrication techniques. These experimental units had approximately ten times the work capacity of ordinary dry cell batteries of the same weight.[1]
Jordan and Birden fabricated seven experimental units in total, and the third unit (Figure 1.2) was the prototype of the remaining generators built. These later units employed twelve thermopiles, each consisting of thirty‐seven chromel‐constantan thermocouples supported by mica cards that were vertically mounted and radially spaced on aluminum rings. Figure 1.2 also shows an assembled and disassembled thermopile.
Figure 1.2 One of the latter prototype thermoelectric generators designed by Jordan and Birden.
Credit: Mound Science and Energy Museum Association.
Jordan and Birden made extensive measurements on these units to determine efficiencies and the effects of various types of insulation, including vacuum, noise levels, ambient temperatures, matched and unmatched loads on the units’ performance.[8] In general, these latter prototypes produced approximately 50 milliwatts of power for a total efficiency of 0.32%. The last units in this series of prototypes were designed and built based on specifications that delineated load voltage, power, durability, and design life requirements. It was the first step to ensuring that future generators would be sufficiently rugged to withstand the vibrational and quasi‐static forces associated with space launches.
In 1955 the AEC formally initiated the Systems for Nuclear Auxiliary Power (SNAP) program, which focused on experimental radioisotope and fission systems. The objective of this program was to develop compact, lightweight, reliable atomic electric devices for use in space and terrestrial applications. Under the SNAP program, odd numbers designated RTGs systems, and even numbers represented fission reactor systems. In 1957, the Martin Company developed the SNAP‐1 RTG, which was assembled at the AEC Mound Laboratory. As the development of SNAP‐1 progressed, the Martin Company subcontracted with Westinghouse Electric and the Minnesota Mining and Manufacturing Company (3M) to develop the SNAP‐3 RTG. In 1958, 3M delivered the SNAP‐3 to the Martin Company, which fueled the unit with encapsulated polonium‐210 from Mound Laboratory. The SNAP‐3 produced 2.5 We, and President Eisenhower displayed the power system in the US White House’s Oval Office on 16 January 1959 (Figure 1.3).[9]
