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Failure Analysis of the
Arecibo Observatory 305-Meter
Telescope Collapse
Committee on Analysis of Causes of Failure
and Collapse of the 305-Meter Telescope at
the Arecibo Observatory
Board on Infrastructure and the Constructed
Environment
Division on Engineering and Physical Sciences
Consensus Study Report
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NATIONAL ACADEMIES PRESS 500 Fifth Street, NW Washington, DC 20001
This activity was supported by Grant CMMI- 2135084 from the National Science Foundation to the National
Academy of Sciences. Any opinions, findings, conclusions, or recommendations expressed in this publication do
not necessarily reflect the views of any organization or agency that provided support for the project.
International Standard Book Number-13: 978-0-309-XXXXX-X
International Standard Book Number-10: 0-309-XXXXX-X
Digital Object Identifier: https://doi.org/10.17226/26982
Cover: Photo courtesy of the Arecibo Observatory, a facility of the National Science Foundation.
This publication is available from the National Academies Press, 500 Fifth Street, NW, Keck 360, Washington,
DC 20001; (800) 624-6242 or (202) 334-3313; http://www.nap.edu.
Copyright 2024 by the National Academy of Sciences. National Academies of Sciences, Engineering, and
Medicine and National Academies Press and the graphical logos for each are all trademarks of the National
Academy of Sciences. All rights reserved.
Printed in the United States of America.
Suggested citation: National Academies of Sciences, Engineering, and Medicine. 2024. Failure Analysis of the
Arecibo Observatory 305-Meter Telescope Collapse. Washington, DC: The National Academies Press. https://
doi.org/10.17226/26982.
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The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President
Lincoln, as a private, nongovernmental institution to advise the nation on issues related to science and
technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is
president.
The National Academy of Engineering was established in 1964 under the charter of the National Academy
of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for
extraordinary contributions to engineering. Dr. John L. Anderson is president.
The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the
charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are
elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president.
The three Academies work together as the National Academies of Sciences, Engineering, and Medicine
to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex
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recognize outstanding contributions to knowledge, and increase public understanding in matters of science,
engineering, and medicine.
Learn more about the National Academies of Sciences, Engineering, and Medicine at
www.nationalacademies.org.
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Consensus Study Reports published by the National Academies of Sciences, Engineering, and
Medicine document the evidence-based consensus on the studyâs statement of task by an authoring committee of
experts. Reports typically include findings, conclusions, and recommendations based on information gathered by
the committee and the committeeâs deliberations. Each report has been subjected to a rigorous and independent
peer-review process and it represents the position of the National Academies on the statement of task.
Proceedings published by the National Academies of Sciences, Engineering, and Medicine chronicle the
presentations and discussions at a workshop, symposium, or other event convened by the National Academies.
The statements and opinions contained in proceedings are those of the participants and are not endorsed by
other participants, the planning committee, or the National Academies.
Rapid Expert Consultations published by the National Academies of Sciences, Engineering, and Medicine are
authored by subject-matter experts on narrowly focused topics that can be supported by a body of evidence. The
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COMMITTEE ON ANALYSIS OF CAUSES OF FAILURE AND COLLAPSE OF
THE 305-METER TELESCOPE AT THE ARECIBO OBSERVATORY
ROGER L. McCARTHY (NAE), McCarthy Engineering, Chair
RAMÃN L. CARRASQUILLO,1 Carrasquillo Associates
DIANNE CHONG (NAE), Boeing Engineering, Operations & Technology (retired)
ROBERT B. GILBERT (NAE), The University of Texas at Austin
W. ALLEN MARR, JR. (NAE), Geocomp, Inc.
JOHN R. SCULLY, University of Virginia
SAWTEEN SEE, See Robertson Structural Engineers
HABIB TABATABAI, University of WisconsinâMilwaukee
Study Staff
CAMERON OSKVIG, Board Director, Study Director
JAYDA WADE, Research Associate (until July 31, 2023)
JOSEPH PALMER, SR., Program Assistant
RADAKA LIGHTFOOT, Financial Business Partner (until March 20, 2023)
DONAVAN THOMAS, Financial Business Partner (from March 20, 2023)
1 Deceased on February 2, 2024.
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BOARD ON INFRASTRUCTURE AND THE CONSTRUCTED ENVIRONMENT
JESUS M. DE LA GARZA, Clemson University, Chair
BURCU AKINCI, Carnegie Mellon University
STEPHEN AYERS, Ayers Group
BURCIN BECERIK-GERBER, University of Southern California
LEAH BROOKS, The George Washington University
MIKHAIL V. CHESTER, Arizona State University
JAMES (JACK) DEMPSEY, Asset Management Partnership, LLC
LEONARDO DUENAS-OSORIO, Rice University
DEVIN K. HARRIS, University of Virginia
DAVID J. HAUN, Haun Consulting, Inc.
CHRISTOPHER J. MOSSEY, Fermi National Accelerator Laboratory
ANDREW PERSILY, National Institute of Standards and Technology
ROBERT B. RAINES, Atkins Nuclear Secured
JAMES RISPOLI, North Carolina State University
DOROTHY ROBYN, Boston University
SHOSHANNA D. SAXE, University of Toronto
Staff
CAMERON OSKVIG, Board Director
JAMES MYSKA, Senior Program Officer
BRITTANY SEGUNDO, Program Officer
JOSEPH PALMER, SR., Senior Program Assistant
DONAVAN THOMAS, Finance Business Partner
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Dedication
This report is dedicated to committee member Dr. Ramón L. Carrasquillo, who unexpectedly passed away
before this reportâs release. His pragmatic and insightful contributions strengthened the report. In addition to his
extensive engineering and materials science expertise, his deep connection to Puerto Rico helped the commit-
tee develop a nuanced understanding of the community and culture surrounding the Arecibo Observatory. He is
remembered by the committee as a thoughtful, warm, and generous colleague.
NOTE: Image courtesy of Carrasquillo Associates.
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Reviewers
This Consensus Study Report was reviewed in draft form by individuals chosen for their diverse perspec-
tives and technical expertise. The purpose of this independent review is to provide candid and critical comments
that will assist the National Academies of Sciences, Engineering, and Medicine in making each published report
as sound as possible and to ensure that it meets the institutional standards for quality, objectivity, evidence, and
responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the
integrity of the deliberative process.
We thank the following individuals for their review of this report:
DONALD CAMPBELL, Cornell University
GREGORY G. DEIERLEIN (NAE), Stanford University
LENNARD FISK (NAS), University of Michigan
DAVID GOODYEAR (NAE), Independent Consultant
MARTHA HAYNES (NAS), Cornell University
LT. COL. (RET.) CLARENCE (BART) KEMPER, Kemper Engineering Services, LLC
MATTHYS LEVY (NAE), Thornton Tomasetti
MOHAMMAD MODARRES, University of Maryland
JANINE PARDEE, Independent Consultant
RANDALL POSTON (NAE), Pivot Engineers
Although the reviewers listed above provided many constructive comments and suggestions, they were not
asked to endorse the conclusions or recommendations of this report nor did they see the final draft before its
release. The review of this report was overseen by WILLIAM F. BAKER, Skidmore Owings and Merrill, LLP,
and STEVE BATTEL (NAE), Battel Engineering. They were responsible for making certain that an independent
examination of this report was carried out in accordance with the standards of the National Academies and that all
review comments were carefully considered. Responsibility for the final content rests entirely with the authoring
committee and the National Academies.
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Contents
PREFACE xiii
SUMMARY 1
1 INTRODUCTION 7
History of the Arecibo Telescope, 7
Arecibo Telescope Cable System, 12
Statement of Task, 16
2 THE COLLAPSE: WHAT HAPPENED 18
Arecibo Telescope Failure Sequence, 18
Hurricane Maria Hits Arecibo Telescope, 18
Post-Maria Arecibo Telescope Inspections, 22
The Hurricane Maria Aftermath, 26
Bureaucratic Delays in Funding Arecibo Telescope Hurricane Repairs, 28
Sequence of Cable Failure Events, 30
3 ANALYSIS 35
Cable Socket Zinc Creep Failure, 35
Cable End Sockets, 48
Wire Breaks, 49
Earthquake, 55
Wind Speed Consideration in the Arecibo Telescopeâs Design, 56
Governing Cable Design Standards, 56
Arecibo Telescope Cable Load, 58
Risk Considerations, 61
Structural Robustness, 63
Monitoring, 65
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xii CONTENTS
4 ARECIBO TELESCOPEâS MANAGEMENT AND OVERSIGHT 70
5 OTHER LESSONS LEARNED 74
State of Knowledge, 74
Continued Research, 75
BIBLIOGRAPHY 76
APPENDIXES
A Committee Member Biographical Information 81
B Information-Gathering Activities 84
C Arecibo Telescope Cable Failure Mechanisms Considered by the Committee 86
D Arecibo Telescope Design Issues Considered by the Committee 94
E Acronyms and Abbreviations 96
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Preface
It has been my privilege to chair this committee of distinguished subject-matter experts in its investigation
and final probable cause determination of one of the most publicized and baffling failures of the modern era. It
became clear shortly after the Arecibo Telescopeâs collapse that the zinc used to anchor the steel supporting cable
wires into their sockets had allowed the failed cables to slip out of their sockets, known as spelter sockets. The
sockets slowly lost their grip on a critical number of the cable wires via slow zinc âcreep,â a process where the
zinc deformed slowly at a load below half the socketâs nominal strength. Although the committee agrees with
the conclusions from other forensic reports regarding zinc creep at the connection being the failure mechanism,
the baffling question was, âWhy was there excessive zinc creep at such loading?â Such a failure had never been
reported previously in over a century of widespread zinc spelter socket successful use.
Fortunately, the committee had the benefit of the detailed analysis and well-documented reports from NASA;
Wiss, Janney, Elstner Associates, Inc.; and Thornton Tomasetti, Inc., without which it could not have completed its
task. Building on their work, the committee presents a clear and plausible explanation of why the telescopeâs sockets
failed when no such sockets have ever been reported to have failed before. Unfortunately, there was not enough
data available to prove our explanation. It is simply the most plausible hypothesis based on the data we do have.
Without the depth and breadth of expertise on the committee, its task would remain uncompleted. I think I
speak for everyone on the committee when I say that none of us could have done this alone. I want to thank my
colleagues for their unwavering dedication to the task. Their professionalism and competence made my job an
enjoyable one.
Roger L. McCarthy, Chair
Committee on Analysis of Causes of Failure and Collapse
of the 305-Meter Telescope at the Arecibo Observatory
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