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Protecting the Space Shuttle from Meteoroids and Orbital Debris Protecting the Space Shuttle from Meteoroids and Orbital Debris Committee on Space Shuttle Meteoroid/Debris Risk Management Aeronautics and Space Engineering Board Commission on Engineering and Technical Systems National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1997
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Protecting the Space Shuttle from Meteoroids and Orbital Debris NATIONAL ACADEMY PRESS 2101 Constitution Avenue, N.W. Washington, DC 20418 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competencies and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. This study was supported by Contract No. NASW-4938 between the National Academy of Sciences and the National Aeronautics and Space Administration. Any opinions, findings, conclusions, and recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the organizations or agencies that provided support for this project. International Standard Book Number: 0-309-05829-5 Library of Congress Catalog Card Number: 97–80863 Available in limited supply from: Aeronautics and Space Engineering Board, HA 292, 2101 Constitution Avenue, N.W., Washington, DC 20418, (202) 334–2855 Additional copies available for sale from: National Academy Press, 2101 Constitution Avenue, N.W., Box 285, Washington, DC 20055, 1–800–624–6242 or (202) 334–3313 (in the Washington Metropolitan area), http://www.nap.edu Copyright 1997 by the National Academy of Sciences. All rights reserved. Cover Illustration: The large picture of the shuttle orbiter was taken from the Mir space station during shuttle mission STS-71 in July 1995. The inset is a scanning electron micrograph of a 0.6 mm diameter crater found on the Solar Maximum Mission Satellite, which was recovered from space in April 1994 by the crew of shuttle mission STS-41C. Source: NASA. Printed in the United States of America.
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Protecting the Space Shuttle from Meteoroids and Orbital Debris COMMITTEE ON SPACE SHUTTLE METEOROID/DEBRIS RISK MANAGEMENT FREDERICK H.HAUCK (chair), AXA Space, Bethesda, Maryland KYLE T.ALFRIEND, Texas A&M University, College Station DALE B.ATKINSON, consultant, Springfield, Virginia DALE R.ATKINSON, POD Associates, Inc., Albuquerque, New Mexico G.TAFT DEVERE, Space Warfare Center, Falcon Air Force Base, Colorado DONALD H.EMERO, Rockwell International (retired), Fountain Valley, California GEORGE J.GLEGHORN, TRW Space and Technology Group (retired), Rancho Palos Verdes, California DARREN S.MCKNIGHT, Titan Research and Technology, Reston, Virginia WILLIAM P.SCHONBERG, University of Alabama in Huntsville, Huntsville Aeronautics and Space Engineering Board Liaison WILLIAM H.HEISER, U.S. Air Force Academy, Colorado Springs, Colorado Aeronautics and Space Engineering Board Staff PAUL SHAWCROSS, Study Director JOANN CLAYTON-TOWNSEND, Aeronautics and Space Engineering Board Director (until July 11, 1997) MARVIN WEEKS, Senior Project Assistant
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Protecting the Space Shuttle from Meteoroids and Orbital Debris AERONAUTICS AND SPACE ENGINEERING BOARD JOHN D.WARNER (chair), The Boeing Company, Seattle, Washington A.DWIGHT ABBOT, Aerospace Corporation, Los Angeles, California STEVEN AFTERGOOD, Federation of American Scientists, Washington, D.C. GEORGE A.BEKEY, University of Southern California, Los Angeles GUION S.BLUFORD, JR., NYMA, Inc., Brook Park, Ohio RAYMOND S.COLLADAY, Lockheed-Martin Astronautics, Denver, Colorado BARBARA C.CORN, BC Consulting, Inc., Searcy, Arizona STEVEN D.DORFMAN, Hughes Telecommunications and Space Company, Los Angeles, California DONALD C.FRASER, Boston University, Boston, Massachusetts JAMES M.GUYETTE, Rolls-Royce North America, Reston, Virginia FREDERICK H.HAUCK, AXA Space, Bethesda, Maryland WILLIAM H.HEISER, U.S. Air Force Academy, Colorado Springs, Colorado WILLIAM HOOVER, U.S. Air Force (retired), Williamsburg, Virginia BENJAMIN HUBERMAN, Huberman Consulting Group, Washington, D.C. JAMES G.O’CONNOR, Coventry, Connecticut GRACE M.ROBERTSON, The Boeing Company, Long Beach, California GEORGE SPRINGER, Stanford University, Stanford, California Staff JOANN C.CLAYTON-TOWNSEND, Director (until July 11, 1997) GEORGE M.LEVIN,* Director (from July 14, 1997) * George Levin was Orbital Debris Program Manager at NASA before becoming ASEB director. To avoid a potential conflict of interest, he did not participate in any work related to this report after joining the National Research Council.
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Protecting the Space Shuttle from Meteoroids and Orbital Debris Preface In 1983, three days into my first shuttle mission, I noticed a small pit in one of the windows of the crew cabin. Spectrographic analysis of the residue left in this tiny pit revealed the presence of titanium and aluminum, suggesting that the orbiter had been hit by a chip of paint that had flaked off of some unknown spacecraft or rocket body. This was one of the first indications that orbital debris might pose a hazard to the space shuttle. By 1995, the number of reported window impacts had increased dramatically, and the debris hazard had forced planners to modify plans for shuttle mission STS-73. In September 1995, the space shuttle program manager established a Space Shuttle Meteoroid and Debris Damage Team to review the environment modeling and orbiter modeling, to assess the potential for damage from meteoroids and orbital debris, and to “recommend concepts and methods to reduce risk to critical orbiter areas” (Holloway, 1995). In 1995 and 1996, significant impacts occurred on the orbiter’s payload bay door and rudder speed brake, as well as on the tethered satellite pallet. In May 1996, the manager of the space shuttle program established interim guidelines to “minimize the time spent in sensitive attitudes, minimizing the probability of orbital debris impact to the wing leading edge and orbiter radiators.” He further stated that “mission planning and design should be implemented with the objective of not exceeding a probability of critical penetration of 1/200 while also minimizing the exposure of the orbiter radiators to orbital debris as much as possible” (Holloway, 1996). The allowable risk of 1/200 means that the hazard from meteoroids and orbital debris is, on some missions, the single greatest threat to the shuttle and crew, slightly larger than the hazard from ascent. To gain an independent, outside
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Protecting the Space Shuttle from Meteoroids and Orbital Debris assessment of the threat, and of measures to address it, the National Aeronautics and Space Administration (NASA) asked the National Research Council (NRC) to review the space shuttle program’s strategy for assessing and mitigating the threat posed by meteoroids and orbital debris. In response, the NRC formed the Committee on Space Shuttle Meteoroid/Debris Risk Management, under the auspices of the Aeronautics and Space Engineering Board. (The charge to the committee is contained in Appendix A.) The committee met in April and June of 1997 to receive briefings from NASA and NASA contractors and to deliberate on findings and recommendations. This report is the product of those meetings and of additional data gathering, writing, and discussion during the summer and fall of 1997. The committee concurs that the threat to the shuttle from meteoroids and orbital debris is real, although the magnitude of the threat and the resulting hazard are not clear. In recent years, researchers have greatly improved models of the debris environment and conducted numerous tests and studies to assess the damage caused by the impact of meteoroids and orbital debris, but no end-to-end assessment has been made of the orbiter’ s survivability in the face of the meteoroid and debris hazard. Such an assessment is needed, and needed soon. Until the magnitude of the threat—and the uncertainty of the threat assessment—are better known, program managers and mission planners will be forced to balance crew safety against cost and mission goals based on very incomplete information. The assessment will have other benefits as well—improvements in NASA’s environment and impact models will benefit space activities worldwide. NASA has developed a world-class center of expertise on the meteoroid and orbital debris hazard. Many experts from NASA and NASA contractors briefed the committee and provided us with information essential to this study. The committee thanks them for their professional and candid presentations. I extend my warm thanks to Dr. Bill Heiser, NRC Aeronautics and Space Engineering Board liaison to this project, for his active participation, his counsel, and his insightful critique of our process and text. In closing, I want to thank the members of the committee personally for their time and effort on the study and on writing this report, as well as Paul Shawcross, the study director, for his tireless efforts in bringing this project to fruition. RICK HAUCK Committee Chair REFERENCES Holloway, T.W. 1995. Space shuttle meteoroid and debris damage team. MA2–95–074. Houston: NASA Johnson Space Center. September 28, 1995. Holloway, T.W. 1996. Orbital debris mission planning guidelines. MA2–96–082. Houston: NASA Johnson Space Center. May 30, 1996.
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Protecting the Space Shuttle from Meteoroids and Orbital Debris Contents EXECUTIVE SUMMARY 1 1 INTRODUCTION 4 Reference, 6 2 RISK TO THE ORBITER AND CREW 7 Orbiter Susceptibility, 7 Orbiter Design, 11 Orbiter Vulnerability, 15 Extravehicular Activity, 17 References, 18 3 RISK MANAGEMENT STRATEGY 19 Current Approach, 19 Analysis and Findings, 23 Recommendations, 26 References, 26 4 TOOLS FOR RISK ASSESSMENT 27 Current Approach, 27 Analysis and Findings, 29 Recommendations, 34 References, 34
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Protecting the Space Shuttle from Meteoroids and Orbital Debris 5 COLLISION AVOIDANCE 36 Current Approach, 36 Analysis and Findings, 39 Recommendations, 41 References, 41 6 RISK MITIGATION 42 Current Approach, 42 Analysis and Findings, 46 Recommendations, 49 References, 49 ACRONYMS 51 APPENDICES A Statement of Task 55 B Biographical Sketches of Committee Members 56
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Protecting the Space Shuttle from Meteoroids and Orbital Debris List of Tables, Figures, and Boxes TABLES 2–1 Predicted Number of Impacts on Orbiter, 9 2–2 Damage Thresholds for Orbiter Components, 15 2–3 Risk during EVA, 17 3–1 Total Calculated Risk of Critical Failure, 23 FIGURES 2–1 Survivability analysis, 8 2–2 Comparison of meteoroid and debris flux in ISS orbit, 10 2–3 Orbiter primary structure, 12 2–4 Orbiter systems concentrated along the fore-aft axis, 14 3–1 On-orbit impact analysis methodology, 21 3–2 Relative critical risks for orbiter components after refinement of critical failure limits, 22 4–1 Particle lifetime as a function of diameter and solar activity, 31 5–1 The space shuttle alert and maneuver boxes, 37 6–1 Window replacements vs. shuttle orientation, 43 6–2 Critical penetration risk vs. shuttle orientation, 44 6–3 Modification of radiator tube shielding, 45 6–4 Use of remote manipulator system to survey orbiter for damage, 48 BOXES 1–1 Meteoroids and Orbital Debris, 4 1–2 High-Speed Collisions, 5 5–1 NASA Flight Rule A4.1.3–6, 38
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Protecting the Space Shuttle from Meteoroids and Orbital Debris The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce M.Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. William A.Wulf is interim president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I.Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce M.Alberts and Dr. William A.Wulf are chairman and vice-chairman, respectively, of the National Research Council.
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Protecting the Space Shuttle from Meteoroids and Orbital Debris Have I not walked without an upward look Of caution under stars that very well Might not have missed me when they shot and fell? It was a risk I had to take—and took. “Bravado” Robert Frost
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