1、 APPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED NASA TECHNICAL STANDARD NASA-STD-5018 National Aeronautics and Space Administration Approved: 08-12-2011 Washington, DC 20546-0001 STRENGTH DESIGN AND VERIFICATION CRITERIA FOR GLASS, CERAMICS, AND WINDOWS IN HUMAN SPACE FLIGHT APPLICATIONS MEASU
2、REMENT SYSTEM IDENTIFICATION: METRIC/SI (ENGLISH) Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5018 APPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED 2 of 47 DOCUMENT HISTORY LOG Status Document Revision Approval Date Description Basel
3、ine 08-12-2011 Initial Release Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5018 APPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED 3 of 47 FOREWORD This Standard is published by the National Aeronautics and Space Administration (NASA)
4、to provide uniform engineering and technical requirements for processes, procedures, practices, and methods that have been endorsed as standard for NASA programs and projects, including requirements for selection, application, and design criteria of an item. This Standard is approved for use by NASA
5、 Headquarters and NASA Centers, including Component Facilities and Technical and Service Support Centers. This Standard establishes uniform design and development requirements across NASA Centers for the design of glass and ceramic components that require high structural reliability and integrity wi
6、thin a human-rated space vehicle, space suit, or habitat. Requirements contained herein also provide design hazard controls for the unique hazards presented by brittle materials, including non-structural components, in an enclosed area inhabited by humans. Documenting these requirements in a NASA St
7、andard allows each NASA program to rely upon an established set of practices that have a proven heritage and that have evolved from lessons learned across the spectrum of previous programs and designs. This Standard was prepared by Johnson Space Center. It has evolved from a series of program requir
8、ements documents implemented by Apollo, the Space Shuttle, and the International Space Station. This document also benefits greatly from certification and verification experiences encountered during the development of each of these programs. Requests for information, corrections, or additions to thi
9、s Standard should be submitted via “Feedback” in the NASA Standards and Technical Assistance Tool at http:/standards.nasa.gov. Original Signed By: 08-12-2011 _ _ Michael G. Ryschkewitsch NASA Chief Engineer Approval Date Provided by IHSNot for ResaleNo reproduction or networking permitted without li
10、cense from IHS-,-,-NASA-STD-5018 APPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED 4 of 47 SECTION TABLE OF CONTENTS PAGE DOCUMENT HISTORY LOG . 2 FOREWORD . 3 TABLE OF CONTENTS . 4 LIST OF TABLES 5 LIST OF EQUATIONS . 5 1. SCOPE . 6 1.1 Purpose . 6 1.2 Applicability 6 1.3 Tailoring 7 2. APPLICAB
11、LE DOCUMENTS . 8 2.1 General 8 2.2 Government Documents . 8 2.3 Non-Government Documents . 8 2.4 Order of Precedence . 8 3. ACRONYMS AND DEFINITIONS 10 3.1 Acronyms and Abbreviations . 10 3.2 Definitions 11 4. REQUIREMENTS . 15 4.1 Introduction 15 4.2 Planning and Reporting 15 4.3 Environments and L
12、oads 16 4.4 Design Factors 20 4.5 Window Life . 21 4.6 Window Coating Requirements 21 4.7 Structural Analysis Requirements 22 4.8 Safety and Structural Integrity Assurance Requirements . 26 4.9 Manufacturing Requirements . 28 4.10 Window Maintenance Design Requirements . 30 4.11 Non-Structural Glass
13、 31 4.12 Requirements for Windowpanes, Glass, and Ceramic Structure for which a Proof Test is not Feasible 32 5. VERIFICATIONS 33 5.1 Introduction 33 5.2 Planning and Reporting 33 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5018 APPROVED
14、 FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED 5 of 47 SECTION TABLE OF CONTENTS, continued PAGE 5.3 Environments and Loads 33 5.4 Design Factors 35 5.5 Window Life . 36 5.6 Window Coating Requirements 36 5.7 Structural Analysis Requirements 37 5.8 Safety and Structural Integrity Assurance Requirement
15、s . 40 5.9 Manufacturing Requirements . 41 5.10 Window Maintenance Design Requirements . 42 5.11 Non-Structural Glass 44 5.12 Requirements for Windowpanes, Glass, and Ceramic Structure for which a Proof Test is not Feasible 44 APPENDICES A Data Item Descriptions . 45 B Reference Documents . 47 LIST
16、OF TABLES TABLE PAGE 1 Flaw Growth Analysis Uncertainty Factor Versus Design Life . 21 LIST OF EQUATIONS EQUATION PAGE 1 Flaw Growth Velocity . 23 2 Stress Intensity . 23 3 Static Fatigue Life 24 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-S
17、TD-5018 APPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED 6 of 47 STRENGTH DESIGN AND VERIFICATION CRITERIA FOR GLASS, CERAMICS, AND WINDOWS IN HUMAN SPACE FLIGHT APPLICATIONS 1. SCOPE 1.1 Purpose The purpose of this Standard is to specify the minimum structural design requirements for the design
18、, development, and verification of windows, glass, and ceramic structure included in National Aeronautics and Space Administration (NASA) vehicles/elements, habitats, space suits, all orbital support equipment (OSE), and flight support equipment (FSE). Although this Standard primarily addresses stru
19、ctural design requirements for glass and ceramics, it also includes design and verification requirements for non-structural glass and ceramic components. Optical performance and radiation specifications are not provided in this document. 1.2 Applicability This Standard is applicable to all human-rat
20、ed flight vehicle and element hardware, including orbital replacement units, space suits, OSE, and FSE. The requirements in this Standard also apply to all human-inhabitable structures built beyond Earths surface. This Standard does not apply to windowpanes made from non-brittle materials, including
21、 plastics. Windowpanes designed with non-brittle materials are to comply with standard engineering design requirements for primary structure. Adherence to this document in and of itself does not exempt flight windows, glass, or ceramics from any safety, fault-tolerance, or hazard control requirement
22、s. Any such reduction in requirements shall be established and approved by the appropriate NASA Technical Authority of the program invoking this document. This Standard is approved for use by NASA Headquarters and NASA Centers, including Component Facilities and Technical and Service Support Centers
23、, and may be cited in contract, program, and other Agency documents as a technical requirement to ensure the structural integrity and reliability of human-rated spacecraft. This Standard may also apply to the Jet Propulsion Laboratory or to contractors, grant recipients, or parties to agreements onl
24、y to the extent specified or referenced in their contracts, grants, or agreements. Requirements are numbered and indicated by the word “shall.” Explanatory or guidance text is indicated in italics beginning in section 4. Provided by IHSNot for ResaleNo reproduction or networking permitted without li
25、cense from IHS-,-,-NASA-STD-5018 APPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED 7 of 47 1.3 Tailoring Tailoring of this Standard for application to a specific program or project shall be formally documented as part of program or project requirements and approved by the Technical Authority. WAR
26、NING: Significant inherent risks exist with the use of brittle materials, such as glass and ceramics, in spacecraft, either as structural components or as non-structural components. The requirements specified in this Standard have been established by decades of lessons learned in window designs duri
27、ng Apollo, Shuttle, and International Space Station programs. These requirements guide window and glass/ceramic designs that ensure the safety of flight. Tailoring of these requirements is not recommended and should only be accomplished with close consultation with the appropriate knowledgeable NASA
28、 Technical Authority. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5018 APPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED 8 of 47 2. APPLICABLE DOCUMENTS 2.1 General The documents listed in this section contain provisions that constitu
29、te requirements of this Standard as cited in the text. 2.1.1 The latest issuances of cited documents shall be used unless specific versions are designated. 2.1.2 Non-use of specific versions as designated shall be approved by the responsible Technical Authority. The applicable documents are accessib
30、le via the NASA Standards and Technical Assistance Resource Tool at http:/standards.nasa.gov or may be obtained directly from the Standards Developing Organizations or other document distributors. 2.2 Government Documents NASA NASA-STD-6016 Standard Materials and Processes Requirements for Spacecraf
31、t 2.3 Non-Government Documents ASTM, International (ASTM) (formerly American Society for Testing Materials) ASTM C1368 Standard Test Method for Determination of Slow Crack Growth Parameters of Advanced Ceramics by Constant Stress-Rate Flexural Testing at Ambient Temperature ASTM C1421 Standard Test
32、Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature ASTM C1576 Standard Test Method for Determination of Slow Crack Growth Parameters of Advanced Ceramics by Constant Stress Flexural Testing (Stress Rupture) at Ambient Temperature 2.4 Order of Precedence This
33、Standard establishes requirements for the minimum structural design requirements for the design, development, and verification of windows, glass, and ceramic structure included in the vehicle/element, habitats, space suits, all OSE, and FSE and does not supersede nor waive established Agency require
34、ments found in other documentation. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5018 APPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED 9 of 47 2.4.1 Conflicts between this Standard and other requirements documents shall be resolved by
35、 the responsible Technical Authority. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5018 APPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED 10 of 47 3. ACRONYMS AND DEFINITIONS 3.1 Acronyms and Abbreviations registered trademark degree(s
36、) C degree(s) Celsius F degree(s) Fahrenheit greater than greater than or equal to 1 year 1.1 *The required uncertainty factor is larger for shorter design life because the flaw growth velocity is sensitive to small variations in the stress intensity. 4.5.2 Life Factor A life factor of 4 shall be ap
37、plied to the design life to account for scatter. 4.5.3 Assembly Life The installation of the window into the vehicle/element shall not cause: a. Damage to the glass over the service life of the vehicle. b. Deterioration of the sealing capabilities over the service life of the vehicle. 4.5.4 Induced
38、Residual Stresses The glass design shall preclude any potential source of strength degradation caused by induced residual tensile stresses or local stress concentrators. Features that concern designers include certain bonds on glass, localized structural deformation, localized thermal gradients, ins
39、ide curves or cuts, and sharp corners. 4.6 Window Coating Requirements 4.6.1 Strength Degradation Caused by Coatings Thermal cycling and thermal shock testing of glass coatings in previous designs have initiated coating cracks that have propagated into the glass, causing strength degradation. The st
40、rength effects of coatings selected for glass components shall be determined. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5018 APPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED 22 of 47 4.6.2 Coated Windowpane Structural Integrity Win
41、dowpane coatings shall be located on surfaces to minimize structural degradation of the panes. 4.6.3 Windowpane Coatings for Infrared and Ultraviolet Photography or Sensing In the event that a vehicle/element window is to be used for infrared (IR) and ultraviolet (UV) photography or sensing, the loc
42、ation of the window coatings shall provide for IR and UV viewing through windowpanes without degrading the structural integrity. 4.7 Structural Analysis Requirements The primary critical loading condition in windowpanes is typically the bending stress resulting from applied pressures. All polished g
43、lass or ceramic windows contain invisible micro cracks critical to the strength and life of the finished product. Fracture mechanics and static fatigue analyses, which are valid for most spacecraft windows, are based on the assumption that the critical flaws are much smaller than the thickness of th
44、e glass. 4.7.1 Structural Analysis Requirements for Windowpanes, Glass, and Ceramic Structure a. Fracture mechanics technology and the related flaw growth methodology as detailed herein shall be used to assure adequate life of any glass structure. b. All static fatigue assessments on the structural
45、glass life shall consider all load events to which the component has been and will be exposed. c. The glass/ceramic component predicted life shall be greater than the design life with the appropriate life factor applied (section 4.5.2 of this Standard). 4.7.2 Analysis Methods for Annealed Glass a. O
46、ne of the methods in sections 4.7.3 or 4.7.4 of this Standard shall be used to verify the life requirement. b. Other analytical techniques may be used, but NASA Technical Authority approval shall be obtained before implementation. 4.7.3 Use of NASGRO The analysis method provided in the NASGRO comput
47、er program is an acceptable method for analysis of vehicle/element glass structure with the following constraints and assumptions: a. The exponential equation model of flaw growth shall be selected. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NAS
48、A-STD-5018 APPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED 23 of 47 b. The length-to-depth ratio of the initial flaw shall be assumed to be 20. The appropriate material critical strength intensity (KIC) in the NASGRO database may be used, or test-derived KIC in accordance with section 4.7.5 of this Standard may be entered manually into the program. 4.7.4 Flaw Growth Analysis for Annealed Glass a.
