SSP30559RD-Errata.pdf

SSP 30559 Revision D

National Aeronautics and Space Administration Space Station Program Office Lyndon B. Johnson Space Center Houston, Texas

Structural Design and V erification Requirements

Revision D - ERRATA July 27, 2007

International Space Station esa european space agency

National Space Development Agency of Japan

EXPORT CONTROLLED - The technology or software is subject to the Export Administration Regulations (15 C.F.R. Parts 730-774). Export, re-export or retransfer contrary to U.S. law is prohibited. EAR/ECCN EAR99

SSP 30559 Revision D 27 July 2007

REVISION AND HISTORY PAGE

REV. DESCRIPTION PUB.

DATE

BASELINE ISSE (REFERENCE SSCBD BB003053B EFF. 07−30−91) 06−91

CHANGE 1 (REFERENCE SSCBD BB003457 EFF. 03−04−93) 03−93

CHANGE 2 (REFERENCE SSCBD BJ003053C EFF. 03−08−93) 04−93

A Revision A (Reference SSCBD 000002 dated 2−7−94) 04−18−94

B Revision B (Reference SSCBD 000008R1 dated 06−03−94 09−30−94

The following DCNs have been cancelled. The content of the SSCNs authorizing release of the DCNs has been incorporated into Revision C.

DCN 001 (SSCN 000480) (Administrative Cancellation)

DCN 003 (SSCN 000913) (Administrative Cancellation)

DCN 002 (SSCN 000548) (Administrative Cancellation)

DCN 004 (SSCN 001356) (Administrative Cancellation)

DCN 005 (SSCN 000151) (Administrative Cancellation)

DCN 006 (SSCN 000256) (Administrative Cancellation)

DCN 007 (SSCN 000258) (Administrative Cancellation)

DCN 008 (SSCN 000549) (Administrative Cancellation)

C 04−16−01

09−20−01

D

Revision C incorporates SSCDs 000151, 000256, 000258, 000480, 000548, 000549, 000913, 001356, and 001285.

DCN 012 incorporates SSCN 001285

Revision D incorporates SSCNs 001285, 003286, and 009111

Errata: Export Control Classification updated to reflect EAR/ECCN EAR99

02−19−08

ERU: /s/Beth Mason 02−19−08

Export Controlled – EAR/ECCN EAR99

08-15-18 i

INTERNATIONAL SPACE STATION PROGRAM OFFICE

STRUCTURAL DESIGN AND VERIFICA TION REQUIREMENTS

27 JULY 2007

ii

PREFACE

SSP 30559, Structural Design and Verification Requirements, presents common structural design and verification requirements to ensure consistent design, development, and verification of International Space Station flight hardware.

Chapter 3.0 of this document describes general design requirements, design loads, factors of safety and margins of safety, design and stress analysis requirements, and structural materials criteria and discusses secondary structure accommodation for human interface and nonstandard fasteners. Chapter 4.0 contains verification requirements.

This document is under the control of the Space Station Control Board, and any changes or revisions will be approved by the Program Manager.

iii

CONCURRENCE

INTERNATIONAL SPACE STATION PROGRAM

STRUCTURAL DESIGN AND VERIFICA TION REQUIREMENTS

27 JULY 2007

PREPARED BY:

CHECKED BY:

SIGNATURE

SUPERVISED BY

PRINT NAME ORGN

DATE

SIGNATURE

PRINT NAME ORGN

DATE

SUPERVISED BY

SIGNATURE

PRINT NAME ORGN

DATE

SIGNATURE

PRINT NAME ORGN

DATE

DQA:

SIGNATURE

PRINT NAME ORGN

DATE

(BOEING):

(NASA):

Kornel Nagy

Merry Roberts

Karen Thomas

Quentin Henry

Scott West

AG−92−J3ES

ES2

/s/ Karen Thomas

AG−92−J3EH

2/13/08

/s/ Quentin L. Henry 8/15/07

/s/ Scott West

AG−92−J3EQ

11/12/07

/s/ Kornel Nagy 2/12/08

AG−92−J3EA

/s/ Merry Roberts 2/13/08 iv

NASA/ASI

INTERNATIONAL SPACE STATION PROGRAM

STRUCTURAL DESIGN AND VERIFICA TION REQUIREMENTS

27 JULY 2007

DATEFor NASA

See Directive

For ASI DATE

See Directive v

NASA/CSA

INTERNATIONAL SPACE STATION PROGRAM

STRUCTURAL DESIGN AND VERIFICA TION REQUIREMENTS

27 JULY 2007

DATEFor NASA

See Directive

For CSA DATE vi

NASA/ESA

INTERNATIONAL SPACE STATION PROGRAM

STRUCTURAL DESIGN AND VERIFICA TION REQUIREMENTS

27 JULY 2007

DATEFor NASA

See Directive

For ESA DATE

See Directive ref: SSP 50019, Para. 3.1.4.1 and JESA 30000, Section 3, Appendix B vii

NASA/JAXA

INTERNATIONAL SPACE STATION PROGRAM

STRUCTURAL DESIGN AND VERIFICA TION REQUIREMENTS

27 JULY 2007

DATEFor NASA

See Directive

DATE

For JAxA Concurrence viii

INTERNATIONAL SPACE STATION PROGRAM OFFICE

STRUCTURAL DESIGN AND VERIFICA TION REQUIREMENTS

LIST OF CHANGES

27 JULY 2007

All changes to paragraphs, tables, and figures in this document are shown below:

SSCBD ENTRY DATE CHANGE PARAGRAPHS

1285 07/27/07 2.0 Applicable Documents

3.2.1 Shuttle Payload Configuration Design

Loads

3.5.7 Structural Life Requirements

3.6.2.2 “B” And “S” Allowables

4.1.4 Functional Configuration Audit/Physical

configuration Audit

4.1.4.3 Formal FCA/PCS Stress Report

4.1.4.4 Stress Analysis For FCA/PCA

9111 07/27/07 3.8 Fastener Requirements

TABLES

1285 07/27/07 3.3.1−1 Factors of Safety for Test Verified Structure

FIGURES

None

APPENDIX

1285 07/27/07 Appendix A Abbreviations and Acronyms

3286 07/27/07 D3.3.1 Factors of Safety − Test Verified Structure

TABLE OF CONTENTS

PARAGRAPH PAGE

ix

1.0 GENERAL 1 − 1

1.1 INTRODUCTION 1 − 1

1.2 PURPOSE 1 − 1

1.3 SCOPE 1 − 1

1.4 INTENDED USE 1 − 1

1.5 APPROVAL BY NASA AND INTERNATIONAL PARTNERS 1 − 1

1.5.1 INTERNAL TO USOS 1 − 1

1.5.2 INTERNAL TO INTERNATIONAL SEGMENTS 1 − 1

1.5.3 SEGMENT TO SEGMENT INTERFACES 1 − 1

1.5.4 OVERALL ISSA DESIGN AND VERIFICATION 1 − 2

1.6 PRECEDENCE 1 − 2

2.0 APPLICABLE DOCUMENTS 2 − 1

3.0 DESIGN REQUIREMENTS 3 − 1

3.1 GENERAL 3 − 1

3.1.1 DESIGN ORGANIZATION STRUCTURAL ASSESSMENT PROGRAM 3 − 1

3.1.2 APPROVAL OF DETAILED DESIGN CRITERIA 3 − 1

3.1.3 STRENGTH AND STIFFNESS 3 − 1

3.1.3.1 ORBITER SAFETY 3 − 1

3.1.4 THERMAL EFFECTS 3 − 1

3.1.4.1 CONTINGENCY DEORBIT THERMAL EFFECTS 3 − 1

3.1.5 DAMAGE TOLERANCE 3 − 2

3.1.5.1 EXTERNAL STRUCTURE DAMAGE TOLERANCE 3 − 2

3.1.5.2 INTERNAL STRUCTURE DAMAGE TOLERANCE 3 − 2

3.1.6 FRACTURE CONTROL 3 − 2

3.1.7 GLASS, WINDOW, AND CERAMIC DESIGN CRITERIA 3 − 2

3.1.8 DESIGN REQUIREMENTS FOR SHUTTLE PAYLOADS 3 − 2

3.1.9 DESIGN REQUIREMENTS FOR PRESSURE SYSTEMS 3 − 2

3.1.9.1 FRACTURE CONTROL 3 − 2

3.1.9.2 PRESSURE CONTROL 3 − 2

3.1.9.3 DEWARS 3 − 3

3.1.9.4 SECONDARY VOLUMES 3 − 3

3.1.9.5 FLOW INDUCED VIBRATION 3 − 3

3.1.9.6 PRESSURE STABILIZED VESSELS 3 − 4

3.1.9.7 BURST DISCS 3 − 4

3.1.10 STRUCTURAL DEGRADATION FROM MATERIAL EROSION 3 − 4

3.2 DESIGN LOADS 3 − 4

3.2.1 SHUTTLE PAYLOAD CONFIGURATION DESIGN LOADS 3 − 5

3.2.2 INTEGRATED ON−ORBIT LOADS 3 − 5

3.2.3 DETAILED DESIGN LOADS 3 − 5

3.2.4 MATH MODELS 3 − 5

3.2.4.1 ON−ORBIT FLIGHT HARDWARE LOADS MATH MODELS 3 − 5

3.2.4.2 PAYLOAD MATH MODEL REQUIREMENTS 3 − 6

3.2.5 REDISTRIBUTED LOADS 3 − 6

3.3 FACTOR(S) OF SAFETY 3 − 6

PARAGRAPH PAGE

x

3.3.1 FACTORS OF SAFETY − TEST VERIFIED STRUCTURE 3 − 6

3.3.2 FACTORS OF SAFETY − ANALYSIS ONLY 3 − 8

3.3.2.1 SHUTTLE TRANSPORT TO/FROM ORBIT 3 − 8

3.3.2.1.1 EMERGENCY LANDING 3 − 8

3.3.2.1.2 NEGATIVE DIFFERENTIAL PRESSURE 3 − 8

3.3.2.2 ON−ORBIT 3 − 8

3.3.3 HANDLING AND TRANSPORTATION 3 − 8

3.4 MARGIN(S) OF SAFETY 3 − 8

3.4.1 CRITERIA FOR LOCAL YIELDING 3 − 8

3.5 DESIGN AND STRESS ANALYSIS REQUIREMENTS 3 − 9

3.5.1 STRESS/LOAD COMBINATION RESTRICTIONS 3 − 9

3.5.1.1 COMBINING WITH PRESSURE STRESS/LOAD 3 − 9

3.5.1.2 COMBINING WITH THERMAL STRESS/LOAD 3 − 9

3.5.1.3 COMBINING LOW FREQUENCY AND RANDOM LOADS FOR

COMPONENTS AND ATTACHMENTS 3 − 9

3.5.2 BUCKLING AND CRIPPLING 3 − 10

3.5.3 MATERIAL DESIGN AND ANALYSIS THICKNESS 3 − 10

3.5.4 DESIGN FACTORS 3 − 10

3.5.4.1 JOINT FITTING FACTOR 3 − 10

3.5.4.2 BEARING FACTOR 3 − 11

3.5.4.3 CASTING FACTOR 3 − 11

3.5.5 PRELOADED JOINT CRITERIA 3 − 11

3.5.6 COMPOSITES/BONDED STRUCTURE DESIGN 3 − 11

3.5.7 STRUCTURAL LIFE REQUIREMENTS 3 − 11

3.5.7.1 PROOF TEST FOR FLAW SCREENING 3 − 11

3.5.7.2 FATIGUE 3 − 12

3.5.7.2.1 FATIGUE STRESS VERSUS CYCLE LIFE CURVE FACTOR 3 − 12

3.5.7.2.2 LIFE FACTOR 3 − 12

3.5.7.2.3 STRESS CONCENTRATION FACTORS − FATIGUE ANALYSIS 3 − 12

3.5.7.3 CREEP ANALYSIS 3 − 12

3.5.7.3.1 CREEP ANALYSIS FACTOR 3 − 12

3.5.7.3.2 CREEP LIFE FACTOR 3 − 12

3.5.7.4 SERVICE LIFE 3 − 12

3.6 STRUCTURAL MATERIALS CRITERIA 3 − 13

3.6.1 STRUCTURAL MATERIAL SELECTION 3 − 13

3.6.2 STRUCTURAL MATERIAL ALLOWABLE PROPERTIES 3 − 13

3.6.2.1 “A” ALLOWABLES 3 − 13

3.6.2.2 “B” AND “S” ALLOWABLES 3 − 13

3.7 SECONDARY STRUCTURE ACCOMMODATION FOR HUMAN

INTERFACE 3 − 13

3.7.1 INSPECTION, MAINTENANCE, AND REPAIR 3 − 13

3.7.2 INTERIOR CLOSE OUT 3 − 13

3.7.3 GROUND AND ON−ORBIT OPERATIONAL ACCESS DOORS 3 − 13

3.8 FASTENER REQUIREMENTS 3 − 14

4.0 VERIFICATION REQUIREMENTS 4 − 1

PARAGRAPH PAGE

xi

4.1 STRUCTURAL VERIFICATION REQUIREMENTS 4 − 1

4.1.1 STRUCTURAL VERIFICATION PLAN 4 − 1

4.1.2 MATH MODEL VERIFICATION 4 − 1

4.1.2.1 DYNAMIC LOADS MATH MODELS 4 − 1

4.1.2.1.1 NATIONAL SPACE TRANSPORTATION SYSTEM MATH MODELS 4 − 1

4.1.2.1.2 ON−ORBIT MATH MODELS 4 − 1

4.1.2.2 STATIC INTERNAL LOADS MATH MODELS 4 − 1

4.1.3 STRENGTH AND LIFE VERIFICATION 4 − 1

4.1.3.1 FOR SHUTTLE LOADS 4 − 2

4.1.3.2 FOR ON−ORBIT LOADS 4 − 2

4.1.3.2.1 STATIC TEST TO ULTIMATE LOADS 4 − 2

4.1.3.2.2 PROTOFLIGHT STATIC TEST 4 − 2

4.1.3.3 LIFE VERIFICATION 4 − 2

4.1.3.4 LIFE VERIFICATION FOR COMPOSITE/BONDED STRUCTURE 4 − 3

4.1.3.4.1 GENERAL QUALITY REQUIREMENTS 4 − 3

4.1.3.4.2 COMPOSITE/BONDED FRACTURE CRITICAL STRUCTURE 4 − 3

4.1.3.5 ACCEPTANCE TEST OF COMPOSITE/BONDED STRUCTURES 4 − 3

4.1.3.6 VERIFICATION OF BERYLLIUM STRUCTURES 4 − 3

4.1.4 FUNCTIONAL CONFIGURATION AUDIT/PHYSICAL CONFIGURATION

AUDIT 4 − 4

4.1.4.1 STRESS ANALYSIS FOR PRELIMINARY DESIGN REVIEW 4 − 4

4.1.4.2 STRESS ANALYSIS FOR CRITICAL DESIGN REVIEW 4 − 4

4.1.4.3 FORMAL FCA/PCA STRESS REPORT 4 − 4

4.1.4.4 STRESS ANALYSIS FOR FCA/PCA 4 − 4

4.1.4.5 STRESS ANALYSIS FOR FLIGHT READINESS REVIEW 4 − 4

4.1.5 STRUCTURAL VERIFICATION TESTS − PRIOR TO FLIGHT 4 − 5

4.1.5.1 GENERAL REQUIREMENTS 4 − 5

4.1.5.2 STRENGTH TESTS 4 − 5

4.1.5.2.1 DYNAMIC TESTS 4 − 5

4.1.5.3 TEST BOUNDARY CONDITIONS 4 − 5

4.1.5.4 TEST REPORTS 4 − 5

4.1.5.5 ENGINEERING ANALYSIS REPORTS 4 − 5

4.2 LOAD VERIFICATION 4 − 5

4.3 STRUCTURAL MAINTENANCE REQUIREMENTS 4 − 6

APPENDIX PAGE

A ABBREVIATIONS AND ACRONYMS A − 1

B GLOSSARY B − 1

C REFERENCE AND BIBLIOGRAPHIC DOCUMENTS C − 1

D APPROVED REQUIREMENTS EXCEPTIONS D − 1

TABLE OF CONTENTS − Continued

TABLES

xii

3.3.1−1 FACTORS OF SAFETY FOR TEST VERIFIED STRUCTURE 3 − 6

3.5.1.3−1 LOAD COMBINATION CRITERIA FOR COMPONENTS 3 − 9

1 − 1

1.0 GENERAL

1.1 INTRODUCTION

Structural design requirements for flight hardware are related to the methods to be used for structural design verification. This requirements document includes both structural design and verification requirements to assure that both are considered in the specification of detailed requirements for a component of the Space Station Program flight hardware. Where appropriate, this document specifies design methodology to prevent conflicting analytical approaches utilized by different design and procurement organizations and the related impact on Program cost and schedules.

1.2 PURPOSE

The purpose of this requirements document is to specify common structural requirements for consistent design, development, and verification of all Space Station flight hardware.

1.3 SCOPE

The requirements in this document shall apply to all Space Station flight hardware including all Program elements, Orbital Replacement Units, Orbital Support Equipment, Flight Support Equipment, and payloads.

1.4 INTENDED USE

This document is intended for use by the Space Station Program and shall be a requirement for each Program participant.

1.5 APPROVAL BY NASA AND INTERNA TIONAL PARTNERS

Structural design and verification approvals required by this document shall be as specified for each of the following categories:

1.5.1 INTERNAL TO USOS

For structures that are wholly internal to the U.S. On−orbit Segment (USOS), the National Aeronautics and Space Administration (NASA) shall provide the required approvals.

1.5.2 INTERNAL TO INTERNATIONAL SEGMENTS

For structures that are wholly internal to an International Segment, the International Partner responsible for that segment shall provide the required approvals.

1.5.3 SEGMENT TO SEGMENT INTERFACES

Structural design and verification approvals which affect segment to segment interfaces shall be obtained from both NASA and the affected International Partner.

1 − 2

1.5.4 OVERALL ISSA DESIGN AND VERIFICA TION

Structural design and verification approvals which affect overall ISSA design and verification shall be obtained from NASA and all affected International Partners.

1.6 PRECEDENCE

SSP 41000, System Specification for the Space Station, defines the performance requirements for the Space Station and invokes this document for Space Station structural design and verification requirements. In the event of any conflict between SSP 41000 and this document, SSP 41000 takes precedence.

2 − 1

2.0 APPLICABLE DOCUMENTS

The following documents of the exact date and issue in SSP 50257 form a part of this document to the extent specified herein. Inclusion of applicable documents herein does not in any way supersede the order of precedence specified in paragraph 1.6.

DOCUMENT NO. TITLE

SSP 41000 System Specification for the Space Station References Paragraphs 1.6 and 3.1.5.1

SSP 30233 Space Station Requirements for Materials and Processes

References Paragraph 3.6.1

SSP 30558 Fracture Control Requirements for Space Station References Paragraphs 3.1.3, 3.1.6, 3.1.9, 4.1.4, and Appendix B

SSP 30560 Glass, Window, and Ceramic Structural Design and Verification Requirements

References Paragraph 3.1.7, and Table 3.3.1−1

D684−10019−01 Space Station Structural Loads Control Plan References Paragraph 3.2, 3.2.2, 3.2.3, 3.2.4.1, 3.2.4.2, and 4.2

MIL−HDBK−5 Metallic Materials and Elements for Aerospace Vehicle Structures

References Paragraph 3.6.2, Appendix B

MIL−HDBK−17 Plastics for Aerospace Vehicles References Paragraph 3.6.2

SSP 50005 International Space Station Flight Crew Integration Standards (NASA−STD−3000/T)

References Paragraph 3.1.5.2

NSTS−21000−IDD−ISS Space Shuttle System Payload Accommodations References Paragraph 3.2.1

NSTS 08307 Criteria for Preloaded Bolts References Paragraph 3.5.5

NSTS 14046 Payload Verification Requirements References Paragraphs 4.1.2.1.1 and 4.1.3.1

20M02540 Assessment of Flexible Lines for Flow Induced Vibration

References Paragraph 3.1.9.5

NSTS 08123 Certification of Flex Hose and Bellows for Flow Induced Vibration

References Paragraph 3.1.9.5

2 − 2

MSFC−SPEC−626 Test Control Document for Assessment of Flexible Lines for Flow Induced Vibration

References Paragraph 3.1.9.5

3 − 1

3.0 DESIGN REQUIREMENTS

3.1 GENERAL

3.1.1 DESIGN ORGANIZATION STRUCTURAL ASSESSMENT PROGRAM

The organization responsible for structural design shall establish and maintain an effective structural analysis, structural test, and structural assessment program to evaluate and verify the structural integrity of Space Station flight hardware structure for both transport to and from orbit, and for on−orbit operations.

3.1.2 APPROVAL OF DETAILED DESIGN CRITERIA

Any detailed design criteria used by the responsible design organization shall be consistent with this requirements document. Detailed criteria which are not consistent with the requirements of this document shall be approved by NASA and/or International Partner.

3.1.3 STRENGTH AND STIFFNESS

Space Station structure shall have strength and stiffness in all necessary configurations and stages to support ultimate load without failure. Detrimental deformation shall not occur at limit loads imposed during Shuttle transportation and on−orbit operations, or during proof or acceptance testing. All flight primary structure shall be designed to be fail−safe, or have safe−life, or be a low risk fracture part as defined in SSP 30558, Fracture Control Requirements for Space Station.

3.1.3.1 ORBITER SAFETY

If, during assembly operations, an Orbiter payload element or its ASE is deployed, extended, or otherwise unstowed to a condition where it cannot withstand subsequent induced loads, there shall be two−failure tolerant design provisions to safe the Orbiter. Safing may include deployment, jettison, or provisions to change the configuration of the payload to eliminate the hazard.

3.1.4 THERMAL EFFECTS

Space Station shall meet its performance requirements when thermal effects are combined, when applicable, with induced static and dynamic loads.

3.1.4.1 CONTINGENCY DEORBIT THERMAL EFFECTS

Minimum design factor of safety for pressure vessels shall be maintained under conditions encountered at any continental United States or contingency landing site without postlanding services. Thermal analysis of postlanding conditions shall consider the following: a) worst−case Orbiter−induced initial conditions due to an abort from orbit to a contingency landing site with the payload subjected to the planned mission most−severe on−orbit thermal attitude; b) heat input from normal payload sources; c) heat input from up to two payload failures (Orbiter power busses are de−energized at landing plus 30 minutes.); and d) the envirionments defined in

NSTS−21000−IDD−ISS.

3 − 2

3.1.5 DAMAGE TOLERANCE

3.1.5.1 EXTERNAL STRUCTURE DAMAGE TOLERANCE

Space Station mm/od critical flight structure shall be designed to meet the performance requirements when exposed to impacts by meteoroids and space debris as defined in SSP 41000.

Space Station structure shall meet its performance requirements when exposed to EVA Crew Induced Loads defined in SSP 41000.

3.1.5.2 INTERNAL STRUCTURE DAMAGE TOLERANCE

Space Station internal structure shall meet its performance requirements when exposed to IVA crew induced loading as defined in SSP 50005, International Space Station Flight Crew Integration Standards.

3.1.6 FRACTURE CONTROL

The International Space Station shall be designed and verified for fracture control per the requirements of SSP 30558, Fracture Control Requirements for Space Station.

3.1.7 GLASS, WINDOW, AND CERAMIC DESIGN CRITERIA

The structural design and verification requirements for windows, glass, and ceramic structure shall be in accordance with SSP 30560, Glass, Window, and Ceramic Structural Design and Verification Requirements.

3.1.8 DESIGN REQUIREMENTS FOR SHUTTLE PAYLOADS

Space Station hardware in the Shuttle payload configuration shall meet Shuttle requirements for payloads as defined in NSTS−21000−IDD−ISS, Shuttle/Payload Interface Definition Document for International Space Station.

3.1.9 DESIGN REQUIREMENTS FOR PRESSURE SYSTEMS

3.1.9.1 FRACTURE CONTROL

Pressure vessels shall be designed and fabricated under an approved fracture control program and be in accordance with requirements specified in SSP 30558, Fracture Control Requirements for Space Station, Section 4.4.

3.1.9.2 PRESSURE CONTROL

Where pressure regulators, relief devices, and/or a thermal control system (e.g., heaters) are used to control pressure, they shall collectively be two−fault tolerant from causing the pressure to exceed the MDP of the system.

3 − 3

3.1.9.3 DEWARS

Dewar/cryostat systems shall be designed in accordance with the pressure vessel requirements in SSP 30558, section 4.4 and the following:

a) Pressure containers shall be leak−before−burst (LBB) designs where possible as determined by a fracture mechanics analysis. Containers of hazardous fluids and all non−LBB designs must employ a fracture mechanics safe−life approach to assure safety of operation.

b) MDP assessment for the pressure container shall envelop the pressure achieved under maximum venting conditions.

c) Outer shells (i.e., vacuum jackets) shall have pressure relief capability to preclude rupture in the event of pressure container leakage. If pressure containers do not vent external to the dewar but instead vent into the volume contained by the outer shell, the outer shell relief devices shall be capable of venting at a rate to release full flow without outer shell rupture.

Relief devices shall be redundant and individually capable of full flow.

d) Pressure relief devices which limit maximum design pressure shall be certified to operate at the required conditions of use. Certification shall include testing of the same part number from the flight lot under the expected use conditions.

e) Nonhazardous fluids may be vented into the cargo bay if analysis shows that a worst case credible volume release will not affect the structural integrity or thermal capability of the Orbiter.

f) The proof test factor for each flight pressure container shall be a minimum of 1.1 times MDP.

Qualification burst and pressure cycle testing is not required if all the requirements of 3.1.9 are met. The structural integrity for external loads shall be demonstrated in accordance with

NSTS 14046.

3.1.9.4 SECONDARY VOLUMES

Secondary compartments or volumes that are integral or attached by design to pressure system components and which can become pressurized as a result of a credible single barrier failure shall be designed for safety consistent with structural requirements. Redundant seals in series which have been acceptance pressure tested individually prior to flight shall not be considered credible single barrier failures. Failures of structural parts, such as pressure lines and tanks, and properly designed and tested welded or brazed joints shall not be considered single barrier failures. In order to be classified as a non−credible failure, the item shall be designed for a safety factor or 2.5 on the MDP, and shall be certified for all operating environments including fatigue conditions. If external leakage would not present a catastrophic hazard, the secondary volume shall either be vented or equipped with a relief provision in lieu of designing for system pressure.

3.1.9.5 FLOW INDUCED VIBRATION

All flexible hoses and bellows shall be designed to exclude or minimize flow induced vibrations in accordance with 20M02540. Certification of hardware shall be in accordance with NSTS 08123. When certification by test is required, requirements in MSFC−SPEC−626 shall apply.

3 − 4

3.1.9.6 PRESSURE STABILIZED VESSELS

Pressure vessels which are pressure−stabilized and must contain a minimum pressure to maintain the required ultimate factors of safety to insure structural integrity under launch and landing loads shall meet the following requirements:

The existence of the minimum required vessel pressure shall be verified prior to the application of safety critical loads into the system. This verification shall include a single fault tolerant pressure decay monitoring technique which is implemented such that the system pressure decay characteristics can be certified to insure minimum design safety factors will exist at the time of subsequent structural load application.

3.1.9.7 BURST DISCS

When burst discs are used as the second and final control of pressure to meet the requirements of 3.1.9.2, they shall be designed to the following requirements:

a) Burst discs shall incorporate a reversing membrane against a cutting edge to insure rupture.

b) Burst disc design shall not employ sliding parts or surfaces subject to friction and/or galling.

c) Stress corrosion resistant materials shall be used for all parts under continuous load.

d) The burst disc design shall be qualified for the intended application by testing at the intended use conditions including temperature and flow rate.

e) Qualification shall be for the specific part number used, and it shall be verified that no design or material changes exist between flight assemblies and assemblies making up the qualification database.

f) Each flight assembly shall be verified for membrane actuation pressure either by, (1) use of special tooling or procedures to prevent cutting edge contact during the test or, (2) demonstration of a rigorous lot screening program approved by the Shuttle Payload Safety Review Panel.

3.1.10 STRUCTURAL DEGRADA TION FROM MATERIAL EROSION

Potential structural erosion, e.g., Plasma Environmental Effects Compatibility−induced, atomic oxygen, etc., during the design life shall be included in the design and analysis of the structure.

3.2 DESIGN LOADS

The Space Station shall meet its performance requirements when exposed to all appropriate static, transient, and random loads, pressure, and thermal effects for all phases of hardware service life, considering, when applicable, combined loading effects. Limit load and load spectra shall be derived in accordance with the Space Station Structural Loads Control Plan, D684−10019−01.

Loads shall be generated for all significant forcing functions and appropriate combinations of forcing functions. Limit loads and load spectra shall be published for design and stress assessment. Load uncertainty factors for design and assessment may be used.

3 − 5

On−orbit structural design loads shall be defined to a 3 sigma level for limit load during the Program life for time−consistent loads. When time consistency is unknown, a 3 sigma equivalent load probability for each independent event on each type of load shall be used and load combinations shall be root sum square of the 3 sigma peak independent event consistent loads;

or, a monte carlo analysis producing a 3 sigma load combination may be used. For major independent system failures, 2 sigma or equivalent loads shall be used. Random limit loads shall be defined as 3 sigma. A 3 sigma level shall be defined as a 99.73 percentile level for loads which are characterized by a 1−sided Gaussian or non−Gaussian distribution. A 2 sigma level shall be defined as a 95.45 percentile level for loads which are characterized by a 2−sided Gaussian distribution and a 97.72 percentile for loads which are characterized by a 1−sided Gaussian or non−Gaussian distribution. Launch transient and random vibration loads shall be derived in accordance with the Space Station Loads Control Plan, D684−10019−01.

3.2.1 SHUTTLE PAYLOAD CONFIGURATION DESIGN LOADS

For lift−off, ascent, on orbit, descent, and landing using Shuttle, Space Station structure shall be designed to maintain required functionality and positive margins when subjected to all static and dynamic loads and thermal environments as defined in NSTS 21000−IDD−ISS, Shuttle/Payload Interface Definition Document for International Space Station. Space Station structure shall be designed to maintain positive margins when subjected to emergency landing loads as defined in

NSTS−21000−IDD−ISS.

3.2.2 INTEGRATED ON−ORBIT LOADS

The coordination, generation, and dissemination responsibility for Space Station on−orbit, integrated element interface loads is defined in the Space Station Structural Loads Control Plan, D684−10019−01.

For integrated on−orbit flight, ISS Program elements shall be designed to maintain required functionality and positive margins when subjected to all static and dynamic loads and thermal environments. All integrated on−orbit configurations from first launch through assembly complete configuration shall be considered.

3.2.3 DETAILED DESIGN LOADS

Detailed design loads shall be derived for all life cycles of hardware in accordance with the Space Station Structural Loads Control Plan, D684−10019−01.

3.2.4 MATH MODELS

3.2.4.1 ON−ORBIT FLIGHT HARDWARE LOADS MA TH MODELS

Structural math models of on−orbit element flight hardware consistent with each phase of the Program shall be forwarded to the Prime Contractor in accordance with the Space Station Structural Loads Control Plan, D684−10019−01.

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3.2.4.2 PAYLOAD MATH MODEL REQUIREMENTS

The Prime Contractor shall receive Shuttle payload math models in accordance with the Space Station Structural Loads Control Plan, D684−10019−01.

3.2.5 REDISTRIBUTED LOADS

Structures that are deployed, extended, or otherwise unstowed to a configuration where they cannot withstand subsequent induced loads, or whose load paths are controlled by electro−mechanical devices shall be designed to maintain the factors of safety of section 3.3 on the redistributed loads after 1 or 2 credible system failures to the appropriate hazard levels.

Operational procedures may be used to restore the load path or limit the applied loads after the first failure in order to maintain the required factors of safety.

3.3 FACTOR(S) OF SAFETY

3.3.1 FACTORS OF SAFETY − TEST VERIFIED STRUCTURE

All Space Station flight hardware structure shall be designed to the factors of safety (FS) specified in Table 3.3.1−1, Factors of Safety for Test Verified Structure, or as modified by the factors specified in paragraphs 3.0 and 4.0 of this document. See appendix D for the approved exceptions to this requirement.

TABLE 3.3.1−1 Factors of Safety for T est Verified Structure

Yield Ultimate

A. Minimum Factors of Safety for Metallic Flight Structures

Space Shuttle 1.0 1.4

On−orbit 1.1 1.5

B. Minimum Factors of Safety for Non−metallic Flight Structures

Non−discontinuity areas

Space Shuttle N/A 1.4

On−orbit N/A 1.5

Discontinuity areas

Space Shuttle N/A 2.0

On−orbit N/A 2.0

C. Minimum Factors of Safety for Pressure

1. Design factors for windows, glass and ceramic structure are defined in SSP 30560, Glass, Window, and Ceramic Structural Design and Verification Requirements.

The proof and ultimate factors for windows shall not be less than the following:

Proof Pressure1 =2.00 X MDP

Ultimate Pressure =3.00 X MDP

2. Engine Structures and Engine Compartments

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TABLE 3.3.1−1 Factors of Safety for T est Verified Structure

UltimateYield

Proof Pressure1 =1.50 X MDP

Ultimate Pressure =2.00 X MDP

3. Hydraulic and Pneumatic Systems

a. Lines and fittings less than 1.5 inches (38 mm) dia. (OD)

Proof Pressure1 =1.50 X MDP

Ultimate Pressure =4.00 X MDP

b. Lines and fittings, 1.5 inches (38 mm) dia. or greaer

Proof Pressure1 =1.50 X MDP

Ultimate Pressure =2.00 X MDP

c. Reservoirs/Presure Vessels

Proof Pressure1 =1.50 X MDP

Ultimate Pressure =2.00 X MDP

d. Actuating cylinders, valves, filters, switches, line−installed allignment bellows and heat pipes

Proof Pressure1 =1.50 X MDP

Ultimate Pressure =2.50 X MDP

e. Flex hoses, all diameters

Proof Pressure1,3 =2.00 X MDP

Ultimate Pressure =4.00 X MDP

4. Doors, Hatches and Habitable Modules

a. Internal pressure only

Proof Pressure1 =1.50 X MDP

Yield Pressure =1.65 X MDP

Ultimate Pressure =2.00 X MDP

b. Negative pressure differential =1.40 X differential pressure

c. Combined loading conditions (Ref. NSTS 14046, paragraph 5.1.1.5c)

5. Combined pressure and mechanical loading2

Yield Ultimate

Space Shuttle 1.0(pressure+mechanical)1.4(pressure+mechanical)

On−Orbit 1.1(pressure+mechanical) 1.5(pressure+mechanical)

Notes:

1. Proof factor determined from fracture mechanics service life analysis must be used if greater than minimum factor.

2. See paragraph 3.5.1.1 when pressure loads have a relieving or stabilizing effect on structural capability.

3. In a system with fluid lines and flex hoses, the individual flex hoses to be proof tested to 2.00 X MDP and the assembly level tested to 1.5 X MDP or proof factors as per note 1.

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3.3.2 FACTORS OF SAFETY − ANALYSIS ONLY

3.3.2.1 SHUTTLE TRANSPORT TO/FROM ORBIT

For Space Shuttle payloads, verification of primary payload structure for strength integrity by analysis only is not considered to be a viable option without prior and written approval of the Space Shuttle/Payloads Structural/Mechanical Working Group.

3.3.2.1.1 EMERGENCY LANDING

The structural design shall comply with the ultimate design load factors for emergency landing loads that are specified in the ICDs between the Orbiter and the payload. Structural verification for these loads may be certified by analysis only.

3.3.2.1.2 NEGATIVE DIFFERENTIAL PRESSURE

Negative pressure differential on primary payload structure shall use an ultimate factor of safety of 2.0 if certification for these loads is by analysis only.

3.3.2.2 ON−ORBIT

For on−orbit loading conditions, structural verification using analysis only may be used where the type of structure is amenable to prediction of ultimate capability by analysis. This analysis−only option shall require increased factors of safety of 1.25 on yield and 2.0 on ultimate. Use of this option requires prior approval of NASA and/or International Partner.

3.3.3 HANDLING AND TRANSPORTA TION

Flight structure design shall be based on flight loads and conditions rather than on transportation and handling loads, with the exception that handling attachment points for flight hardware may be designed locally for the handling loads at the attachment.

3.4 MARGIN(S) OF SAFETY

Space Station flight hardware structure shall have +0.00 or positive Margin(s) of Safety (MS) for all yield and ultimate design load conditions.

3.4.1 CRITERIA FOR LOCAL YIELDING

Local yielding of ISS structure shall be acceptable only if all of the following conditions are satisfied:

— The structural integrity of the component shall be demonstrated by adequate analysis and/or test.

— There shall be no detrimental deformations which adversely affect the component/system function.

— The service life requirements are met.

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3.5 DESIGN AND STRESS ANALYSIS REQUIREMENTS

3.5.1 STRESS/LOAD COMBINA TION RESTRICTIONS

Structural margins of safety for yield and ultimate failure criteria shall be evaluated in order to ensure that adequate margin exists for the combination of mechanical, pressure, and thermal loads. Guidelines for combining mechanical loads may be found in NASA−TM−X−73305. The following restrictions shall be applied for load combinations.

3.5.1.1 COMBINING WITH PRESSURE STRESS/LOAD

In circumstances where pressure loads have a relieving or stabilizing effect on structural load capability, the minimum value of such relieving loads shall be used and shall not be multiplied by the FS in calculating the design yield or ultimate load. Factors of safety for combined load conditions are defined in paragraph 3.3. For example, the ultimate compressive load in pressurized vehicle tankage shall be calculated as follows:

Ult Load = (FS X Mechanical Load) − (Min Pressure Load)

3.5.1.2 COMBINING WITH THERMAL STRESS/LOAD

Thermal stresses/loads shall be combined with mechanical and pressure stresses/loads when they are additive but shall not be combined when they are relieving.

3.5.1.3 COMBINING LOW FREQUENCY AND RANDOM LOADS FOR COMPONENTS AND

ATTACHMENTS

Low frequency loads and random vibroacoustic loads shall be combined according to Table 3.5.1.3−1, Load Combination Criteria for Components.

TABLE 3.5.1.3−1 Load Combination Criteria for Components

Axis Steady State Load1

(Limit) Low Frequency Transient Load

Random Load

Vi QSi +/− Si +/− Ri

Combined Loads Load in Each Axis Acting Simultaneously

Load Set V1 Axis V2 Axis V3 Axis

1 QS1 +/−(S1

2 + R1

2)1/2 +/− S2 +/− S3

2 +/− S1 QS2 +/−(S2

2 + R2

2)1/2 +/− S3

3 +/− S1 +/− S2 QS3 +/−(S3

2 + R3

2)1/2

Notes:

1. Resulting from 1.5 g’s in Orbiter negative X−axis

2. The loads calculated in a Space Shuttle/Payload coupled lift−off loads analysis include the low frequency transient and steady state effects, i.e. (Si + QSi)

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3.5.2 BUCKLING AND CRIPPLING

Buckling shall not cause structural members that are subject to instability to collapse when ultimate loads are applied, nor shall buckling deformation from limit loads degrade the functioning of any system or produce unaccounted changes in loading.

Evaluation of buckling strength shall consider the combined action of primary and secondary stresses and their effects on general instability, local or panel instability, and crippling.

All structural components that are subject to compressive and/or shear in−plane stresses under any combination of ground loads, flight loads, or loads resulting from temperature changes shall consider buckling failure modes. Design loads for collapse shall be ultimate loads, except that any load component that tends to alleviate buckling shall not be increased by the ultimate factor of safety. Destabilizing external pressure or torsional limit loads shall be increased by the ultimate FS but stabilizing internal−pressure loads shall not be increased unless they reduce structural capability. Diagonal tension designs are not precluded.

Analyses of buckling of thin−walled shells shall use appropriate “knockdown factors” (correlation coefficients) to account for the difference between classical theory and empirical instability loads. Typical knockdown factors are listed in NASA SP−8007, Buckling of Thin−Walled Circular Cylinders.

3.5.3 MATERIAL DESIGN AND ANAL YSIS THICKNESS

The drawing minimum thickness shall be used in stress calculations of pressure vessels, stability critical structure, and single load path structure. The drawing mean/average thickness may be used for stress calculations of all other structure. Actual as−built dimensions may be used in stress calculations when available.

3.5.4 DESIGN FACTORS

3.5.4.1 JOINT FITTING FACTOR

If required under the conditions outlined below, a fitting factor of 1.15 shall be used on yield and ultimate loads in the structural analysis of fittings.

— A fitting factor shall be used for joints which contain fittings whose strength is not proven by limit and ultimate load tests in which the actual stress conditions are simulated and measured in the fitting and surrounding structure.

— This factor shall apply to all portions of the fitting, the means of fastening, and the bearing on the members joined.

— In the case of integral fittings, the part shall be treated as a fitting up to the point where the section properties become typical of the member away from the joint.

— A fitting factor need not be used with limit and ultimate loads where the type of joint, such as a continuous row of fasteners in sheet or plate, a welded or bonded joint, or a scarf joint in metal or plastic, etc., is strength−verified based on comprehensive limit and ultimate tests.

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3.5.4.2 BEARING FACT OR

A bearing factor of 2.0 shall be used in conjunction with the yield and ultimate FS for the design of a joint subjected to shock or hammering action.

3.5.4.3 CASTING FACTOR

If metal castings are utilized as a fabrication process, an appropriate casting factor shall be developed by the design organization. The casting factor shall be applied in conjunction with the FS. Approval for the appropriate casting factor shall be obtained from NASA and/or International Partner. If a casting is a fitting, then the fitting factor shall be applied in conjunction with the casting factor and applied with the respective yield and ultimate FS.

3.5.5 PRELOADED JOINT CRITERIA

Bolt design in preloaded joints shall be in accordance with NSTS 08307, Criteria for Preloaded Bolts. Alternative methods to NSTS 08307 require prior NASA approval. A preloaded joint is a joint in which the preload is necessary to preserve linear structural behavior and to have adequate life due to cyclic loads, or to assure that no joint separation and resulting stiffness change occurs up to limit load, or to assure that no joint separation occurs at limit load which would affect pressure seals.

3.5.6 COMPOSITES/BONDED STRUCTURE DESIGN

Composite/bonded structure shall be designed to the factors of safety listed in Table 3.3.1−1, and to the life verification requirements of paragraph 4.1.3.4.

3.5.7 STRUCTURAL LIFE REQUIREMENTS

All structural components shall be evaluated for their capability to sustain static and cyclic load conditions which are part of the design environment. For those components whose design is subjected to a cyclic or repeated load condition, or a randomly varying load condition, a cyclic life analysis shall be performed.

Fracture analyses per the requirements of paragraph 3.1.6 shall be performed to demonstrate structural life for fracture critical structure. Fatigue or durability analyses shall be performed as necessary to demonstrate life for non−fracture critical structure. Structural life is defined as 4.0 times the service life loading environment for safe−life or fatigue analysis and 2.0 times the service life for durability analysis to account for material data scatter. The assumed flaw for durability analysis is a 0.005 inch corner crack or equivalent in the worst location and orientation.

3.5.7.1 PROOF TEST FOR FLAW SCREENING

When proof tests are used for flaw screening, the proof test factor shall be the larger of the values determined by the fracture mechanics analysis derived proof test requirements to meet service life or those specified in Table 3.3.1−1.

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3.5.7.2 FATIGUE

All flight hardware structure shall be designed to preclude failure resulting from cumulative damage due to cyclic loading and sustained stress during the design service life. Structural life shall be demonstrated by analysis and/or test based on a rationally derived cyclic loading spectrum that includes Shuttle transport to and from orbit, on−orbit, transportation, and testing loads.

3.5.7.2.1 FATIGUE STRESS VERSUS CYCLE LIFE CURVE FACTOR

The limit stress/strain shall be multiplied by a minimum factor of 1.15 on typical properties or

1.0 on lower bound properties prior to entering the stress versus cycle life (S/N) design curve to determine the low−cycle/high−cycle life.

3.5.7.2.2 LIFE FACTOR

The low−cycle/high−cycle fatigue analysis shall demonstrate a minimum calculated life of 4.0 times the required service life.

3.5.7.2.3 STRESS CONCENTRATION FACTORS − FATIGUE ANALYSIS

The alternating and mean stress/strain shall include the effects of stress concentration factors when applicable.

3.5.7.3 CREEP ANALYSIS

All flight hardware structure shall be designed to preclude cumulative strain as a function of time, i.e., creep, which could result in rupture, detrimental deformation, or collapse, (e.g., buckling) of compression members during the design service life.

Materials shall be selected to preclude accumulated damage from creep in the Space Station environment. If selection of a structural material which exhibits creep phenomena in the Space Station environment is unavoidable, then NASA and/or International Partner approval shall be obtained prior to use. All structural elements subject to creep shall be assessed to demonstrate the following factors.

3.5.7.3.1 CREEP ANALYSIS FACTOR

The limit stress/strain shall be multiplied by a minimum factor of 1.15 prior to entering the design curve to determine creep life.

3.5.7.3.2 CREEP LIFE FACTOR

The analysis shall demonstrate a minimum calculated life of 4.0 times the required service life.

3.5.7.4 SERVICE LIFE

The on−orbit design service life for Space Station structures shall be 15 years. Periodic inspection, maintenance, and replacement of parts, i.e., ORUs, may be used to attain the 15−year requirement but shall be used only with approval of NASA and/or the International Partner.

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3.6 STRUCTURAL MATERIALS CRITERIA

3.6.1 STRUCTURAL MATERIAL SELECTION

Material selection and documentation requirements shall be as defined in SSP 30233, Space Station Requirements for Materials and Processes.

3.6.2 STRUCTURAL MATERIAL ALLOW ABLE PROPERTIES

Space Station material structural properties in the design environment shall be determined from MIL−HDBK−5, Metallic Materials and Elements for Aerospace Vehicle Structures;

MIL−HDBK−17, Plastics for Aerospace Vehicles; or other sources which provide reliable and statistically valid data. Structural material property data obtained specifically for Space Station shall be generated by the procedures outlined in MIL−HDBK−5.

3.6.2.1 “A” ALLOWABLES

Material “A” or equivalent allowable values shall be used in all applications where failure of a single load path could result in a loss of structural integrity in primary structure. Equivalent material properties shall be approved by NASA and/or the International Partner.

3.6.2.2 “B” AND “S” ALLOWABLES

Material “B” or “S” or equivalent allowable values may be used in redundant structure in which the failure of a component would result in a safe redistribution of applied loads to other load−carrying structure. MIL−HDBK−5 material “S” allowables may be used for materials in lieu of “A” or “B” allowables where batch lot acceptance testing is a procurement requirement.

Equivalent material properties shall be approved by NASA and/or International Partner.

3.7 SECONDARY STRUCTURE ACCOMMODATION FOR HUMAN INTERFACE

3.7.1 INSPECTION, MAINTENANCE, AND REPAIR

Interior secondary structures, stand−offs, attachment hardware, utility runs, partitions, walls, and close−out structure of the Space Station shall be designed for accessibility to other hardware for inspection, maintenance, and repair.

3.7.2 INTERIOR CLOSE OUT

Close−out structure shall be used on the Space Station to prevent items from becoming lost in the low−gravity environment.

3.7.3 GROUND AND ON−ORBIT OPERATIONAL ACCESS DOORS

Secondary structures such as compartment doors and access panels which provide access shall be operational in both ground and Earth orbit environments.

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3.8 FASTENER REQUIREMENTS

Threaded fasteners that perform a safety critical function shall incorporate two separate verifiable locking features. Preload may be used as one of the features combined with a conventional aerospace secondary locking feature that is positive locking, vibration rated, and verifiable. Fasteners that are used in joints that are subject to rotation during operation shall use at least one non−friction type−locking device. The principal objective is to prevent inadvertent back out of the fastener in the event of loss of preload, due to acoustic, thermal, cyclic loading, and vibration induced distortions produced by all mission phase environments. For the purpose of this requirement, a fastener, or group of fasteners, is considered to be performing a safety critical function if the loss of that fastener, or group of fasteners, could result in a catastrophic hazard including the generation of FOD in the Shuttle payload bay. For use of liquid−locking compounds in safety−critical fasteners, refer to SSP 30233, section 4.5.5.3.

NASA and/or International Partner approval shall be obtained for the use of nonstandard or specially manufactured fasteners.

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4.0 VERIFICATION REQUIREMENTS

4.1 STRUCTURAL VERIFICATION REQUIREMENTS

The responsible organization shall show by analyses and sufficient tests that the hardware meets Program design requirements and has adequate strength, stiffness, service life, and integrity to assure function and personnel safety. The responsible organization shall submit stress analyses and verification test reports which will verify the capability of the respective flight hardware to meet the design requirements of this document.

4.1.1 STRUCTURAL VERIFICATION PLAN

A structural verification plan for the flight hardware shall be submitted to NASA and/or International Partner and coordinated with the Space Shuttle/Payloads Structural/Mechanical Working Group for Shuttle−launched ISSA hardware. The structural verification plan shall identify the methods of verification for each hardware element and shall identify the proposed development, verification, and qualification tests.

4.1.2 MATH MODEL VERIFICATION

Loads and deformations utilized in the Space Station Program verification shall be based on verified structural math models.

4.1.2.1 DYNAMIC LOADS MA TH MODELS

4.1.2.1.1 NATIONAL SPACE TRANSPORTATION SYSTEM MATH MODELS

Dynamic math models of Shuttle−launched ISS cargo elements and on−orbit Shuttle−attached configurations shall be test−verified in accordance with NSTS 14046, Payload Verification Requirements.

4.1.2.1.2 ON−ORBIT MATH MODELS

The Prime Contractor shall develop a plan describing the methodology and additional testing on the ground and on−orbit, required to verify the integrated system math models.

4.1.2.2 STATIC INTERNAL LOADS MA TH MODELS

The math models used to generate internal loads for structural analysis shall be verified by the methodology selected from the requirements in paragraph 4.1.3 of this requirements document.

4.1.3 STRENGTH AND LIFE VERIFICATION

The integrity of structure shall be verified by analysis or a combination of test and analysis.

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A test plan showing the proposed loading conditions, structural configuration to be tested, and method of test, including load application and instrumentation, shall be prepared and submitted to NASA and/or International Partner.

4.1.3.1 FOR SHUTTLE LOADS

The Space Station structural design and verification requirements for the transport phases to and from orbit shall be consistent with the requirements for Shuttle payloads specified in NSTS 14046. ISS elements shall be verified by test and/or analysis to the ascent vibro−acoustic environment defined in NSTS−21000−IDD−ISS.

4.1.3.2 FOR ON−ORBIT LOADS

Strength verification shall be demonstrated by analysis and successful completion of any one or a combination of the following options. Analysis−only strength verification requires prior approval of NASA and/or International Partner.

4.1.3.2.1 STATIC TEST TO ULTIMATE LOADS

For components whose critical failure modes result from on−orbit loads, a designated structural test article shall be static tested to ultimate loads for the critical load conditions to demonstrate the minimum required factors of safety per Table 3.3.1−1. Sufficient instrumentation shall be utilized to identify high strain areas and verify that the internal loads distribution and displacements are consistent with the loads model and the internal loads model.

4.1.3.2.2 PROTOFLIGHT STATIC TEST

For structures whose critical failure modes result from on−orbit loads, protoflight structure shall be static tested to 1.2 times the design limit loads. Sufficient instrumentation shall be utilized to identify high strain areas and verify the internal loads distribution, displacements, and the internal loads model. The minimum yield factor of safety shall be 1.25 for the structure to be verified by this option. Use of this option requires prior approval of NASA and/or International Partner.

4.1.3.3 LIFE VERIFICATION

In addition to the foregoing static test options, the responsible organizations shall identify the approach for life verification for cyclic and sustained loads in the design environment, which includes atomic oxygen, plasma environmental effects incompatibilities, debris, and meteoroid environments.

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4.1.3.4 LIFE VERIFICATION FOR COMPOSITE/BONDED STRUCTURE

4.1.3.4.1 GENERAL QUALITY REQUIREMENTS

All composite/bonded structures shall, as a minimum, meet prescribed structural verification requirements specified in this document. Furthermore, the designer/manufacturer shall use only manufacturing processes and controls (coupon tests, sampling techniques, etc.) that are demonstrated to be reliable and consistent with established aerospace industry practices for composite/bonded structures. Test articles shall be designed and fabricated to the same requirements, drawings, and specifications as the flight article.

4.1.3.4.2 COMPOSITE/BONDED FRACTURE CRITICAL STRUCTURE

Composite/bonded fracture critical structures shall be verified for…